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International Molding Report: International trade: Ways to boost exports

This report is prepared for IMM by Agostino von Hassell of The Repton Group, who provides IMM’s monthly Molders Economic Index.

Are molders to your right and left sending product overseas while you struggle to enter global markets? Online tools can help balance the scale.

For molders in the United States, Mexico, and Canada, the opportunities to export goods to major markets such as Asia, Europe, and Latin America have enormous attraction. At the same time molders are faced with increasing competitive pressures from imports from the same regions.

To find a profitable market niche can be exceptionally difficult as North American molders have an increasingly hard time competing with low-labor-cost countries. Exports of commodity injection molded products have been declining for the past 20 years—products such as low-grade housewares, packaging, caps and closures, or relatively simple automotive parts. Yet at the same time exports of high-value-added, highly engineered, low-tolerance parts have been booming. Sophisticated medical devices are one such market; others are “nano” parts and complex automotive subassemblies.

How can molders benefit? The reality is that few molders are direct exporters these days. They sell their components to major medical device makers or other product integrators who have the marketing muscle to export. Yet exports constitute a significant portion of the overall output of North American molding operations.

Import and Export Data
The Society of the Plastics Industry reported that in 2000, overall the U.S. had a trade surplus with the rest of the world. Much of the surplus was due to resin exports. With Mexico alone, the U.S. had a trade surplus of $3.8 billion in 2000 and $3.3 billion in 2001.

For 2001, the SPI reported that the trade surplus in all plastic products fell sharply from $1.6 billion in 2000 to just $560 million. Based on the first six months of this year, 2002 may very well see another major drop. With China alone, the SPI reported, the trade deficit in all plastic products grew from $2.7 billion in 2000 to just more than $2.9 billion in 2001.

We believe that for molders the reality is somewhat different—and starker. Accurate data are hard to obtain. For example, the U.S. has a giant trade deficit in automotive parts and electronics products. But there are no detailed data available that break out the percentage of injection molded items in products such as automotive parts. SPI data also include products that are not molded, such as sheets or plastics bags.

Over the past years we have conducted several detailed analyses of export and import data. By counting all product categories that included injection molded parts—and not limiting ourselves to the somewhat inadequate customs categories for plastics parts—we believe that the U.S. is running a sizable trade deficit in injection molded parts with the rest of the world.

After deducting the internal NAFTA trade, true exports from the U.S., Canada, and Mexico account for about 5.8 percent of total molded parts. That figure is for 2001 and is based on a detailed review of trade statistics and other data. Exports have grown about 4.5 percent in each of the last 10 years.

The import picture is quite different. Of all injection molded parts sold in the NAFTA territory, more than 24 percent are imported. That figure has doubled since 1990, according to U.S. Dept. of Commerce statistics. Such imports grow far more rapidly than exports—on average about 8 percent per year. We believe that in 2001 the U.S. had a trade deficit in molded parts of about $9 billion, and that deficit is growing.

Trade Can Be a Success
Success stories in foreign trade can be found across various product categories served by the injection molding industry. For almost every domestic molder who lost market share due to low-cost imports, you can find another that has been able to boost output due to exports.

How do you succeed in exports? How do you benefit from global markets? Molders who have had concrete success are reluctant to share their secrets. But several interesting common elements emerge:

  • Molders have found growth through exports of highly engineered and often very low-tolerance parts. These are components with very high value added and where, in the overall production and developments costs, labor expenses are only a small fraction. 
  • Injection molded products with expanding foreign markets include subassemblies for medical devices, ultralow-tolerance parts used in applications such as electronics, small appliances, complete subassemblies like rearview mirrors for cars and trucks, telecommunications items, and components for keyboards. 
  • Several molders told us that their research showed a very limited market for molded parts as such. These molders did, however, boost their exports by finding major assemblers of “black boxes” for all types of industries and are exporting to countries such as China, Singapore, South Korea, and Japan. The trick was hard work: endless research, competitive analysis, and frequent, often exhausting sales presentations in Asia.

    Trade Politics
    The Bush administration is making massive efforts to open up trade opportunities, break down trade barriers, and create growth for manufacturing through exports. At the same time, while pushing the concept of “free trade,” the Bush administration is taking a protectionist stance, as can be seen with the antisteel import action. Yet this position seesawed again in late August, when more than 178 imported steel products were excluded from steep tariffs imposed earlier this year.

    This summer President Bush signed into law a trade bill giving him the power to negotiate free trade agreements. It has been eight years since a U.S. president has held the power to make trade deals, which Congress can either approve or reject, but not change.

    The bottom line here for molders is simple. Will the new trade law benefit molding shops? Perhaps. Will the U.S. administration help protect domestic molding operations from low-cost imports? Not likely.

    For example, Taiwan and the U.S. may now develop a free trade agreement, after Taiwan’s President Chen Shui-bian proposed a free trade zone to counter China’s growing influence. (Data collected by the U.S. government show that the mainland Chinese injection molding output is growing on average 18 percent/year, and accelerating.) The ultimate goal is a U.S.-Japan-Taiwan free trade zone that might counter China’s “magnet effect” on trade and investment, one Taiwanese official said.

    It will take several years to negotiate such a trade deal. And the likelihood of including Japan in a free trade zone is somewhat remote, as Japan is unlikely to list historically and culturally based restrictions on agricultural trade.

    Once an agreement is in place with Taiwan, it means initially only the removal of import barriers such as duties. It does not open the doors to “easy marketing.” The hard job—to sell molded products—will follow.

    The same applies to the stated U.S. goal of creating a North and South American free trade zone by 2005. That zone will help reduce trade barriers but it will not take care of marketing efforts for molders.

    Voting With Their Feet
    Many molders and major users of molded parts have abandoned goals to grow U.S.-based operations through exports. Rather, they moved such operations abroad. For instance, Flextronics International Ltd., one of the world’s largest contract manufacturers, is closing its last two major operations in the U.S., in Elk Grove Village, IL and New Braunsfels, TX. The manufacturer of electronics enclosures is being moved to Mexico and China.

    Many smaller molders are taking similar steps, retaining tiny manufacturing operations in North America while benefiting from low labor costs in China, Poland, and India.

    Fighting Back
    Does it make sense for molders to fight back against low-cost imports? Should molders take actions similar to those of the domestic steel industry and look for help from the federal government for import relief?

    The most obvious and logical target is imports from China. Chinese firms are aiming to grab as much of the U.S. market for manufactured goods as possible, and are doing the same in Europe.

    Molders serving markets such as toys, plastic cutlery, and housewares have seen much of their market evaporate in past years. Increasingly you also see Chinese imports grab market share in more sophisticated areas such as automotive parts, electronics, low-grade medical disposables, or electrical parts.

    Are we dealing with unfair trade here? Are Chinese firms dumping goods into U.S. markets? The probability is high, but proving so is difficult and time consuming.

    Getting the Office of the U.S. Trade Representative to support molders here is another challenge. The various markets served by molders do not have the same political pull as industries such as steel and automotive. Thus it is very hard to get molded products high up on the agenda in trade talks.

    This writer has worked on such trade actions for 15 years. Molders have numerous tools available to them to fight against unfair imports. The problem with such actions is that they are expensive and complicated. However, if successful, they could provide measurable relief for some time.

    The most effective but most costly measure would be to file an antidumping petition with the International Trade Commission. This has been done for numerous products in past years and has been effective in most cases.

    Another option is to use the so-called “safeguard” exception in the WTO rules. While the WTO is meant to break down trade barriers (including those in China), some exceptions allow a country to take quick and aggressive measures to head off a sudden wave of imports. This was used by the Bush administration against steel imports this year.

    U.S. Government Help
    The most immediate help would be from the Trade Adjustment Assistance for Firms (TAA, www.taacenters.org), a federal program that provides financial assistance to manufacturers affected by import competition. Sponsored by the U.S. Dept. of Commerce, this cost-sharing federal assistance program pays for half the cost of consultants or industry-specific experts for projects that improve a manufacturer’s competitiveness. Such cost supports are capped at $75,000.

    Online U.S. government resources for growing an export business:
  • www.taacenters.org 
  • www.export.gov 
  • www.buyusa.com 
  • www.sba.gov/financing/
  • A number of molders told us that they have not made use of the government’s resources. The reason: They are concerned with the possible complexity of such help and often believe that their businesses are too small or “unimportant” to deserve Washington’s attention. This is a major mistake. Molders—often small shops with sales of less than $5 million—who succeeded in foreign trade have told us repeatedly that using the U.S. government’s help works.

    Several agencies in Washington employ highly dedicated people whose only job is to help you increase exports. Assistance is available in all key areas such as finding leads, negotiating contracts, opening doors, and even financing exports. Some of these experts express amazement at just how few U.S. manufacturers seek out their help.

    So what’s available?

  • www.export.gov. This is the U.S. government’s online entry for U.S. exporters. The site has export-related programs, services, and market research information from 19 federal agencies; it might be the best place to start.       
  • While visiting www.export.gov, also look for information on the International Trade Administration (a unit of the U.S. Commerce Dept.). Within the ITA, the government has organized numerous offices dedicated to specific end markets and boosting exports in those areas. One such office is the Office of Automotive Affairs. OAA’s job is to help facilitate and expand global business opportunities for U.S. automotive vehicle and parts manufacturers. OAA achieves its objective through a variety of programs, ranging from market access and other trade policy initiatives, market analysis, and business counseling to selected export promotion initiatives. Another such unit is the Office of Consumer Goods.       
  • www.buyusa.com. This e-marketplace sponsored by the Commerce Dept. brings together suppliers of U.S. products and services with international companies, and gives both groups the advocacy and services they need to conduct successful business worldwide.       
  • Another critical resource for molders is the little-known U.S. Trade & Development Agency. Its only mission is to help boost U.S. exports and the development of emerging markets.       
  • www.sba.gov/financing/. Concrete help can be found for export financing from the Small Business Administration. The SBA can guarantee up to $1.25 million for a combination of fixed-asset (facilities and equipment) financing and Export Working Capital Program assistance. The fixed-asset portion of the loan guaranty cannot exceed $1 million and the nonfixed-asset portion cannot exceed $750,000.

    Contact information
    The Repton Group, New York, NY
    Augustino von Hassell
    (212)750-0824; [email protected]

  • The lure of cheap labor hurts Mexico

    Cheap and plentiful labor, along with the ability to ship components into Mexico duty-free as long as the finished goods were exported, was the carrot for many U.S. and Asian manufacturers to move operations south of the border over the past three decades.

    Now, Mexico is hearing a giant sucking sound from the Far East. China, with its plentiful and even cheaper labor, is luring manufacturing away from Mexico. With it goes the promise of good jobs and a better life for thousands of Mexican people. The maquiladora legacy has taken an ironic twist: higher wages but fewer jobs.

    One report noted that more than 500 foreign-owned factories have closed over the past two years, in large part because an entry-level worker in Mexico makes nearly four times what a Chinese entry-level worker earns—$2/hr vs. $.50/hr. Some 250,000 factory workers along the U.S.-Mexico border lost their jobs during that time frame.

    Asian companies were some of the first to set up shop in Mexico, particularly in the consumer electronics industry where lots of labor-intensive assembly is required. Benefits included the ease of shipping bulky items such as large television sets to the U.S., a primary market for consumer electronics OEMs due to the geographic proximity.

    Things have changed. Sales of consumer electronics have declined in the U.S. Sales in Central and South America and Asia have increased. A spokesman for LG Electronics recently told a group of plastics industry professionals that U.S. market softness will continue.

    Following Customers
    Technimark Inc.’s president, Don Wellington, says that the molding business in Mexico is like a roller coaster ride. The Asheboro, NC-based company has three facilities in Mexico, in addition to three plants in North Carolina. “We followed [customers] to Mexico, and now they’re not as sure Mexico will cut it anymore because of increasing labor rates,” says Wellington. “Mexico and China are competing neck-and-neck all the time. You just about need to have your molding machines on roller skates.”

    Wellington points to one customer, a maker of consumer products, that decided at the last minute to tool a new product in China  rather than Mexico. Overnight, Technimark lost $8 million in business from the plant in Mexico that served the customer. “You know changes like this will happen, but the speed of these changes is what’s frightening,” says Wellington.

    Operating in today’s global marketplace is a huge challenge for molders primarily because of the volatility as companies continue to chase the low labor rate, explains Wellington. “The Chinese are ravenous,” he says. “They want anything they can get their hands on, and the Chinese workers make less than a dollar an hour, which gives them a tremendous labor advantage.”

    Asian OEMs Feel the Pinch
    As Asian markets pick up and consumers there gain greater disposable income, sales of consumer electronics could easily outpace U.S. sales. That gives Asian OEMs a good incentive to manufacture in China. Another incentive to leave Mexico is the 18 percent duty companies operating in Mexico pay on components coming from China.

    A poll taken in March by the Japanese Maquiladora Assn. showed that 40 percent of the 71 companies surveyed were considering eliminating some operations or moving entire factories elsewhere. This reflects the changing climate in Mexico since new tariff regulations were put into effect in January 2001. Those new rules removed tariff exemptions for maquiladora companies in an attempt to bring Mexico’s policies in line with those of the U.S. and Canada. To compensate for the resulting increase in costs, Mexico created 20 special categories in which companies pay up to 5 percent tariffs on thousands of items imported from outside the NAFTA region.

    For materials that fall outside these categories, however, companies pay the equivalent of the difference between the highest tax in the NAFTA region and the lowest.

    Japanese OEMs represent the second largest group of maquiladora companies in Tijuana, and they haven’t been happy about the changes. These added costs come at a time when competition for consumer electronics is fierce and prices are ratcheting downward in an effort to gain market share.

    In March of this year, Canon Inc. announced its decision to close Canon Business Machines Inc. of Costa Mesa, CA and the manufacturing plant in Tijuana, Mexico—Canon Business Machines de Mexico SA de CV. A competitive environment for its products and a soft U.S. market were the reasons given for the decision. Both companies made ink jet printers and related consumables for the U.S. market. Operations ceased at the end of May, idling around 30 office workers in Costa Mesa and more than 400 production workers in Tijuana.

    A statement released by the company said that “because of the rapid drop in prices and fierce competition for higher performance of ink jet printers in the marketplace, Canon has been continuously challenged to find ways of achieving more efficiency in its ink jet printer business operations. Consequently, in accordance with the company’s production strategy, Canon’s overseas ink jet printer manufacturing will be centralized in two Asian factories, one in Thailand, the other in Vietnam.”

    Outlook for U.S. Molders
    The move of these companies to Asia affects U.S. molders as well. Many molding firms have molded components for a variety of Canon’s office equipment since Canon established U.S. operations in 1974. SimRidge Technologies (formerly Arizona Jacobson) in Tempe, AZ was a primary, award-winning supplier to Canon for many years. However, the work began gradually moving offshore and the company hasn’t done any molding for Canon for more than a year, said a company spokesperson.

    Technimark’s Wellington strongly believes there are advantages for manufacturers in Mexico vs. China. He cites the cost of transporting finished goods to major markets in North America; the cost of increased inventory companies must carry due to a six-week shipping time vs. a week or less from plants in Mexico; and the ability of manufacturers in Mexico to react quickly when consumer demand in North America spikes during peak buying seasons.

    Still, the impact of currency valuations keeps business uncertain and in a state of flux. When the relative price of pesos per dollar increases, the costs go up because manufacturers must buy pesos with U.S. dollars to pay employees, Wellington explains. “Now we’re seeing a swing back to around 10 pesos to the dollar, which is making Mexico more competitive with China,” he says, adding that one customer was ready to pull work from Technimark and send it to China.

    “However,” says Wellington, “since the peso’s gotten stronger, that’s on hold. Everyone is chasing the low labor rate.”

    IMM Editorial: Greetings From the Tightrope

    Jeff Sloan 

    In the March 2002 issue I wrote about how the molding industry is evolving, and how molders are evolving or must evolve with it to survive (see: “Notice: You are Not a Molder” March 2002 IMM).  In response, I received one particularly strong e-mail from Paul Tontsch, a molder. There’s not room to publish it all, but I will excerpt quotes:

    I am stunned that a serious magazine is taking such a “whatever” approach to what is THE issue facing the injection molding industry, for that matter all of the manufacturing industry—that of cheap product coming from Asia and Mexico.

    How can we compete with such places that do not have the rules and regulations that North American suppliers have to deal with, such as minimum wage, health and safety, workers’ compensation, and insurance and environmental preservation issues?

    You stated that in order to compete with Mexico and Asia the molders in North America need to offer contract services. I question this. If we cannot compete on a molding basis because our costs are too high, driven specifically by labor costs, how can we compete doing assembly work and other “value-added” tasks? This is why contract manufacturing went offshore in the first place. To think that we can ever compete by playing them at their game is folly and unsound. Only when our standard of living is as low as those elsewhere in the world will work come back. However, the industry will be decimated by then and unable to respond effectively.

    My second question is this: Why are companies, manufacturing associations, and industry-related magazines not lobbying government to create a more even playing field, as is happening in the steel industry? Does it boil down to the simple fact that North America does not want manufacturing? The argument that we need to invest more in equipment, in training, and to find niche markets will not cut it any longer. I have done all of that in my own company and still I cannot compete. The industry needs help and support from government if it is going to survive. Government won't do anything unless it understands that manufacturing is key to a vibrant economy.

    Your article in no way helps the vast majority of injection molders, your readers. To me it said, “shut up shop and go do something else,” because the option that was put on the table is not a viable solution for the majority of us out here, doing battle on the front line. I suggest that you seriously consider the condition of our industry and make efforts to support its interests before we lose those skills already present and turn away the new blood that is looking to become part of its future.

    Magazines like this one are often forced to walk a fine line when it comes to establishing “position” on critical issues. On the one hand, IMM has a responsibility to promote, support, and defend the injection molding industry, especially when it faces the threat that currently confronts us. On the other hand, we are also obliged to be as honest, fair, objective, and realistic as possible about the state of the industry and where market forces are leading it—whether to Mexico, China, or Eastern Europe. The question is, are you better served by IMM as cheerleader and advocate of government protectionism, or by IMM as laissez-faire reporter of industry trends? The answer, I think, is both; rather, we aspire to do both.

    As part of IMM’s effort to do more of the former (advocacy), we are starting in November a series of regional lunches called Crossroads Roundtables. Named after the Crossroads editorial series we are launching next year to take a closer, more in-depth look at the exodus of molding jobs and how it might be slowed, the Roundtables will bring together molders, moldmakers, OEMs, and industry suppliers. Moderated by IMM, they will discuss the current state of the industry, the trend to take manufacturing offshore, and how we can and should respond to help keep those jobs here. The first stop on our tour will be Cleveland. Other planned stops include Detroit, Chicago, Boston, Baltimore, Atlanta, Phoenix, and Los Angeles. Reports of these Roundtables will be published in future issues of IMM.

    I don’t think IMM has ever taken a “whatever” approach to molding, and we hope that the Crossroads Roundtables and next year’s series are further proof that this is the case.

    Editor
    [email protected]

    Technology Notebook: Supplemental oil filtration protects IMM hydraulic systems

    Editor?s note: Jack Berg is president of Serfilco Ltd. in Northbrook, IL. He has extensive experience in filtration of hydraulic oil on a wide range of industrial equipment, including injection molding machines.

    Injection molders tend to have characteristic responses to the idea of using supplemental hydraulic oil filtration to protect their equipment. One is, "Our systems are old. They leak a lot so we just replace the oil and put some absorbent around the machine." Others say their systems are new and include inline filters on the machines so there is no need for additional filtration. Some maintenance superintendents replace seals and pump packing or fix other sources of leakage to keep molding machines running.
    The plastic injection molding machine above is typical of the type of equipment that can benefit from the supplemental filtration of hydraulic fluid.
    Hydraulics Basics
    A hydraulic system creates pressure by using a pump to build force against a noncompressible liquid. Through a series of valves opening and closing, and without manual involvement, the hydraulic system creates the back-and-forth sliding movement of a shaft, which, in turn, with cams, makes another part of the equipment go up or down, open or close.

    We could say the hydraulic system works like the human body. For instance, it has a heart (pump) and lungs (breather), which allow the system to work. The pump, driven by a motor, is made with tight clearances to create the pounds of pressure needed to perform the task.

    What Causes Hydraulic System Malfunction?
    Hydraulic system failure very often involves contamination in the fluid. How does a brand-new system, flushed clean at the manufacturer's facility and filled with new, clean fluid, become contaminated? After all, isn't the fluid contained in a closed loop? Yes, but pumps involve gears and other close-tolerance components that move against each other and are separated only by the thin film of fluid in the system. Over time in operation, the action of metal against metal causes wear, which results in small (micron and even submicron-sized) particles to be suspended in the circulating fluid.

    The breather, another source of contamination, allows atmospheric air to enter the fluid reservoir to replace the fluid as the fluid forces a shaft to move forward. As a shaft makes its reverse movement, the fluid returns to the reservoir and the air is pushed out of the breather.

    Another source of contamination is the shaft. It moves out of the system during forward operation and is wiped clean by a seal on the way back into the system. Subjected to this continuous abrasion, the seal ultimately fails, causing fluid to leak out or abrasive particles to enter the recirculating fluid.

    Therefore, all hydraulic systems include filters (sometimes referred to as strainers) installed in the circulating system of the fluid, and a filter is also installed in the breather to perform the same duties. But alas, nothing is perfect.

    Although the human body may be able to operate under severe conditions for a limited or even an extended period, a hydraulic system subjected to ongoing adverse conditions simply self-destructs. A pump does not replace the wear caused by contamination, but rather continues to wear more and more from the effect of the previously created particles. It then fails to create the needed pressure due to slippage.

    This is a portable filter system equipped with a large-capacity filter chamber for removing solid contaminants from hydraulic oil, and a coalescing chamber for removing water. The unit can be wheeled from machine to machine as needed.
    Addressing Fluid Contamination
    The logical answer to prevent wear and service downtime is to remove the particles as quickly as possible from recirculating hydraulic fluid. The challenge is to remove any particles from the pumps or valves that are finer than the thickness of the oil film, and most importantly, to do it before any damage occurs.

    A well-designed hydraulic system includes a myriad of devices to remove the damaging particles. The question is: Will the filtration within the fluid system perform the needed cleansing or is additional filtration capacity desirable? Is particle removal worthwhile? When continuous, uninterrupted reliability is expected, the cost of downtime is the determining factor. In this scenario, more filtration is better.

    It is important to determine how much space such a system occupies, the flow rate, and the particle-size retention of the filter media. Answers usually can be arrived at mutually by the user and the equipment supplier.

    Portable Filtration
    Some maintenance personnel use a portable filtration system?one that contains its own pump, filter chamber, filter media, and piping?that can be moved from machine to machine and become integral to the fluid system through the use of quick disconnects. Others employ hoses inserted into the breather opening of the hydraulic reservoir, or add a filter in a shunt system to provide additional filtration by processing a small quantity of fluid diverted from the pressurized piping.

    A system individually piped to the hydraulic reservoir provides good results. The pump can be energized independently to remove particles even when the hydraulics are not operating. It may provide additional purification of the fluid from acid-removing media, or provide moisture reduction. Since the system is independent, as the filter flow rate is reduced or backpressure in the filter is increased, the performance of the hydraulic system is not affected.

    However, some users choose not to energize the hydraulic reservoir filtration systems independently, instead energizing them only when the main motor starter of the machine starts the electrical motor that runs the hydraulic pump. This has two advantages: No one has to remember to turn the filtration on or off, so when the machine is running, the oil is continuously filtered.

    Permanent Supplemental Filtration
    A supplemental filtration system permanently mounted on the machine and piped to the hydraulic reservoir may provide low maintenance and reliable operation. By tying the system to the motor start function of the machine, the oil reservoir is filtered whenever the machine is running. Piping the system with shutoff-type quick disconnects at the filtration pump and the reservoir allow for easy maintenance access to both.

    A machine-mount filter system is mounted directly to hydraulically operated equipment. Above, a filter assembly is mounted at the top of a molding machine. Below, the unit is mounted on the side of a machine.
    Additional oil filtration may benefit the machine operator in an unexpected way by relaying to the maintenance department the true importance of clean oil in the machine. When the closed loop hydraulic system of a machine must be opened for maintenance, personnel will surely take greater care to prevent contamination of the system.

    Monitoring, Analysis, and Supplemental Filtration
    With today's sophisticated machine controls, in combination with the personal computer, maintenance personnel can carefully monitor the actual hourly service life of the hydraulic oil and the frequency of filter cartridge changes. One injection molder reports that a preventive filtration maintenance program should include a cartridge change at 720-hour intervals?actual time logged on the machine?or when the differential pressure between in and out on the filter chamber reaches 25 to 30 psig. This molder goes on to say that the filter system keeps his oil so clean that the pressure differential never reaches 30 psig, so he uses the 720-hour schedule to maintain his equipment.

    When the filtration system is first installed, this interval should be cut in half and oil analysis should be performed frequently until a noticeable difference in the clarity of the fluid is detected. Using this procedure, the clarity of the oil can be monitored and the maintenance interval can gradually be increased until the 720-hour interval is reached.

    Oil changes in the injection molding machine or other equipment incorporating a hydraulic system can become rare with an extensive program of regular oil analysis. It is a common misconception that hydraulic oils break down in service. While this is untrue, it is true that the anti-foam, rust, and oxidation inhibitors contained in premium grade hydraulic oils can be depleted at an accelerated rate if contaminants?such as particulate matter and water?are not routinely removed from the oil during uptime. Thus, coalescing systems with filtration capability are an asset.

    Today's sophisticated oil analysis instruments can monitor the level of the various additives and signal when more are needed. Additional filtration not only saves the cost of hydraulic oil, but also downtime to change the oil is reduced.

    The history of another injection molder illustrates the benefits that can be derived from supplemental filtration and close monitoring of the hydraulic fluid. At this firm, a new general manager learned that his predecessor had replaced the hydraulic oil in all six injection molding machines four years earlier. This maintenance expense cost the company $4312 (1540 gal or $2.80/gal). This plantwide oil replacement did little to minimize the hydraulic breakdowns that constantly plagued the shop. In nearly every case, the breakdown, or poor and inconsistent machine performance, was traced back to contamination in the hydraulic system.

    The plant budget again presented the opportunity to change the oil in all of the machines. Although the new general manager made a similar expenditure, he chose instead to buy filtration equipment rather than change the oil. Each machine was equipped with a permanently mounted, external, 3-gpm filter unit. These filter units are wired and piped in place so that whenever the hydraulic system pump motor is running the filter unit is also operating, constantly filtering the machine's hydraulic reservoir.

    Prior to installing the filtration units, the general manager tracked machine downtime using machine hour meters and a personal computer. He used the computer to monitor operational downtime with a numerical scale to predict future trouble. He determined when downtime reached an unacceptable level and it was time to overhaul a machine or replace it, and he found that the six machines averaged a total of two hours of downtime per month attributable to hydraulic problems.

    During the first six months of operating the machines with the externally mounted filters, the downtime rate for hydraulic problems was cut in half. Throughout the next 12 months, the instances of hydraulic downtime continued to diminish, and the rate of hydraulic downtime leveled off at 18 minutes per month?an 85 percent reduction from the original rate. In addition to reducing downtime, the use of the filtration units eliminated the need for oil replacement in the machines.



    Contact Information

    Serfilco, Ltd., Northbrook, IL
    Jack Berg
    (847) 509-2900
    www.serfilco.com

    Tooling Corner: Advanced sequencing and protection of valve gate systems

    Editor's note: Thomas P. Linehan is manager of engineering at D-M-E Co. in Madison Heights, MI. He is responsible for the development and support of injection molding control products sold by D-M-E, and a registered professional engineer in Michigan.
    The air-powered hydraulic pump above is used to actuate hydraulic valve gates. This type of pump generates no heat and saves energy by only operating when needed. The accumulator on top provides stored energy to power large valve gate cylinders.
    The control of valve gate sequencing used to be limited to timers, but the current and growing trend is to use screw position and even cavity pressure to determine when to open and close the valve gates in a hot runner system. In some cases, a combination of control parameters may be used.

    Sequencing systems can also be made to protect valve gate systems from misuse. For example, the accidental application of injection pressure when no valve gates are open can be avoided, as can the exposure of material to high temperatures when mold cooling isn't present.

    Time-based Control

    For years, valve gate sequencers used panel-mounted timers to program the opening and closing of valve gates. Typically, the start of the sequence was triggered by the injection-forward signal from the press or a signal just preceding it?the high-pressure clamp, for example. Alternatively, a limit switch mounted to the mold or tie bar could sense the closing of the mold and initiate the process.

    In the simplest of applications, the valve gates are all opened and closed simultaneously. They are opened at the beginning of injection and closed during pack or hold. This method does not allow for control of balanced fill. However, it does provide better gate vestige than sprue gates. It also allows for earlier implementation of screw rotate since it is not necessary to wait for the gate to freeze. The latter provides for faster cycle times. In this application a single, large air or oil source can operate all valve gates simultaneously.

    The D-M-E sequencer cabinet above is shown next to a Milacron Maxima injection molding machine. The photo shows the similarity in technology with the Milacron operator station.
    In some cases, the valve gates are all opened at the onset of injection and then closed independently with timers. However, the more typical approach is to open the harder-to-fill cavities at the beginning of injection and the easier-to-fill cavities later during the first stage (fill). Each of the valve gates is then left open for the required time to achieve the desired part weight and size. This is typical of a family mold application, or one that is not adequately balanced by the design of the hot runner system. This requires that each of the cavities has two timers?one that delays the opening of the valve gate and another that controls the time it is open.

    Screw Position and Cavity-pressure-based Control

    Recent advancements include the use of screw position (shot size) and cavity pressure to control the sequencing of the valve gates. Both of these parameters are considered better than timers because timer settings do not correct for changes in the viscosity of the material and therefore the velocity of injection and fill. Screw position corrects for variation in injection velocity by ensuring that an accurately metered amount of material is injected into a cavity. This assumes that the nonreturn valve ahead of the screw is in good repair and not leaking.

    Cavity pressure provides optimum control, if properly implemented. Peak cavity pressure is an accurate indicator of part weight and therefore size. Simply put, if you want to know what is going on in a cavity, look in the cavity, not the countless other upstream input parameters. Virtually all other inputs can be detected by the cavity pressure profile. This is an important consideration when using an injection molding machine that lacks the ability to accurately control the molding process.

    Regardless of the approach taken, it is highly recommended that valve gates not be closed until the second stage (pack) or third stage (hold) to make sure that the cavities are properly packed out.

    In none of the aforementioned applications is there any feedback from the valve gate control to the molding machine. Additional capability comes from an expanded logic interface between the molding machine and the valve gate control.

    Improved Sequencing Control Features

    One of the key improvements has been in the flexibility of control. Whereas older systems are built from hardwired timers, the newer ones are built from programmable industrial computers. A good example of this is cascade molding, where multiple valve gates fill a single large part.

    In cascade molding, the flow front is guided from one side of the part to the other (left to right for example). This process avoids weldlines otherwise associated with multiple gates in a single part. For example, the first, or leftmost, valve gate opens and as the flow front passes the second valve gate, a pressure sensor to the right of the second valve gate senses the passing flow, and a trigger opens the gate. This same trigger may also close the first (leftmost) valve gate. As the flow front continues to press forward, it passes yet a third valve gate and another pressure sensor triggers the opening of the third valve gate and possibly the closing of the second. Once a sensor to the far right of the part picks up the flow front, the first two valve gates can be reopened to begin symmetrical pack out of the part. The valve gates are then closed after a predetermined time or when the desired peak pressure is detected inside the cavity.

    While this kind of operation could be hardwired, it is convenient if it can be reprogrammed for different applications.

    The above application has a couple of unique requirements. First, any sensor (analog input) must be able to be assigned to open or close any of the valve gates. This requires that the control software allow for flexibility in configuring the setup.

    Second, a feature that allows for reopening a valve gate for pack out requires that a transfer signal be routed from the injection molding machine to the valve gate control. This signal indicates the end of the fill stage and the beginning of packing. Note that if the valve gate controller were part of the molding machine control, this and other interface signals would be inherently available.

    Another effective and easy-to-implement setup is to provide cascade control as described previously but with screw position-based control. Upon receiving the high- to low-volume transfer signal from the machine, the valve gates could be opened again for pack out. A benefit of screw position control is that a single sensor can be used to control multiple valve gates.

    Only a single analog input is required and it is the only one that needs to be calibrated. However, it is important that the nonreturn valve of the injection unit be in good shape to prevent leakage. Otherwise, screw position does not provide any better control than time.

    Table 1: Signals

    SIGNAL SOURCE AND DESTINATION
    SignalSource and Destination
    Injection forwardInjection molding machine to valve gate
    Injection transferInjection molding machine to valve gate
    Alarm outputValve gate to injection molding machine
    Inhibit injectValve gate to injection molding machine
    High oil temperatureWithin valve gate
    Low oil levelWithin valve gate
    No air pressureWithin valve gate
    No water coolingMold to valve gate
    Valve gate(s) openMold to valve gate
    Valve gate(s) closedMold to valve gate
    Screw positionSensor to valve gate
    Cavity (other) analog sensorSensor(s) to valve gate
    Additional interface signals between the injection molding machine and mold are required for an advanced valve gate sequencer. This table outlines the signal source and destination.
    Improved Protection of the Hot Runner System
    Despite numerous improvements in the sealing of hot runner systems (e.g., cold clearance compensation), avoiding potential threats to the hot runner system is a good practice. This is especially true when such threats can be avoided automatically.

    With additional signal interface between the molding machine control and valve gate control, new protective measures can be implemented.

    For example, it is easy for the industrial computer to determine that no valve gates are open when an injection signal from the molding machine is received. In this case, an "inhibit inject" signal can be sent back to the injection molding machine before significant buildup of pressure within the hot runner system occurs. This can help prevent accidental damage to the hot runner system sealing.

    Similarly, the detection of nonfunctioning valve gates is desirable. If a valve gate doesn't open, it doesn't make a part.

    Additionally, if a valve gate doesn't open, the material in the related nozzle and manifold passages experiences an extended heat history, leading to degradation and possible crosslinking. If detected immediately, this degradation can be avoided. Additional digital inputs can be used in conjunction with limit switches to detect cycling (or lack thereof) of the valve gate cylinders.

    If a valve gate is programmed to be opened, but is not open according to the limit switch sensor, inhibit-inject and alarm signals can be output to the injection molding machine. The valve gate controller can also output an audible signal and display an indication of which of the valve gates is not functioning properly.

    Valve gate position can be sensed with one or two limit switches. However, typical system designs, space limitations, and temperature usually dictate that only one switch is used and that it is placed behind the cylinder in the clamp plate.

    When the cylinder pulls back, it contacts and closes the limit switch. When forward (closed), the limit switch is open. Also, by having the limit switch in the clamp plate, adequate cooling can be applied to safeguard the switch.

    Sensing water temperature can help spare water seals from potential damage. While this could be part of the hot runner temperature control function, it could be part of the valve gate or injection molding machine control as well.

    For example, water-cooled gate inserts often have elastomer seals that could be damaged if water cooling isn't present. The preferred embodiment would include the ability to sense the lack of cooling and provide at minimum an alarm and description of the problem. If integrated with the hot runner system, it could also provide shutdown of the hot runner nozzles or the entire hot runner system.

    Control software sample screens

    Figure 1. Valve gate settings


    Figure 2. Individual zone setup


    Figure 3. Analog input setup, p. 1


    Figure 4. Analog input setup, p. 2
    Figure 1 is the main page for inputting settings once the valve gate system is set up. On this screen, you can see the option to reopen after high- to low-volume transfer.

    Figure 2 shows the screen that programs each of the individual valve gate settings. Specific names can be given to each gate, and all of the related options are made available on this screen. Analog channels can be individually selected for opening and closing valve gates.

    Figure 2 also shows where the user selects either a hydraulic or air-powered system. This in turn selects which protective elements are put into place. If it is an air-based system, the presence of air pressure is sensed. If it is a hydraulic system, oil level and temperature are sensed, as is a signal indicating that the hydraulic pump is running. If the improper signals are sensed, an alarm output is made and an accompanying message is displayed.

    An analog input must be configured before it is used. If the user attempts to select an analog input that has not been configured, a warning is displayed and the user is prompted to initiate the setup. If the user elects to begin setup, they are taken to the screen shown in Figure 3. Figures 3 and 4 are part of the analog input setup. Figure 3 defines what the input is. In this case position is selected, which defines the next screen, Figure 4.

    Figure 4 initiates calibration of the particular input. With screw position, subsequent screens direct the user to go to zero (screw bottom) and then retract the screw to calibrate position. Upon completion, the computer calculates, displays, and stores the calibration information.

    The calibration of pressure sensors is done in a similar fashion. During setup, the controller requests that the user input the low limit (zero pressure) and the high limit. For a strain gauge pressure sensor, the high limit may be simulated by shunt calibration of the transducer.

    One last feature is the ability to name and store a perfected setup for later use. When recalling a previous setup, it may be necessary to recalibrate analog input(s). This is especially true of a portable screw position sensor.


    Additional Signal Interface Required
    All of this new functionality and protection requires additional interface signals to the injection molding machine and mold. Table 1 (above) outlines the additional logic required. However, if the valve gate sequencer is part of the injection molding machine control, much of the logic is built into the system.

    Sensing valve gate position and the presence of water cooling requires additional connections to the mold.

    When the sequencer is not part of the injection molding machine, full implementation of the aforementioned features and protection require the interface presented in Table 1. Implementation requires additional programming and signal inputs in the injection molding machine.

    Assuming some may not want to go through the additional time and expense, a means must be provided to shut off undesired features to prevent false alarms. Some of those options are shown in the sidebar, Figure 2.

    Older relay-based molding machines can be easily modified to implement the additional signal interface. Newer PLC or industrial computer-based machines require additional inputs and outputs.

    However, additional protection may be gained even without an additional injection molding machine interface. For example, the valve gate sequencer can provide an audio and/or visual alarm should no valve gate be open when the injection signal is received.

    It should be noted that the added protection also applies to operators and setup personnel. Inhibiting injection and valve gates from opening when safety guards are open can help prevent serious injury. Furthermore, preventing injection when none of the valve gates is open prevents leakage inside the hot runner system and thereby potential leakage outside the hot runner system.

    Contact Information

    D-M-E Co., Madison Heights, MI
    Thomas P. Linehan
    (248) 398-6000; www.dme.net

    This article was adapted with permission from an article submitted by the author at the 2002 SPE ANTEC.

    Words of Wisdom: Automation vs. emigration

    Glenn Beall is president of Glenn Beall Plastics Ltd. After years of experience in product and mold design, moldmaking, and molding, he turned to his current role of consulting and teaching.
    In 1973 the Organization of Petroleum Exporting Countries (OPEC) imposed its first oil embargo. That was a wake-up call for the plastics industry. The cost of oil went up and the price of plastic materials increased accordingly. Plastics processors passed these increases on to their original equipment manufacturing (OEM) customers in the usual manner. Much to everyone's surprise, some OEMs rebelled against these understandable increases. The entire plastics industry came under pressure to improve its productivity in order to offset higher material costs. Impressive productivity improvements were made, starting a trend that continues today.

    In the 1980s there was a significant increase in the volume of imported products. American consumers were quick to accept these high-quality, low-cost products. This was a wake-up call for OEMs. Once again OEMs pressured the plastics industry to improve quality and reduce cost. Once again plastics processors responded with impressive improvements.

    By the early 1990s many of the emerging nations of the world had learned how to produce commercially acceptable plastic products. All of these countries wanted to sell their products in the world's largest and richest consumer market, which was the U.S.

    The low labor rates in these countries reduced costs to levels that were difficult, or impossible, for domestic manufacturers to match. The OEMs' answer to this dilemma was to move production to these low-labor-rate countries to reduce their costs. Many OEMs were hesitant to have their products manufactured so far away from their markets. The lure of increased profits was, however, too strong to be denied. The labor-intense toolmaking industry was first. Processing was next, followed by assembly, and now the whole product is being produced offshore.

    A Buyer's Market
    Sometime in the mid-1980s the plastics processing industry became so efficient that it could produce more than it could sell. This led to the change from a seller's to a buyer's market. This, in turn, led to mandatory annual cost reductions, give-backs, reverse auctions, and demands for additional free services.

    The current trend appears to be to minimize the OEMs' costs by reducing processors' profit margins. This is a recipe for failure. The automobile industry pioneered the reduced supplier base, open-book costing, and mandatory cost reductions. In 1999 domestic automakers produced approximately 17 million cars while 13 of their top suppliers filed for bankruptcy. These reduced profits may also be one of the reasons why so many processing and moldmaking companies have not survived the current recession.

    OEMs preach quality, but worship the lowest cost, which is a politically correct way of saying increased profits. As a result, the plastics industry is under continuing pressure to reduce costs. Quality, cost, and delivery have steadily improved, but not enough to placate OEMs. The plastics industry is justifiably proud of the improvements that have been made, and processors find it difficult to accept the fact that their OEM customers judge these improvements to be inadequate. These diverging opinions stem from very different images of the processing industry.

    OEMs cherish the trade show image of an automated injection molding machine that drops 48 molded parts onto a conveyer every 10 seconds. Across the aisle there is an unattended extruder quietly producing a continuous, brightly colored profile that is cut to length and dropped into a box ready for shipping. Another image is of an inline thermoforming machine producing 83,000 yogurt cups per hour. The cups are automatically trimmed, stacked, and packaged, and the trimmed sheet is reground and pneumatically conveyed back into the hopper of the sheet extruder. These impressions of a fully automated industry are fortified by the plastics magazines that have a propensity for publishing glowing accounts of unattended, lights-out processing plants.

    Most plastics processing techniques can be mechanized, but full automation is the exception, not the rule. The truth is that the U.S. plastics industry is more labor-intensive than manufacturing overall. The Contributions of Plastics to the U.S. Economy report issued by SPI in 1997 indicated that the plastics industry's productivity, based on the value of product shipped divided by the number of employees, was 28 percent lower than the average for all other types of manufacturing. The SPI 2000 report revealed that plastics productivity had declined to 33 percent less than manufacturing overall. Plastics are losing the productivity improvement race with other manufacturing industries. This does not paint a rosy picture for the future.

    Missed Opportunities
    This situation is hard to understand considering recent improvement in the industry. Plastic materials are of higher quality and more uniform in processing than at any time in the past. Toolmakers are now capable of quickly producing very sophisticated, automatic, high-cavitation molds. Processing machines are more energy efficient and dependable, with less cycle-to-cycle variation than ever before. This magazine is full of all kinds of auxiliary equipment that can help a processor reduce labor.

    Today, most custom processors probably believe that they are operating efficiently and that any further reductions in profit will put them out of business. A tour of their plants often tells a different story. A shocking number of plastic parts are being produced on slow, obsolete, energy-guzzling machines. The new energy-efficient all-electric machines have not been widely accepted outside of the medical and electronic industries.

    Automatic material storage, conveying, and hopper loading equipment have been available for more than 30 years. Yet plastic material is still put into the machine and finished parts removed manually in all too many cases.

    Many molding plants have press operators whose only function is to trim gates and pack parts. Robots that perform these functions have been in widespread use for 15 years. One report indicated that robots have had a market penetration of only 30 percent in the injection molding industry.

    Even in these enlightened times there are still molding plants that do not have a single runnerless mold, stack mold, or a mold with hot-half positive ejection. One of the problems in this regard is that too many custom molders don't have the courage to coerce their OEM customers into purchasing a faster but more costly automatic mold with efficient cooling. Very few molders are taking advantage of the benefits offered by scientific molding.

    Many injection molders believe that their customer's demand for just-in-time delivery limits the length of production runs and requires so many mold changes that automation is impractical. Automatic mold changing equipment is used by less than 25 percent of the industry. Even fewer molders have adopted magnetic platens for mounting molds.

    The plastics industry is now operating in a global economy. OEMs can purchase their plastic products from any processor in the world that has the lowest cost, highest quality, and shortest delivery. In spite of its image, plastics manufacturing is still too labor intensive. The high wages paid in the U.S. produced a high standard of living that is the envy of the rest of the world. The combination of high labor input and high wages is making it increasingly difficult for U.S. processors to compete in the global economy. Americans are not willing to even contemplate reducing their standard of living. If a processor cannot reduce wages the only alternative is to reduce labor.

    Since the plastics industry is, on the average, more labor intensive than other manufacturing industries, there's room for improvement. The nature of the plastics industry is such that it should at least be as labor efficient as manufacturing overall. Just think what a 30 percent reduction in labor costs would do for your bottom line.

    No one wants to reduce the number of good-paying American jobs, but the name of the game today is to automate before your customers emigrate.

    Contact Information

    Glenn Beall Plastics Ltd.
    Libertyville, IL
    Glenn Beall
    (847) 549-9935
    Fax (847) 549-9935


    Learning to love lists

    Making a list of equipment suppliers should be a simple and straightforward proposition, no? We wish it were so. Every magazine and association in the business publishes some form of list or directory, each with its particular strengths. We make no attempt to duplicate any of them, but rather to present lists in simple, compact formats that identify a few categories of machinery on each list and provide multiple forms of contact information. Our Buyer's Guide topics for all of 2003 are listed on our editorial calendar. In addition, we occasionally do less formal lists to accompany feature articles.

    So what are some glitches in listmaking? In the first place, we compile lists for a North American audience. This is not an exhibit of American jingoism, just a reflection of our current circulation. Many of the suppliers on our lists are European or Asian, but they have established a North American presence, whether by setting up an office, mounting a show exhibit, creating editorial or advertising presence (in any industry publication, not just ours), or recently installing equipment. Any plausible demonstration of an ongoing presence in North America is enough for us.

    We don't mean to be making excuses, but there are good reasons why perfection in lists is elusive. The following examples are real, but the identities of the companies involved are not revealed, to protect the innocent, or the guilty as it may be.

    In a case involving a supplier of robotic equipment, we initially did not include the company, as we were unaware that it had established a U.S. office. To remedy matters, we published the listing in a subsequent issue. By the time that issue came out, the U.S. office had been closed. If it was still actively marketing into North America, we could continue to include them in our list, but in any case all of the original contact information was obsolete.

    In a second case, this one involving injection molding machines, we included a listing of a well-known company, but did not include it as producing a particular category of machine. It later came to light that the company did in fact produce machines in that category. However, it did so only under specific demand from customers. The company did not want to be in the business of producing that kind of machine, and did not want to be so listed!

    In a third case, a company name change threw us for a loop. The original name(s) were well known, but the new name was less familiar.

    Our lists are not dead once published. We repeat Buyer's Guide topics, generally on an annual basis. We also update our lists on our website. Additions, corrections, modifications, or deletions can be made there. Our Buyer's Guide list for this issue is posted here. It identifies suppliers of dryers, hoppers, and loaders. An additional list of suppliers of hydraulic-powered injection machines is posted here.

    We welcome your participation in our listmaking. If you have any information that would make our lists more accurate or complete, I would welcome hearing from you. Thank you in advance for your help.




    Merle R. Snyder
    Editor
    Plastics Auxiliaries & Machinery

    Designing Screws for Profitable Injection Molding

    Screw design is just one of the hundreds of details required for successful injection molding, but like many processing details in the industry, it only receives a small percentage of the attention it deserves. Unfortunately, this disrespect can cost molders anywhere from 10 to 30 percent in lost profits, and can also lower overall part quality. Given 15 minutes and data that shops already possess, it's not hard to prove there is money to be made with correct screw design.
    The image at left shows a portion of the plastic in one flight from a metering zone of a screw. It contains black specks, or a carbon shower.

    After 72 hours of run time, the polyethelene below was peeled off the screw flights and shows evidence of carbon buildup on the back side of the flights.
    Let's put screw design in perspective. While it can alleviate many processing problems, alone it will not solve all of them. In order to have an overall successful plastics application you must practice correct part design, plastic selection and handling, tool design and construction, and processing.

    Screw design falls under the processing category. Specifically, it relates to melt temperature or uniformity. If you do not have uniformly melted plastic at the correct temperature coming out of your molding machine's nozzle, your chances of getting a part with dimensional stability are small to nonexistent. So let's discuss how a screw melts plastic.

    The Anatomy of a Screw

    It is important to identify the components of a screw?the feed, transition, and metering sections (see Figure 1, below)?and understand what happens in each. Normally, the feed section, which features constant, deep flights, is 50 percent of the flight length. The tapered flight depths of the transition section and the constant shallow flight depths of the metering sections each account for 25 percent. For example, a 20:1 length-to-diameter (L/D) ratio screw has 10 flights of feed, five flights of transition, and five flights of metering. It's recommended that the minimum L/D used in injection molding be 20:1. Shorter L/D ratios, like 16:1, tend to have melt uniformity problems even with proper screw designs.


    Plastic that is not uniformly melted or at the correct temperature yields faulty parts. The picture of a filter core above shows evidence of unmelted granules in the darker areas.
    As the granules travel through the hopper and feedthroat by gravity, they fill the deep flights of the feed section. The feedthroat should be warm?90 to 140F?to provide screw recovery time consistency (a consistent plasticating rate) and to prevent condensation of volatiles like residual moisture and off-gases from the resin. Moisture and off-gases can be a cause of splay. Often times, the feedthroat is run at too cool a temperature, but it's also important that the feedthroat isn't so hot that the granules stick together and block any gravity feeding. For best results, the feedthroat requires electronic temperature control. The use of cool tower water for temperature control is not acceptable for optimizing screw performance.

    Technically, the purpose of the screw's feed section is to auger the granules forward to the transition zone, compacting and pressing out as much air as possible. There should be no melting within the first five flights. Sometimes the feed section does a bit more, with some heating occurring and some fines melting. As the granules are augered forward, the heater bands start the melting process by forcing the granules to stick to the barrel. Once this occurs, the real driving mechanism for melting takes over. It is the transition section that compresses the granules and forces them up against the barrel wall. As the screw rotates it shaves the melted plastic off the barrel wall and rolls it into the flight, forming what is called the melt pool. As it moves forward toward the nonreturn valve and screw tip, the melt pool gets larger while the solids bed gets smaller (see Figure 2, below). The diagram displays why it is important that the screw be smooth and polished with no nicks to allow the plastic to slide on it.

    Eventually, the flight mostly contains melted plastic, or a melt pool as mentioned above, and a bit of unmelted or taffy-like resin that is the solids bed. About 50 to 90 percent of the energy needed to melt the plastic comes from this shearing action as the pellets change from solid to melt. This mechanical shear should not be confused with the shear rate developed when molten plastic in front of the screw is injected into the mold.

    Consider the situation for a minute. Is the flight completely full? What is there to push this last bit of solids up against the barrel/wall and flight/land interfaces so all the plastic gets treated equally and uniformly? Some practical experience may shed some light on the answers.

    A Closer Look at the Screw

    What do you see when the screw is removed from the barrel? Note especially the rear of the flights at the end of the transition zone and beginning of the metering zone. About 95 percent of the time, you find a carbon layer at that location (see top item in top-left photo, above). Further, many processors report finding granules of a color they ran weeks before the most recent color processed.

    These granules of carbon and previously run colors prove that the new melt coming down the screw does not push the rest of the melt out of the flight. This is why it takes so long to purge materials and change colors. We have unequivocal proof that this space behind the flights is simply dead space.

    This is the same issue found in poorly designed nozzle tips and hot runner systems. Since this is dead space, the suggestion is to fill in this area with metal that has a large radius. Ideally, it should look like a farmer's plow.

    The majority of the time the flights are not running full, and they have varying amounts of plastic in them depending on backpressure, viscosity, screw rpm, and other variables. Whenever you upset the status quo, such as running out of resin or changing backpressure or screw rpm, you can start a carbon shower. The carbon from the back side of some flights peels off and leaves black specks in the melt. Consider how many dollars are lost trying to purge black specks. Further, the solids bed can break up and get mixed into the melt pool, producing unmelted or partially melted plastic in the melt stream. These granules often move on to plug up the gate.

    Figure 1. The basic components of a screw are shown here. The feed section has constant deep flights and takes up 50 percent of the flight length. The transition section has a tapered flight depth and is 20 percent of the flight length, and the metering section has constant, shallow flight depths and is 25 percent of the flight length.
    Figure 2. Shown here is the transition of plastic granules from an unmelted solids bed to a melt pool. As the plastic moves toward the screw tip, the melt pool gets bigger and the solids bed gets smaller.
    Figure 3. This diagram illustrates good melt-uniformity screw design. The metering/transition section of the screw should be designed to tumble the melt gently and end in a slow taper. It should provide distributive mixing, but not dispersive or high-shear mixing. This is not an example of a mixing screw, or a high-intensity mixer.
    Achieving Melt Uniformity

    Not all single-flighted, general purpose screws produce uniformly melted plastic. Let's define in general terms what is needed to melt plastic granules uniformly. Pooling data from work done by material suppliers, screw makers, and industry experts helps us identify the characteristics of a screw that produces consistent, uniform melt.

    Let's define the "melt-uniformity" screw (see Figure 3, above). It isn't necessary to have a specially designed screw for each resin you process; that isn't practical for most molders. Having a single screw that provides uniform melt for several resins is possible, and you don't have to pay for uniform melt with slow plasticating rates.

  • The melt uniformity screw should have a significant radius on the rear of the flights at the end of the transition section and the beginning of the metering section.
  • It should have a mechanism that prevents unmelted or partially melted granules from getting through the system and into the molded part.
  • It should handle most resins, engineering and commodity, except those that are easily degraded.
  • Along with an extended wear life, it should not make the plastic too hot, and it should provide distributive mixing, but not dispersive or high-shear mixing. The high radius and greater melt homogeneity will help save money in the long run.
  • The screw material should be chemically inert, highly polished, and have sharp flight land edges. Its hardness should range between 50 and 65 Rockwell C. The screw's surface may be treated to aid wear slip and chemical resistance. The metal should be softer than the barrel metal by 3 to 5 Rockwell C points to prevent galling, since screws are often easier and cheaper to replace than barrels.
  • Resin should be run near the midrange temperature recommended by the resin supplier, and at backpressures in the 1000- to 1500-psi plastic pressure range. Backpressure is important to provide shot size volume consistency and fill the flights. Easily degraded resins should be run with less backpressure. Screw rpms should be set so that the screw is in the full shot position approximately 2 seconds before the clamp opens.

    Case histories have shown that screws like this provide a return on investment in two to three months. The savings come from faster changeovers, less wasted plastic, stronger/less-visible weldlines, more consistent shrinkage, and stronger overall parts.

    To learn more, talk to your screw supplier. The overall cost shouldn't be much greater than a standard screw if you're comparing similar materials of construction. The nonreturn valve should be the freeflow type with stepped angles and no sharp corners. The end cap nozzle body and tip should also have a smooth flow path, with no more than a .001-inch positive transition. Standard tips are not acceptable since they also have dead space.

    Contact Information

    Injection Molding Solutions, Midland, MI
    John Bozzelli
    (989) 832-2424; www.scientificmolding.com

  • Are full hydraulic injection molding machines yesterday's news?

    The question of hydraulic presses' continuing relevance is raised once again. If they are old news, why? If not, why not? In this two-part discussion we first focus on the injection molders and machine manufacturers who stand by their hydraulics, and hear their arguments in favor of the technology. In the November/December issue we'll hear from the molders and manufacturers who disagree.
    Engel showed there's a lot of life left in full hydraulic technologies with its 990-ton Duo twin-platen multimolding system. Try fitting a 990-ton all-electric toggle with a rotating platen in this compact footprint.
    Hydraulics vs. all-electrics? Oh no, not again! That was the first reaction from some of the injection molders and molding machine manufacturers when asked the questions posed above. Some said that they were sick and tired of seeing the hydraulic vs. all-electric story in the trade press, and that the issue has been beaten to death. Others were equally fatigued from tossing the questions around in their own heads.

    Nevertheless, once they calmed down we got some very fresh and thought-provoking comments from the field. Before presenting what they had to say, some definitions are in order. Our questions concerned full hydraulic presses?those with a hydraulically powered shooter and a straight hydraulic clamp, not hydraulically powered toggle-clamp machines or hybrids.

    After reviewing the responses, we stretched things a bit to include the hydromechanicals, which may use a little juice to power a mechanical clamp-locking mechanism, and hydraulically powered twin-platen machines.

     WHO'S WHO IN FULL HYDRAULICS 

    AmeriPlas Machinery Corp.

    www.ameriplas.com
    Arburg Machinerywww.arburg.com
    Autojectors Inc.http://plastics.milacron.com/
    autojectors/autojectors.htm
    Battenfeld of America Inc.www.battenfeld.com
    Boy Machines Inc.www.boymachines.com
    Carver Inc.www.carverpress.com
    Chen Hsongwww.chenhsong-machinery.com.hk
    Demag Ergotech USAwww.demag-ergotech-usa.com
    Dimawww.askdima.net
    Engelwww.engelmachinery.com
    Ferromatik Milacron NAhttp://plastics.milacron.com/
    injectionMM.htm
    Fortune Internationalwww.fortune-cnc.com
    Gluco Inc.www.gluco.com
    HPM Div.www.hpmcorp.com
    Hettinga Equipment Inc.www.hettingatechnology.com
    Hull/Finmac Inc.www.hullcorp.com
    Husky Injection Molding Systemswww.husky.ca
    Illinois Precision Corp.www.illprec.com
    Italtech SpAwww.italtech.it
    Jaco Mfg. Co.www.jacomfg.com
    Jon Wai Machinery Workswww.plasticscommerce.com/jonwai
    Krauss-Maffei Corp.www.krauss-maffei.de
    LG International America Inc.www.lginjection.com
    Lien Fa Injection Machinerywww.lienfa.com
    MCP Equipmentwww.mcp-group.com/imm
    Meiki Americawww.meiki.com
    Mitsubishi-MHI Injection Molding Machinery Inc.www.mhiinj.com
    Mini-Jector Machinery Corp.www.mini-jector.com
    Mir USA Corp.www.mirpresse.it
    Multiplas Enginery Co. Ltd.www.multiplas.com.tw
    Nissei America Inc.www.nisseiamerica.com
    Nissin Machine Co. Ltd.www.nissin-mfg.co.jp
    Oima SpAwww.oima.com
    Presmawww.presma.com
    Sandretto USA Inc.www.sandrettousa.com
    Sumitomo Plastics Machinerywww.sumitomopm.com
    TMC Jiangmen Magnetics& Machinerywww.tmcint.com
    Tomken Tool & Engineering Inc.www.tomkentool.com
    Toshiba Machinewww.toshiba-machine.com
    Van Dorn Demag Corp.www.vandorndemag.com
    Wabash MPIwww.wabashmpi.com
    Wilmington Machinerywww.wilmingtonmachinery.com
    Table 1 (left) lists all the machinery OEMs actively selling their full hydraulic iron in North America that we could find. If we overlooked anyone, we'll probably be hearing from them soon, and we'll pass the info along. Meanwhile, are full hydraulics yesterday's news? Some say yes, indeed. You'll hear from them in the next issue of PA&M. But first we'll hear from those who just say no.

    Familiarity
    Like many other injection molders responding to our questions, Curt Watkins, president of Alltrista Unimark (Rye, NY), says full hydraulics are here to stay, at least for now. "From a president's perspective, I would, in response, ask you a question: Is the internal combustion engine yesterday's news?"

    Watkins offered three reasons why he thinks there's still a tomorrow for hydraulic presses:

  • Sheer volume of usage and cost to replace them.
  • Applications like packaging, thin-wall parts, and parts requiring large-tonnage machines that at present just can't be economically filled with the current level of the newer technologies.
  • Certain ultrahigh-level requirements that still need full hydraulic presses. These, he says, include injection rates of more than 1000 mm/sec, pressure requirements exceeding 40,000 psi, and locking/holding requirements that are longer than 20 to 30 seconds, due to heat buildup in the motors.

    "I feel that current hydraulic technology will continue to be driven to higher levels of performance and economy by the growth of the electric technology, in the same manner that internal combustion engines are being driven to new levels by the hybrid and total electric technology offerings," Watkins says.

    Still, he shifts gears a bit in his conclusions. "However, I would like to clarify that I do firmly believe that the electric technologies are the wave of the future, just as the PC eventually outpaced the mainframe. That's outpaced, by the way, not replaced."

    Trevor Spika of micromolder Makuta Technics (Columbus, IN) also believes that although it may be too soon to sound the death knell for full hydraulics, it could be sounding soon. "Our hydraulic machines are not quite as precise as our electric, but they are still a more robust machine in the same tonnage range," he says.

    "We have not seen the electric systems perform as strongly as the hydraulics yet. However, this will most likely change in the near future."

    Dale Smith of Technical Industries Inc. (Canton, CT) is another full hydraulics micromolder who's giving all-electrics a go. Smith agrees that hydraulic presses are still a viable alternative, especially when it comes to reliability. "We have excellent-performing hydraulic machines with over 25 million cycles. For us, this makes our all-electric an unproven machine.

    "The mold protection capabilities of a hydraulic machine also is a known factor for us." Smith says there are still unknowns surrounding the electrics and adds, "We are familiar with the setup of a hydraulic, which makes us less prone to making mistakes."

    TII's strategy is to buy all-electrics where they make economic or processing sense, says Smith, but the company has no intention of going 100 percent electric at this time.

    Turning back to bigger machines and bigger parts, Russ LaBelle of Wilmington Machinery (Wilmington, NC) has something to add about the maintenance advantages of full hydraulic presses. "The ability to take a single motor with a set of hydraulic pumps and rotate the feedscrew, actuate the injection ram, open/close nozzles, open/close a press, provide core pull actuation, and open/close a safety gate is tough to beat by either all-electric or hybrid approaches."

    LaBelle says that when you add features such as cavity pressure feedback and mold protection, the capabilities of fluid power go on and on, but he adds a note of caution. "This could change, of course. When and if all-electric control and actuating devices come along that match the simplicity, cost, and performance of hydraulic devices such as cylinders and valves, designers will be quick to apply them. These devices are lacking today."

    Maintenance of all-electric machines may in the long run be simpler, LaBelle says. "However, today's maintenance person is more mechanic than electrician or electronics guru, for that matter. There will be the need for a different type of person, probably of greater skills."

    Van Dorn Demag sources say that presses 300 tons and less will probably all be all-electric in the next five to seven years. More than 300 tons, full hydraulics, like this Spectra 880, will remain as more affordable alternatives.
    Technology
    Joel Thompson of Twinshot Technologies & Community Products (Rifton, NY) thinks there is still plenty of news in full hydraulics. "It's just a fact that plastic melt is a high-pressure liquid, and therefore the molding process itself will always be hydraulic.

    "Take clamping for instance," Thompson says. "What better way to oppose the force of a large liquid-filled cavity in the mold than another matching liquid-filled cavity, as in a hydraulic cylinder? Especially in large machines, the benefits of hydraulic clamping over toggle clamps have been well proven. Suddenly toggles are back in style, only because you can't do anything else with an all-electric?not because it's better."

    Thompson says electric drives are superior at controlling position and its associated derivatives, velocity and acceleration. But he believes electrics are inferior to hydraulics at controlling pressure.

    "Since the molding process is based just as much on pressure as on position, there's something to be said for both," says Thompson. "In the end, even a hydraulic machine is electric. But the conversion from electrical, through mechanical, to fluid power happens earlier in the process."

    Sources at LG International, manufacturers of a line of full hydraulics, say all-electrics have technical limitations that restrict their use to only specific injection molding applications.
    Charles C.D. Won of machinery maker LG International (Goldstar; Schaumburg, IL) says full hydraulics will retain their place in the market for technical reasons. "Technically, hydraulics cannot be replaced by electrics, since all-electrics cannot meet all of the existing production requirements. The electric machine has limitations, which include the capacity of its servomotor, speed, and injection pressure capabilities."

    There is no one machine on the market that can compensate for the human element, says Don Hardin of Fabrïk Molded Plastics (McHenry, IL). He adds that state-of-the-art repeatable machines are crucial to the overall process, but you can't overlook the need for good plantwide process and quality control.

    "I think it has been proven that the linear repeatability of the electric machine is superior to that of the hydraulic machine," Hardin says, "but there are other molding-related factors involved that affect the quality of the finished part, such as inconsistent nonreturn valves, inherent lot-to-lot viscosity variation of plastic resins, and the natural unbalanced flow that takes place in multicavity molds."

    Fabrïk has found the use of cavity pressure control yields very good results. Hardin says the cavity-pressure transfer method compensates for the varying viscosity and inconsistent nonreturn valves.

    Ferromatik Milacron, like many other OEMs, offers a diverse selection of machines with several different types of drive systems for its customers, including its European-built K-Tec line of high-performance hydraulics.
    More on Technology
    Though it also produces hybrids, John Ward of Van Dorn Demag Corp. (Strongsville, OH) says Demag Ergotech GmbH fully intends to produce presses capable of meeting both the simplest and the most demanding applications of custom molders, as well as specialized segments of the injection molding industry, and that includes full hydraulics.

    "We will continue to design and build machines that lead the industry, but not for the sake of technology. At this time if you do not want to compromise performance, you have to compromise on the combination of drives available," Ward notes.

    He says full hydraulics can only become obsolete when all-electric technology advances to become the most cost-effective solution for meeting all the processing demands of the market. "We will continue to bring new products to market, but not as a 'me-too' approach."

    Mark Zulas of Niigata Plastics Machinery (Itasca, IL) agrees. "As I am sure you are aware, the latest and greatest new toy gets all the press. As for hydraulic molding machines being obsolete, my personal opinion is no. There are still parts that require a hydraulic machine's ability to maintain an extensive amount of injection pack and hold pressure for a period of time that cannot be achieved by an all-electric molding machine."

    Zulas says that most of these molds could be modified to run on an electric machine with faster cycle times, but convincing a supplier to pay for a mold modification is, to put it mildly, "frequently impossible."

    "Also, molds with large hot runner systems require a large amount of nozzle touch pressure to the mold," he says. "Many electric molding machines have a smaller amount of nozzle touch force when compared to the hydraulic equivalent. Our company had to address this issue many years ago, but much of our competition is still trying to figure it out."

    Nissei sources say full hydraulics will survive well into the future, especially in applications requiring ultrahigh-speed filling. Its UH 2000, possibly the fastest production machine in the world, has a 2000-mm/sec injection rate.
    Price

    Mention of the "cost-effective solution" raises a major point of the full hydraulics partisans, namely the high price of all-electrics. Mark Sporysz, of molder Caplugs (Buffalo, NY), says full hydraulic machines will be around for a very long time. "Electric machines have their place. It's clean molding, with no oil or tower water," he says. "But hydraulic machines are durable and repeatable with a proven track record. And mechanics are trained to service hydraulic machines."

    The best way to compare machines is over a time span of about eight years, according to Sporysz. "Compare the machine purchase price to the maintenance and downtime cost, along with energy consumption. This answer may vary from machine manufacturer and molding application."

    Price is one of the major reasons why Neal Elli of Empire Precision Plastics (Rochester, NY) says hydraulic machines are still a viable alternative today. "They are tens of thousands of dollars less than electrics, and they are sufficiently fast and flexible enough for many applications," Elli explains.

    He says good hydraulic machines also can be reasonably energy efficient, especially considering the cost of power in most locations such as the Midwest and South. He also believes that the fastest machines will still need to run hydraulically.

    "The cost of the electric machine would need to drop almost 25 percent to make a big negative impact on the sales vs. hydraulic," says Elli. "If and when this occurs, then the hydraulic machine will really start to decline."

    Kurt Kendall of Motor City Plastics (Dundee, MI), which specializes in the high-speed/thin-walling of cosmetics packaging parts, says that hydraulic presses will survive as long as they are less costly to buy and are well-suited to applications that are not very demanding. He says the fast cycling and precision that high-speed electrics provide "will not make a hill-of-beans difference in a less demanding application."

    "However," Kendall adds, "if the market brings pricing down on all-electrics, then this could be the beginning of the end of the hydraulic squeeze-and-squirts in the 1000-tons-and-down range." He thinks OEMs should be able to build electrics for less when using mass-assembly economies of scale.

    Sumitomo plans to convert its smaller-tonnage series of hydraulic machines, like this 50-tonner, to all-electrics, and has begun building them in Georgia. But it's keeping its larger-size hydraulics, from 100 to 350 tons, at least for the time being.
    More on Price

    Robert Koch, president of Boy Machines (Exton, PA), takes up the cost issue with concern. He says that one of the major selling points of all-electrics is their energy efficiency and admits that they can generate power savings. However, he says, there's a big but. "When you measure the energy usage of some all-electrics and a fully hydraulic Boy, then compare prices of the two machines, energy doesn't accrue through to the bottom line. The ROI you can expect is 32 years with one all-electric . . . 23 years in another case, in our machine size range, which is under 100 tons."

    Koch says that rather than ask how much a machine costs, the real question should be how much does it cost to make a part? "Ultimately, when you're talking about paying $40,000 for a machine vs., say, $80,000 for a comparably-sized all-electric, how can you possibly select the all-electric machine on the basis of cost per part?"

    Since he came on board in April, he's visited several customers of Boy Machines and has asked them how they cost-justify purchasing an all-electric machine that's often double the cost of a full hydraulic. "What can you afford to pay to get the same quality part?" Koch says he has asked them. "When the fully hydraulic machine makes a consistently good part, isn't that all it's about?"

    Koch also is concerned about states that award tax subsidies to molders who purchase all-electrics, just because they are perceived as being more energy efficient. "That's unfair," he says. "These rebates shouldn't be based just on the price of a machine. That drives people to buy all-electrics in a vacuum.

    "What are the comparative savings?" he continues. "What are they comparing it against? These rebates should be based on a fair comparison of the two different technologies when it comes to the energy required to run a part. They should run a part on a MY2002 all-electric, then run the same part on a MY2002 fully hydraulic to calculate rebates."



  • Water temperature controls available in three sizes


    A new line of circulating water temperature controllers reportedly offer simplicity in setup, reliability in use, and competitiveness in price. Available in three sizes, the line also promises ease of operation and maintenance. The smallest are the subcompact models, measuring 13 by 26 by 26 inches. These come with .5-, .75-, or 1-hp motors and use direct-inject cooling for a rapid response. The next size unit?standard heavy duty?provides direct-inject or indirect cooling with separate cooling and process circuits that permit the use of ethylene glycol and prevent waterline damage. These range in size from .33 to 3 hp, and stand 26 inches high with a 16-by-27-inch footprint. A line of vertical units measuring 17 inches wide and 21 inches deep is available to further save floor space. This unit's height places the control panel at an accessible height of 49.5 inches. These also come in direct and indirect versions with up to a 3-hp motor.

    The entire line uses autotuning microprocessor controls to maintain temperatures and offers easy setup and troubleshooting. Other features include a seal-flush system for long-lasting seals and a 9-kW heater, which maintains immersion and is insulated for efficiency. Use of a horizontal pump mounting minimizes cavitation and maximizes flow. For safety, the units come with an internal bypass waterline, a heater/pump interlock, as well as a high-pressure relief valve and a low-pressure cutout. Complete schematics with labeled and numbered wiring and access panels reportedly simplify maintenance.

    Molders Choice Inc.
    Solon, OH
    (440) 349-6174
    www.molderschoice.com