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Articles from 1997 In November


Ceramic feedstocks simplify design, molding problems

Thanks to a chemical gel, one of the barriers to widespread ceramic injection molding recently became a thing of the past. While the basic molding technology has been in place for more than 30 years, feedstock materials haven't exactly been easy to use. For one, removing the polymer or wax binders can be time consuming. For another, this debinding step produces a brittle as-molded part.


Parts molded from ceramics with Allied Signal's new binder system span a broad range of markets, from fine porcelain cups to zirconia oxygen sensors.

Instead, imagine molding ceramic parts that gingerly drop into a bin as they are ejected from the mold, stiff but elastic enough to hold their own before firing. Then envision reducing costs by as much as 40 percent over traditional ceramic processing. When Allied-Signal Engineered Materials created a new binder, made from water and agar (a seaweed-derived polysaccharide not unlike Jell-O), these visions became reality.

How real? At the company's Autolite plant (Fostoria, OH), a 22-ton production molding machine pumps out 1 million parts annually using the water-based feedstock. During a visit, IMM spoke with Cliff Ballard, director of powder injection molding ventures for AlliedSignal, about the potential for this technology.

"Compared to the traditional shape forming ceramic processes, molding offers to reduce the number of steps required and, thus, take out cost," says Ballard. "But polymer and wax binders have held back growth. Parts have 40 to 50 percent binder content by volume. Removing it generates toxic effluent and may take days. The end result is a brittle part that must be carefully handled. In addition, part thicknesses are limited to less than .25 inch."

By comparison, Allied-Signal's water-based system requires no separate debinding step - the water simply evaporates after molding, leaving intergranular pores open. Of course, concerns over toxicity are also eliminated. As for the agar binder, it adds only 2 to 3 percent by weight to the feedstock. According to Ballard, there are no part thickness limitations, although thickness does determine drying time. And like polymer/ wax systems, tolerances can be controlled to ±.3 percent.

What really sets this new feedstock apart, from a designer's point of view, is the greater freedom it allows. "We're producing parts that were formerly impossible to mold," says Richard Schultze, manager of ceramic applications. At the plant, workers are able to mold spark plugs with a 7-mm wall thickness, vs. 12 to 14 mm for standard processing. Parts with combined thick and thin cross sections, undercuts, and complex geometries all benefit from the moldability of the feedstock. As an example, he cites a turbine blade produced via traditional methods at a cost of $1300. "Our customers are now molding prototypes of that part, and the price could drop to between $50 and $150."

Savings are a big driver for ceramic molding. Last year, a vendor told Autolite it could no longer supply an intricate component, formed traditionally in two half shells, because the cost was prohibitive. Jason Hogan and David Lyons, part of the CIM team at Autolite, had a prototype mold running parts within eight days after the announcement. This year, Lyons estimates the company has saved more than $250,000 on these parts. "In fact, because of the freedom this process allows, we were able to add features that the vendor could not produce ," says Lyons.

Differential shrinkage rates for the new molding compound are greater than those for most thermoplastics, ranging from 16 to 20 percent (depending on the material). However, notes Ballard, these are the same rates found in traditional ceramic forming. This has a lot to do with the composition of the new ceramic molding compound - by volume, 53 percent ceramic powder (alumina, zirconia, or silicon nitride), 47 percent polymer dissolved in water. It is this latter component that makes the mixture act like a thermoplastic.

Processing is another area where the Allied system saves money. Cycle times are similar to those for thermoplastic parts. But because injection pressures don't exceed a 500-psi maximum, and temperatures rarely go above 185F, prototype parts can be molded using aluminum- filled epoxy or even SLA masters. There is no mixing in the barrel; instead, material is moved along by a screw with no compression, then injected through the nozzle at a consistency similar to toothpaste. Parts bounce out of the mold, with strengths after drying about four times higher than those of conventional green ceramics. Molding machinery need not be modified for the process. At the production facility in Fostoria, technicians use three 22-ton Boy machines and a 27-ton Arburg.

Melt flow rates for the ceramic are difficult to measure using traditional thermoplastic equipment. However, spiral flow tests confirm that the material will fill complex geometries at low pressure. A turbine vane test part, 7 inches long with a feathered edge, had no problem filling. When it comes to wear, the compound acts like a 30 percent glass-filled nylon. Total wear for production molds, in stainless 440C, rarely exceeds .004 inch for 500,000 shots.

Material properties for the first commercial Allied compound--AS194 alumina--are equivalent to traditional 94 percent Al2O3 materials. With an initial raw-material cost of $5.50/lb, the gel-based material can be easily recycled in-plant, either by grinding parts and adding water, or by adding still-wet scrap directly to the hopper.

The gel technology developed for this first ceramic compound is also being applied to metal injection molding materials with similar benefits, Ballard adds. He shares a product development roadmap, which targets commercial release for additional ceramics as well as stainless steel products within the next 12 months. Stay tuned.

Opportunity knocks in unlikely places

Going global among U.S. manufacturers has become tantamount to a divine directive. Dutifully, if not enthusiastically, American companies have opened new plants overseas and begun to address a world market. Wouldn't the picture change if the concept of expanding your business to another country not only meant serving market demands better but improving your financial picture significantly? Emerging nations in the Caribbean are offering just such enticements, and one country in particular believes it is well suited for plastics processing.

At 166 sq miles, Barbados, a small island in the West Indies, is roughly the size of JFK International Airport. And indeed, the Concorde lands here once a week bringing European travelers seeking sand and sun. Before you write it off as a tropical vacation paradise rather than a productive manufacturing environment, however, consider some eye-opening statistics. You'll find that its small size belies some very real business possibilities for molders.

First and foremost, Barbados has an ideal location for shipping to the U.S., South America, and Europe. And thanks to several trade agreements, Barbadian-made products can enter the U.S., Europe, Canada, Venezuela, and other Caribbean nations free of duty. Secondly, export-oriented manufacturing concerns are exempt from taxes on corporate profits for 10 years. After that time, they receive a special tax rate of 2.5 percent. Also, any raw materials, machinery, and other purchased components are also exempt from import duties.

Manufacturers receive assistance through the Barbados Investment Development Corp. (BIDC), an agency of the Barbados government. For example, the agency helps manufacturers by securing government subsidized factory space that can be rented for roughly $3/sq ft/year.

IMM spoke with BIDC's Peggy Griffith, director international business, and Donville Inniss, business development officer. Griffith explains, "BIDC also offers a range of free services, and administers several programs, including a Training Grant Scheme to help companies offset training costs during start-up and expansion phases." When it comes to training, Barbados has a potential workforce of 126,000 out of 257,000 residents with an overall literacy rate of 98 percent. A British schooling system, recognized by the U.N. as one of the best in the world, is free to all residents and includes a campus of the West Indies university system, numerous secondary schools, and a variety of primary schools.


One of only two molding operations on the island of Barbados, CPM Ltd. and its five employees provide the domestic market with a variety of products - disposable utensils and plates, combs, ice trays, soap dishes, and pharmacy vials - molded in HDPE, LDPE, PP, PS, and HIPS. Director Shiu Shun Yeung, who relocated here from Hong Kong, tells IMM that his biggest challenge is maintaining molds. "We have no toolmakers locally, so I must rely on periodic mold maintenance from Hip Wo Co., an overseas partner," he explains. Yeung's immediate plans include expanding to a larger facitly. And like the current 2400-sq-ft space, it will be subsidized by the Barbadian government.
Various initiatives across the West Indies and abroad are designed to boost trade. For example, the Caricom (Caribbean Community Common Market) agreement allows products made in Barbados to be exported free of customs duties to 12 other islands within the West Indies, including Jamaica and Trinidad. The Caribbean Basin Initiative allows Barbadian-made products duty-free entry into the U.S. For Canada, a similar agreement is known as Caribcan. Legislation known as the Lome Convention allows companies manufacturing in Barbados to ship to the European Union countries without paying duties.

Concerned about infrastructure? Barbados is self-sufficient in natural gas. Its crude oil production supplies 30 percent of the country's electrical needs, while the other 70 percent is imported. A pilot wind power plant financed by the government seeks to make use of another natural resource - powerful sea breezes. Roads are relatively narrow by U.S. standards, but adequately handle the smaller-sized vehicles prevalent on the island. Phone, fax, and shipping capabilities are equivalent to most industrialized countries. You can even choose from several overnight courier services, including FedEx and UPS.

Molding Opportunities

Timing is everything when making a business decision, and conditions in Barbados today are fertile ground for investment. Here is the condensed version of current available opportunities:
  • Many of the products made here require molded plastic components, which are currently purchased abroad by necessity. For instance, lack of domestic molders forces a large state dairy to purchase its HDPE yogurt and ice cream containers from a Canadian processor. Electronics manufacturers buy housings from the U.S., then assemble products here. If manufactured on the island, these same components would be much less expensive, according to Andrew Applewhaite, a former director of electronics firm Bel-tronics. He believes that not only would ocean freight costs be eliminated, but the 10-year tax abatement may allow a molding operation more leeway in its pricing.
  • According to a 1994 United Nations seminar, environmental sustainability for a small island means successfully recycling solid waste such as PET and HDPE containers. One company, Envirotech Inc. (St. Michael, Barbados), is in the preliminary stages of building such an operation. Andrew Simpson, director of the firm, currently has 1 million lb of PET bottles shredded, baled, and stored as a result of a government "bottle bill" inducing consumers to return the containers for a 10-cent return. But rather than selling the bales on the open market, where prices have fallen considerably, Simpson hopes to utilize new technology that would allow him to mix PET and HDPE flake without separating them. The end result: a roofing and tile product suited to the conditions in the sunny Caribbean.
  • As chief environmental engineer, Jeffrey Headley tells IMM that Barbados wants to attract industries that generate little or no waste. "Because of our limited land space, we stress technology rather than waste-producing industry," he says. "Plastics processing fits well into this scheme, because in-plant scrap can be reground and used again or sold."

    In a similar vein, any environmental endeavors are supported by government incentives: "There are several such initiatives now that illustrate the level of public and private sector cooperation."

  • The island contains its own bottling operations for Coca-Cola. To produce the PET bottles, this concern must buy the injection molded parisons for use in the stretch-blow process. A local supplier could consolidate both processes at considerable savings, according to potential investor Boney Mathew of Mathson Industries (Clarkston, MI).
  • Another potential - moldmaking shops. There are currently a few molding operations, but they must rely on outside toolmaking and maintenance because there are no moldmakers in the country.
  • While the Barbadian government is seeking to diversify its country's economy, the fact remains that tourism is one of the three largest industries, next to sugar and rum. As such, molded wares in demand include disposable service items, recreation goods, and souvenir items. Again, most of these products are purchased abroad at a relative premium.

Investor's Snapshot of Barbados

It's not a typical postcard, but the following facts definitely beat "wish you were here" for investors:
Electric rates 30 cents/kwh
Currency Bds$ 2 to US$ 1 (only Caribbean nation that has not devalued its currency)
Banking system 34 offshore banks with total assets of US$ 4.8 billion
Population 257,000
Labor force 126,000
Literacy rate 98 percent
Language English
Health care government-sponsored system, free to all residents
Education free public schooling through university level, rated by U.N. as one of the best in the world.

Dissecting sides on the PVC issue

Welcome to the great vinyl debate - not unlike a recent heavyweight title bout, minus the biting. In this corner, wearing green and weighing in with a genuine concern for Mother Earth, we have environmental watchdog groups such as Greenpeace who contend that polyvinyl chloride is a big contributor to dioxin production. In the opposite corner, wearing a different shade of green, are manufacturers and industry groups such as the Vinyl Institue, presenting evidence of PVC's recyclability and environmental friendliness. Ready to rumble?

Marketing campaigns don't always attempt to sell products. Sometimes, the target is perception. Following in the advertising industry's "perception-is-reality" footsteps, environmental groups such as Greenpeace use the familiar symbol for poison as a logo for PVC. And to the general public, skull-and-crossbones images married to vinyl might actually wash. Tactics such as these play on awareness of and concern for the environment. But selling this image to an audience of plastics industry insiders is a different story. Here, the group can knowledgeably digest the facts required to fully understand all of PVC's facets, including its environmental impact.

With that premise in mind, IMM set out to uncover both sides of the controversy over PVC's alleged role in releasing dioxin to the environment. As with most issues in life, we found that there are quite a few gray - make that light green - areas in the fracas surrounding vinyl.

Forest Green Defined

Defining the controversy over PVC's environmental impact is relatively simple, especially compared to resolving it. Essentially, environmentalists contend that the significant amount of chlorine inherent in vinyl's manufacture and released upon its combustion is a primary contributor to dioxin in the soil and air. Chemically speaking, during the combustion process, chlorine can combine with organic matter to form dioxin. Dioxins, according to the Chlorine Chemistry Council, are a family of 75 solid chemical compounds, both colorless and odorless, based on chlorine, hydrogen, and oxygen. These compounds do not dissolve readily in water, but are highly soluble in fatty substances and organic matter.

An EPA study of laboratory animals given high doses of the most toxic form of dioxin - 2,3,7,8-TCDD - concluded that this form may cause cancer in humans. But the carcinogenic properties of this and other forms of dioxin are still under debate among scientists. For example, the EPA currently lists an ADI (allowable daily intake) for TCDD as .01 picograms (pg) (1 x 10-14g) per kg of body weight per day. At this dosage, the calculated cancer risk would be 1 in 1 million. By comparison, the World Health Organization sets that level at 10 pg (1 x 10-11g).

Black-and-White World?

Just as there are shades of gray in life, so there are shades of green in the PVC controversy. D'Lane Wisner, manager of environmental solutions for PVC manufacturer Geon (Avon Lake, OH) states that vinyl is half chlorine, and points out that nearly all plastics use chlorine in some way. "Remember also that 60 percent of all chemistry involves chlorine, including products used in water purification systems," he says. During a recent Geon seminar, Wisner cited an example: "The government of Peru decided to stop chlorinating the water supply several years ago in an attempt to prevent chlorine exposure. The result was 20,000 deaths from cholera, malaria, and other diseases before Peruvian officials did a quick about-face, returning chlorine to the country's water.
Uses for PVC range from computer housings to appliances to toys. It is recyclable, offering up to eight heat histories without property loss. Although it has been maligned recently by environmental advocates, PVC supporters and manufacturers contend that vinyl provides us with both function and environmental friendliness.

Whether or not dioxin is carcinogenic, a 1996 study points to the fact that environmental dioxin is on the decline. At the same time, PVC usage and manufacture is climbing. Researchers from both Europe and the U.S. measured dioxin in lake sediments, going layer by layer to determine the age of the deposit. They determined that around 1960, dioxin deposits (measured in pg/sq cm/year) peaked at about 35. Sediments from 1996 show dioxin at about 10. In comparison, vinyl production measured 2.5 billion lb annually in 1960 while reaching almost 13 billion lb last year. Groups such as the Vinyl Institute and Chlorine Chemistry Council assert that if PVC was directly responsible for dioxin in the environment, the study would have shown a direct correlation.

On the flip side, Greenpeace cites a study from 1984 that found an abrupt increase in dioxin concentrations in lake sediment after 1940. This study found agreement between the production of chloro-organic compounds and the level of deposited dioxin.

Study Wars

As you may have already surmised, each side in the vinyl debate fortifies its opinions by performing scientific research, compiling the results into massive studies. On the environmental side, Greenpeace most recently published "PVC The Poison Plastic." Trade organizations point to the 1995 study conducted by the American Society of Mechanical Engineers and authored by scientists Rigo, Chandler, and Lanier.

Briefly, the Greenpeace study concluded with recommendations to decrease chlorine-containing vinyl as the primary method of reducing dioxin. In the ASME study, researchers found that the production of dioxin had no correlation to the amount of PVC or chlorine in the feedstream. Rather, they concluded, the presence of dioxin in stack gases depended upon combustion temperature and incinerator design and operation.

While Greenpeace acknowledged that facility design, operating conditions, and catalysts also contribute to dioxin formation, the group attempted to discredit Rigo et al in the report, "Chlorine and Dioxin." But again, related research failed to find positive correlation between chlorine in the feed and dioxin in the stack gases in more than 80 percent of the municipal incinerators examined.

The Burning Question

These and other studies point to the central issue in the PVC controversy: what really happens when it is burned in an incinerator? In summary, environmentalists contend that dioxin is formed due to the heavy concentration of chlorine from PVC in the waste stream. Trade organizations point out that any incinerator, whether it contains a high concentration of PVC or not, will emit dioxins if the temperature of incineration is below 2000F and if the design and operation are shoddy. Another problem, these groups say, is that chlorine can be introduced from many sources, both natural and synthetic.

Now a word from the neutral corner: The Environmental Protection Agency considers incineration one of the viable alternatives for handling solid waste. In a report entitled "An Agenda for Action," the EPA's Municipal Solid Waste Task Force advocates developing environmentally safe incineration facilities as part of an overall plan to reduce solid waste that also includes recycling, reuse, and reduction. Now for the burning question - where are these incinerators going to be located? One of the problems facing implementation of this option is the Nimby syndrome, a.k.a. "not in my back yard." It is difficult to convince communities of environmental safety when visions of dioxin-emitting incinerators still exist. Currently, less than 10 percent of unrecycled waste in the U.S. is incinerated; the remainder goes to landfills.

Other countries offer a contrasting perspective on this issue. Sweden, for example, one of the only countries with specific dioxin regulations, sends 55 percent of all solid waste to incinerators, where it becomes fuel for energy plants. Twelve years ago, the country conducted a one-year study of air emissions, concluding that modern incinerator technologies such as electrostatic precipitators, lime scrubbers, and fabric filters could reduce harmful emissions by more than 95 percent. Solid waste-to-energy conversion also runs successfully in Japan (46 percent) and Germany (35 percent).

Environment Canada, a government agency, also offered input on this question. It conducted a study in which two pilot air-pollution control systems were connected to a mass-burning incinerator in Quebec City that contained a significant amount of plastic in the feedstream. Testing showed that higher flue gas temperatures - 1800 to 2200F - removed 95 percent of all pollutants.

A rebuttal to these findings from environmentalists comes from the EPA in Denmark. A 1993 Danish study found that "doubling the PVC content of an incinerator's wastefeed increases dioxin emissions by 32 percent," according to Greenpeace's Thornton. He also reports that the German EPA found that combustion of chlorinated wastes containing plastics and other chemicals produced higher dioxin concentrations in ash residues than combustion of chloride-containing but chlorine-free paper, wood, cotton, or wool.

Recycling: Just Say Yes

Recycling could represent a mutually agreeable solution to the PVC controversy. Unfortunately, recycling vinyl and other plastic products generally remains yet another solid-waste alternative that causes government, industry, and environmental advocacy groups to differ. That's because efforts to create viable recycling infrastructures have stalled. Government involvement is nil at present, and while a few notable companies are operating profitably, there are almost no economic incentives to set up the collection, cleaning, and separating systems necessary to generate revenue. Without a thriving industry, the hope of successfully and economically recycling PVC or any thermoplastic remains dim.

Compare this to the bright outlook on PVC's ability to be recycled. Geon's Wisner explains: "Vinyl retains its properties upon remelting - on average, it can see eight heat histories before significant property losses occur. Also, the end-use applications for recycled PVC are numerous. When recycling becomes widespread, vinyl will be one of its star performers." - Michelle Maniscalco

Analyzing plastics with FEA: Part 8

At times, the product development process can provide some unwelcome reality checks. Take a look at the following scenario, for instance, based on the real-life adventures of David Ruscak, principal design engineer for Polaroid's engineering model shop; it may offer a painfully familiar plot:

Step 1 - Polaroid creates a new camera design, consisting of roughly 30 molded parts.

Step 2 - Designers begin to source multiple molders.

Step 3 - Model makers download separate design databases.

Step 4 - Ruscak manually reviews part designs for moldability, performing additional reviews after each engineering change.

Step 5 - Parts suspected of being difficult to fill are sent to FEA analyst for mold filling review.

Step 6 - Results from analyst take several weeks.

Step 7 - Because of time constraints, some parts are not reviewed; in other cases, engineering revisions also bypass review.

Step 8 - Ruscak spends precious time at the production stage debugging parts that have unacceptable weld lines or won't fill.

Mold filling analysis may well be the key to shortening product development times; unfortunately, when designers need a quick yes-or-no answer on moldability, they don't often have the time needed to build a finite-element mesh.


After an initial analysis identified weld lines and air traps in a shutter design, Polaroid made modifications using Part Adviser. Within 30 minutes, the analysis showed Polaroid that the cmplex part would fill correctly and that a change in the tooling would be successful.

Recently, though, no-mesh versions of traditional mold filling analysis packages have appeared on the scene. Working seamlessly with 3-D solid models, the software attempts to quickly give users information such as confidence of fill, location of weld lines, and potential air traps. But does analysis without a user-created mesh really work?

Designers we polled say yes, unanimously, then tell us about a particular project or two that "sold" them on the idea. What follows are two of those success stories.

First, let's get back to Polaroid. Last November, Ruscak incorporated the beta version of a no-mesh analysis package, hoping to reduce the number of steps in the process. "At the time, we were developing the Digital Microscope Camera (DMC)," says Ruscak, "a competitively priced camera for medical and industrial imaging markets, and based on an electronic imaging camera design already in production." One change, a modified shutter design, required Ruscak and company to rework an existing tool. Manufacturing members of the product development team were uncertain about the new design's moldability.

To alleviate concerns, Ruscak put the new software, Part Adviser from Moldflow, to work. "I downloaded the existing gate location data and, using the software, demonstrated how the shutter would fill, as well as the weld line locations. Color hard-copy examples helped to convince everyone that the tool could be modified successfully." As a result, nine months after product conception, the DMC began shipping. Ruscak adds, "Part Adviser allows us to recognize problems we just can't see on a drawing or a 3-D solid model. It's a fantastic communications tool, especially for naysayers."

On reflection, Ruscak and other managers realize that deploying analysis early in the design cycle had a ripple effect throughout the project. As a result, Polaroid has organized a "Barrier Removal Team" to identify factors that hinder getting products to market faster and more affordably. "With the advent of Windows NT replacing Unix workstations, more engineering environments can access an integrated toolkit of solutions," says Ruscak, "For us, that consists of Part Adviser, Pro/E, SolidWorks, and Office 97. With these tools, we can extract the data we need to communicate."

Communication seems to be the rallying cry among designers, especially those working in teams. Ray Douillard, sourcing engineer for Digital Equipment Corp. (Maynard, MA), has found that the ability to evaluate moldability at the concept stage helped shorten time to market.

"I collaborate with early involvement design teams to help determine feasibility," he says. At Digital, Douillard uses Part Adviser to evaluate concept designs. "The team needs to know if a design will be difficult to gate or create flow problems. Often, I find that we need to do something smarter, perhaps make two parts instead of one, to contain cost targets for the project." Other pertinent parameters - optimum resin selection and potential knit lines and air traps - are accounted for via no-mesh analysis. Douillard can then use that information to roughly determine tool cost.

A second major benefit, according to Douillard, occurred when Digital wanted to revamp an older product line by switching to a precolored compound. "We had contracted with compounding companies for precolored ABS. The tools had previously been designed for polystyrene, and all of the molds were in the Far East, making mold trials cost prohibitive." Instead, Douillard used Part Adviser to perform virtual mold trials. The product, a front bezel for Digital's line of Alpha servers, required no modifications to the tool based on analysis results. "More than 20,000 sets are molded per year," he says, "and we haven't missed on one yet." The current plan is to use Part Adviser on every design.

Is CAD a barrier to good molds?

It's a question molders continue to ask: Why is it that in spite of all the computer aided design, engineering, and manufacturing software available, molds are still built that can't run good parts? Many times, it's the result of designers who don't understand processing parameters or prototypes that fail to reflect the actual part.

But all too often CAD/ CAE technology becomes a barrier to building better molds because management has been encouraged to believe that the technology will "automate" the design process, says Anne Bernhardt, president of Plastics & Computer Inc., a software provider and consulting firm in Dallas. "At the same time, management also expects it to reduce mistakes, improve quality, shorten lead times, provide documentation, and be a cornerstone to simultaneous engineering," she adds.

The result of these unrealistic expectations is often big mistakes that are rapidly executed. This, Bernhardt believes, may have a long-term negative impact on both the technology and the molding industry. One of the first things Bernhardt advises her clients to do is look at CAD/CAE as "decision support," rather than automation. CAD/CAE technology is a tool to be used in conjunction with the experience, know-how, and creativity of all those involved in the mold design and build process. Technology gives designers the ability to consider more things than they could consider before CAD/CAE became available, and software options mean designers must make more decisions than before, Bernhardt explains.

"The automation phase will come with time," says Bernhardt. "You can't automate what does not exist and if you try, you'll get automated chaos." Bernhardt says that at issue are the kinds of results you get from CAD/CAE. "Anyone can be taught to run software and what keys to hit, but CAD operators need to be knowledgeable in more than just software."

However, the usual expectation in companies is that the designer - using the software - should be able to consider all the manufacturing/mold design issues. "Unfortunately, many designers lack the experience and practical knowledge to effectively evaluate the validity of results and consider economic and plant productivity constraints," Bernhardt says.

Many plastic part designers focus so completely on the part that they forget the mold and the molding. Designers who lack a molding knowledge often design in problems for the molder. Everyone needs to understand that part design and mold design are just two aspects of the entire process, in which the goal is parts that conform to specifications and/or are functional. Those involved with the project need to know more about the process than just the one aspect over which they have control.

This is why the team approach is critical. In many cases, however, a company rewards each individual involved in the project without thought to whether or not his or her vested interests are in the best interest of the overall project. "This can hurt success," says Bernhardt. "Reward the whole team based on final outcome."

Bernhardt advises companies to develop teams comprised of people taken from different disciplines and with varied experience levels. "Get your most experienced people to transfer their knowledge to the newer employees," she says. "The teams then also function to provide some on-the-job training."

CAD/CAE suppliers are increasing the bells and whistles of their programs to provide software to fill the knowledge gap, and to promote the widespread use of concurrent engineering. However, this approach can result in expensive problems. First, CAD/CAE often limits the input and consideration of issues only to those covered by the software, rather than other, hard issues raised by the team members actually responsible for manufacturing the part or mold. Secondly, the "designer/analyst often lacks the knowledge to judge the validity of the results generated by the computer," Bernhardt explains. "Make sure people with practical experience understand the software, and also evaluate the results based on their practical experience and rules of thumb," she states.

Bernhardt says the software industry is notorious for promising "futures," that is, the next release will fix the problem in this version. "The industry also has a tendency to use fancy screen displays and new file structures," she says. "But these features can sometimes mask fundamental program flaws or user incompetence." She advises clients to make sure the software user gets feedback from the production floor for practical validation of his/her work. Then use that feedback to critically evaluate results and, if changes are necessary, to limit when certain assumptions are made. "It is also a good idea to validate new releases of any CAE software by reanalyzing some parts that you already have feedback on."

Another important piece of advice: Software must be managed. Improper file and system management often results in errors going undetected. Although there are some glitches in the electronic data transfer process, Bernhardt says that even a new translator won't fix a bad design.

Bernhardt sees poor file management as a big problem, and one that is a management issue. "I think we're a long way from managing these CAD files," she explains. "I am still amazed at the number of times that a perceived file transfer problem served to identify major problems in the CAD geometry database." Advises Bernhardt: Establish file-naming conventions. Also, try to limit and standardize how some of the CAD system options are used. For example, limit designers to certain types of surface entities, or require that certain information be on certain layers.

Bernhardt believes optimizing the use of CAD to enhance a molder's or moldmaker's capabilities involves management, as it decides what goals it expects to reach with the technology and the people. "It's not the keys you hit," Bernhardt says, "it's how you use the system." And that is a people and a management issue.

The tools may be technical but how they're used is a strategic management decision. How much information do you want or need before you cut steel or even take on a new job? What's your propensity for risk? It then takes knowledgeable people to utilize the technology tools and maximize the benefits they offer. However, the process is also crucial. Bernhardt likes to quote Mike Hammer, president of Hammer & Co., a management consulting firm: "You can put good technology and good people in a bad process and all you succeed in doing is making the people and the technology look bad."

Chronic heater burnout leads to loaner leads to solution

It's a hard way to run your tool," says Angelo Morra, technical services manager at Tradesco Mold in Toronto. Morra is talking about a mold he delivered late last year to Medline Industries, a molder in Mundelein, IL. It is a four-cavity tool with a hot runner system, designed to mold polypropylene water pitchers for hospital and healthcare use. The problem was that the hot runner heaters were burning out, not just on this particular tool but on several throughout the shop, to the tune of one burnout every other week.

Medline is a molder of disposable medical devices such as bed pans, wash basins, water pitchers, and carafes. Its 500,000-sq-ft plant holds 40 presses ranging from 80 to 750 tons. Shifts of the 120 employees work 24 hours a day, seven days a week to keep things humming. The material of choice here is polypropylene, and operations are supposed to be fast and efficient, with lots of robots and dependent secondary operations.

Jack Maze, vice president of manufacturing at Medline, was frustrated and losing money over the heater burnouts. "I would classify it as a big problem," he says. "The real problem was not the cost of new heaters, but the cost of taking the mold out, the downtime of the machine itself." Heaters, he says, cost about $200 to replace, plus the $800 to $1000 lost in the 2 to 3 hours it takes to shut down the machine, pull the mold, replace the heater, and reinstall the mold. At $1000 to $1200 per change every other week, Medline was losing between $26,000 and $31,000 per year dealing with burned out heaters.

Those figures, however, don't reflect money lost in poor part quality - particularly in the new water pitchers. If the melt temperature was too cool, parts would short. If the temperature was too high, a blush formed at the gate, negatively affecting the appearance of the part. Maze, unsure of what to do, got back in touch with tool builder Morra, who in turn placed a call to the Gammaflux office in Sterling, VA. Gammaflux regional sales manager Mike Brostedt called Maze and offered to loan Medline one of its Series 9000 hot runner control systems to see if maybe it would do the trick. Maze agreed and soon Brostedt was at the pitcher mold, installing the controller and giving the operators a crash course on the operation of the unit. Then he left.

"What we kind of expected was that we'd try this unit on a machine for 24 hours or so," explains Maze, "and then Brostedt would call us back and we'd have to decide if we wanted to buy it or not." But Brostedt didn't call after 24 hours - or 48 or 72. "I'd wondered if he'd forgotten about us," Maze says. Brostedt didn't forget, he just wanted to give the controller time to prove itself. He didn't call, in fact, until 10 days later, and even then gave Medline another week to try it.

In the meantime, the unit was running the pitcher mold almost flawlessly. In the time he had the loaner, Maze says he never once had to replace a heater. And temperature fluctuations, previously 10 to 15 deg F, were reduced to 2 to 3 deg F, a fivefold decrease. Sold on the concept, Maze told Brostedt he'd take the system. But since it was a loaner, a new one had to be ordered, which would be another 14 weeks (given the mold integration at Tradesco). Gammaflux agreed to let Medline keep the loaner until its new unit arrived. "It was like someone handed me the keys to his car and told me to drive it for four months to see how I liked it," Maze says.

What makes the Gammaflux controller work, says Brostedt, is that it is a voltage proportioning device, not a time proportioning device like some controllers. This means that the controller applies to the heaters only the voltage required to maintain the set temperature. For example, on startup, the Series 9000 controller applies 5V of power, not the traditional 240V that a time proportioning device might apply to a cold heater. Such high-voltage peaks can quickly burn out the heater.

The Gammaflux controller, says Brostedt, decides what voltage to apply to a heater based on its assessment of the voltage lost to ground. On start-up the voltage lost to ground, he says, should be about 10 percent, or less. During operation, this figure should be 1 percent or less. By evening out the peaks and valleys in voltage application, heater life is prolonged and temperature setpoints are more accurately maintained.

At Medline, Maze says the consistent melt temperature and viscosity allow him to produce parts of high quality in cycles running about 15 to 20 percent faster than they did prior to the installation of the controller. He now has six controllers installed, with plans in the works for the addition of seven more. And although the cost for the controllers is higher than others he's considered, Maze says he never hesitated. "In some cases we tripled our cost. But they work," he reports.

The Troubleshooter, Part 18: Dimples in overmolded TPR

This article continues our series of troubleshooting reports from one of the leading on-the-spot problem solvers in the molding industry. Bob Hatch is manager of technical service and customer support for Prime Alliance, the Des Moines-based resin distributor. Before his present assignment, Bob managed a molding oeration for 25 years.


Figure 1. Dimples mysteriously began to form on the overmolded tread portion at the gates of this part. Nothing had changed on the molds, the nozzle checked out, sprue bushings hadn't changed, runners and gates were the same, vents were still self-cleaning, and the material was the same. What happended?

A customer called with a complaint about dimples at the gates of a glass-filled polypropylene roller overmolded with a thermoplastic rubber material. The problem was with the gates on the overmolded part. I knew the part well. I had helped the company with the design of the two molds several years ago. We had used a glass-filled polypropylene to mold the hub and a 40 shore A TPR to mold a tread on the circumference of the hub in a second mold. Both molds were eight cavities and each had a balanced runner feeding material into the cavities (Figures 2 and 3).

Figure 2. The roller's humb is molded from a glass-filled polypropylene, then overmolded with the TRP tread. A ring gate is used on the hub mold to keep the parts a round as possible.
Figure 3. Horseshoe runners for tread overmold gate into the hub from two points that are opposite each other. The single subgate of .125 inch was changed to two subgates, side by side, of .090 inch each.

We had used a ring gate on the hub mold to keep the parts as round as possible, and it worked well. For the tread we used a horseshoe runner to go around the outside of the hub and gate into the hub from two points that were opposite each other.

Everything worked well except for the gates for the TPR part of the molding. The size of the subgate we had to use for volume considerations was causing a chunk of the material to be pulled out with the gate when the part ejected. So we changed the single subgate of .125 inch to two subgates, side by side, of .090 inch each.

It turned out to be a blessing in disguise for us after all, because the two side-by-side subgates actually did a better job of filling and packing than the single subgate, plus the smaller gates didn't pull a chunk of the material out with them.

What Had Changed?

We had two molds that have been running well for four or five years, and now the customer says he is getting a sink hole or dimple at the gate areas in the tread portion of the part. I reviewed both molds to see if anything had changed since I last worked with them. I looked to see if the company was using a nozzle with an orifice that was smaller than it should be, which would change the machine's ability to fill and pack the parts correctly. But the molder had drilled out a nozzle to use for each mold, which were still being used, so that ruled out the nozzle as a problem.

Next I looked to see if the sprue bushings had been changed and they had not. I looked to see if the gates and runners were different than before and they were still like we left them. I also wanted to be sure some overzealous toolmaker hadn't tried to reduce the size of the runners or gates to keep from generating extra regrind or to keep from slowing down the cycle. Nothing had been changed. Then I looked at the runner and part venting to see if the vents had been hobbed shut or were full of material residue. Nope, we had made the vents self-cleaning originally and they were still working great.

What was left to look at, the material? The molder was still using the same original materials, and since we had optimized the tooling, we could pretty much be assured the slight differences in lot-to-lot variations of the material would not cause us much of a problem in filling and packing either part.

All that was left now was to look at the setup sheets to double check the processing conditions to see if any changes had been made. The heats, speeds, pressures, mold temps, backpressure, and screw rpm were all pretty close to what they should have been.

Next I went out to the molding machine and watched the mold that puts the TPR treads on the hub insert. I like to watch the screw go forward and visualize the material being injected into the mold and see what is going on with the cushion and whether or not it holds properly.

The Slipping Cushion

I like to use a medium to medium/slow injection speed for thermoplastic rubbers, even urethanes for that matter, and this was still a slow injection speed, which is good. The cushion was about .25 inch, which was what we wanted, but during the hold pressure portion of the injection sequence, I noticed the cushion slipped to about .125 inch. Something was wrong there. Either the check valve was leaking or extra material was being pushed through the gate after the inject, pack, and hold pressure sequence was finished.

I like to use the hold pressure in this manner to fill voids as they form on thick-walled parts, but this wasn't a thick-walled part. It had some thick to thin transitions but not the traditional thick walls and definitely not at the gate.

I turned the hold pressure down from 400 psi to 200 psi, and the dimples at the gates went away. We watched several cycles and the problem did not return. I went back to the setup sheet to see why I had not noticed the problem there. Then it hit me; we are used to seeing the hold pressure being about half of the inject pressure. But in this case the hold pressure was originally set at about a quarter of the inject pressure.

No doubt one of the molding technicians had accidentally raised the hold pressure, thinking it was too low, and caused the dimples to form at the gates. The dimples probably didn't show up until the next full shot and by then he had walked away to get a cup of coffee. The operator probably didn't notice the problem until the quality control person spotted the dimples, so the molding technician did not relate the dimples to his change in the hold pressure.

It is pretty easy to miss a problem like this by just looking at the setup sheet. You have to watch the machine run to get a feel for the plastic injecting into the mold, check the cushion and see what it does, watch the screw recover, and then watch it all over again.

From what I've seen, this problem pretty much shows up only on the soft materials, such as flexible PVC, thermoplastic rubbers, thermoplastic elastomers, and the softer polyurethanes. The customer made the changes to his setup sheet, threw the old ones away, and vowed to use only master copies of the setup sheets so this kind of problem would not bother him again.

Automotive winners and losers

Injection molders serving the lucrative automotive market will need to carefully pick their targets in the coming years, according to Jim Best of Market Search Inc. (Toledo). In his just-published report, "Automotive Plastics Report-1997," Best claims that usage of injection molded thermoplastics in passenger cars and light trucks assembled in the United States and Canada will grow from 1.74 billion lb this year to 2.28 billion lb in 2007 (see table). However, Best cautions, this growth will not be uniform.

Areas of growth and decline for injection molded components in the automotive market.
Market Area Million lb.
TPO bumper covers 105.5
Nylon intake manifolds 51.2
Injection molded body panels 11.2
Clutch/accelerator pedals 2.4
PVC steering wheels -6.6
Polyolefin egg-crate bumper energy absorbers -9

U.S. and Canadian injection molding material consumption for automotive applications.
Year Million lb.
1992 1223
1997 1742
2002 2049
2007 2284

Opportunities

Injection molded nylon intake manifolds will see a new competition between fusible-core vs. welded processing, says Best, and between nylon 6/6 vs. nylon 6. Usage of injection molded intake manifolds is forecast to grow a spectacular sixfold, to reach 65.6 million lb per year by 2007. This application, according to Best, is just the start of a new generation of underhood engineering plastics components from water pump impellers to throttle bodies.

Bumper covers are converting from RIM to injection molded TPO and ionomer in one application after another and are forecast by Best to grow to 284 million lb per year by 2007. Also, injection molded clutch and accelerator pedals are forecast to see 20-fold growth to reach 2.7 million lb per year by 2007.

Model changes from specific automotive OEMs are fueling some big opportunities for molders of exterior body panels. Saturn, for instance, is working on a larger model for 1999 that will essentially double the number of vehicles with injection molded bodies. Chrysler is developing its injection molded Composite Concept Vehicle (CCV), and in Europe, Mercedes is preparing to introduce its Smart car, which features an injection molded body. Owing to all of this, Best estimates total growth of injection molded exterior body panels to increase 19.5 percent to reach 45.9 million lb per year by 2007.

On the instrument panel (IP) side of things, Best sees the trend going toward injection molded integral structural ducts. A recent example he cites is the Jeep Cherokee. But the 1997 Jeep Wrangler goes the other direction, saving money with an unpainted polypropylene IP. And Chrysler's 1997 minivan instrument panels start a new trend to unpainted TPO. Because of the nearly 100 percent penetration of injection molding for interior applications, says Best, there will be no significant growth in IPs.

Areas to Avoid

On the negative side, bumper energy absorbers injection molded into an egg crate design will continue to give way to foamed polypropylene. Best projects this transition to cost injection molders more than 9 million lb of business per year by 2007. Also, steering wheels injection molded from PVC are being replaced by RIM urethane. This will cost molders more than 6.6 million lb of business per year by 2007.

About the Report

Best analyzes a total of 238 specific injection molded applications and materials systems in his 1076-page report. Current usage, historical usage, and five- and 10-year forecasts are provided for each application. Specific new applications and developmental programs, based on interviews with automotive OEM engineers, are described as well. "Automotive Plastics Report-1997" costs $3100; copies and sample pages are available from Market Search by calling (419) 535-7899.

The Materials Analyst, Part 3: The case of the missing filler


This series of articles is designed to help molders understand how a few analytical tools can help diagnose a part failure problem. Michael Sepe is our analyst and author. He is the technical director at Dickten & Masch Mfg., a molder of thermoset and thermoplastic materials in Nashotah, WI. He has provided analytical services to material suppliers, molders, and end users for the last 10 eyars. He can be reached at (414) 369-555, Ext. 572.

Fillers and reinforcements provide a valuable option for improving the property profile of many thermoplastics and thermosets. Semicrystalline thermoplastics such as nylon, polypropylene, and polyester are especially big users of these additives, but they can also be found in amorphous materials like polycarbonate and PPO. Glass fiber is one of the most important reinforcements used to increase strength, stiffness, creep resistance, and fatigue properties. When a processor or an end user specifies that a part is to be made in a reinforced material, the percentage of that reinforcement is one of the key items that must be controlled in order to ensure that the properties of the compound are consistent and achieve desired levels.

While plastic materials are based on organic chemistry and will degrade at relatively low temperatures, fillers such as glass fiber are inorganic and can resist extremely high temperatures without changing their structure. This basic difference makes it possible to detect the amount of most fillers in a compound by using heat to burn away the plastic, leaving behind the filler. One instrument that makes use of such a technique is called a thermogravimetric analyzer (TGA). The TGA uses a furnace to generate high temperatures. The material to be tested is placed in a weighing pan that hangs on the end of a quartz beam. Weight changes of as little as .005 mg can be detected with this type of instrument. A small sample is heated at a regular rate and the weight of the sample is monitored as a function of temperature. As the sample is heated it begins to decompose. A gas stream sweeps away the byproducts and the weight declines as the polymer burns away.

Figure 1 shows a typical result from a TGA test. Using a thermogravimetric analyzer (TGA), weight loss for unfilled polypropylene is graphed. The plastic used in this example is an unfilled polypropylene. The polymer decomposes in a single step and leaves no residue, indicating that it is an unfilled material. The weight is usually plotted in terms of percent rather than the actual weight of the sample. The second curve is the derivative of the weight loss, or the weight loss rate. In future articles, this will be shown to be useful in detecting mixtures of polymers or additional ingredients that change the thermal stability of a material. Because of its ability to shed additional light on the composition of a material, TGA is often used in conjunction with DSC in identifying an unknown compound.

One of our customers submitted some parts that were exhibiting premature failure. The material used to mold the parts was supposed to be a 40 percent glass-reinforced polypropylene. Along with the molded parts, the customer also sent some of the raw material from which the part was being molded. The customer had asked for a number of tests, but one of the first tests that we typically will conduct on a filled material is the TGA test. Because fillers like glass fiber, glass bead, and talc are inorganic, they will not burn off at the normal test temperatures. Instead they remain as residue or ash. The filler content is easily determined by observing the percentage of the material that remains in the weigh pan at the end of the test.

Figure 2 shows a comparison of the weight loss for the raw material and the molded part, using a TGA analysis. While the raw material had the proper amount of glass fiber, the molded part contained only 20 percent glass. This reduced the strength and stiffness by approximately 50 percent and turned out to be a major factor of the problem with part failure.

This type of test for filler content is also a valuable tool for routine incoming inspection. All suppliers of filled compounds produce their materials to a specified range. If a customer receives certification on incoming materials, the filler content will frequently be a property tested on each lot. The TGA provides a means of verifying the lot-to-lot values. In addition, these tests provide a means of evaluating the consistency of competitive suppliers. Over time, one supplier of a 30 percent glass-reinforced material may hold a range of 28 to 32 percent while another may allow a range of 27 to 33 percent. This will be evident in the historical data developed by testing different lots over an extended period of time. The molded part cannot be any more consistent than the incoming material.

Surface definition improves at the core

This cetrifugal blower is part of an air conditioner designed by Trane Corp. in Mechanical Desktop 2.- using the Acis 3.0- modeling kernel. Surface details for the molded housing (yellow) are accurately created using a new 3-D sweep feature, then translated into the moldmaker's CAM system using an SAT file format.

For mold designers and manufacturers, surfaces are everything. If cavity and core surfaces are not accurately defined, the resulting tool paths for CNC equipment will also contain errors. On the flip side of the spectrum, product designers often prefer to work in 3-D solids. When a solid CAD file is imported into the mold designer's system via IGES translation, surface definition can be lacking. As a result, surfaces either have to be created anew or tend to need a lot of repair.

While software vendors are waking up to this lapse, many rely on a "modeling kernel" or geometry core that supplies solid modeling and surface design engines. If the core lacks the necessary capabilities for creating or extracting surfaces, incorporating this function into a program becomes next to impossible.

Spatial Technologies, developers of the Acis modeling kernel, believes the answer lies in its newest release, dubbed Acis 3.0. You'll find it in the newest releases of Autodesk's Mechanical Desktop, Baystate Technologies' Cadkey, Delcam's PowerMill, and SmartCAM from SDRC/Camax. The new kernel enables these and other applications to add advanced surface modeling features. According to David Prawel, marketing director at Spatial, Acis 3.0 contains several functions aimed at easier, more accurate mold design. Users can now sweep a profile along an arbitrary 3-D path, use a rolling ball blend, and "sheet" blend between two surfaces rather than having to blend two faces that reside in a solid. Surfaces are also more easily extended and trimmed.

Prawel tells IMM that two years ago, Spatial brought two developers on board whose expertise in surfaces was put to use in creating new surface functions. One of the results is a new subsystem that uses mathematical functions, or laws, to define surfaces. Now, rather than using B-spline approximations for curves, users can input the exact equation to define the surface. "One benefit for mold design is that applying the draft angle becomes simple," says Prawel. "It's a straight-line linear sweep of a profile through a mathematical equation."

Another advantage to any Acis-enabled program is that it offers SAT interoperability. The SAT file format, created by Spatial, contains all the attributes and topology of a model created in any Acis application. Currently, there are 104 commercial applications available, the largest customer base of the three modeling core vendors by far. (In addition to Spatial, the group includes Parasolid by EDS and Designbase by Ricoh.)

An example of SAT file format benefits involves an IM tool for a logo badge. Several failed attempts at recreating the complex front surface of the badge put the project seriously behind schedule. Satellite Models (Mountain View, CA), a firm that specializes in prototypes and short production runs, got the S.O.S. call. "Our customer had created the badge in a solid modeling program, and sent the 5.7-Mb IGES file," says Kelly Hand, president, "which we translated into SmartCAM. Unfortunately, the surfaces everyone was concerned about were missing." Satellite contacted the designer, who sent an SAT file created in Mechanical Desktop 2.0. It transferred smoothly into SmartCAM, and supplied all of the surfaces. Tool paths were generated in less than 2 hours, and the tool was express shipped the same day.