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Articles from 2002 In August

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.


AmeriPlas Machinery Corp.
Autojectors Inc.
Battenfeld of America
Boy Machines
Demag Ergotech
Ferromatik Milacron NA
Hettinga Equipment
Husky Injection Molding
Illinois Precision
Jaco Mfg.
Jon Wai Machinery
LG International America
Lien Fa Injection
Mitsubishi-MHI Injection Molding Machinery
Mini-Jector Machinery
Multiplas Enginery Co.
Nissei America
Nissin Machine Co.
Sandretto USA
Sumitomo Plastics
TMC Jiangmen Magnetics&
Tomken Tool & Engineering
Van Dorn Demag
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.

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.
    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.

    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."

  • Dryer handles two-shot molding

    The dual-hopper PDII Series dryer is designed for automated two-shot, two-color molding. The unit handles two different resins simultaneously, with individual control of drying temperatures and times. Each hopper has adjustable volume control, allowing the operator to adjust the capacity to accommodate different shot sizes and processing rates. One loading system conveys dried material to each injection unit separately. Various hopper sizes and two- or four-bed drying technology are available.

    Dri-Air Industries
    East Windsor, CT
    (860) 627-5110

    Flow regulator tracks eight cooling zones

    By specifying an individual zone's temperature and optimizing mold cooling, a new water flow regulator can reportedly reduce cycle times, improve part quality, and prevent condensation problems. The FlowCon uses a microprocessor to monitor and regulate up to eight different cooling zones. By checking the temperature of each cooling circuit, the FlowCon regulates the amount of cooling water sent to different zones based on setpoints. Water flow is controlled by an electromagnetic solenoid valve. The maximum difference in temperature settings between the various circuits is 55F, and the FlowCon can operate with cooling water temperatures as high as 212F.

    By controlling temperatures automatically, the FlowCon reportedly maintains settings to within ±1 deg F. Temperatures outside set ranges can be set to trigger alarms, and further programming allows fixed on and off pulsing of water flow. Water flow rates of 2.6 gpm/zone are reportedly possible. If cooling isn't needed during a production lag, the control prevents further mold cooling. The cooling circuits also remain closed during mold startup to reduce overall warmup time.

    To further optimize control, the circuits can be placed in the mold close to the cavity, in the circuit's return line, or in the water flow regulator's return line. If sensors can't be located in the cooling circuits they can be slave controlled by another, user-specified circuit.

    Seven mold setups can be stored in the unit. Data transfer to the press is handled by a serial interface port. Each module has its own connection to the mold, and cooling supply is provided by a single connection.

    Wittmann Inc.
    Torrington, CT
    (860) 496-9603

    Granulator reclaims thermoform trim

    The TG series of thermoforming granulators are designed for continuous reclamation of skeletal web directly from the thermoform trim process. The units are 23.25 inches high and are positioned underneath the trim press for inline operation with continuous pneumatic removal.

    The unit provides low-power, low-rpm operation with a six-knife offset-mounted configuration, and two adjustable stationary knives with double cutting edges for maximum lineal inches of cut. Dual feed rolls are polyurethane-covered for high wear resistance. To permit slippage as needed, one roll is driven while the other is spring-loaded.

    TG Series granulators are available with 8-by-36-inch or 8-by-56-inch throat sizes with throughputs ranging from 800 to 1500 lb/hr depending on type and form of the materials. Standard features include a 7.9-inch-diameter cutting circle with a solid steel cutting chamber up to 4 inches thick. The high-alloy steel, full-body rotor has six high-chrome, high-carbon steel rotor knives. Easy-access, removable front doors allow cleaning and adjustment of screens and bed and rotor knives.

    Ball & Jewell
    South Attleboro, MA
    (508) 399-3100

    Reaction injection molding lines improve accuracy and maintenance

    The OmegaRim RX and RimCell RX reaction injection molding (RIM) lines now include Rexroth A2VK positive displacement axial piston metering pumps for volume and ratio accuracy, open construction and straight tubing runs for easy maintenance, and accurate digital flow readout that eliminates the need for wet calibration.

    Additionally, the RimCell RX line has a mechanism that allows the motor to slide away from the pump, with a mounting bracket that doubles as a seal-changing workbench. The mechanism makes pump unbolting and extensive chemical tube disassembly unnecessary, and speeds pump seal replacement.

    Gusmer Corp.
    Lakewood, NJ
    (732) 370-9000

    Air ring has adjustable bolts to correct film deviation

    The Manual Gauge Control air ring (MGC) permits selective adjustment to correct film gauge deviation?caused by extruder, die, or ambient anomalies?by as much as 30 percent. The film thickness control is external to the film bubble, and can be manually operated.

    Depending on die size, the MGC is equipped with anywhere from 100 to more than 200 individually adjustable control bolts in 10-mm-wide air channels. Bolt covers ensure that only authorized personnel can make adjustments.

    Making gauge corrections with the MGC can be compared to adjusting die bolts to correct uneven film thickness distribution. A spot is marked on the film bubble indicating its orientation, the gauge of the film sample with the marking is measured offline and plotted, and the relevant adjusting bolts are turned in or out to make corrections. The amount of correction per bolt turn can also be determined with before-and-after measurements.

    Addex Inc.
    Hingham, MA
    (781) 741-9801

    Crosshead designed for thin-wall extrusion

    The MicroFlow spiral, a low-volume stainless steel crosshead designed for multilayered, thin-wall extrusion, is reportedly adaptable to all extruders. It's suitable for OEM and medical fluoropolymers as well as thermoplastics extrusion manufacturers. A balance flow design offers easy assembly and disassembly of the crosshead.

    The crosshead has an adjustment in the die holder, and a cartridge-style ball assembly that doesn't require the loosening of retaining screws to make adjustments. It also has a system that eliminates leakage between the deflectors and is maintained through self adjustments, thereby reducing potential errors during assembly. The spiral model is available in three standard designs?single, double, and triple extrusion capabilities?and for custom designs up to five layers.

    The spiral is adaptable to all extruders and is manufactured in stainless steel to meet the requirements of medical and other FDA-type applications. A balance flow design offers easy assembly and disassembly of the crossheads. The spiral core diameter is .375 inch and the maximum product size is .5 inch. The inner layer includes a fixed center and the outer layer's adjustable concentricity function uses retaining screws.

    The gum space adjustment operates via rotation of the core tube. Quick-change tooling is said to ensure easy removal of the tip from the back and the die from the front.

    Guill Tool & Engineering
    West Warwick, RI
    (401) 828-7600

    Retrofit multicomponent system yields a two-component product

    The combination of a Sandretto injection molding machine and a Windsor PlugXPress multicomponent retrofitting unit is said to yield flexibility at a lowinvestment, since all PlugXPress units can reportedly be quickly installed and easily moved from one machine to the next. The PlugXPress unit is connected to the injection molding machine with a mechanical and electrical interface and can be installed on machines of any make, type, and clamping force. The units have their own control and hydraulic system. Sandretto reports that a two-component injection molded side airbag cover with a hard-soft combination of polypropylene/ABS and TPE has been produced on a 13,000-kN injection molding machine and a PlugXPress unit with a screw diameter of 42 mm.

    Sandretto USA
    Freedom, PA
    (724) 775-4255

    Robot arm combines y and z axes

    By combining features from linear and articulated robots, a new automation line promises accuracy and speed at a reduced cost. The Viper robot line, designed for material handling and processing applications in the plastics industry, reportedly draws on the best attributes of articulated and linear-style robots.

    The AS 212 model reportedly offers high performance-vs.-costs ratios and is designed for small molding machines. Its intrusion time is only 1 second or less, and it boasts a payload of 2.2 lb. The design of the Viper's arm combines the y and z axes and uses integrated servocontrols with relay-isolated input/output, Panasonic drive technology, and a programmable handheld pendant that can save 16 operations.

    The top- and side-entry robots also feature a 120V plug-and-play system, quick-change EOAT components, and high safety standards with a three-position dead-man switch.

    Ventax Robot Inc.
    Ayr, ON
    (519) 632-7834

    Underwater pelletizer reduces wear

    An underwater pelletizing system produces glass-fiber-filled products. The system reportedly alleviates the wear that occurs during transport and drying of the pellets. It uses a specially constructed centrifugal dryer as well as special coating methods throughout the pelletizing system. The system is said to be reliable for PP, PC, PA, and other products with up to 50 percent glass fiber content, and output capacities of up to 5500 lb/hr.

    Kreyenborg Industries
    Lawrenceville, GA
    (770) 339-4177