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For SMC/GMT compression molding: new high-tech equipment at K'89.

For SMC/GMT Compression Molding: New High-Tech Equipment at K'89

High-speed, high-tech compression presses for SMC and glass-mat thermoplastic (GMT) sheet "stamping" were much in evidence at the K'89 show in Dusseldorf. It was evident that microcomputer controls for these presses have become at least as sophisticated as for injection molding or any other plastics process.

Much of the compression molding emphasis at the show was on superfast presses for GMT molding, though molders are also interested in them for speeding cycles with fast-curing polyester SMC compounds. Hoesch Maschinenfabrik Deutschland AG (represented by Girard Associates, Inc., Middleburg Heights, Ohio) is now claiming fast-close speeds of up to 2362 in./min on its latest-generation OKP presses, together with pressing speeds of 140 in./min and full-tonnage build-up times of only 0.5 sec.

At the company's plant in Dortmund, W. Germany, Hoesch demonstrated molding of a production part of PP/glass GMT, a BMW engine cover, on a 1400-ton press. It took 10 sec to unload formed parts and load fresh, heated charges, 4 sec to close the press and build 800 tons of pressure, 10 sec to cool the part in the mold, and 4 sec to open the press - for a total of only 28 sec. (A less-than-optimal charge-heating oven slowed the actual cycle down to 40 sec.)

Another new feature is a remote diagnostic system, designated SMDC, which permits Hoesch technicians to receive process data and pressure and velocity programs directly from the press control to the Dortmund plant, 24 hr/day, for service consultations. Also, test programs can be downloaded to the press control from Dortmund to aid in fault analysis. (CIRCLE 24)

Wemhoner Spezialpressen of W. Germany is new name in the U.S. (represented by Eurohansa, Inc., High Point, N.C.). It is now also claiming closing speeds of 2362 in./min and 0.5-sec tonnage build-up times for its GMT presses up to 3660 tons (see PT, Sept. '89, p. 101). (CIRCLE 28)

Dieffenbacher of W. Germany (represented by Marvel Equipment Corp., Farmington Hills, Mich.) has new press control features, including a "pressure-optimizing system" to simultaneously achieve excellent parallelism control and maximize available press tonnage. Initial closing tonnage is normally set a bit lower than maximum, so that it doesn't overpower the "pushback" parallelism-control cylinders. The resistance of those cylinders further reduces the effective pressing tonnage. With Dieffentonnage new control program, press tonnage is increased after maximum parallelism has been attained, so that at least 95% of full tonnage is available for final pressing. Company sources say this can permit use of a smaller press in some cases.

Also new is something called "flow-front control," which can be useful with in-mold coating (IMC) or BMC injection/compression. After IMC or BMC injection, deliberately nonparallel closing can be programmed, so as to squeeze the coating material over the part or the BMC over the mold surface. In addition, the control can memorize the exact positions of all four press corners before it opened for IMC injection, so as to return to those same positions afterward. After curing, the press can open while maintaining the platen corners in the same relative degree of parallelism, rather than in a "zero" attitude, so as to avoid damaging the newly cured surface. (CIRCLE 29)

Muller-Weingarten of W. Germany has supplemented its high-tech SKEV series of short-stroke presses (built under license from MTS Systems) with two new series of simpler, lower-cost, short-stroke machines from 660 to 2200 tons. The new KFD series is aimed at SMC and the faster KFT series at GMT. Both series have a central pressing cylinder, two rapid opening and closing cylinders, and four pushback parallelism cylinders. Only the top platen moves (unlike the SKEV series). Fast-closing speeds are up to 1872 in./min, opening speeds to 936 in./min, and pressing speeds to 19 in./min. Parallelism is said to be controlled to less than 0.1 mm corner-to-corner at speeds under 12 in./min, and double that at higher speeds. Tiebar spacing can be up to 60 x 80 in.

The company has just established its first direct-sales operation in North America, called Muller-Weingarten Corp., located at the facilities of its former representative, Cosa Corp., Rochester, Mich. (CIRCLE 30)

Meanwhile, Muller-Weingarten has formed a partnership with SMC Technologie Derek & Kuper OHG of W. Germany, a small electronics-oriented firm, to develop press controls, automation systems and peripherals. For example, D & K offers the PO-100 Cycle Optimizer press control. It continously monitors the in-mold pressure and opens the press automatically when the pressure falls to zero, indicating cure is complete. The device also stores pressure and temperature data and can download them to a printer or PC for SPC analysis. (CIRCLE 31)

D & K also developed three quality-control testing devices for SMC. The Reaktometer is an instrumented lab press and mold, which measures temperature, pressure and platen displacement in real time. With accompanying personal-computer software, it prints out a report showing times to start and end of exotherm, reaction time, a reactivity coefficient, shrinkage, max. speed of shrinkage, and coefficient of thermal expansion of the cured material. (CIRCLE 32)

The Plastometer measures the room-temperature viscosity of a molding compound by means of a weighted plunger. The device connects to a PC, which records a curve of how fast the plunger sinks into the material. In addition, the Orifice Flow Tester (OFT) measures flow of a compound through an orifice under pressure, similar to a melt-index test. Each of these systems is available through M-W Corp. (CIRCLE 33)


As we reported in December (p. 89), Cannon USA Inc., Mars, Pa., plans to begin marketing a broad line of compression presses in the U.S. starting late this year. This is a result of the Cannon Group of Italy having acquired press maker TCS of Italy in mid-1988.

Cannon TCS discussed two new press series at the show. One is a traditional long-stroke press, called Polifiber C, with some new features suggested by a molding customer. These include a floating upper platen, with a certain amount of horizontal "play" allowed until the mold guides engage during closing. Then the platen is locked in position by pistons pressing against guide columns. This is said to reduce wear of mold shear edges. A type of "passive" leveling, in which all four corners are pressurized equally, is available, as is a more sophisticated version. Cannon builds these presses up to 3000 tons, with fast-closing speeds up to 1872 in./min. (CIRCLE 34)

Cannon also recently delivered a new 880-ton short-stroke SMC press to DSM of Holland, dedicated to SMC molding with IMC, and utilizing a highly sophisticated CRT control system. This system mechanically locks the upper platen against smooth columns after parallelism has been established and before actual pressing begins. Pressing is accomplished by a short-stroke working platen, which descends from the locked upper platen. (The lower platen does not move.) The working platen can begin its motion even before the upper platen is locked.

The color CRT screen can show a schematic of the platen in motion with real-time position readouts for all four corners. Other displays include realtime graphs of velocity, pressure or position vs. time, leveling tonnage and position deviation at the four corners, and a "bubble leveler." The control permits programming 20 steps of velocity vs. position and pressure vs. time, as well as three-step profiles for IMC injection or BMC injection/compression. As noted above for Dieffenbacher, the platen can be deliberately titled for either of these operations. (CIRCLE 35)

Cannon TCS also offers simpler, long-stroke, column-type presses (Polifiber E) for nonautomotive SMC in sizes from 220 to 1760 tons; and smaller Moldmatic presses of 143-495 tons for dinnerware, electrical parts, and the like. (CIRCLE 36)

Vickers of Switzerland and Troy, Mich., displayed the new System 235 color CRT control system for SMC presses. One of these systems has been running since the summer of 1988 at Sterling Products, Inc., Sterling Heights, Mich. It's an upgraded version of the System 230 originally developed for injection molding. It can provide 10-step speed/pressure profiling, parallelism control, IMC control, three-step opening speed profile with parallelism control, quality and production data recording, fault diagnostics, ejector and core-pull controls, preheating and vacuum controls, and an interface for robotic auxiliaries. A "Quality Data" screen shows current, last-cycle and average cycle times, leveling position and tonnage for each corner at the switchover point, and end of leveling, and at the end of IMC leveling. You can program a new job setup while the machine is running, and you can also do programming off-line. (CIRCLE 37)

Another new name to North American SMC and GMT molders is Aplicator System AB of Sweden (represented by Euromer Polymers Inc., Granmorie, Quebec), which has just come out with an automatic press loader. It consists of a patented shuttle with an endless belt. The precut charge is placed on the belt and carried by the shuttle into the press "within millimeter accuracy," according to the company. It can be used on existing presses without modifications, requires low opening height of the press, can handle sticky materials and complicated charge shapes, and is mobile to permit tool changes. Simple "teach-in" programming is used to set up different charge placements. (CIRCLE 38)

PHOTO : New automated press loader for SMC and thermoplastic sheet compression molding comes from Aplicator AB of Sweden via a Canadian representative. K'89 introduced other new names in compression molding equipment.
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Author:Naitove, Matthew H.
Publication:Plastics Technology
Date:Feb 1, 1990
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