While Arburg GmbH + Co. KG and Wittmann Battenfeld GmbH & Co. KG clearly agree on the potential opportunities in the micromolding sector, the two companies are following quite different routes to meet market needs.
Arburg is offering a modified standard machine, while Wittmann Battenfeld is continuing with its dedicated approach.
Arburg presented its latest micromolding development an 8-millimeter-diameter injection module at its Technology Days open house at its Lossburg headquarters. The new module enables conventional machines to be used at will in micromolding or conventional molding roles.
Arburg's add-on module combines a servo-electric-driven 8mm screw with non-return valve for injection with a second three-zone pre-plasticizing screw with an almost conventional flight design. This is mounted piggy-back style at 45 degrees and is used simply to melt and convey the plastic material to the last section of the 8mm injection screw, which has a purely material transport function.
Technical director Herbert Kraibuhler says this approach enables extremely small parts to be molded with standard-size granulates, avoiding the need for the costly microgranulates typically required with screw diameters below 15mm.
The module was shown producing 1.58mm-diameter gearwheels weighing 0.001 gram on a standard all-electric Arburg Allrounder 270A Alldrive machine, using 35 metric tons of clamping force. A special pneumatically driven gripper system from Stamm AG in Hallau, Switzerland, removed the parts from the eight-cavity mold.
Kraibuhler said the system has been developed around a screw rather than the plunger-based injection units, more typically favored for micromolding, because of quality concerns. He says the Arburg engineering team is wary of material hanging up with the plunger systems, which has led to a risk of black specks in the part.
Meanwhile, Wittmann Battenfeld, which launched its first dedicated Micro System 50 micromolding machine in 1998, now has launched the MicroPower 5 and 15 machines. The new machines replace the original model but retain the dedicated design and plunger-based injection system.
The company demonstrated its 15-metric-ton MicroPower 15 machine at an open house at its factory in Kottingbrunn, Austria, in May. It was molding a 0.0035- gram 28-pin subconnector part in a two-cavity mold on a cycle time of 4.5 seconds.
The MicroPower retains the 14mm plasticizing screw and plunger injection system of the Micro System 50. The company said this also can handle standard granulates and it is confident that material hang-up is not a concern.
Wittmann Battenfeld's micromolding specialist Martin Ganz said other technical aspects of the machine have changed with the introduction of the MicroPower, aside from the 15-metric-ton machine now joining the original 5-tonne model.
Melt-pressure measurement and control has been improved, and the two-stage plunger injection system is now available in 5mm and 8mm diameters. Other new features include a Wittmann handling system, Unilog B6 control in place of the earlier B4, and a rotary table.
Ganz said further improvements have been made in the price, down from 90,000 euros ($111,300) to 66,000 euros ($81,600).
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