Niigata Engineering Co. Ltd. has expanded its MDS-IV range of all-electric injection presses, with three new models, and an unusual electric press to mold thermosets.
* The LP in the MDS-IV LP stands for long-period holding pressure. With no limit on molding conditions, the press pack and hold can be maintained for up to 30 seconds. Under some molding conditions, the MDS-IV LP can maintain continuous holding pressure for as long as 100 seconds, according to Peter Gardner, vice president and general manager for Niigata at DJK-Global Ltd. in Itasca, Ill.
Typically, electric servomotors heat up, and can burn out, when attempting the very long pack and hold times required by parts such as thick polycarbonate lenses. That often meant using a hydraulic machine.
But Niigata uses a new, low-speed and high-output motor that runs at ultralow inertia. A torque-loss reduction control is used during holding pressure. The LP machine comes in four clamping-force sizes: 55, 82, 110 and 200 tons.
* With the MDS-IV HP, Niigata has ratcheted up the injection speed to 500 millimeters per second for very-thin-wall molding and precision parts such as narrow-pitch connectors. The standard MDS maxed out at 300mm per second.
Gardner said the HP has a stiff frame with a robust design. Another feature is Q-DVP injection control for quick deceleration and pressure reduction.
The MDS-IV HP is available in two 35- and 55-ton models.
* In a highly specialized press, Niigata designed the MDS-IV AP for molding light guide plates - the screens for laptop computers. The presses do the coining process, also called injection/compression, to make the very thin and flat optical screens. The machine holds low pressure during filling, opening slightly as the melt enters the mold. Then the press closes during clamping, in the compression stage.
Niigata offers the MDS-IV AP in two sizes: 500 and 700 tons.
* The MDTPS-IV was developed for processing bulk molding compound. Gardner said Niigata believes this is the first all-electric press for molding thermosets. The fully sealed system keeps contamination off the ball screw and servomotors. Scratches, pinholes and burning are reduced because of a special low-pressure clamping mold mechanism that allows gas to exhaust from the mold.
Gardner said Niigata is targeting the automotive industry for the MDTPS-IV, which comes in 385 and 500 tons. Niigata has sold several of the presses to Japanese auto customers, he said in a July 22 interview at Niigata in Itasca.
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