Electric Presses Handle Long Hold Times

A new clamp design, injection unit, and all-digital servo control mark the fifth generation of compact all-electric machines from Niigata Machine Techno Co.

A new clamp design, injection unit, and all-digital servo control mark the fifth generation of compact all-electric machines from Niigata Machine Techno Co. Ltd. (represented by Niigata Plastic Machinery, Itasca, Ill.). At the IPF show in Tokyo, Niigata introduced the 55-ton model MD50xi 1.0. Other sizes to come are 82, 110, and 200 tons. Standard injection speed is 250 mm/sec, and the new control reportedly affords a 55-millisec response time. The new injection unit can handle long holding pressures—up to 19,575 psi for 60 sec. The clamp features extended mold height. Niigata also upgraded its larger all-electric machines, exemplified by the new 198-ton model MD180W i6.5. Its platens are 60 mm wider and mold height is 100 mm greater than on the previous model. Max. injection speed is 200 mm/sec, and a Long Holding Pressure (LP) feature allows for dwell times up to 200 sec at 19,575 psi for molding thick parts. This feature utilizes high-output, low-torque motors and a special reduction control that prevents the electric servo motors from heating up or burning out during long hold times. Niigata has also brought the LP function to vertical presses. Its MDVR50 S-IV LP model for lens molding can maintain 19,575 psi holding pressure for 60 sec. Also new from Niigata at the show was a new 715-ton electric press with compression molding/coining capability for large, flat, thin-wall articles such as diffuser plates for tv screens or light-guide plates for computers. Such products previously were possible only through “extrusion molding,” Niigata says. The MD650S-IV AP achieves mold-gap positions accurate to +/-0.02 micron using Niigata’s Active Press (AP) control.