CHICAGO — Arburg Inc., which makes injection molding machines in clamping forces of 17-220 tons, showed two small-tonnage presses and a new technology that controls the machine by monitoring mold cavity pressure.
A modular 28-ton press, the 270S, features an electrically actuated universal clamp, which allows the injection and clamp units to move to various positions.
For crowded molding environments, Arburg also showed a 55-ton 320S machine running with a parts picker robot that fits ``under the hood,'' within the mold area and behind the safety hood.
Arburg of Newington, Conn., also announced it has added a hydraulic oil accumulator to boost injection speed on its 520V-2000 machine. Arburg developed the system for a customer molding a closure for a takeout soup container.
The machine can fill a two-cavity mold with more than 2 ounces of polypropylene in a four-second cycle.
Arburg also showed its process regulation control, which monitors cavity pressure continuously during each molding cycle. The controller stores a cavity pressure reference curve, then repeats the curve on each shot in real time. Unlike other controllers, Arburg said, its unit can repeat the shape of curves, within very tight tolerances.
The switchover from injection velocity control to holding pressure control happens when a point is reached on the cavity pressure curve. Arburg said this method compensates for fluctuation in the period of screw recovery, so the cavity pressure at the switchover point is always the same.
If the system detects a change in cavity pressure, a hydraulic valve in the injection cylinder will increase or decrease hydraulic pressure.
Also in Chicago, Arburg showed its midsize models, including a 520M-2000 machine that was molding stackable bins from regrind resin.