Engel designed a new toggle clamp for this line, focusing on high speed and extremely quiet operation. The ratio between locking cylinder speed and platen is relatively constant across the large stroke range to ensure an optimized sequence of movements independent of the opening stroke. To save time at the end of the closing stroke, the toggle doesn?t move all the way to lock. Instead, part of the clamping force is transmitted to the mold by the clamping cylinder.
Engel says high clamp rigidity permits a mold-open force of 10-15% of clamp force, which is needed for parts with negligible draft and/or undercuts, such as those found on tubs and other bucket-type containers. The moving platen is guided by a mechanism mounted on the machine frame for stability. The tiebars play no role in guidance, and in fact do not make contact with the moving platen. The guide unit extends far enough beyond the platen to ensure that even large, heavy molds do not tilt.
The Speed Series? newly developed injection units use barrier screws optimized for typical packaging materials such as PS, PP, or HDPE, with a peripheral rotating speed of 1 m/sec or more for high feedrates plus gentle melt handling. The screw drive and its rotating plunger are in the extension of the screw axis and torque is transmitted via an integrated friction clutch that eliminates any notch effects from a positive clutch. This lengthens the machine somewhat, but Engel says it considerably reduces the mass that is accelerated during injection while supporting advance speeds of more than 1000 mm/sec. The needed injection pressure of more than 2000 bar (29,000 psi) is a standard feature. Optional electric screw drives offer still higher screw speeds and feedrates.
Dry cycle time on the Speed Series is 1.1-2.2 seconds, depending on machine size. At Fakuma, a 275-ton Speed system made yogurt cups using a six-cavity mold from Systec Komplettsysteme (Ulrach, Germany) and an Engel ERS 1 (Speedy) robot for removal. An Engel ERC 13 robot stacked the parts in cartons, and total cycle time was less than 3 seconds.?RN
IMM - January 2006