Milacron Demonstrates New Process for Two-shot Molding of Automotive Glazing without Rotary Tooling
Share:
Cost- and space-saving concept combines standard Cincinnati Milacron Maxima MG 1100, piggyback injection units, and coining with innovative Exatec mold
May 2006 - Milacron is teaming with Exatec to demonstrate at NPE a new process for two-shot molding of automotive windows without the cost, complexity or machine size required for rotary tooling. A Cincinnati Milacron Maxima MG 1100 two-platen press will mold a fixed sidelight of clear polycarbonate overmolded with black polycarbonate bezel. The approach combines Milacron's creative design for piggyback injection units with an innovative mold from Exatec. Milacron mounts the secondary injection unit on an innovative injection sled directly above the primary injection unit. The sled is mounted to the stationary platen offering superior alignment. "Piggybacking" the injection units reduces machine footprint and avoids compromises to the integrity of the stationary platen, points out Ron Hertzer, Director of Technology. "There is no impact whatsoever on the compact size of the press, while we're able to eliminate the need for two holes and any effect on platen stiffness."
The integrated molding system at NPE features a Milacron robot for part take-out. The robot places the part in an inspection box where an imaging sensor measures the bifringence of the part, then places it on a conveyor. The Maxima is equipped for quick-mold change (QMC) with Staubli magnetic mold clamping system and a tie-rod puller. About once an hour at NPE Milacron will demonstrate QMC capability.
"The superior parallelism provided by Maxima's direct-acting "pancake" ram makes it an excellent press for automotive window molding," says Hertzer. The direct-acting ram reduces effective platen deflection by 50 percent compared with typical two-platen designs that build tonnage on the corners, he notes. The large surface area of the ram distributes clamp force evenly across the back of the die plate, similar to a conventional three-platen machine. Fully supported strain rods, long guided length, and extra large skates all contribute to superior parallelism and stability.
The short stroke of the pancake ram helps minimize cycle times with full tonnage build in 0.6 sec., Hertzer notes. The Maxima design also allows fast breakaway at the end of the mold cycle with full decompression of the clamp and opening of the split nuts during cooling.
"Automotive glazing typically requires an injection/coining process to avoid stresses that can compromise optical quality," Hertzer explains. "In the NPE demonstration, the machine closes the mold to within less than 1mm of finished thickness of the part, then the part is filled. Full tonnage applies compression in the mold in the coining phase. A retractable core in the Exatec mold pulls back after the clear shot, creating the cavity for shooting the black boarder. Shot weights are 2.15 lbs. for primary injection, 8.4 oz. for secondary injection.
The Maxima MG 1100 comes standard with Milacron's new Mosaic control. The new control's operator panel is all-sealed, with an embedded operating system that requires no hard-disc drive or back-up power source. It has extensive capabilities for connectivity and security, with Ethernet LAN and Powerlink, dual USB ports, optional ID card reader, and web-based or network access to process data and machine status. The 15-inch touchscreen display includes standard multilingual and inch/metric support, setup wizards and a single-page overview of all critical set points. The Mosiac control is interfaced with the robot and a particle counter on the oil system.
The Maxima design combines a compact footprint with short cycle time and energy conservation to deliver
