A new line of liquid injection molding (LIM) machines has been introduced by Milacron Inc.'s Plastics Technologies Group of Batavia, Ohio. Milacron's first LIM machines are built around the company's "Prowler" open-frame presses in the 100-190 ton range with shot sizes of 3.51 to 28 oz.
According to product manager Jim Esser, the Prowler's large platen size is a good fit with LIM molding, which requires relatively low clamp pressure and is usually limited more by platen size.
LIM systems eventually will be available on all Milacron machines under 300 tons, including Vista V-Series toggle presses, Vector vertical machines, and Roboshot all-electrics. Milacron also plans to offer multi-shot systems that can mold both LIM and thermoplastics.
Milacron's standard LIM package includes a water-cooled barrel with a low-compression screw; cooling plates on both platens; and a pumping system from Fluid Automation Inc., Wixom, Mich. Controls are tailored to LIM molding, says Esser.
To minimize leakage, the injection unit features a water-cooled, pneumatic shut-off valve for the nozzle, while an end-cap seals the rear of the screw. Leaks are also prevented by constant hydraulic pressure on the nozzle against the sprue bushing throughout the molding cycle.
Options include pneumatic valve-gate controls that can shut off up to eight individual cavities.