Gas-assisted injection molding technology supplier Cinpres Gas Injection Ltd. has applied for patents on what it calls an improved variety of its plastic expulsion process, called PEP 4.
The goal is to link more precisely the plastic injection with the introduction of injected gas into the plastic melt, Cinpres said.
Under PEP 4, the initiation of the gas pressure cycle is started by a signal, when a predetermined pressure is reached during the injection of plastic from the molding press as it fills the mold cavity. The pressure may be detected with a sensor placed almost anywhere in the mold cavity or runners, or from the molding machine itself.
Also, the gas may be started by a signal from a position sensor, such as a linear displacement transducer that measures forward screw movement.
Cinpres said the advantage is that any variation in the speed of injection will change adversely the integration of the injection of plastic and the gas. PEP 4 can be installed easily, since Cinpres said its PPC and CPC gas controllers already allow for monitoring movement of the screw.
Another improvement to the PEP technique is the activation of the opening of PEP valves to allow the plastic to be expelled to fill overflow cavities, from a signal when the gas pressure reaches a selected pressure.
Cinpres is based in Middlewich, England. Its U.S. headquarters, Cinpres Gas Injection Inc., is in Ann Arbor, Mich.
Tel. (734) 663-7700, fax (734) 663-7615, e-mail [email protected]