Injection Molding of Profile-Like Plastic Parts
Extruded plastic profiles always exhibit a constant cross-section. The thickness of contours and ribs cannot be varied, Reinforcing ribs or fastening elements oriented transversely with respect to the direction of extrusion cannot be incorporated. Furthermore, the surface of profile-like extrudates cannot be textured in a defined manner. In contrast, with injection molding, long plastic parts can be designed with relative freedom in terms of direction, and have ribs, fastening elements and almost any surface texture. Until now, injection molding of long, thin-walled, profile-like plastic parts has always been limited by the flow properties of the resin.
The newly developed Exjection process combines the benefits of extrusion with those of injection molding. Using only a single gate, long profiles with integrated fastening, terminating, reinforcing and decorative elements can be produced economically in a single operation.
In the Exjection process, a mold insert is shifted transversely with respect to the machine’s lengthwise axis while the melt is being injected into the mold. Shifting of the insert in the mold creates unfilled space that is filled continuously with the incoming melt. To provide texture and eliminate sink marks, the melt is held under pressure at the gate.
Engel will be exhibiting the Exjection process during the K2007 on an all-electric e-motion Model 200/55 injection molding machine with a clamping force of 550 kN. The product molded will be a 930 mm long, thin-walled profile with a wall thickness of 1.2 mm. The Exjection process is well-suited for applications in the construction, automotive and aerospace industries. Typical applications include mouldings, seals and decorative elements.
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