Workpiece Ejection Systems

If a minimum of 0°30' conicity exists on any side of the workpiece without thread or undercut, useing ejector pins is the simplest means for removing the workpieces from the mold(Fig6.16).

Operation: following solidification of the plastic material, the injection mold opens and the Z-shaped puller 6 draws sprue out off the sprue bush. And following the support plate 5 of the mold impacts the ejector bar of the injection machine and prevents eiector plates 2 and support plate 5 from further movement, although the lower part of the mold is still in motion. Ejector pin 1 fixed between ejector plates 2 and support plate 5 lifts the workpiece off the cavity of mold.

When the mold is closed, the ejector pin I is returned to their initial position by a coil spring 9 (Fig. 6. 16b) or returning pin 7(Fig. 6. 16a). The spring 9 is dimensioned so as to function reliably even if the fitting gaps are soiled, otherwise the ejector pins I may be damaged during closing of the mold. In critical cases the mold with undercut and ejector pin that interferes each other. the use of return pins is recommended. The advantage is the mold in simple and inexpensive.