Mold Base Terminology - E

Early Ejector Return

Devices that use mechanical levers and toggles mounted on the mold to push the ejector plate back before the mold is fully closed.

EDM

Acronym that stands for electrical discharge machine. These machines are used for any shape or work piece, and any form or part shape that cannot be machined with a round cutter.

Ejection

Removal of the molded part from the mold by mechanical means or with compressed air.

Ejection System

The hydraulic or mechanical system of the machine that is used to move the ejector plate.

Ejector Bottom Plate

This plate is the back-up plate to all the of all ejector pinheads. It has stop pins mounted in it on the opposite side to keep the plate flat in the mold base. It has the knock out taps for the ejector rods, which requires it to be thicker than the retainer plate. It can also have water in it to keep the plate temperature stabilized with the rest of the mold base. If the mold base runs hotter than the ejector plate in a big mold the thermal expansion will cause the clearance to be too tight and the ejector pins will have premature wear and breakage.

Ejector Pins

These pins are mounted in the ejector plate to eject the part. It is important to note that the standard size ejector pin tolerances are too loose to provide the proper clearance in crystalline material and must be selected so the ejector pin clearance is small enough to prevent flash in-between the ejector pin and the ejector pin hole.

Ejector Retainer Plate

- This plate has counter bores in it and through holes for the ejector pins. It can also have guided bushing holes and return pins. It will have tapped holes that attach the bottom ejector plate to it.

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