Core pull systems are another method used to free a hole core that is not in line with ejection travel. It must be cleared before ejection or damage will occur. Typical methods used to pull the core are air cylinders, hydraulic cylinders and motor driven rack and pinions. Timing of the cylinder is independent of the mold action.
Core Pull System – Application
This drawing shows a typical application of a core pull system. A hole in the molded part is required 90 degrees to ejection travel. An air or hydraulic cylinder is used to pull the core pin away before part ejection and to close it for perfect shut-off on the core.
Core Pull System – Actuation
In the situation shown here, the core pull pin must be pushed forward by the air or hydraulic cylinder to shut off on the core. After mold cooling and before part ejection, the cylinder must pull the core pin out of the molded hole. Timing on the cylinder can be set independent of the mold action. Then the mold opens at the parting line and the molded part is ejected from the mold by the stripper plate.
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