How to Assemble Pins for Ejector Block Systems
Key Takeaway: Block pins are press-fit into the ejector plate with 0.01–0.02mm interference. Pin protrusion must be 2–3mm longer than the longest ejector pin to ensure the plate is fully returned before mold close.
Installation Steps
- Ream ejector plate bore to H7 tolerance (the pin will be a light press-fit).
- Press-fit the pin using an arbor press. Apply steady force — do not hammer (this damages the pin head and can crack the plate).
- Verify protrusion: The pin tip must extend 2–3mm beyond the longest ejector pin. Measure from the ejector plate face.
- Check perpendicularity: The pin must be perpendicular to the plate face within 0.02mm over the pin length. Use a square and feeler gauge.
- Test return: Manually push the ejector plate forward and release. The block pins should contact the A-plate face and push the plate back smoothly.
Common Installation Errors
- Pin too short: If pin protrusion is less than 2mm longer than ejector pins, the ejector plate may not fully return before mold close, causing pin damage.
- Pin too long: If pin protrusion is excessive (>5mm), the block pin absorbs excessive closing force, leading to premature pin mushrooming (tip deformation).
- Wrong material: Using M2 or H13 pins instead of S45C will damage the A-plate contact surface. Block pins must be softer than the mold plate.