Technical Guide3 min read

How to Prevent Rotation in Free-Flange Ejector Blades

Key Takeaway: Blade free-flange pins use a split-block clamp (not collet) for anti-rotation. The rectangular shaft profile locks against flat block surfaces, preventing rotation up to 400N ejection force.

Anti-Rotation Mechanism

Unlike round-shaft free-flange pins that use collets, blade-type free-flange pins use a split-block clamp. Two half-blocks clamp around the rectangular shaft and are secured by a through-bolt. The rectangular profile provides two benefits: (1) the flat faces prevent rotation mechanically, and (2) the clamp can be repositioned along the shaft for length adjustment.

Installation Tips

Align the blade orientation before tightening the through-bolt. Use a square to verify the blade is perpendicular to the mold parting line.
Tighten the through-bolt to 2.0–3.0 Nm for blade widths up to 6mm, and 3.0–4.0 Nm for widths above 6mm.
Verify anti-rotation by applying gentle twisting force after installation. The blade should not rotate.

Frequently Asked Questions

Can the split-block clamp loosen over time?+

Under normal ejection loads (<400N), the split-block clamp maintains position for 500,000+ cycles. For high-force applications, add a drop of medium-strength threadlocker to the through-bolt.

What if the blade rotates during operation?+

Increase through-bolt torque by 0.5 Nm. If rotation persists, the block bore may be worn — replace the flange assembly (blocks + bolt). Do not attempt to re-machine the blocks.