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Design of die-casting ejector system, ejector pin arrangement, synchronization, ejector pin failure and deformation prevention and control

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  • 解放時間: 2026-11-07

Design of die-casting ejector system, ejector pin arrangement, synchronization, ejector pin failure and deformation prevention and control
The ejection system is responsible for smoothly removing the casting from the mold cavity. Uneven ejection is the most common cause of pulling, deformation, whitening, and piercing. The ejection plan for foreign trade molds should be matched with the customer's machine in advance.
1、 Principle of top pin arrangement
Balanced layout with even center of gravity; Prioritize placement in locations with thick walls, hot spots, and strong rigidity; Avoid thin walls, exterior surfaces, and sealing surfaces; Add top pins to the inverted and deep reinforcement positions. The center of gravity of the casting must have a top pin to prevent tilting and pulling. Alloy wheel mold wheels often use a circular uniform protrusion.
2、 Top pin specifications and fitting tolerances
The commonly used ejector pin is SKD61, quenched and tempered; Cooperate with segment H7/h6, control the gap between 0.005-0.015mm; if the gap is too small, it will be locked up due to heat, and if the gap is too large, it will cause aluminum and flash. The top pin hole should be vented to prevent the back of the top pin from holding air and causing top marks.
3、 Top four types of failure
Top pin locking: temperature rise expansion, insufficient clearance, aluminum chip jamming; Top pin breakage: excessive force on a single point, too small diameter, stress concentration; Top out strain: unsynchronized top pins, mold sticking of castings; Top white/top convex: Local top force is concentrated, and the casting has not fully solidified.
4、 Synchronous control scheme
Top out plate with guide column and reset rod; Increase travel limit for large molds; Multiple top needle plates are synchronized with connecting rods; It is not allowed to push out the force unilaterally. The reset rod must be reset before the parting surface is closed to prevent mold collision.
5、 Top out and process linkage
Insufficient cooling, high temperature ejection of castings, and high susceptibility to deformation; Severe aluminum adhesion can take away the nitride layer on the surface of the top pin, accelerating wear. Prioritize nitriding treatment for the top pin to enhance wear resistance and anti stick aluminum. Low pressure casting results in slow cooling of castings and a narrower ejection temperature window. Google's "die casting ejection system design" is aimed at structural designers.
FAQ
Can the ejector pin be placed on the surface of A?
Try to avoid it as much as possible, and if necessary, make a sinking table and polish it later.
2. How to deal with aluminum running due to the large gap between the top pins?
Replace the top pin, grind the hole position, and control the fit clearance.
What are the reasons for the broken top pin?
Small diameter, concentrated force, and premature ejection of castings before cooling.
What is the function of the reset lever?
Ensure that the ejector plate is fully reset before closing the mold to prevent mold collision.
5. Should the back of the ejector pin be vented?
Yes, holding your breath will leave ejector pin bubble marks on the surface of the casting.
Is it better to have more ejector pins?
Excessive processing will increase the workload and increase the risk of aluminum leakage.
Why is a circular top ring preferred for wheel hub protrusion?
Uniform force distribution to avoid deformation of the wheel hub caused by single point protrusion.
8. Is it still easy for the top pin to stick to aluminum after nitriding?
Nitriding enhances wear resistance, and when combined with release agents and coatings, results in better performance.

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