The layout principle of Ejector Pin

Ejector pins are the “bouncers” of the injection molding world. They apply a force to eject a part from the mold, and in some cases can leave marks. … Once the mold is opened, the pins extend into the mold cavity, push the part out, and then retract, allowing the mold to close and be refilled.

The ejection of a plastic product is the last step in the plastic injection molding process. The quality of the ejection determines the quality of the plastic product. When the mold opens, the plastic product must be retained on the mold half (usually the core) with the ejector mechanism that is used to release the plastic product.

     1.The ejector pin layout should make the ejection force as balanced as possible

The demolding force for complex structures is relatively large, so the number of ejectors should be increased accordingly.

2. The ejector pin should be set in effective places

The effective places include the rib, column, step, metal insert and other complex structures. The ejector pin on both sides of the rib and column should be arranged symmetrically as much as possible. In addition, try to ensure the ejector pin on both sides of the column position.

3. Avoid arranging ejector pinon the inclined surface or overstepping

The top surface should be as smooth as possible, and we should arrange it in the structural part of the rubber with better force.

4. Flat ejector pin should be chosen in some cases

In the deep rib (depth ≥20mm) or it is difficult to arrange the dome ejector pin, we should adopt flat ejector pins. When we use it, try the insert form to facilitate processing.

5. Avoid sharp and thin steel

When layout the ejector pin, we should avoid those sharp and thin steel. And the top surface of the ejector pin should not touch the cavity side.

6. Consider the distance between the ejector pin and the waterway

Avoid affecting the processing and water leakage of the waterway.

7. Consider the exhaust function of the ejector pin

In order to exhaust during ejection, it should be arranged in the part which is easy to form a vacuum. For example, in the larger plane of the cavity, although the packing force of the rubber part is small, it is easy to form a vacuum, which leads to an increase in the demolding force.

8. The ejector pins cannot be placed in some places

For plastic parts with appearance requirements, it can not be in the appearance surface, and we should adopt other ejection methods. For transparent plastic parts, it can not be arranged in the part that needs to transmit light.

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