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How to solve ejection issues?

Sep 23,2023 | Views: 1505


The injection parts stick to the mold, making it rather difficult for ejection.


Below are some reasons that caused the issue:

1. Too much injection materials.

2. Overhigh injection pressure, overlarge dwell pressure and overlong dwell time.

3. Overhigh melt temperature.

4. Overhigh mold temperature.

5. Incorrect design of draft.

6. Improper design of ejector unit, ejector pins and ejection force; no air intake device for the core, resulting in vacuum during ejection.

7. Rough molding surface of cavity.

8. Inadequate dosage of mold release agent or incorrect spraying.


Here are E-Mold’s solutions:

1. Avoid excessive injection of melt.

2. Reduce injection pressure and dwell pressure, shorten dwell time.

3. Reduce injection rate and barrel temperature, optimize dimension of nozzle, runner and gate, avoid overhigh shearing heating during the flow and filling of melt, so that the melt temperature can be properly reduced.

4. Property adjust mold temperature, since under overhigh temperature, the plastic parts can be easily stick to the mold, whereas too low temperature shall result in large molding shrinkage and high ejection resistance during ejection.

5. While ensuring proper retaining mode of plastic parts in the mold, increase drafts.

6. Use appropriate ejection mode and ejection mode and ejection parts in accordance with the structural features of plastic parts; carefully analyze the ejection resistance and its distribution, properly select section dimension of ejection pin, increase ejection force. As for plastic, parts such as containers with deep cavity and thin walls, an air intake unit should be applied to the mold core to avoid vacuum during ejection.

7. Reduce roughness for the surface of cavity, and at the final stage of polishing mold, the polishing should be done along the ejection direction of plastic parts.

8. Properly spray mold release agent and properly increase dosage of the agent at places with large ejection resistance.

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Louisa Xiao

Email : louisa@e-moldrapid.com

Tel : (+86)1345 0999 345

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