What Causes Core Pin Bending Injection Molding

Core pin bending in injection molding can result from several factors related to the process, materials, and equipment. Here are the main causes:

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1. High Injection Pressure:
   • Excessive injection pressure can exert a high force on the core pin, leading to bending or deflection.
2. Improper Gate Location:
   • If the gate is improperly located, the flow of molten plastic can create uneven forces on the core pin, causing it to bend.
3. High Melt Temperature:
   • High melt temperature can reduce the viscosity of the plastic, increasing the force on the core pin during injection.
4. Poor Core Pin Design:
   • Insufficient diameter, length, or inadequate material strength of the core pin can make it susceptible to bending under injection forces.
5. Inadequate Support:
   • Lack of proper support for the core pin within the mold can cause it to bend under pressure.
6. Non-uniform Cooling:
   • Uneven cooling can lead to differential shrinkage and stress on the core pin, causing it to bend.
7. Material Selection:
   • Using a core pin material that is not strong enough to withstand the injection and holding pressures can result in bending.
8. Mold Misalignment:
   • Misalignment of mold components can cause uneven distribution of forces, leading to core pin bending.

Mitigation Strategies

1. Optimizing Injection Pressure:
   • Adjust the injection pressure to a level that is sufficient for proper filling without exerting excessive force on the core pin.
2. Gate Location and Design:
   • Ensure that the gate is properly located and designed to distribute the flow evenly and reduce the force on the core pin.
3. Temperature Control:
   • Maintain appropriate melt temperatures to control the viscosity of the plastic and minimize force on the core pin.
4. Strengthening Core Pin:
   • Design core pins with appropriate dimensions and use materials with higher strength and rigidity.
5. Providing Adequate Support:
   • Ensure that the core pin is well-supported within the mold to withstand injection forces.
6. Uniform Cooling:
   • Implement uniform cooling methods to reduce differential shrinkage and stress on the core pin.
7. Material Selection:
   • Choose core pin materials that are strong enough to withstand the injection molding pressures.
8. Mold Alignment:
   • Regularly check and maintain the alignment of the mold components to ensure even distribution of forces.

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