Common mold problems and solutions in custom plastic injection molding services

In custom plastic injection molding services, the performance of the mold directly affects the quality and production efficiency of plastic products. The following are some common mold problems and their solutions.

1. Methods to prevent mold cracks

1. Causes of mold cracks

– Insufficient mold rigidity: The mold design is unreasonable, resulting in insufficient overall rigidity.

– Stress concentration at the corners of the mold cavity: Stress concentration is prone to occur at the corners of the mold cavity, leading to the appearance of cracks.

2. Related knowledge

– Wall thickness design: The wall thickness design of the mold is one of the key parameters, and strength calculations are required to ensure the necessary thickness of the mold. The overall rigidity of the mold can be improved by adding grooves.

– Corner processing: The corners of the mold cavity should be processed into a rounded R shape to reduce stress concentration and avoid crack formation.

3. Solution

– Process the corners of the mold cavity into a rounded R shape, and process the grooves on the mold parting surface to enhance the rigidity of the mold.

2. Methods to prevent mold sticking and bending

1. Causes of mold sticking and bending

– Insufficient mold rigidity: Insufficient rigidity due to unreasonable mold design.

– Expansion caused by injection pressure: Excessive injection pressure may cause mold expansion and affect molding.

2. Related knowledge

– The cavity will expand slightly under the action of injection pressure. If the mold fails to return to its original state in time, it may generate a reaction force during the cooling and solidification process.

3. Solution

– Immediate management: Control the injection pressure to ensure that it does not exceed the set value.

– Long-term solution: Set grooves to force the mold shape to enhance its rigidity.

3. Causes and solutions for mold pin breakage

1. Causes of demolding pin breakage

– Insufficient toughness: The demolding pin has insufficient toughness, which makes it easy to break.

– Incomplete root rounded corner R: Improper rounded corner treatment at the root of the demolding pin can easily cause stress concentration.

2. Related knowledge

– The demoulding pin hole is related to the position of the mold locking screw. The slender demoulding pin is easy to bend and break under the molding pressure.

3. Solution

– Heat treat the demoulding pin to improve its toughness and hardness to ensure that it is not easy to break during use.

IV. Methods for removing products remaining in the mold cavity

1. Use a brass sheet to squeeze into the mold gap and gently pry the product out of the mold cavity. Be careful when using non-iron alloy molds.

2. A brass sheet with a thickness of 3MM and a width of 300MM is available on the injection molding machine. The front end is molded into a knife shape to squeeze into the gap.

3. Using a screwdriver may cause damage to the mold, so it is not recommended.

4. For products that cannot be cut or cracked, use a blowtorch to heat it to soften it and then remove it. Be careful to stay away from flammable materials.

5. For small pieces of residue, you can apply a solvent such as acetone, wait for it to dissolve, and then remove it with a brass rod.

5. Methods to prevent mold rust

1. Causes of mold rust
– Products of mold material decomposition: gas and residue will corrode the mold.
– Mold rehumidification: moisture forms water droplets on the mold surface, causing rust.

2. Related knowledge
– Chrome plating can prevent mold rust, but it has limited effect on deep corrosion.

3. Solution
– Short-term countermeasures: wipe the surface of the mold cavity with a dry cloth to ensure that the molding material is fully dry.
– Long-term countermeasures: Use materials that are not easy to decompose and spray rust inhibitors when the mold is out of use.

Conclusion

In customized plastic injection molding services, it is crucial to understand and solve mold-related problems. Through reasonable design, material selection and appropriate