There can be several reasons for the demolding difficulties of injection molded products. Some of the main reasons include:
1. Undercut or complex geometry: If the product design includes undercuts or complex features, removing the molded part from the mold can make it challenging. Undercuts are regions where the part geometry extends inward or outward, creating obstacles for easy demolding. Special mold features like side actions, slides, or lifters may be required to facilitate demolding in such cases.
2. Insufficient draft angle: The draft angle is the taper given to the vertical walls of the part to aid in its removal from the mold. If the draft angle is inadequate or absent, the part may get stuck in the mold, resulting in demolding difficulties. Ensuring sufficient draft angles based on the material and surface finish requirements is essential.
3. High part shrinkage: Some materials have a higher tendency to shrink during cooling, leading to tighter adhesion to the mold surface. This can make it challenging to remove the part without causing damage. Adjusting the mold design processing parameters or using mold release agents can help alleviate this issue.
4. Insufficient cooling time: If the part is prematurely ejected from the mold before it has cooled adequately, it may deform or stick to the mold surfaces. Sufficient cooling time should be provided to allow the part to solidify completely and reduce its adhesion to the mold.
5. Improper gate and ejector pin placement: The gate is where molten material enters the mold cavity. If the gate is correctly placed or ejector pins interfere with the part’s geometry, demolding can be easy. Proper gate and ejector pin placement should be considered during mold design to ensure smooth demolding.
6. Material selection: The choice of material can also influence demolding difficulties. Some materials have higher coefficients of friction or greater adhesion to the mold surfaces, making them more challenging to remove. Proper material selection is crucial, considering the desired properties and demolding characteristics.
To solve demolding difficulties, it is essential to carefully consider the part design, mold design, material selection, and processing parameters. Collaboration between designers, mold makers, and injection molding experts can help identify and mitigate demolding challenges early in the product development process.