1: The mold design of this product cannot be demolded, what should I do? 2: If the demolding slope is not done well, the mold cannot be demolded no matter how good it is! 3: It is actually not difficult to demold the mold pusher! 4: The structure of the mold slider (slide position), demolding is easy once you understand it! Cracking includes surface filiform cracks, micro cracks, top whitening, cracking, and trauma caused by mold sticking or runner sticking. According to the cracking time, it is divided into demolding cracking and application cracking. There are mainly the following reasons:
1. Processing:
(1) Excessive processing pressure, too fast speed, too much filling, too long injection and holding time will cause excessive internal stress and cracking.
(2) Adjust the mold opening speed and pressure to prevent demolding cracking caused by rapid and strong pulling of the parts.
(3) Appropriately increase the mold temperature to make the parts easy to demold, and appropriately lower the material temperature to prevent decomposition.
(4) Prevent cracking due to weld marks and plastic degradation causing low mechanical strength.
(5) Use mold release agent appropriately, and pay attention to frequently removing aerosol and other substances attached to the mold surface.
(6) Residual stress of the workpiece can be eliminated by annealing heat treatment immediately after molding to reduce the generation of cracks. 2. Mold:
(1) The ejection should be balanced, such as the number of ejector pins and the cross-sectional area should be sufficient, the demoulding slope should be sufficient, and the cavity surface should be smooth enough to prevent cracking caused by the concentration of residual ejection stress due to external force.
(2) The structure of the workpiece should not be too thin, and the transition part should be arc transition as much as possible to avoid stress concentration caused by sharp corners and chamfers.
(3) Use metal inserts as little as possible to prevent the internal stress from increasing due to the different shrinkage rates of the inserts and the workpiece.
(4) For deep-bottomed parts, appropriate demoulding air inlet channels should be set to prevent the formation of vacuum negative pressure.
(5) The main channel should be large enough to allow the gate material to be demoulded before solidification, so that it is easy to demould.
(6) The joint between the main channel bushing and the nozzle should prevent the cold hard material from being dragged and causing the part to stick to the fixed mold.
3. Material:
(1) The recycled material content is too high, resulting in low strength of the part.
(2) Excessive humidity causes some plastics to react chemically with water vapor, reducing strength and causing ejection cracking.
(3) The material itself is not suitable for the processing environment or is of poor quality, and contamination will cause cracking.
4. Machine:
The plasticizing capacity of the injection molding machine should be appropriate. If it is too small, the plasticizing will not be sufficient and cannot be completely mixed, making it brittle. If it is too large, it will degrade.
