Mold failure There are many reasons for bad sticking an […]
There are many reasons for bad sticking and demoulding, and mold failure is one of the main reasons. The causes and methods of handling products are as follows:
1. The surface of the mold cavity is rough. If there are surface defects such as chiseling, nicks, scars, and depressions in the cavity and runner of the mold, the plastic parts can easily adhere to the mold, resulting in difficulty in demolding. Therefore, the surface finish of the mold cavity and the runner should be improved as much as possible. The inner surface of the cavity is preferably chrome-plated. During the polishing process, the movement direction of the polishing tool should be consistent with the direction of the mold filling.
2. The mold is worn or scratched or the gap at the insert is too large. When the melt produces flash in the scratched part of the mold or in the gap between the inserts, it will also cause difficulty in demolding. In this regard, the damaged part should be repaired and the gap between the inserts should be reduced.
3. Insufficient mold rigidity. If the mold cannot be opened when the injection is started, it means that the mold is deformed under the effect of injection pressure due to insufficient rigidity. If the deformation exceeds the elastic limit, the mold cannot be restored to its original shape and cannot be used any more. Even if the deformation does not exceed the elastic limit of the mold, the melt is cooled and solidified under high conditions in the mold cavity to remove the injection pressure. After the mold is restored to deformation, the plastic part is clamped by the elastic force and the mold cannot be opened.
Therefore, when designing the mold, sufficient rigidity and strength must be designed. When testing the mold, it is best to install a dial indicator on the mold to check whether the cavity and the mold frame are deformed during the filling process. The initial injection pressure during the initial mold test should not be too high, and the deformation of the mold should be observed While slowly increasing the injection pressure to control the amount of deformation within a certain range.