Common failure causes and troubleshooting methods of plastic mold accessories (2)

5. The ejector rod is bent, broken or leaking. The self-made ejector rods are of better quality, but the processing cost is too high. Nowadays, standard parts are generally used, and the quality is poor. If the gap between the ejector pin and the hole is too large, leakage will occur, but if the gap is too small, the ejector pin will become stuck due to the increase in mold temperature during injection. What's more dangerous is that sometimes the ejector rod will not move and break when it is ejected for a normal distance. As a result, the exposed ejector rod cannot be reset during the next mold clamping and will damage the die. In order to solve this problem, the ejector rod was re-ground, and the mating section of 10~15 mm was retained at the front end of the ejector rod, and the middle part was ground 0.2 mm smaller. All the ejector rods must be strictly checked after assembly, and the clearance is generally within 0.05~0.08 mm. It is necessary to ensure that the entire ejector mechanism can move forward and backward freely.
6. Poor cooling or water leakage. The cooling effect of the mold directly affects the quality and production efficiency of the product, such as poor cooling, large shrinkage of the product, or uneven shrinkage, resulting in defects such as warping deformation. On the other hand, the overall or partial overheating of the mold prevents the mold from forming normally and stops production. In severe cases, the movable parts such as ejector rods are thermally expanded and jammed and damaged. The design and processing of the cooling system depends on the shape of the product. Don't omit this system because of the complex structure of the mold or the difficulty in processing. Especially for large and medium-sized molds, the cooling problem must be fully considered.
7. The fixed-distance tensioning mechanism fails. Fixed-pitch tensioning mechanisms such as swing hooks and buckles are generally used in fixed mold core pulling or some secondary demolding molds. Because such mechanisms are set in pairs on both sides of the mold, their actions must be synchronized, that is, The mold is buckled at the same time when the mold is closed, and the mold is unhooked at the same time when the mold is opened to a certain position. Once the synchronization is lost, it will inevitably cause the template of the drawn die to be skewed and damaged. The parts of these mechanisms must have higher rigidity and wear resistance, and it is difficult to adjust. The life of the mechanism is short. Avoid using it as much as possible. You can switch to other mechanisms. When the core pulling force is relatively small, the spring can be used to push out the fixed mold. When the core pulling force is relatively large, the core can be used to slide when the movable mold is retracted. A hydraulic cylinder can be used to pull the core on the mold. The oblique pin slider core pulling mechanism is damaged. The more common problems of this kind of organization are mostly inadequate processing and too small materials. There are mainly the following two problems.
The oblique pin inclination angle A is large, and the advantage is that it can produce a larger core pulling distance in a shorter mold opening stroke. However, if the inclination angle A is too large, when the extraction force F is a certain value, the bending force P=F/COSA of the inclined pin during the core pulling process is larger, and the inclined pin deformation and the inclined hole wear are prone to occur. At the same time, the upward thrust N=FTGA generated by the inclined pin on the slider is also greater, which increases the positive pressure of the slider on the guide surface in the guide groove, thereby increasing the frictional resistance of the slider when sliding. It is easy to cause uneven sliding and wear of the guide groove. According to experience, the inclination angle A should not be greater than 25
8. Some molds are limited by the area of ​​the template, and the length of the guide groove is too small. The slider is exposed outside the guide groove after the core pulling action is completed. This will easily cause the slider to tilt during the core pulling stage and the initial stage of mold closing and resetting, especially in When clamping the mold, the slide block is not reset smoothly, which damages the slide block and even breaks it under bending. According to experience, after the slider completes the core pulling action, the length left in the chute should not be less than 2/3 of the full length of the guide groove.
9.Finally, when designing and manufacturing the mold, it should be based on the requirements of the quality of the plastic parts, the size of the batch, the requirements of the manufacturing period, etc., which can not only meet the requirements of the product, but also the most simple and reliable mold structure, easy to process, and cost-effective Low, the production of such a mold is excellent.