The problem of appearance strain of injection molding products has always been a relatively difficult problem in injection molding industry, especially in the products with high appearance requirements, such as coating products, lamp mirrors, and products with special appearance marks on the surface. In addition to mold design and mold processing defects, such as drawing Angle is not enough, poor polishing of the mold, local position inverted, unreasonable positioning of the mold, injection molding machine aging, front and rear plate parallelism is not good. What details should be paid attention to to avoid in the process?
Ⅰ Too much pressure
1, Product parts in the process of injection molding pressure is too high, leading to the product in the cavity is too full to produce strain.
2, The product parts in the process of injection molding pressure is too large to lead to the local position of the stress is too large to make the product parts warped deformation, deformation position is just close to the inner wall of the mold cavity, mold opening will inevitably produce strain. This is also why some products are always in the same position of the strain repeatedly not easy to remove the reason.
3, The product parts in the process of injection molding pressure is too large, resulting in no shrinkage space after cooling, the product parts as a whole attached to the mold cavity internal vacuum adsorption phenomenon (especially mirror products with deep concave products). When the mold is opened, the local position of the product will move first so that the product will be misaligned. After the misalignment, the local position of the product will inevitably be close to the mold cavity.
Ⅱ Temperature influence
1. The local temperature of the mold is overheated, which leads to the deformation and strain of the injection molding in the local position of the product. We can use a point thermometer to check. In addition to the mold design reasons (such as the slender core can not increase the waterway to lead to heat dissipation, the design of waterway is not considered properly, etc.), we need to check whether the mold waterway is smooth, mold temperature machine connection is wrong and other waterway problems can be solved. Sometimes the problem can even be caused by a pipe with a thick gasket that causes a pipe to blow out.
2. In the process of injection molding, in order to meet some special requirements, such as molding problems, surface finish problems, melting problems, etc., the screw temperature needs to be increased, and the material makes the material flow after increasing the temperature, so that the required pressure is reduced, and the cooling time becomes longer. Not adjusting the pressure at high temperatures will result in excessive injection pressure. If the cooling time is not adjusted, the product will be overheated at the time of mold release, resulting in reduced strength and strain.
Ⅲ The impurities
1. When closing the mold, the parting surface of the mold is partially hit too heavy. In the repeated opening and closing of the mold due to collision produced similar to rust like ash. When the mold is repeatedly opened and closed, it falls into the mold cavity and is injected again. This kind of defect needs the mold to cooperate gradually to make the local collision reduce. Temporary measures in production can be applied to the corresponding position of a layer of white oil.
2. The failure of the local position of the mould leads to the pulling off of the foams. This kind of defect is easy to occur in the matching of inclined guide column and slide block. It's easy to spot on the mold. Such problems need to be timely maintenance and increase the frequency of maintenance.
3. Impurities in the air (such as toner, foam, dust, etc.) may also form such defects, which should improve the 5S work on site.
4. The mold will produce a certain vibration when opening and closing the mold. If the product needs high mold temperature for a long time, the maintenance oil of the mold will be dried or deteriorated, and some dust and other impurities will be wrapped in the maintenance oil.
Ⅳ Clamping force
The setting of clamping force is absolutely not how much clamping force is used in the equipment, but the lower the better to meet the needs of production. This will not only prolong the life of the injection molding machine, reduce energy consumption, but also make the collision between the mold and the mold lighter. In this way, the local position of the die is turned over or crushed because of too much clamping force. Strain is inevitable when the mold turns over.
In short, in order to the output of qualified products, in order to improve the qualified rate, in the actual production process to treat different problems to learn how to accurately and quickly judge. Grow up in constant learning a