What are the factors affecting precision injection molding?

 Precision injection molding generally refers to a process that requires high precision and surface quality of molded parts. It is also believed that precision injection molding refers to an injection molding process with a dimensional accuracy of 0.01 to 0.001 mm. In recent years, with the rapid development of electronics, medical care, communications, automobiles, and other industries, people’s requirements for high precision and high performance of plastic products are increasing day by day. Traditional plastic molding processes have been difficult to meet the current high standards. At the same time, injection molding is one of the most important plastic molding methods. Therefore, the precision injection molding technology has received more and more attention, which has made the precision injection molding technology continue to advance and new technologies continue to emerge.

Precision injection molding requires products not only to have high dimensional accuracy, low warpage deformation, excellent transfer characteristics, but also excellent optical properties, etc. Therefore, it is important for injection molding machines, injection molds, molding processes, and raw materials. Performance and formula have special requirements, and there are many factors that affect precision injection molding.

According to the current actual production, the difficulties of precision injection molding mainly include the following aspects:

(1) Plastic shrinkage rate: When designing precision plastic products, the shrinkage rate of plastics should be considered.

(2) Product shape and size: The shape and size of the plastic part have a great influence on the accuracy of the part. Production practice shows that the more complex the shape and the larger the size of the product, the lower the accuracy.

(3) Mold structure: The accuracy of injection molded parts is closely related to the number of mold cavities and production batches. It also shows that the precision of the single-cavity mold structure is higher than that of the multi-cavity mold structure, and the precision of small batch production is higher than that of large batches.

(4) Mold processing accuracy: Since the injection molded product must be molded in the mold cavity, the accuracy of the product will never exceed the accuracy of the mold cavity. Under normal circumstances, the accuracy of injection molded products is one to two tolerance levels lower than the accuracy of the mold. As far as the current mold manufacturing technology is concerned, most of the mold cavities are manufactured by high-speed milling, grinding, polishing, or electrical machining, etc. These processing methods can achieve the highest precision required.

(5) Injection molding machine: Because precision injection molding has higher precision requirements for products. Therefore, they generally need to be carried out on a special precision injection molding machine. The injection power of the precision injection molding machine must be large, the control accuracy must be high, the response speed of the hydraulic system must be fast, and the mold clamping system must have sufficient rigidity.

Selection of precision injection molding plastics The shrinkage rate of plastic products fluctuates greatly during molding. In addition, due to the different types of polymers and additives used in different plastics, their flow performance and molding performance during injection molding will be different. There are big differences. Due to factors such as the manufacturer, the factory season, and environmental conditions, there are also problems with the stability of the shape and size of the products molded by them.

Therefore, in addition to having good flow properties and molding properties, precision injection molded plastics also require shape and dimensional stability. Otherwise, the accuracy of the product is difficult to guarantee. Therefore, when injection molding precision plastic products, we must consider the variety of plastics and their molding properties, and choose materials with low shrinkage and good long-term stability as much as possible.