The external and internal shapes of plastic injection molds are directly formed by the cavity and core. These complex three-dimensional surfaces are difficult to machine, especially the blind hole type inner forming surface of the cavity. If traditional machining methods are used, it not only requires high level of workers' skills, but also many auxiliary tools and cutting tools, and the machining cycle is long.
As the production batch of molds is small, they generally belong to single-piece production. However, molds require many standard parts, from large mold frames to small ejector pins. It is impossible for these parts to be completed by a single manufacturer alone, and the manufacturing process is complex, with uneven use of ordinary equipment and CNC equipment.
The dimensional accuracy of the plastic parts is generally required to be IT6-7, and the surface roughness is Ra0.2-0.1μm. The corresponding dimensional accuracy of the plastic injection mold parts needs to reach IT5-6, and the surface roughness needs to be below Ra0.1μm. The roughness of the laser disc recording surface needs to reach the level of mirror processing at 0.02-0.01μm, which requires the surface roughness of the mold to reach below 0.01μm. Long-life injection molds are necessary to improve efficiency and reduce costs. Currently, the service life of injection molds is generally required to be more than one million times. Precise injection molds require a high stiffness mold frame, increased template thickness, and increased support columns or conical positioning elements to prevent deformation of the mold under pressure, which can sometimes reach 100MPa. The ejector device is an important factor affecting product deformation and dimensional accuracy, so the optimal ejector point should be selected to ensure uniform mold release. High-precision injection molds mostly use inlaid or full-fit structures in their structure, which requires a significant improvement in the machining accuracy and interchangeability of mold parts.
Mold manufacturing is not the end goal, but rather, mold manufacturers design and manufacture molds based on the customer's final product design requirements. In most cases, plastic injection molding production of the product is also done by other manufacturers. This creates a situation where product design, mold design and manufacturing, and product production are carried out in different locations.
For injection molded parts, most of them are matched with other components to form a complete product. In many cases, they are waiting eagerly for the injection molded parts to be ready when other parts have already been completed. Because of the high requirements for the shape or dimensional accuracy of the product, and the fact that resin materials have different properties, after the injection mold is completed, it needs to be repeatedly tested and corrected, making the development and delivery time very tight.