The external and internal shapes of plastic parts are directly formed by the cavity and core. The processing of these complex three-dimensional surfaces is difficult, especially for the processing of the cavity blind hole forming surface. If the traditional processing method is adopted, not only the workers' technical level is high, but also there are many auxiliary fixtures, many cutters and long processing cycle.

High accuracy and surface quality requirements, long service life.

At present, the dimensional accuracy of plastic shell is generally it6-7, and the surface roughness is ra0.2-0.1 μ m. The dimensional accuracy requirements of corresponding injection mold parts are it5-6, and the surface roughness is ra0.1 μ Below M.

The roughness of the laser recording surface of the optical disc should reach 0.02-0.01 of the mirror processing level μ m. This requires the surface roughness of the mold to be 0.01 μ M below, long-life plastic shell mold is necessary to improve efficiency and reduce costs. At present, the service life of plastic shell mold is generally required to be more than 1million times.

For the precision plastic shell mold, the rigid large mold base should be used to increase the thickness of the mold, and the support column or conical positioning element should be added to prevent the mold from deforming after being pressed. Sometimes the internal pressure can reach 100MPa.

Ejection device is an important factor that affects the deformation and dimensional accuracy of plastic shell. The best ejection point should be selected to make the demoulding uniform everywhere. The structure of high-precision injection mold mostly adopts inlay or full inlay structure, which requires the processing accuracy and interchangeability of mold parts to be greatly improved.

Long process flow and tight manufacturing time.

For plastic shells, most of them are integrated products supporting other parts. Many times, other parts have been completed, waiting for the matching and listing of injection molded parts. Due to the high accuracy requirements of the shape or size of the plastic shell and the different characteristics of resin materials, the mold needs to be tested and modified repeatedly after being manufactured, which makes the development and delivery time very tight.

Design and manufacture in different places.

Mold manufacturing is not the ultimate goal. The final plastic shell design is put forward by users. Mold manufacturers design and manufacture molds according to users' requirements. In most cases, the injection molding production of products is also in other manufacturers. As a result, product design, mold design and manufacturing, and product production are all carried out in different places.

Professional division of labor, dynamic combination.

Mold production batch is small, which generally belongs to single piece production, but mold needs many standard parts, from template to thimble, which can not be done by one manufacturer alone, and the manufacturing process is complex, and the use of ordinary equipment and CNC equipment is extremely uneven. Adopting traditional processing methods requires not only high technical level of workers, more auxiliary fixtures and tools, but also long processing cycle.