Cell phone cases are an important branch of injection molding production. There are 2 major series of cell phone cases, hard rubber and soft rubber. Hard rubber materials generally have PC, PC/ABS, etc. Soft rubber materials generally have TPE (TPR, TPU, etc.), hard rubber materials are injection molding, soft rubber materials are also injection molding.
Soft rubber has many advantages, mainly resistance to stretching, not deformed, soft, good toughness, non-slip, impact resistance, good fall resistance. Disadvantages are easy to stick to dust, poor heat dissipation, hair "sticky", easy to lose color, the product is thicker. Soft plastic cell phone cover injection molding production later generally have to post-processing, such as screen printing, color printing, transfer printing, drip processing and other more complex. But the injection molding itself does not seem to be complicated but it is quite difficult. The defects that are easy to appear in the production of soft plastic cell phone cover injection molding: sticky mold, shrinkage, batch front, bubble, long cycle time. The solution of the above problems depends on good mold design, material selection, parameters and machine selection.
The case is a high-grade soft plastic cell phone case injection molding production. One of the high grade is reflected in the thickness, the thickness of common soft rubber is more than 1mm, but this product is only 0.55mm, the second is the material, high-grade TPE material. The size of the product is about 125*60*8mm, the single weight of the product is about 8g, and the total weight of the product with water outlet is about 30g.
First is the material, the customer has specified TPE. second mold design. This product is characterized by thin, too weak strength, easy to stick film, in order to increase the effect of release, double-sided with a local fine skin pattern design. Four sides of the power hole opening key and other structures with side core. In order to improve the production efficiency and consider the stability of the production, the mold cavity one out of one. Considering the beauty of the product, the mold parting line is designed at the bottom edge. Considering the low temperature of the mold, which is also a common practice for soft plastic injection molds, a three-plate design is used.
The runner is manufactured with direct fire pattern. The gate design is critical. There are generally 2 kinds of entry points for this type of mold in the industry.
1) It is the edge of the bottom edge. 2) At the part of the camera hole. Considering the beauty of our high-grade products, we adopt the camera hole water entry design, and at the same time, considering the exhaust, the camera hole water outlet part of the wall is empty. At the same time this split water outlet in the subsequent processing of punching and cutting to remove.
The third is the machine selection. Because the product is very thin, just the product body flow length ratio of about 120 / 0.55 = 220, and then take into account the water mouth, flow length ratio of about 250, such a large flow length ratio for the general machine is very long to eat, to use high-speed machine.
The fourth is the parameters. Parameter test process is more complex, mainly sticky mold problems, shrinkage and batch front problems. After several tests, the following parameters were determined. Low mold temperature, high material temperature, short injection time, precise switching position, and precise holding pressure. On this basis, the cycle time is gradually shortened.