PC high precision plastic injection mold parts meet two problems were encountered: weld lines and brittle moldings?

The high precision plastic injection mold parts Weld Line

Weld lines are caused by the cooling of the front end portion of the molten resin from different directions and the incomplete fusion at the joint.

(1) The reasons are as follows:

①The material is too cold

②The size of gate or runner is too small

③Mold temperature is too low

④Nozzle runner hole is too small

How to do?

①Adjust molding conditions to improve fluidity. For example, increase the material temperature, increase the surface temperature of the injection mold, increase the injection pressure and speed, etc.

②Adding an exhaust groove, increasing the diameter of the gate or runner, and setting a push rod at the place where the weld line occurs is also conducive to exhausting.

③ Minimize the use of mold release agents.

④Set the process flash as the place where the weld line is generated, and then cut and remove it after forming.

⑤ If it only affects the appearance, you can change the burning position to change the position of the weld line. Or the part where the weld line is generated is treated as a dark glossy surface, etc., to be modified.

When the PC high precision plastic injection mold parts face to fragile

It is manifested that the injection molded parts are broken during ejection, or are easily broken after ejection. Most of the brittleness is caused by internal stress. There are many reasons for the brittleness of products. The factors involved may include injection molding machines, molds, processes, raw materials and product design.

(1) Injection molding machine

①There is no dead angle or obstacle in the barrel, which can easily promote the degradation of the melt, and needs to be thoroughly cleaned.

②The plasticizing capacity of the machine is too small, and the plastic is not sufficiently plasticized in the barrel; the plasticizing capacity of the machine is too large, the plastic is heated and sheared in the barrel for too long, and the plastic is easy to age, making the product brittle, Therefore, the plasticizing capacity should be increased.

③ The ejector device is inclined or unbalanced, the ejector cross-sectional area is small or the distribution is improper, and it should be adjusted according to the specific situation.

(3) high precision plastic injection mold process

①The temperature of the melt glue is too low, and the plastic raw materials are easily degraded, so the temperature of the barrel (rear area) and the temperature of the nozzle should be increased.

②The melting temperature is too high, and the plastic raw materials are easily degraded. It is necessary to reduce the barrel temperature in each area and the pre-plastic back pressure and speed of the screw.

③If the mold temperature is too high, it will be difficult to demold; if the mold temperature is too low, the plastic will be cooled prematurely, and the fusion seam will be poorly fused and easily cracked. Set the appropriate mold temperature.

④Increase the injection speed to ensure the fusion strength.