What is the cause of the flash of plastic parts and how to eliminate it?

(1) Defect characteristics

The main performance of plastic flash is that in the injection process, the melt spills into the gap between the mold and the remaining material on the plastic part, forming a thin flash.

(2) Causes of defects and their elimination methods

The main reason for the flash is that the clamping force is not enough during the injection and pressure holding process, or the mold can not be locked and sealed along the parting line, and the melt leakage is caused by. The specific analysis is as follows:

1) Injection mold

A. If the injection mold is rough, it can not be completely closed when the mold is closed, resulting in overflow, which should improve the manufacturing accuracy of the injection mold.

B. If the moving or fixed template is not parallel, or deformation occurs, so that the template does not close, or cannot close strictly and produce a flash, in this case, the installation requirements of the template should be checked and corrected.

C. If the sliding part between the cavity and the core is worn too much, and the excessive gap leads to the flash, the excessive worn part should be repaired in time.

D. If there is foreign body adhesion on the parting surface, so that the template can not close and produce a flash, in this case, it is necessary to wipe the foreign body on the parting surface in time.

E. If deflection or dislocation occurs when moving or fixing the mold, it is easy to produce flash, which should check whether the guiding mechanism is normal.

F. If the use of parting surface gap exhaust, the gap is too large when it is easy to produce flash, in this regard, should be appropriate to reduce the exhaust gap.

2) Injection molding process

A. If the temperature of the plastic melt is too high, the melt fluidity is good at this time, and the flash is easy to appear, in this case, the material and the temperature at the nozzle should be reduced.

B. If the injection pressure is too large, the plastic melt is easy to overflow through a small gap, in this regard, the injection pressure should be appropriately reduced.

C. The injection pressure is unevenly distributed in the cavity, which makes the filling rate different, and the pressure of each part of the mold is unbalanced and flash occurs. In this regard, the injection pressure and filling rate should be balanced.

D. If the injection amount is too much, the pressure in the cavity is too large, and it is easy to overflow, in this regard, the injection amount of melt should be controlled.

3) injection molding equipment

A. If the pull rod of the injection molding machine is deformed or uneven in length, so that the moving and fixing template is not tightly closed and produces A flash, the pull rod should be repaired in time.

B. If the clamping force is less than the injection pressure, the parting surface of the mold will be difficult to close and produce a flash, should check whether the supercharger is overpressurized, the product of the projected area of the plastic part and the molding pressure exceeds the clamping force of the injection molding machine. In addition, it can be replaced with a large pressure injection molding machine.

4) Plastic raw materials

A. Some plastic with good fluidity, such as PA, PS, PE, etc., is easy to produce A flash during molding, which can be properly reduced temperature to reduce its fluidity.

B. If the lubricant is used too much, the fluidity of the melt is excellent, easy to appear flash, in this regard, to control the amount of lubricant added.