Causes and solutions of flash in plastic injection molding

Flash, also known as overflow, burr or burr, usually occurs at the parting position of the mold, such as the parting surface of the dynamic mold and the static mold, the sliding part of the slider, the absolute gap of the insert and the pore of the ejector pin. The generation of flash is largely due to the failure of the clamping force of the mold or the machine. The following are several main causes of flash:

1. Insufficient clamping force of the machine:

– The maximum clamping force of the machine is not enough, and a machine with suitable clamping force should be selected.
– The hinge of the clamping machine is worn or the sealing element of the clamping cylinder is worn, resulting in oil dripping or backflow, which causes the clamping force to decrease.
– The heating system is out of control and the actual temperature is too high. It is necessary to check whether there are problems with the thermocouple, heating coil, etc.

2. Problems in mold design and component force in Electronic product shell processing factory:

– The mold cavity is unevenly distributed or the parallelism is insufficient, resulting in unbalanced force, resulting in local flash or local dissatisfaction. The runner should be set at the mass symmetry center as much as possible, without affecting the integrity of the product.
– Uneven force on the movable components or sliding cores in the mold can also cause flash.
– Poor mold exhaust, compressed air will cause the parting surface to expand and flash. A good exhaust system should be set up, or an exhaust groove should be dug on the parting surface.

3. Plastic characteristics:

– The fluidity of the plastic is too large or too much lubricant is added. The pressure, speed and temperature should be appropriately reduced, the amount of lubricant used should be reduced, and plastics with lower fluidity should be selected if necessary.

4. Processing and adjustment issues:

– The set temperature, pressure and speed are too high, and segmented injection should be used. Excessive injection time, holding time and feed amount will cause flash.
– When adjusting, the hinge of the clamping machine is not fully straightened, or the mold adjustment nut moves frequently during mold opening and clamping, resulting in insufficient clamping force and flash.
– The parallelism between the adjustment head and the diode is insufficient or the pressure of the adjustment system is too high.

5. Repeated occurrence of flash and dissatisfaction of parts:

– Uneven particle size of plastic raw materials leads to unstable feeding amount.
– Severe wear of the screw’s rubber head, rubber ring and rubber gasket may cause the melt to slide or flow back between the screw and the barrel, resulting in flash or dissatisfaction.
– The cooling system of the inlet fails, affecting the feed adjustment.
– The injection amount set by the barrel is insufficient, that is, the buffer pad is too small, resulting in unstable injection amount, flash or dissatisfaction of parts.

By identifying these problems and taking corresponding solutions, the flash phenomenon can be effectively reduced and the production efficiency and product quality of plastic injection molding can be improved.