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  • Have you encountered these problems during the injection molding process?

Have you encountered these problems during the injection molding process?

The wavy pattern on plastic parts

When the dissolved plastic pushes the cured part forward due to the narrow gate or other parts, the surface will have a wavy pattern. 

1 Increase the diameter of the injection nozzle; 2 Increase the temperature of the injection nozzle and mold; 3 Increase the temperature of the barrel; 4 Increase the injection speed; 5 Slow down the injection rate; 6 Change the cooling water inlet level of the mold so that it is far from the gate; 7 Enlarge the gate.

The plastic parts appear silver pattern

Due to water content of plastic, uneven mixing, air entrapment during injection, too many additives or mold release agents.  

1 Strengthen the backpressure; 2 Slow down the injection speed; 3 Clean the barrel; 4 Increase the mold temperature; 5 Change the gate position; 6 Enlarge the runner and gate; 7 Bake the material; 8 Install infrared light in the hopper.  

Bad plastic interface

The plastic temperature is too low to dissolve or the gas discharge is not enough to cause the mixing of more than two strands of shunts and produce fine lines of hair or bubbles. 

1 Increase the material temperature; 2 Increase the nozzle temperature; 3 Increase the injection speed; 4 Set up a cold pool at the seam line; 5 Add a venting port; 6 Change the gate position or increase the gate; 7 Do not use mold release agent; 8 Switch to low viscosity raw materials that flow easily.

Hollow in plastic parts

The cavity is caused by the surface of the plastic contacting the low-temperature mold wall during the curing of the melt, and the shrinkage is concentrated in the thick wall section, or the cavity is caused by air entrapment. 

1 increase injection pressure and secondary pressure; 2 extend injection time; 3 lower the barrel curing temperature; 4 reduce the mold wall thickness to less than 6mm, set equal wall thickness rib line if necessary, and remove excess wall thickness; 5 enlarge the gate; 6 shorten the runner; 7 even out the mold temperature; 8 change the gate position to eliminate air entrapment.

Under-injection of plastic parts

Due to insufficient mechanical injection and plasticizing performance, bad material flow or lack of material, too thin gate section, too thin mold wall, or bad air release. 

1 increase the injection rate, if still insufficient, change to a bigger machine; 2 install anti-leakage injection valve screw; 3 increase the injection pressure; 4 increase the barrel, injection nozzle curing, and mold temperature; 5 check the electric heating fault; 6 checks whether the injection nozzle is blocked, increase the cycle speed; 7 improve the mold bleeding capacity; 8 increase the gate cross-section; 9 increase the product wall thickness; 10 add helpline, transform the material flow; 11 choose low-viscosity raw materials; 12 add lubricant.

Extruding plastic by closing the mold

Due to high material temperature or injection pressure, or insufficient clamping force, mold defects.

1 lower the injection pressure or barrel temperature; 2 shorten the injection time; 3 reduce the injection rate; 4 change to high clamping force machinery; 5 modify the clamping surface and clean the clamping surface; 6 switches to low-viscosity raw materials.

Dents on the surface of plastic parts

Dents on the surface of the molded part are caused by the wrong cooling time.

1 Increase the injection rate; 2 Increase the pressure in the mold groove; 3 Lower the barrel temperature; 4 Increase the injection flow rate; 5 Increase the injection rate; 6 Extend the injection time; 7 Make the mold temperature uniform; 8 Change the gate position; 9 Enlarge the gate; 10 Shorten the mold runner.

The plastic part is twisted and deformed

The plastic part is distorted due to the relaxation of residual stress. 

1 lower the injection pressure; 2 lower the barrel temperature; 3 extend the cooling time; 4 adjust the wall thickness of the plastic part and adjust the release lock action; 5 install additional release locks; 6 change the gate position; 7 adjust the mold temperature.

The plastic parts stick to the mold cavity

Due to the fine taper of the mold, too high injection pressure or bad model. 

1 lower the injection pressure; 2 lower the barrel temperature; 3 increase the mold taper; 4 improve the model and remove the groove; 5 adjust the mold temperature; 6 switches to materials with good mold release.

The surface of the plastic parts appear lines or discoloration

The plastic decomposes due to overheating and the marquee ring wears out.

1 lower the barrel temperature; 2 shorten the intermediate operation time; 3 reduce the injection speed; 4 increase the air release rate of the mold; 5 enlarge the gate; 6 replace the wear-resistant head and head ring.

Color deviation of plastic parts

The color deviation is caused by the temperature of color powder and mechanical cleaning. 

1 adjust the temperature of beer and plastic; 2 clean the machinery; 3 deviations of the raw material color base; 4 uneven mixing; 5 change the machinery; 6 deviations of color powder; 7 different molds; 8 baking material.

The color starting point of plastic parts

Due to pigment diffusion performance or operation procedure problem.

1 Adjust the reel time; 2 Increase the spreading oil; 3 Increase the diffusing agent or diffusing oil; 4 Sieve the color powder through.

Black pattern on plastic parts

The black pattern is caused by the operation, cleaning, and environmental problems. 

1 Mechanical cleaning, nozzle cleaning; 2 Reduce the amount of residual material; 3 Environmental cleanings; 4 Change to wear-resistant tipped fingers.

Streaking of plastic parts

The black pattern is caused by the pigment diffusion and molding process. 

1 Increase the backpressure; 2 Reduce the amount of residual material; 3 Extend the material storage; 4 Adjust the temperature; 5 Change the color powder; 5 Use diffusion agent.

Black spots on plastic parts

Black spots are caused by contamination.

1 Clean up the machinery; 2 Clean up the environment; 3 Replace the raw material; 4 Check whether the pigment is contaminated.

White spots on plastic parts due to white clouds.

White spots caused by temperature, mold, raw material, color powder diffusion performance, and rewinding procedure. 

1 adjust the temperature; 2 improve the mold; 3 switches to fast flow material; 4 add diffusing agent or oil to help; 5 check the reeling procedure if the color is light.
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