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What are the common problems in mold injection

Update:18-09-2021
Summary:

Question 1: The surface of the plastic part is dented r […]

Question 1: The surface of the plastic part is dented
reason:
Because the surface of the plastic part is cooled by mistake, because of its surface dents.
Solution:
①Increase the injection rate; ②Increase the cavity pressure (secondary pressure); ③Reduce the curing temperature of the barrel; ④Increase the injection flow rate; ⑤Increase the injection speed; ⑥Extend the injection time; ⑦Make the mold temperature uniform; ⑧Change the gate Location; ⑨Enlarge the gate; ⑩Short the mold runner.
Question 2: The plastic part is silver-patterned
reason:
Due to the moisture content of the plastic, the mixing is not uniform, the air is trapped during injection molding, and there are too many additives or release agents.
Solution:
① Strengthen the back pressure; ② Slow down the injection speed; ③ Clean the barrel; ④ Increase the mold temperature; ⑤ Change the gate position; ⑥ Expand the runner and gate; ⑦ Dry the material; ⑧ Install infrared light in the material door.


Question 3: Extruding plastic while closing the mold
reason:
The material temperature and injection pressure are too high, or the clamping force is insufficient.
Solution:
①Reduce the injection pressure and cylinder curing temperature; ②Short the injection time; ③Reduce the injection speed; ④Use a high clamping force machine; ⑤Modify the clamping surface to tightly fit and clean the clamping surface; ⑥Switch to low-viscosity materials.
Question 4: Poor plastic interface
reason:
Because the temperature of the plastic is too low to melt, or due to insufficient gas excretion, two or more shunts are mixed, resulting in hair-like fine lines or bubbles.
Solution:
①Increase the material temperature; ②Increase the injection temperature; ③Increase the injection speed; ④A cold pool outside the seam line; ⑤Set a vent; ⑥Change the gate position or gate; ⑦Don't use mold release agent; ⑧Easy to switch to Flowing low-viscosity raw materials.
Question 5: Plastic parts are short of injection or lack of material
reason:
Due to insufficient mechanical injection and plasticization performance, poor material flow, too thin gate section, too thin mold wall or poor deflation.
Solution:
①Increase the injection rate. If it is still insufficient, replace heavy machinery; ②Install a leak-proof injection valve screw; ③Increase the injection pressure; ④Increase the barrel, injection nozzle curing and mold temperature; ⑤Check whether the electric hot line is broken; ⑥Check whether the injection nozzle is blocked and increase the circulation speed; ⑦Improve the mold deflation ability; ⑧Increase the gate cross section; ⑨Increase the product wall thickness; ⑩Add auxiliary wires to modify the material flow; ⑪Select low-viscosity raw materials; ⑫Add lubrication Agent.
Question 6: Plastic parts appear hollow
reason:
Because the surface of the plastic contacts the low-temperature mold wall during the solidification of the melt, the shrinkage is concentrated in the thick-walled section and causes a cavity, or it is made into a cavity due to air inclusion.
Solution:
①Increase the injection pressure (and secondary pressure); ②Extend the injection time; ③Reduce the curing temperature of the barrel; ④Reduce the thickness of the mold wall to less than 6mm, set equal wall thickness auxiliary lines if necessary, and remove excess wall thickness; ⑤Expand the casting Mouth; ⑥ shorten the runner; ⑦ adjust the mold temperature evenly; ⑧ change the gate position to eliminate air trapping.

 

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