How to prevent defects in transparent plastic parts processing?

July 12, 2017

I. Crack and Thread

 

(1) raw materials are not sufficiently dry. The pre drying temperature should be increased and the drying time should be prolonged.

 

(2) impurities in the raw material are mixed with foreign matter. Should be completely removed.


(3) the melt temperature is too high. The molding temperature should be properly reduced and the temperature distribution of the barrel can be adjusted.

 

(4) the injection pressure is on the low side. Should be appropriately improved.


(5) the design of the gating system is unreasonable. The layout of the runner and the size of the cross section shall be reasonably adjusted.

 

(6) forming period is too long. Should be properly shortened.


(7) the back pressure of screw is too high or too low. Should be adjusted appropriately.

 

Ⅱ. Moire and Fog halo

 

(1) the melt temperature is too low. The molding temperature should be increased properly.


(2) the injection pressure is too low. Should be appropriately improved.

 

(3) the screw back pressure is too low. Should be appropriately improved.


(4) Molding temperature is too low. Should be appropriately improved.


(5) impurities in the raw material are mixed with foreign matter. Should be completely removed or replaced with new material.

 

(6) the moisture content and volatile content in raw materials are too high. Drying treatment should be carried out.


(7) the temperature distribution of the barrel and its section is not reasonable. Should be adjusted appropriately.

 

 

Ⅲ. Weld line and Flow mark

 

(1) the melt temperature is too low. The molding temperature should be increased properly.


(2) the injection pressure is too low. Should be appropriately improved.


(3) insufficient feed capacity. The amount of feed should be increased or replaced by larger injection machines.

 

(4) holding time is too short. Should be appropriately extended.


(5) the pressurization time is too short. Should be appropriately extended.

 

(6) the pouring system is not reasonable. The runner shall be improved, and the gate shall be re-positioned.

 

(7) the gate and runner have obstructions. Should be completely removed.


(8) Molding temperature is too low. Should be appropriately improved.


(9) poor mold exhaust. Vent holes shall be added or mold clamping reduced. Exhaust at the parting line or at the weld point.

 

Ⅳ. Swirling pattern

 

(1) the melt temperature is too high or too low. Should be adjusted appropriately.


(2) feed capacity is too much. Should be properly reduced.


(3) improper gate location. The openings should be re selected.

 

(4) there is obstruction in the runner. Should be completely removed.


(5) nozzle hole obstruction. Cleaning should be carried out.


(6) Molding temperature is too low. Should be appropriately improved.

 

Ⅴ. Black spots and Stripes

 

(1) impurities are mixed in the raw material. Should be completely removed.


(2) the melt temperature is too high or too low. Should be adjusted appropriately.


(3) the temperature distribution in each section of the barrel is not reasonable. Should be adjusted appropriately.

 

(4) injection pressure is too high or too low. Should be adjusted appropriately.


(5) the cross section of runner and gate is too small. Improper positioning, flow resistance is too large. The gate and runner cross section shall be properly enlarged to check whether there is any obstruction in the runner.


(6) poor mold exhaust. The blowhole should be increased to improve the exhaust performance of the mold.


(7) there are hot spots and dead ends in the cylinder and nozzle. Should repair in addition to get material in dead angle, eliminate excessive hot spot.

 

Ⅵ. Rough surface and Bad luster

 

(1) the melt temperature is too low. The molding temperature should be increased properly.


(2) the injection pressure is too low. Should be appropriately improved.


(3) Molding temperature is too low. Should be appropriately improved.


(4) insufficient feed. Should be increased appropriately.

 

(5) the gate is improperly fixed. The openings should be re selected.


(6) lack of cooling time. Should be appropriately extended.


(7) there is a block in the sprue. Fluid filling is not smooth. The mold block shall be cleaned.


(8) the surface roughness of the mold cavity is too poor. Grinding and polishing should be applied to improve surface finish.

 

Ⅶ. Bubble and Shrink hole

 

(1) raw materials are not sufficiently dry. Drying should be carried out, and the drying temperature should be increased and the drying time should be prolonged.


(2) the melt temperature is too high. The molding temperature should be reduced properly.


(3) the injection pressure is too low. Should be appropriately improved.

 

(4) holding time is too short. Should be appropriately extended.


(5) there is a block in the sprue. Should be completely cleaned up.


(6) Molding temperature is too low. Should be appropriately improved.


(7) the cooling time of the plastic parts in the mold is too long. Should be properly shortened, it is best to release the plastic parts in hot water bath slow cooling.

 

Ⅷ. Decortication

 

(1) impurity of foreign substance in the raw material. Should be completely removed or replaced with new material.


(2) insufficient feed. Should be appropriately increased or replaced with larger specifications of the injection molding machine.


(3) Molding temperature is too low. Should be appropriately improved.

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