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Common problems of PPS

When customers use PPS Composite Application of injection molding process often appear such as lack of material collapse pit, bubble, surface flow marks, deformation, crack, dimensional instability, demoulding difficulty, flying edge problem, please refer to the following solutions.

Common flaws

Reason analysis

prevention measures

Lack and collapse pit of material

1.Cylinder, nozzle temperature was too low or too high 1.Adjust material tube nozzle temperature (for thermoplastic plastics to improve temperature)
2.Mold temperature is too low or too high 2.Adjusting mold temperature
3.Product volume more than injection moulding machine maximum injection quantity 3.Check injection quantity and product volume relations
4.Injection pressure is insufficient or injection is too slow 4.Injection pressure is insufficient or injection is too slow
5.Runner gate is too small 5.Runner gate is too small
6.Injection time is too short 6.Extend the molding cycle
7.Exhaust impeded, prevent mold filling material 7.Remove plugging waste or modify mould


1.In the raw material water or volatile content too large 1.Raw material need drying process
2.Mold temperature is too high or high and low (high, caused by decomposition low brought into gas) 2.Adjusting mold temperature
3.Injection pressure is too small or too fast, and the material into gas 3.Improve the injection pressure, injection speed
4.Pressure relief too early 4.Increase dwell time

Surface flow mark
(joint mark, corrugated, etc.)

1.Material temperature is too low 1. Improve material barrel temperature
2.Mold temperature is too low 2.Improve mold temperature
3. Injection pressure is small, the speed slow 3.Improve the pressure, increase speed
4.Mould exhaust bad 4.Modify mould exhaust slot
5.Gate too much or too small 5.To reduce or increase the gate


1.Curing time is not enough, the die early 1.Extend the curing time
2.Products thickness gap is too big 2.Strict control mould cooling uniformity
3.Demoulding inappropriate position of push rod 3.Adjustment rod make uniform stress
4.Mold temperature and uneven 4.Check and adjust the temperature
5.Gate part overdo 5. Reduce or shorten the secondary injection time


1.Mold temperature is too low, so that products in the mould curing incomplete 1.Improve mold temperature
2. Products thickness are too big, shrinkage uneven 2.In the thick wall part take effective cooling measures
3.Parting in a wrong way, push rod cross section is too small or shortage 3.Correction release method, the products of the demoulding force uniform
4.Insert not preheating or temperature is not enough 4.Insert preheating treatment appropriate
5.Products mucous membrane rupture 5.The correct selection and coating release agent

Unstable gauge

1.Machine preach pressure system unstable 1. Maintenance equipment
2.Molding cycle is not consistent 2. Strictly control the paragraphs molding cycle
3.Die locating rod bending or wear 3.Maintenance mould make joint closely
4.Plus uneven feed 4.Forced quantitative loading
5.Feed back and the new mixing unevenly 5.Ensure that mixing uniformity

Demoulding difficulty

1.Die finish is not enough, there are wounds or indented 1. Improve the mould machining accuracy
2.Die slope is not enough, insert joint is too big 2.Improve mould design
3.Core die without air inlet 3.Core die without air inlet
4. Ejection device structure bad 4.Maintenance ejector mechanism
5.Injection pressure is too great, time is too long 5.Reduce pressure, shorten time
6.Mold temperature not appropriate 6.Die core difficult to throw off the surface, improve the mold temperature or shorten the cooling time ;
7.Sticky die, and it's hard to take off, release agent inequality or failure 7.Choose effective release agent and coating

Flying edge  

1.Mould clamping force shortage 1.Improve clamping force
2. Mold deformation 2.Repair mould
3.The material flow rate is too high 3.Choose liquidity lower material
4.Injection pressure and other improper 4.Adjust injection pressure technology