Normal defects of plastic parts and the reasons analyze

Normal defects of plastic parts and the reasons analyze

 

Normal defects of plastic parts and the reasons analyze

 

1)Defect: welding line

A: Too low injection speed

B:Too low melt temperature

C:Too low mould temperature

D:Bad vent

E:Pigment,injomogeneous melt

F: Mould or part design is not reasonable

 

 

2)Defect: Materail escaping from nozzle

 Reasons:

A. Dosing speed of injection machine is too fast

B. The materail is not dried enough or it is wet

C. The nozzle temperature is too high

D. Recycle material is not good, too much powder in regrinds

E. Not enough retract

F. Not enough force between the injection nozzle and the mould bush

G. The dimension of machine nozzle and mould bush is incorrect.

H. Dirty interface of the injection nozzle

 

3)Defect:Spot

Reasons:

A:Part is ejected not balance

B:Not enough cooling time

C:Too low injection speed

D:Too high pressure to cause sticky on cavities

E: Not homogeneous melt to cause force inside

F:Mould temperature not uniform

 

 

4)Defect: Plastification unstable

Reasons:

A:Regrind rate is unreasonable or unstable

B:Back pressure is too low

C:Long regrind

D:Wet material

E:Cylinder temperature around the hopper is too high

 

5)Defect: Incomplete(not injection fully)

Reasons

A: Wrong setting parameters,such as too low switch point, too high holding pressure,too fast injection speed,too high temperature and so on.

B: Mould is dirty

C:Low temperature in the tip of nozzle

D: Non-return valve or cylinder is broken

E:Too small gate,runners

F: Other material in the regrind

G:wet material

H: machine problem(not enough pressure)

I :The nozzle is not in the centre of mould runner

J:Too little retract to cause the non-return valve closing unstably

 

 

 

6)Defect:Flashes

Reasons:

A:Wrong setting parameters such as too low switch point, too high holding

Pressure,too fast injection speed, too high temperature and so on

B: Mould is dirty

C: Injection machine locking force is not enough

D: Mould is injured

E: Injection machine problem,unstable pressure

F:Nozzle temperature is too low

G:Inhomogeneous melt

H: Too little retract to cause the non-return valve closing unstably

 

 

7)Defect: Dimension is not stable

A:Machine parameter control is not precise

B:Regrind rate is unreasonable or unstable

C:Non-return valve or cylinder is broken

D:Too little retract to cause the non-return valve closing unstably


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