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Flow Marks
Uneven-thickness type
Record type
Staggered type

 
Molding Defects: Flow Marks

Uneven-thickness type flow marks

 
 


Uneven luster in locations where the material thickness varies



Cause
Countermeasures
Immediately after molten plastic has passed through a change in die thickness, factors such as the flow speed, cooling speed, and pressure applied to the die surface will change, and luster differs as a result of this. - Raise the die temperature.
- Increase the speed of the injection flow.
- Raise the runners and gates
- Review the shaped of the molded component and round off corners on steps between areas of different thickness so that smoother flow may be realized.


 

 
Condition of flow mark occurrence due to
Flow
Mark
 
Filling speed
 
Molding temperature
 
 
Filling
direction
Die
 
Die
Filling
direction
Large 240deg.C
Low speed

 

220deg.C
Middle
240deg.C
Intermediate speed

 

240deg.C
Small
240deg.C
High speed
  280deg.C
 
 


Apply colored ink to the die to ascertain the condition of flow mark occurrence.

Result of examining flow-mark start point as caused by level differences:
The corner edge at the level-difference exit constitutes a start point for shear.

 
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