Injection Molding
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ASA surface step defect
Problem Phenomenon
Step-like appearance defects appear on the ASA injection surface along the flow direction, the height difference can be perceived by hand touch, corresponding to the position of filling speed change.
Cause Analysis
Flow instability research shows that ASA step defects are related to melt slip-stick transition; when injection speed switches or flow front shear changes abruptly, the surface layer state is discontinuous, forming visible steps.
Solution
①Smooth transition of the injection speed curve to avoid sudden changes; ②optimize gates and runners to reduce front disturbance; ③mold temperature homogenization reduces slip differences; ④corresponding analysis of defect position locates the speed switching point.
Key Takeaway
ASA step defect is a flow front stability problem; the smoothness of the speed curve is more important than absolute speed; defect position analysis is an effective diagnostic means.
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