Injection Molding
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TPU Injection Speed Control
Problem Phenomenon
After high-speed injection, burning occurs near the gate, while low speed produces flow marks and weld lines
Cause Analysis
TPU is shear-sensitive; shear heat from high-speed injection degrades the gate area; at low speed, the flow front cools and forms flow marks; medium-slow speed is the conventional strategy for TPU; when troubleshooting on site, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
①Injection speed controlled at medium-slow; ②Pass through the gate area at low speed; ③When flow marks occur, increase melt temperature to compensate; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
TPU speed strategy is stability-first; the balance between shear degradation and flow marks relies on medium-low speed plus temperature compensation; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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