Processing Machinery
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TPU screw design low shear
Problem Phenomenon
Processing TPU with a general-purpose screw causes shear degradation leading to product discoloration and performance decline
Cause Analysis
TPU recommends a single-flighted three-zone screw with a compression ratio of 1:2 to 1:3; excessive shear causes local overheating and degradation of the melt; the check valve prevents backflow and avoids dead zone retention
Solution
①select a special screw with a low compression ratio of 1:2-1:3; ②equip a check valve to prevent backflow; ③avoid dead zones in the barrel and nozzle; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
The TPU screw is a low-shear special part; a 1:2-1:3 compression ratio plus a check valve protects the material from the hardware; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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