Molds & Tooling
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PBT Hot Runner Forbidden Zone
Problem Phenomenon
After PBT adopts a hot runner, degradation occurs in the manifold, the product is burnt and discolored, and drooling is difficult to control
Cause Analysis
Both PBT and PET are not suitable for hot runners: the drooling problem caused by low viscosity is difficult to solve by decompression or temperature adjustment; and PBT easily stays and degrades in the manifold, causing burning and discoloration
Solution
①Avoid using hot runner systems for PBT; ②If it must be used, fully evaluate and demonstrate; ③Make the main runner as short as possible and 0.5-1mm larger than the nozzle; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Key Takeaway
The hot runner is a process forbidden zone for PBT; the two major risks of low-viscosity drooling and manifold degradation are superimposed; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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