Material Drying
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PA6 Start-Up Pre-Drying Procedure
Problem Phenomenon
After weekend shutdown, when starting up on Monday, the first few shots show severe silver streaks and bubbles
Cause Analysis
During the shutdown, the PA6 in the barrel and drying hopper is exposed for a long time or insufficiently heat-preserved and re-absorbs moisture; directly using material that has not been re-dried at Monday start-up causes defects
Solution
Establish a start-up procedure: purge the barrel before the weekend shutdown, re-dry the material according to the standard for more than 4 hours before Monday start-up, first expel the residual material in the barrel by low-speed air shots, and confirm the extruded strand has no bubbles before production
Key Takeaway
Restarting after a shutdown must re-confirm the drying state of the material, and the drying results from before the shutdown cannot be carried over; after confirming effectiveness, fix the parameters and practices into the work instructions to prevent recurrence
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