Extrusion & Post
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PET die-to-roll distance 8cm
Problem Phenomenon
The sheet sags and wrinkles with poor smoothness, or crystallizes and whitens due to slow cooling
Cause Analysis
When the distance from the die to the calender rolls is too large, the melt curtain sags and wrinkles; a large distance also slows heat dissipation and cooling; PET stays too long in the fastest crystallization temperature zone and whitens, losing transparency
Solution
① Keep the distance between the die and the three rolls at about 8cm; ② the melt quickly passes through the fastest crystallization temperature zone; ③ control the roll surface temperature at 40-50℃; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
The 8cm roll distance is the geometric guarantee of PET sheet transparency; fast cooling through the crystallization zone plus roll temperature control, a two-pronged approach to keep transparency; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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