Thermoforming
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Webbing (material pile-up) in PP/TPO '2079851475616104458
Problem Phenomenon
During '2079851475616104458 of PP/TPO sheet, material piles up and wrinkles at deep-cavity corners, forming folds and failing to conform to the mold normally.
Cause Analysis
The sheet temperature is too high and too soft, the sag is too large, the sheet area is excessive relative to the mold, and the vacuum is applied too late, so the excess material has nowhere to flow and piles up; olefin materials have low melt strength and are more prone to material pile-up.
Solution
①Lower the sheet heating temperature or shorten the heating time; ②use pre-blow (billow) pre-stretching to 'store' the excess material; ③cut the sheet 5~15mm smaller in the problem direction; ④apply vacuum earlier and add an assist plug to guide the material flow; ⑤enlarge the mold fillets.
Key Takeaway
The key to preventing webbing in olefin sheet '2079851475616104458 is 'pre-blow + temperature control + early vacuum': managing the excess material with pre-stretching is more controllable than simply cutting the sheet smaller, and deep-cavity parts especially cannot do without plug assist.
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