Molds & Tooling
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Flash at the Thread of PE Bottle Necks
Problem Phenomenon
Flash appears at the neck thread of HDPE/PE bottles, causing poor cap screwing and sealing failure.
Cause Analysis
The mating gap of the neck mold becomes larger due to long-term use, or the cutting edge (cutting blade) wears and becomes dull, so high-pressure melt is squeezed into the mating gap during blowing to form flash; insufficient clamping force prevents the mold from closing tightly, likewise letting material overflow from the neck mating area and aggravating flash.
Solution
①Overhaul the neck mold fit and cutting edge, and replace worn parts; ②Adjust the blowing pressure; ③Check the clamping force; ④Establish a regular replacement system for wear parts of the neck mold; ⑤Keep trimming tools sharp.
Key Takeaway
Neck flash = a signal of 'mold fit wear': regularly replacing the cutting edge and wear parts is more economical than post-trimming; the neck precision of sealing parts directly determines whether the cap can lock.
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