Molds & Tooling
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EVA Foaming Uneven Expansion Ratio
Problem Phenomenon
The density difference of foamed products from the same mold exceeds 15%, and the mechanical properties fluctuate greatly.
Cause Analysis
A mold temperature difference greater than 10℃ makes the local decomposition rate of the foaming agent different (AC foaming agent decomposition temperature 160~200℃); incomplete crosslinking with residual crosslinking agent exceeding 10% also causes shrinkage rate fluctuations.
Solution
①Optimize the mold heating channel design; ②adopt a high-precision temperature control system with an error of ±1℃; ③increase the vulcanization temperature to 170~180℃ and add accelerators such as magnesium oxide; ④test the foaming agent decomposition curve for each batch.
Key Takeaway
Foaming ratio uniformity is determined by mold temperature consistency and crosslinking sufficiency; temperature control accuracy and additive batch management are the two handles.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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