Molds & Tooling
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PVC First-Piece Verification
Problem Phenomenon
After material and mold change, discoloration and black specks appeared in batches; the first piece was only checked for appearance and dimensions
Cause Analysis
PVC is sensitive to temperature and residence; stabilizer system differences after material change may alter degradation behavior; without temperature and material state verification on the first piece, batch risk is out of control
Solution
①Perform three first-piece verifications: appearance, dimensions, temperature record; ②strengthen inspection of the first few shots after material change; ③compare against color reference samples to prevent gradual change; after adjustment, continuously sample to verify the effect, and resume mass production after confirming stability
Key Takeaway
PVC first-piece verification must include temperature and color; gradual degradation can only be found early by reference sample comparison; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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