I am hoping somebody can help me to determine the root cause of the Milky bloom issue we experience in one of our new products and we are running out of options/ideas to explore.
Below is some information regarding the part/mold/material:
• The Part is Fender flare(X4)
• We can see this stain/bloom in all 4 tools
• Surface finish of all tools with naked eye looks fine
• Material: PP+EP-TD20 (with UV additive for automotive exterior application)
• MFI: 31
• 3 hot tips with Sequential gating
• wall thickness confirmed to the Cad OK
• tool made as per Moldflow analysis
• part has a grain with 30micron depth
• Trialled with different melt temperature, injection speed, pressure, holding time, cooling time and combination of them: similar result
• (it seems long holding and cooling time disguised it, but the bloom is still there)
• Trialled with dried material: no improvement
• Trialled with similar grade PP with different mineral and UV content, the problem is still there
• Trialled with pure PP copolymer with Black masterbatch, no improvement
• Trialled in a different machine (same result )
• Trial with warm Tool, cold tool didn't help
• Short-run experiment shows material flows uniformly.
• Different sequential gate timing did not help
Note:
1- The locations of the bloom changes with different setups and trials
2-This milky bloom is not visible in the covered space light, only visible on sunlight in a certain direction which picked up by our customer. (See attached photo please, sorry I can't share the whole part photos as the product has not launched officially yet)
Do you have any idea what could be wrong with our process/tooling/material?
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