Processing Machinery
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Zoned scaling of PP precision parts
Problem Phenomenon
The dimensions of precision PP parts with a tolerance of ±0.1mm are unstable, and traditional overall scaling cannot satisfy the requirement.
Cause Analysis
The cooling and shrinkage speeds of the thin and thick areas of precision parts are different, and uniform scaling cannot satisfy both; PP's later aging shrinkage also needs to be compensated.; during on-site investigation, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
①Take the lower limit of the shrinkage rate for thin-wall areas and the upper limit for thick-wall areas for zoned scaling; ②control the shrinkage difference between the flow direction and the perpendicular direction within 0.3%; ③reserve a 0.1~0.2% post-shrinkage margin; ④use conformal cooling to stabilize the mold temperature.
Key Takeaway
The mold design of precision PP parts has entered the era of zoned differentiation; only the trinity of scaling, cooling, and aging can stabilize the ±0.1mm tolerance.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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