Molds & Tooling
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PPO Shrinkage Rate Estimation Deviation
Problem Phenomenon
After designing the mold for PPO precision parts according to empirical shrinkage rates, dimensions are out of tolerance, and shrinkage differences among different grades lead to repeated mold corrections.
Cause Analysis
PPO molding shrinkage is relatively small, generally 0.2~0.7%, but varies with grade, glass fiber content and wall thickness; glass fiber reinforced grades have even lower shrinkage with obvious directionality; applying empirical values causes large errors.
Solution
①Set the shrinkage rate according to the specific grade data; ②consider directional differences for glass fiber reinforced grades; ③leave mold correction allowance for critical dimensions; ④measure and correct during mold trials.; After adjustment, continuously sample to verify the effect, and resume mass production after confirming stability
Key Takeaway
The low shrinkage of PPO brings dimensional stability advantages; but precise values still depend on grade data; glass fiber directionality design cannot be ignored.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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