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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Comparing surface finish of a molded part to a machined part
The company I work for currently is machining a part that I want injection mold. If the surface finish of my machined part is 32 microinch what SPI surface finish do I need to meet on my molded part?
James Wolfemfgr - Memphis, Tennessee, USA
2005
Not very much info to give a satisfactory answer but, as a rule, molded plastic parts replicate the interior surface finish of the mold pretty accurately. Mirror finish is required for transparent parts whereas sandblasted, EDM'ed or chemically etch interior surfaces will show the reverse pattern on the plastic. So, a straight answer would be, a 32 RMS finish inside the mold is what you need. Whether it would be suitable for the injection process is unknown.
Guillermo MarrufoMonterrey, NL, Mexico
2005
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