Investigating Part Warpage…

A technician asked me this question yesterday…

What is the best way to correct for part warpage?

My Response
Typically, part warpage is the result of variable shrinkage. In most cases, the variations in shrinkage causes the part to buckle, bow, or twist. Unfortunately, there are many causes which will contribute to this including mold temp, melt temp, injection speed, pack pressure, cooling time, and packing time. Additionally, both high and low settings can cause warpage for most of these parameters.
To refine my approach, I like to determine whether the part dimensions are the same, larger, or smaller than an unwarped part. It is also important to know if the part is larger or smaller at the gate, end of fill, or consistent across the entire part. This information will give you very valuable information when trying to correct for the part warpage. For example, if the part dimensions are small at the gate, yet consistent throughout the rest of the part, you can refine your troubleshooting approach to causes such as poor gate seal.

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