Hire a thermal imaging camera, as I've done on many occasions, including in the last fortnight. Though the semi-crystallinity will accentuate warpage tendencies compared to amorphous materials, just see how temperatures vary across all surfaces of the part on ejection. Those that are hottest will take longer to cool, shrinking all the while. Simple physics will tell you that variable stresses (a mixture of tensile and compression) are bound to pulls the shape out-of true. Within seconds of seeing the images, you will appreciate why the part shape you actually get once the part has reached ambient temperatures differs from design intent. Flow-induced and variable crystallinity-induced effects will only add to the net effect. I'm dealing with an injection molding in PP with a >15mm wall section and, the forces at play as it cools are huge. Part, tool and process (cooling included) simulation by someone who understands the interrelationships will give you great insight into how to understand reasons for - and to minimize by good part.
The article comes from China injection mold manufacturer - Mold Best Assurance Company Limited, website is www.mbamoldanddesign.com
