Warping
Warpage refers to the tendency of plastic parts to change shape such as twisting after processing. This may occur shortly after molding or after some time in the field particularly after heating. In principle this is caused by strainedf polymer chains in a non-random state. As they return to the random state, the article shape changes. (RDC 8/13/2009)
“Cooling is too short, material is too hot, lack of cooling around the tool, incorrect water temperatures (the parts bow inwards towards the hot side of the tool) Uneven shrinking between areas of the part.” (Wikipedia, Warping, 6/14/2011)
Recent Journal Articles
Test method development for deformation analysis of injection moulded plastic parts
(543-547) Polymer Testing 30 #5 (2011)
Kovács and Sikló of the Budapest University of Technology and Economics, Hungary, have developed a method for the analysis and measurement of the warping of injection moulded plastic parts. A specific part with a special mould design was introduced for the characterisation of the effect of different technological parameters and different mould element design on warpage. The applicability of the system was demonstrated via its experimental use. The effects of mould temperature, mould temperature difference, holding pressure and the glass fibre content of the material were investigated using different gate types in the mould. Additionally, new software was developed to evaluate warpage. Based on the results, it was concluded that the deformation of the corner along the edge length can be described by a curve. (RDC 6/10/2011)
Editor's Notes
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