Plastic Product Shrinkage for Injection Moulds and Blowmoulds

This may help, it is pretty in depth and very interesting, it also has formulas for shrinkage of different profiles and shapes. go to http://tpe-u.de/tpu/emea/en/docguard/A1120.pdf?docId=47374 I think what you are looking for is a list of shrinkage rates for the individual types of plastics but this will help. Shrinkage can be as much as 20 percent of the wall thickness, so if you had a material that is proven to shrink by 20 percent you would want to add this to your mold dimension. If you had a wall thickness of .125" and your shrinkage rate was 20% then you would want your wall cavity in the mold to be 20% greater than the desired size, therefore the wall cavity in the mold would be .150" wide. There is a table that shows shrinkage rates for each type of plastic. Just keep searching for it and you'll get it, also it may help to search images because sometimes tables like these are scanned and put on the net as an image. Here is DSM's company site link it may help too, they are a provider of raw plastic material used in injection molding. http://www.dsm.com/en_US/html/dep/Shrinkage.htm Good Luck!

That is a really great PDF. It explains very well all the shrinkage stuff I have had to learn by experience over the last 34 years and then some. Anyone who has anything to do with molding or casting should have this. The principles also apply to machining both plastics and metals because quite often when you cut them they move and in a similar manner to molded parts although for slightly different reasons. Thanks for sharing.

Gary

Dear Sir,

may i know the shrinkage ss.

many thanks.