Hi, I have modelled a tool based around a plastic part that a client has given me to work on.
Obviously the tool is smaller than the plastic part in SW, due to taking into account the material thickness and draft angles etc.
The contraction rate of ABS is 0.83% and so I need to increase the scale of the molding tool buy a certain amount to allow for the shrinkage of the ABS after it has been Vac formed. Obviously the scale of the model before is 1, and I have increased it to 1.018 to allow for such changes in production.
After looking at the part with the molding tool in the assembly, after I have scaled up it looks to be around the right size to take the contractions and shrinkage into account.
Just want to check wether this is enough?
Cheers,
Tom Haslam
Well, you certainly have a different way of doing mold design compared to just about every other mold designer I've ever known...pretty much completely backwards process from the "norm". Most designers take the model of the plastic part and scale it up to account for shrinkage, then use it to create the models for the steel. So the very first thing that is usually done in a mold design is to scale the part model up to account for shrinkage. By applying shrink at the end of the design you are scaling up a finished tool, so all your holes are going to wind up being at "odd" places instead of at normal distances (like a drilled & tapped hole for mounting the tool to the platen will "move" out of location due to scaling the tool at the end of the design process). That being said, .018 seems like a lot of shrink for ABS, when injection molding ABS the shrink is around .006. I don't have any experience with vacuum forming so not sure if the shrinkage is normally 3x as much as injection molding. Basicly, everything you've said makes me quite leary about your tool design being correct...sorry.