Predicting Blow-Moulding thicknesses

[sbanAviator]

Hello Plastic Gurus,

I need to analyze some blow-moulded HDPE designs for impact strength. I can use a nominal thickness in the analyses, but the actual part ends up having different thickness distributions which gives very different results in the actual tests. Is there a predictive tool which can determine the thickness distribution by simulation?
A good prediction might avoid costly tool-changes later on.

Thanks,
Ace

 

[MikeHalloran]

A Google search on "blow molding simulation software" was moderately productive.

I've never used such a thing myaelf. Mostly I guess at the dimensions of an appropriate parison, and assume that it will expand radially, increasing circumference and reducing wall thickness, until some portion of the parison contacts a mold surface, at which point the material freezes in that vicinity, and any remaining increase in circumference must come by thinning of the walls between the contact areas.

So square bottles with sharp corners tend to have _very_ thin walls in the corners, and the corners get progressively thicker, or less thin, as the corner radii increase. And so forth.

If I get within a factor of 2 either way of what is actually eventually produced, I think I'm doing really, really well.


I think the best teacher of what you can actually expect to achieve is comparative anatomy of the bottles produced for consumer products like detergent, shampoo, soda pop, and especially milk.





Mike Halloran
Pembroke Pines, FL, USA