Gas Assist vs. Structural Foam 1

[Bkerila]

Can anyone offer an unbiased opinion on the strengths of the two respective processes? Gas Assist (from what I can learn) appears to result in somewhat more expensive tooling (higher pressure), but less material used and better surface finishes. This equates to less painting (no fill coat) and additional labor cost savings (beyond material) and should result in a cheaper piece part price.
Obviously Gas Assist parts will have thinner walls and will require additional ribbing to have the same stiffness as a comparative Structural Foam part. It seems to me that this is simply a design challenge - find room for enough ribs, and that Gas Assist is the way to go. (as long as you can justify the tooling cost). My little voice tells me that I'm missing something though.
The material under consideration is Sarlink or Santoprene. Largest parts are about 40"x40"x"12" envelope, smallest are 12"x12"x"6".

Thanks,
Bob Kerila, PE

 

[insideman]

Bob, I think you hit it with your comments about tooling cost and appearance. Gas assist can also use a wider variety of tougher, stronger materials. But be sure to contact the practitioners of the two arts and take their responses with a healty skeptical attitude.

 

Gas assist and structural foam are unique, however, you need to define what type of gas assist you want. You obviously know what a foam part looks like,,,poor surface finish, swirly. Porosity. Can not medically clean the surface. However, there are 2 forms of gas assist. 1 - the type that is produced using an injection machine and 2 - the type that is produced using a structural foam machine. In my experience, sometimes you do not need to add special ribs if all you want is the smooth skin. However, if you want to minimize weight, than you add ribs for the gas to walk around. The only difference in the tool costs for option 2 is the nozzles cost more. In option 1, the mold needs to be out of steel, whereas for option 2, you can build the mold out of aluminum.