Sunday, February 8, 2015


I'm researching materials for my next prop build. Looking to see what in the way of tough, closed-cell foam, and lightweight carve-able foam can be run through the laser cutter. Finding out about turning acrylic on a metal lathe. Looking for suppliers for thermosetting plastic (TechShop doesn't have a lot at the front desk). Looking at existing shapes from Tap Plastics and other suppliers and doing quick calculations to see if any of the cheaper materials at Shapeways will fall within my project budget.

It continues to be a problem that TechShop is not a wide-open shop. Each group of tools requires check-out, and the check-outs cost money. Significant money -- the Water Jet SBU is over two hundred dollars.

Last time I was there, I ran off four M40 grenade bodies. Got it down to about 30-40 minutes each once I got into the swing of it, but my reservation ended, the shop was crowded, and I could feel myself starting to get careless. So time to step back from the whirring implement of doom and come back on Monday. So two more days should finish off my current order. And I have one more to add to my "scratch and dent" collection to put up at the RPF for the bargain hunters.

If I can work fast enough, I can design the armature for the ATG and run that off on the laser cutters during one of those trips next week. I think that one I will foam and glass it, but still contemplating CNC for the basic foam shapes. I wish I had ShopBot access already!

Ouch. I finally found PETG -- which is one of the three most-recommended materials for thermoforming -- at Grainger. I found pink insulation foam in handy 2' squares at Homely Despot -- Orchard seemingly carries it but their web store and search function are useless. Of course that foam can not be laser cut. Depron Foam, the absolute leader in a carve-able, laser cut-able foam, doesn't seem to be anywhere but a few chain hobby stores or online. So if I want to start bending metal...err...carving foam this week, it will have to be expanded polystyrene or one of the pricey carving foams (Balsa Foam) at the local Blick Art. At least OnlineMetals, my go-to for metal stock, has acrylic rod for a good price.

On reflection, easy-carving foam is a bad combination with thermoforming. The buck has to be able to withstand 14 psi plus the temperature of the heaters. So go with something that takes a little longer to carve -- MDF. Which can be laser-cut, so if I can figure out how to slice a model, I can do that to get a pretty good rough of the curves.

Tooling foam can also take the stresses, but I'm not sure what the local suppliers of that are. Or I could hand-cut 1" pink foam with my home scrollsaw, and cast the result in a silicone mold...

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