Let's Make Robots!

Sintra / expanded PVC

Hey all you users of expanded PVC:

I just got a nice big piece of sintra for my next project. Very cool stuff. Light, durable, and best of all, FREE!!! (got it from the showroom of a local plastic supply).

So before I go ahead and ruin it, let me throw out some questions to those who have used it:

1. What do you use to glue it? Super Glue? Plastic bond? Pipe glue?

2. What about cutting it? Jig-saw? Dremel?

3. Has anybody tried molding/bending/shaping it?

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Here's the Dremel blade I use. If you use the solid disk cutting blade the ePVC melts.

As others have mentioned, I generally cut my piece a bit big and then sand them to their final shape on a belt sander. I usually need to cleanup some sections that don't lead themselves to sanding with a sharp knife.

You can use "T" slots, tabs and (normal) slots and make boxes you can bolt together. I use a bit of Polymorph to hold the nut in the "T" slot. Becareful about heating Polymorph next to the ePVC, the ePVC can't take much heat before it deforms.

Expanded PVC can be nasty stuff, as it gives off chlorine gas when heated. I bought a big sheet cheap then learned it could not be laser cut unless it is in a special facility. It can be very dangerous, please do not heat it unless you have adequate ventilation!

double post, sorry

Well I use the following:

 

  1. Regular universal plastics glue. Pipe glue will work, but the stuff i have is very liquid / runny. As far as I know allmost any type of hobby-glue suitable for plastics will do.
  2. I cut the thin plates (2mm) with a sharp knife and the thicker plates (5mm/8mm) with a jigsaw. The pieces I cut with the jigsaw are cut rather wide around the lines I drew and then I sand it with a piece of sanding paper or the sanding tool on my dremel. For the larger round holes I use a large drill and then use the dremel sanding tool to open up the hole. The plates you can buy are cut using hot-wire cutting. This technique also seals up the PVC leaving a smooth surface.
  3. If you put it in hot water, you can bend it. You'll have to practice that a bit. I don't think it will get soft enough to really shape it like polymorph. Another technique is to use a (not too) hot wire to get a nice sharp corner, though I haven't tried that.
If your piece is big enough, cut off a few small pieces and experiment. Drill it, bend it, cut it, break it, sand it and glue it. Just get a feeling how it handles and how much force it can take.  I messed up some pretty pieces because I applied so much force that it broke.
 
 

 

I used super glue, i tried a test piece first and found that the expanded pvc broke before the super glue gave up. To cut it i used a hand saw (hacksaw) but it cuts using a sharp knife.  If its 5mm thick or less it cuts easily with a knife.  Im sure a jigsaw or dremel would cut it ok.
Cutting with a dremel (I have found) melts it badly.
if you are going to use bolts, be careful to use washers everywhere and do not overtighten! If it is too tight It will pull the bolt right through.

For reasons that have nothing to do with robots I was interested in joining pieces of polypropylene. A bit of googling found me a robot builder's web site, would you believe it, where they use it for armour. The answer was plastic welding.

There's some info about gluing plastics or otherwise joining them at www.directplasticsonline.co.uk. This may include sintra

Mike