Questions about working with plastics.

Rolf · Aug 13, 2009

Triode said:
For building robots around the size of an RC car or a desktop computer, I am trying to learn what kinds of plastic would be practical to work with at home. And which methods people here find easiest. Using legos, wood and cardboard are getting old and I can't weld in my apartment.{snip}

Let us be practical about this. There is little sense in talking about material that can not be bought in small quantities. So you need to adept your construction methods to the materials available.
That means the local hardware shop, for aluminum rods angles, Plexiglas (think windows cut to size), epoxy putty, etc.
The automobile parts place for body filler and fiberglass repair kits.
The local sign shop for scrap plastic of many kinds, as well as aluminum sheets scraps.
The welding shop supply store for ss steel, steel and brass welding rods of many different diameters, sold by the lb.
The thiner rods can easily be brazed with a MAP torch.
The list goes on and on.....
PVC water pipe and fittings, electrical boxes....
In my experience all plastics and aluminum can be worked with many wood working tools.

Personally I find there are little difference in the effort of shaping plastic, wood and aluminum if you are using power tools.

arhi · Aug 13, 2009

rolf, you can get sheets of plastic for fairly small amount of money in small quantities ... for e.g.

**broken link removed**

2 or 3 or 6mm 8x12" sheets, ~3$ per sheet

almost all plastics can be shaped using wood working tools - the only issue usually is adjusting the speed in order to cut and not melt it and if you use brittle one, to cut and not break.

be80be · Aug 13, 2009

I used something like shapelock 28years ago in high school we heated it in water and made picture frames with it but I can't for the life of me remember what it was called back then.

Triode · Aug 13, 2009

You have the right idea Rolf, and indeed I use those kinds of materials a lot, and as welding is not an option I use a lot of drill and bolt contruction. But I've found since I've moved to milwaukee getting materials isn't too hard. Its a very industrial city, and even though these plastic, steel and other suppliers are geared towards large industrial customers, I've found that they usually have a part called a will call, where they sell small left over bits for cheap, these are small by industrial standards and can be several square feet. Though if you don't live in a really industrial city these places are around and a will call is a good thing to know about, I had no idea they existed till a few years back.

Be80be, Ive heard it go by many names, including Polymorph, and back in the 80's "friendly plastic" which came in many colors. I havent really used it because of cost, and becase I haven't needed to. Plus its kind of weak.

Arhi, that sintra stuff sounds interesting.

I was thinking, the surplus place nearby has some heat guns that look pretty heavy duty, from boeing, they say that they get up to 400ºF, they might be usable for some bending and forming I think, it wouldent be sharply localized, but with the right guide/jib I think one of them might work nicely on some HIPS or ABS

Rolf · Aug 13, 2009

arhi said:
rolf, you can get sheets of plastic for fairly small amount of money in small quantities ... for e.g.
{snip}
QUOTE]

If you read the OP and my post you will understand we are not just talking about PVC sheets.

arhi · Aug 13, 2009

sintra is just the first thing I found online .. you should be able to get these "plates/sheets" fairly easy... the material does not really matter unless you have some specific request (for example HDPE will withstand more temperature then ABS or PP, PFTE will withstand even more and is very slipery, HDPE is more slippery then ABS, PLA is very easy to work with but cannot withstand high temperature and is not really that strong, PP and (HD|LD)PE are springy while ABS and Acrylic are brittle ... some of them like to burn, other self extinguish....)

I have the RapMan and I make most of the holders out of PP on the RapMan as PP is ~cheapest material I can get (under 10$ for 1Kg) but for the bodywork I still use acrylic as I like the strength vs mass ratio... and if I need a very complex/precise design (lot of holes, square openings, elipses ..) I have a laser cutting service available to provide the single piece I need relatively cheep.

In any case, when you get used to it, with sheets of plastic (any kind, just see what is easiest to find, get different thickness) nuts, bolts, rods and threaded rods you can make almost everything without ever needing to use the glue nor to bend the sheet. If you on top of that find some U and L shaped alu profiles - you are set ... I find the 10x10x1mm aluminium L profile pure gold

Check out the extruder build manual for bitsfrombytes manual ... you will see many good ideas on how to make 3D objects out of sheets of plastic ... (3d models are inside the pdf so get latest adobe reader in order to see them)

for e.g. check out the picture:
**broken link removed**
**broken link removed**

EDIT: ROLF, I did read .. the sheets are imho easiest to acquire, easiest to work with and in combination with alu profiles enough to make almost anything... on top of that - I really do not disagree with you at all ..

Rolf · Aug 13, 2009

Triode said:
You have the right idea Rolf, and indeed I use those kinds of materials a lot, and as welding is not an option I use a lot of drill and bolt contruction. But I've found since I've moved to milwaukee getting materials isn't too hard. Its a very industrial city, and even though these plastic, steel and other suppliers are geared towards large industrial customers, I've found that they usually have a part called a will call, where they sell small left over bits for cheap, these are small by industrial standards and can be several square feet. Though if you don't live in a really industrial city these places are around and a will call is a good thing to know about, I had no idea they existed till a few years back.{snip}

You are lucky, I have to depend mostly on small small local shops and mail order, despite the outrageous S&H fees that some of them charge.

Rolf · Aug 13, 2009

arhi said:
{snip}
EDIT: ROLF, I did read .. the sheets are imho easiest to acquire, easiest to work with and in combination with alu profiles enough to make almost anything... on top of that - I really do not disagree with you at all ..

Great, I like alu profiles also. Locally available 2.3mm plastic (dont know what kind) size 12"x8.5" is available at the local dollar store. It is called a clip board. It is quite a bit sturdier than PVC of the same thickness.

Mr RB · Aug 14, 2009

Re the vacuforming and small apartments, the instructable I saw a couple weeks back he heated the plastic sheet over his stove hotplate, then stuck it over a flat piece of wood with a vacuum cleaner attached to a hole in the wood. It looked pretty easy...

Try a hobby shop, the kind of place where they sell RC cars and aeroplanes. They sell sheet styrene and glue, and also styrene forms like square tubes of assorted sizes etc. They also have things like RC servos and wheels, tiny ball joint linkages, carbon fibre rods and tubes, etc. All great for small robots.

You could look at buying one of the many robot kits that have the chassis pre-made, they are not that expensive and every robot shop has a selection of chassis kits.

Or just design all your chassis parts in a 2d or 3d drawing package and get them laser cut out of 1/8" acrylic for a few dollars. Most local trophy engraver shops and signwriters have lasercut equipment these days and if not there's places on the internet that can do it by mail order.

Questions about working with plastics.

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