Getting parts for Tommelise

Try not to make getting parts a lot harder than it needs to be, for you Americans at least. The problem with looking for a lot of "lowest price" vendors for electronics components, for example, is that you soon find that you are being eaten up on shipping and minimum order charges.

For most of the electronics in the US you can get virtually all of it from either Mouser at very attractive prices. Digikey is just about as good for parts. I tend to order PIC chips directly from Thailand because if you order over $25 worth of chips the price plus shipping beats Digikey and Mouser's catalog prices.

Exceptions are the Hamamatsu limits detector chips, which you can get at...

http://www.acroname.com/robotics/parts/R64-P5587.html

Shipping would be a problem except, iirc, you have one of these bad boys at both ends of each axis which means six which will cost $13.20 so shipping won't eat you alive.

I gather that you all are sticking with unipolar steppers since the last I heard the bipolar board didn't work that well or people simply were avoiding buying them, I don't know which. Until you have a clear idea of how much torque will be required to drive Darwin shopping for those will be a problem.

As to metric threaded rod and the like, Brett Bilmore long ago recommended

http://www.mcmaster.com/

...as having both good prices and high quality. They do.

For the Mk II, you can get the gearmotor from either Pololou in Las Vegas or direct from Solarbotics in Calgary . If you buy direct from Solarbotics have them ship by post in that the courier service charges in Canada are extortionary compared to US charges... and that's saying quite a lot. Be sure and order the 12v versions.

The PTFE bar stock can be had from...

http://www.usplastic.com/catalog/category.asp?catalog%5Fname=USPlastic&category%5Fname=12077&Page=1&gclid=CJau5Nmf0YkCFQRDYwodyRxxRQ

...at decent prices. The only problem is that you need an inch of 1x1 inch bar stock and their minimum length is 1 foot. I think that maybe people need to club together when ordering PTFE and then share it out.

Power supplies with lots of amperage can be had from...

http://www.tigerdirect.com/

for anywhere from $15-25 for a PC power supply with plenty of punch to drive those steppers. I've found power bricks a bit pricey for what you get in the States.

 I was thinking that it might be worthwhile to farm out the board fabrication and perhaps the assembly as well to one of the many hobby robotics companies in the States. They could sell you the board plus a sack of components for the DIY crowd or sell it too you completely assembled. You'd just have to shop the designs around till you found somebody who was willing to do it at a price that wouldn't break the budget. I know Pololou does things like that, though they do most of their designwork in-house as best as I understand.

One last little thing you will need is a 3 mm drill bit to tap the PTFE thermal barrier. 

http://www.smallparts.com

has those in proper lengths for a good price. You will see them cheaper but be careful about buying drill bits in "jobber" lengths. The fluting on those is only 10 x diameter, so you only get 30 mm of fluting on your drill bit, which isn't enough.

You need a #76 wire gage drill bit to do 0.5 mm holes in the end of your extruder barrel. You can get those from...

http://www.gyrostools.com/Default.asp

...or from the better hobby shops, which are getting quite rare these days. You'll need a dremel tool to drill with these, preferably with a drill press add-on. The chucks on regular drills are too big to seat these hair thin drills.

http://www.woodcraft.com/family.aspx?FamilyID=784

If you're in no hurry you might also want to try a spiral hand drill...

http://www.hobbylinc.com/cgi-bin/a3.cgi?back=http://www.hobbylinc.com/htm/gyr/gyr4510272.htm&add=zon37-160

It's cheaper and you probably have more control than with a dremel.

You can get your #32 insulated nichrome 80 wire from

http://www.pelicanwire.com/index.htm

The copper/phosphorus braising rods that I use to make the low thermal inertia extruder barrel for the Mk 2.1 fused deposition modelling (FDM) extruder for Tommelise are made by BernzOMatic. I got mine from an Ace Hardware Store. Four rods come in a little plastic package and they cost about $2.75. A cheap propane torch suitable for doing the braising can also be had for $15-20.

One thing to remember about braising with copper/phosphorus rods is that the fumes coming off of them aren't good for you. You shouldn't do this sort of work in unventilated rooms and you should wear a welder's dust mask while you are doing the work. I got some really good disposable ones from 3M model 8214 N95's. They're about $6.50/mask but you have to buy them in a box of 10. This is another item you might want to club to buy because you're not going to be doing a lot of braising. I'd recommend the N95's over a non-disposable mask with disposable cartridge mostly because they are comfortable to wear and when you have one on you don't have any trouble getting your glasses on and especially good is that you don't get claustrophobic and have fantasies that you're waiting for terrorists to do a gas attack with Sarin.

One other thing about braising. You can't braise things without something that will hold the bits you're trying to braise steady. I bought a cheap vise. The only problem with using a vise is that you have to be careful that you don't set the table it's clamped to on fire with your torch.

You can get 3 mm plastic welding rod in a variety of engineering plastics from any plastic welding supplies distributor. You have to specify coil rather than cut rods but otherwise no problems. If you want CAPA (polymorph) you're going to have to special order from manufacturers.

Other sundries you can get from Radio Shack and your nearest hardware store.