affordable CNC cutting service in the U.S.?

[Joe]

It looks like to make a decent Robo-One bot from scratch, you really need the ability to make custom parts -- most builders in Japan seem to be using aluminum 1 or 1.5 mm thick. This requires two steps:

1. Cutting the aluminum
2. Bending it into shape (most typically, at 90-degree angles)

I wish I could afford my own CNC milling machine (or even better, a laser cutter!), but I can't. I imagine there may be others out there who want to get into the hobby but can't afford their own machine shop, too. I've priced out simple brackets on eMachineShop, but they're ridiculously expensive.

I think maybe what the hobby needs is a hobbyist with access to a CNC machine, who's willing to cut small parts for a reasonable price. The bending we can probably do ourselves -- I don't think the equipment needed for that is very expensive (though I haven't looked into it very deeply yet). So I imagine a process like:

1. We design a part in (say) QCad, or select a part the community has already designed.
2. We translate this into whatever format the CNC machine requires. (I'm a software engineer; I could contribute open-source tools to do this.)
3. We email this to the cutter, and PayPal him an amount to cover the materials, tool wear, and something for his time.
4. He cuts the parts at his earliest convenience and mails them to us.
5. We bend them into shape on our own, and assemble our robots.

I doubt such a person would be inundated with requests -- it seems like you can count the number of from-scratch builders in the U.S. on one hand. But it would be a really valuable service to the community, and could help kick-start the whole robo-one hobby in this country.

(Of course the idea could apply just as well to other parts of the world, too.)

Is anyone here willing to try this role, or know someone who might?

Best,
- Joe

[Joe]

And oh yes, I forgot to mention -- if there is already a reasonably-priced service of this sort which I have simply overlooked, please let me know. (Pololu.com has good rates on laser-cutting plastic and wood, but their machine can't do aluminum.)

Thanks,
— Joe

[MYKL]

I've been considering purchasing a small CNC cutting table (plasma, laser, or router) and offering a service like this. There is also a chance that they would be willing to give me some time on the CNC table we have here at work. I am a mechanical designer, specializing in the last ten years in sheetmetal assemblies, so I could even work out the flat patterns for anyone that just sent in a sketch.

I originally was going to buy it for my personal use only so was going to wait for enough capital to make the purchase without feeling pinched but if enough persons on this site and others are looking for the same thing I could see doing it earlier...

Brakeing the sheet metal is fairly easy, if you use the correct bend radius. Otherwise you'll come out of it with cracked (especially with aluminum parts) or orange peeled bends and uneven parts.

^_^

[Joe]

I've been considering purchasing a small CNC cutting table (plasma, laser, or router) and offering a service like this. There is also a chance that they would be willing to give me some time on the CNC table we have here at work. I am a mechanical designer, specializing in the last ten years in sheetmetal assemblies, so I could even work out the flat patterns for anyone that just sent in a sketch.

Wow, you're certainly qualified for the job! Sherline offers what looks like a decent line of fairly low-cost CNC-ready milling machines, but I imagine you already knew that (and may know of even better options). One advantage we may have, as humanoid robot hobbyists, is that we don't need a very large table -- most parts are under 10 cm long, certainly under 20.

Having your experience behind it would sure make it a valuable service. You'd be the go-to guy for custom brackets!

How much would you expect a simple (cut but not bent) aluminum bracket to cost?

Brakeing the sheet metal is fairly easy, if you use the correct bend radius. Otherwise you'll come out of it with cracked (especially with aluminum parts) or orange peeled bends and uneven parts.

See, that's what I'm talking about. What bend radius would be appropriate for a 90-degree bend in 1 mm aluminum? And, can you recommend tools (or at least appropriate search keywords) for making such bends?

Thanks,
— Joe

[MYKL]

The parts could be marked with lines for where to bend them.

You could use a table mounted vise and some radiused blocks for a simple brake.

[Meltdown]

I've got my own little cnc mill.
I live in the Netherlands.
The problem is getting the right material for a fair price.
In Holland the prices for high grade alu are outragious.

[rockweasel]

Is this material suitable and affordable? www.mutr.co.uk/prodDetail.aspx?prodID=558

[Meltdown]

That's interesting material.
Can't say what grade alu that is.
It only says half hard which could indicate that it won't mill well.
Soft alu tends to smear the tool resulting in a bad cut and broken tool.
Example: Alu sold in normal hardware stores is much to soft and weak for robot brackets.
The brackets used in a KHR-1 for example is high grade dural.
The same stuff used in airplanes.

Second problem could be the anodizing.
It's hard to keep the object from scratching when milling.
Anodizing is typically done after the milling and polishing process not before!
It's worth a try though.

[hivemind]

Perhaps this will do the trick for you:

aircraft aluminum

I believe that is what I am using, it is very tough stuff and rather cheap.

[Meltdown]

Yes that's much better.
You yanks are lucky B........
Would you believe that you pay $50 for such a sheet here in Holland.
I use 7075 grade which is even more tough and expensive for my KHR-1 (when i have it that is)

[hivemind]

really? thats too bad...

Hmm, I find that the 5052 is a nice balance between strength and extreme lightweight. I try to build my designs purely around the servo or add a third demension to each bracket when possible to keep up the strength. I find one doesnt really need a CNC machine if they can work with there hands a bit. Although CNC makes for better consistency.

[Joe]

Hmm, I find that the 5052 is a nice balance between strength and extreme lightweight. I try to build my designs purely around the servo or add a third demension to each bracket when possible to keep up the strength. I find one doesnt really need a CNC machine if they can work with there hands a bit. Although CNC makes for better consistency.

Now this is interesting home-built humanoid robot information!

Can you elaborate on that last comment a bit? I'm afraid I pretty much slept through shop class — and that was a couple decades ago. Are you talking about hand tools? Or just a manual milling machine?

Thanks,
— Joe

[hivemind]

Sure. I will run through my basic process of making a few parts.

First I bring up my CAD program and insert the servos I have modelled. I then put them in the arrangement that I want (ie: measure values and angles until appropriate). I get the views squared up and then measure the sides that I need and start to create the piece right on the screen. I make it flat and then I extrude it the .04'' to its width. I put the correct holes in place to fit servos and the horns and then bend the piece to make sure that it fits. I then measure the lengths to confirm that I can fit a servo inside.

After all checking is done I print to scale on a piece of 8x11 paper off an old cheap black and white printer. I then go downstairs (which has essentially been turned into a robot workshop). I line up the paper with some aluminum and then spray some glue on it.

I prick punch the holes and then using a drill press I drill out the correct sizes. I print them with crosshairs and I only use three/four different sizes usually so thats not too hard. And a little oil on the spots for bigger holes preserves the drill bits.

Then using a scroll saw I cut out the pieces. For smaller details I use a file and a steel nibbler and then sand all of the pieces down when I am done (which usually means I have finished a design and moved on... so i rarely sand down the pieces as I get too excited towards a new project).

I use a small sheet metal brake to bend the larger brackets, and I use a tool steel blade, hammer and anvil to pound out the others (I can actually get a radius of .04 with the hammer as well, and its perfectly flat... which works well) and for the really small parts (like the fingers on my robot hand) I use pieces of aluminum or steel to slide between the sheets and then hammer them out again with the tool steel blade.

I then take a solvent to get the glue and paper off. I file down the holes from the drill press so there isnt any excess metal to scratch my servos and then I have the choice to sand down the pieces and paint them.

So that is essentially the process I use every time I want to make some new parts. It takes a little while to get started, but realistically if i have a drawing it happens pretty quickly. I might have to get some sanding done soon

Hope that helps a little.

[DerekZahn]

For sheet work in aluminum, a waterjet shop is probably more economical than a machine shop. You can usually send them a DXF file and get a quote. One place I have used in the past is http://www.dcwaterjet.com

Most cities will have a local waterjet shop that might be easier than mailing stuff around.

Regarding aluminum, if you're going to bend the brackets you don't want to use 7075 or similar alloys because they don't bend very well (it cracks). 5052 is very bendable and probably best for that application, though 6061 is probably okay too.

[Apeman]

Hi everyone... this is my first post. Lurked for a while. Been interested in Robotics for a while but never really gotten into it. I do have an ER1 and have played around with it for a little while and have been looking at Kondo since 2002 (in Japan) when it was still just the torsal. For the past 6 months... been thinking about getting the RN1.

Anyway,I got a small machine shop with a small Taig CNC mill and a 7x14 lathe (not CNC yet). I'm a hobbiest and not a pro machinest but will help out. I've had my mill for 3 years and have cut quite few parts for my R/C and paintball hobbies. All the brackets looks like 2D parts so it will be pretty simple.

As for $$, this is a hobby (for you and me) and so not sure what everyone can afford. So basically, you pay for all materials and tell me what you want to pay for labor. Also... I'll do the first one for free since I'm not even sure if my quality is up to everyone's stanard.

I use Solidworks for CAD, Visualmill for CAM and Mach2 for controller. You can use anything you want to design as long as the outputted G Code is compatible with Mach2(or 3). If you are not sure... use the basic G Code format.

BTW... I'm in So Cal.