uArm??An open source robot arm

[JimboZA]

The uFactory guys have accommodated me royally... they sent cad drawings and a parts list...

Hi JimboZA,
can you share those cad drawings and part list?
Thank you in advance!

No, they're not mine to share. You'll need to speak to uF about that.

[JimboZA]

My parts are ready to collect...

[keeper63]

My parts are ready to collect...

Did you get the gripper cut as well? The uArm team sent me the drawings as well, but I haven't yet cut them (other things on my plate right now); I was going to do it myself at my local TechShop (I have access to their laser cutter).

I have been helping with some writing and documentation; the directions they sent me aren't too bad, but I did end up re-ordering them in my write up for them to make assembly easier (at least, I think it will be - the original instructions jump from the base to other parts to parts of the arm, back to the base and shoulder, other parts of the arm, etc - when it is actually possible to assembled and concentrate on base components, then back arm, then fore-arm, etc).

Anyhow - good luck with your build; it's actually a very well engineered product, from what I could see. One thing that wasn't mentioned (unless I missed it somewhere?) was how thick of acrylic or other material you are supposed to use - what did you select?

Also - did you have the gripper cut? It was in red on the PDF (and maybe on the DWG file?) - so I am not sure how it would've been interpreted if you sent it off to be cut...

Can't wait to see your build, though! Are you going with standard analog servos, or are you going to upgrade to digital ones? I had planned to go digital, with strong ones for the base and shoulder (also, I was thinking maybe to cut a very thin piece of PTFE or nylon film for a base bearing), and a less strong one for the forearm; probably all with metal gears and ball-bearings...

...all in good time, though.

[JimboZA]

Yep I had everything on the pic cut.

It says on there that that the bulk of the parts are 5mm (the main area on left of pic) and the others- the small area to the right- are 3mm.

I'm fetching it all tomorrow: the cutter guy is near my work.

I have yet to find the hex brass standoffs in all the sizes: my electronics supplier only has very short ones- I suppose for mounting boards in enclosures- and I'm not sure where to try next. But all in good time....

EDIT... re servos.... looks to me like the servos are readily accessible for replacement, at least going by the vids. So for the first build we'll probably just use the crappy 3x  hobby servos we have (4.3kg), then upgrade later. Unless it looks like a pita to replace them, in which case I might spring for 3 decent ones up front.

Our objective here is to give my daughter a decent test- and development-bed for her studies. With a decent arm, and the flexibility this one gives for end-effectors, she can concentrate on the control side without having to worry about a crappy arm made of ice-cream sticks and rubber bands falling apart.

MORE EDIT... This thread relates

[keeper63]

It says on there that that the bulk of the parts are 5mm (the main area on left of pic) and the others- the small area to the right- are 3mm.

Hmm - maybe I'll have to look at the files more closely! So far, I've only looked at the PDF as I don't have any software installed to view the DWG file (need to find something for Ubuntu at some point).

I'm fetching it all tomorrow: the cutter guy is near my work.

Well, that's convenient. We actually have the manufacturer (Universal Laser) of the laser cutter our TechShop uses near my work, but I don't know anybody there who'd take on the project if I wanted it done (which is too bad, because I've been told that if you work there, you can basically use any machine you want!).

I have yet to find the hex brass standoffs in all the sizes: my electronics supplier only has very short ones- I suppose for mounting boards in enclosures- and I'm not sure where to try next. But all in good time....

I've been looking at a variety of options here - I can't say for certain, but I would bet McMaster-Carr would have every fastener part needed. Between them and Grainger, among a few others...

EDIT... re servos.... looks to me like the servos are readily accessible for replacement, at least going by the vids. So for the first build we'll probably just use the crappy 3x  hobby servos we have (4.3kg), then upgrade later. Unless it looks like a pita to replace them, in which case I might spring for 3 decent ones up front.

Well - based on what I have seen for the assembly - you would have to disassemble and re-assemble the base components quite deeply to replace the servos, which wouldn't be easy until after a couple of times doing it (and even then, it might still be a pain to do).

Our objective here is to give my daughter a decent test- and development-bed for her studies. With a decent arm, and the flexibility this one gives for end-effectors, she can concentrate on the control side without having to worry about a crappy arm made of ice-cream sticks and rubber bands falling apart.

Then I would say going with the low-cost "crappy" servos you already have might be more than sufficient to use first time out; you might try to find their spec sheets, and compare them to the spec sheets of the servos that the uArm team use in their current prototypes (they are using some form of "Power HD" brand analog servos - maybe one of the images can give you more detail - or you could ask them).

If your servos seem close enough, it might work out ok (that said, don't try to pick up anything too heavy if they don't have somewhat higher quality gears and/or bearings - or things might break).

Good luck with the project!

[JimboZA]

I can't say for certain, but I would bet McMaster-Carr would have every fastener part needed. Between them and Grainger, among a few others..

I'm in South Africa where I don't know of those brands. I've tried a few places. My brother suggested one chain I hadn't thought of, I'll try them. If I can't find the right ones, I'll use a long screw with a tube-like spacer instead.

Re the servos, my HK hobby servos are 4.3kg cm ones with plastic innards. The 10kg cm steel ones would be nice, for sure.

[keeper63]

I can't say for certain, but I would bet McMaster-Carr would have every fastener part needed. Between them and Grainger, among a few others..

McMaster-Carr and Grainger are to mechanical industrial needs as Digikey and Mouser (and/or RS) are to electronics; they are global suppliers.

That said, they don't tend to be inexpensive, depending on what you are buying (and unless you are buying in bulk - depending on the part). Also - you may have to purchase 100 pcs of say a particular size screw, when this project only needs a handful.

[JimboZA]

I've emailed the local Grainger guy... thanks.

[Chagrin]

http://www.mcmaster.com/#standard-threaded-standoffs

I don't see any at Grainger.

[JimboZA]

Fetched my laser cut parts today  

EDIT.... checked that the servos and bearings fit snugly in their holes, which they do, so the cutting is good. The two halves of the gripper tooth together nicely.

Now to gather all the orther little bits-and-pieces.

[JimboZA]

I'm struggling to get the longer FF standoffs. But one guy quoted MF too, so that gets screwed into a shorter FF and end up with a FF of the right length.

[JimboZA]

So most parts in hand: got all the bearings the other day, and fetching the standoffs tomorrow. Then just need all the screws and nuts, from a place just up the road..... so maybe next weekend we'll start assembly.

Current thinking, is to have the Arduino with Ethernet act as an HTCPCP server responding as contemplated in RFC2324 and have the arm do the work. (Error 418 notwithstanding).

[PaulS]

and nuts, from a place just up the road

You sure you want to go there?

[JimboZA]

I'm nuts enough?

Construction not started yet, but meanwhile, the uArm is featured in the South African national press...

[JimboZA]

Right, I think we have everything.... let construction commence...