Robot catched

OK, I just bring this robot (http://richart-consalt.ru/robot.jpg) to my kitchen. And I'm impressed with construction of it. I will publish some photo of it in future, and now several words:

1) as far as I understand the motors of this robot is non-steppers at all. Instead of this, disk with holes mounted on the axe (just like in mechanooptical mice), and optoswitch used

2) Reed switch and magnets used as endstops.

I'm not sure now if steppers will be tought enought to turn this axes...hm.

Edited 1 time(s). Last edit at 02/06/2008 01:46PM by Assargadon.

Hi Assargadon,

... here i have some images (borrowed from a german CNC-forum with login) showing how to adapt steppers to lathe-axes, where the needed 'horsepowers' are much bigger then in your robot:





So you could drive your robot even with the small-sized steppers salvaged from old floppy-drives or HD's - but then with some bigger scaling factor for the gears ...

Viktor

If one skilled enought to make this kind of reducer, he can just use intrinsic reducers of this robot...hm.

By the way, how can I measure the "rotating force" of a drive to select proper steppers?

By the way again, do this system really use rubber toothbelt? Not metal one?

I think the optical wheel + (DC, probably) motor combination means you have a servo motor.
[en.wikipedia.org]
I would save them for future use to turn your robot into a CNC router.

I believe glass, steel wire, or kevlar reinforced rubber belt is pretty reliable for these applications. Consider the timing belt in a car.
[en.wikipedia.org]
If you are curious, go look up some specifications on
[www.sdp-si.com]

There are a number of ways to measure the torque of motors.
[www.google.com]
You can use a torque wrench or a fishing scale to measure non-rotating torque, or fit a pulley wheel, string, and weight onto it and use basic physics to calculate the rotating or stalling torque.

If you pay a bit, you can get strong steppers. However, I suggest you buy the RRRF steppers. If they aren't strong enough, save them to use with your generation n+1 machine, and buy some stronger ones.

Thanks, Sebastien.

Yes, it's some kind of servo motor, manually created. In russian, "steppers" and "servomotor" are often mixed. Now I understand the difference clearly. Stepper is specially designed motors with lot number of poles, servo is motor with some feedback system - is it correct?

By the way, why should I save this servo-stuff, if I can just use more powerfull steppers in CNC router?

I didn't buy steppers yet, but I plan to do that. As far as I understand I need (maybe) stronger motors than RepRap has. But I need something to measure and something to compare.

Is torque published for steppers? I should search for several stepper-rich places to determine this

Hi Assargadon,

look here [en.nanotec.com] for a list of types and torques.

Viktor

'Yes, it's some kind of servo motor, manually created. In russian, "steppers" and "servomotor" are often mixed. Now I understand the difference clearly. Stepper is specially designed motors with lot number of poles, servo is motor with some feedback system - is it correct?'

Yes. Steppers have the coils on the outside, and a rotor with multiple magnetic regions.
[en.wikipedia.org]

Nomenclature (naming) may get more complicated sometimes, when they mount an encoder on the thing. They then use feedback to control it, and _technically_, you could call it a servomechanism, if you wanted to confuse people.
[en.wikipedia.org]


'By the way, why should I save this servo-stuff, if I can just use more powerfull steppers in CNC router?'

If you use your current machine to print out the parts for a darwin-type reprap, you can mount the steppers on darwin and then remount the old servos on the current machine to use as it a CNC router. Or you can buy a new set of steppers. In either case you'll have to build or buy the appropriate circuitry.

I don't know what is appropriate for your needs.

Thanks Sebastien, thanks Viktor.

Last night I experimenting with robot and I find the way to force it move their axis. It seems fully functional.

Even better: after this experiments I send several requests about this robot to different humans uses it, as was discovered by google. And this morning I receive detailed technical description - unbelievable quickly, isn't it? I plan to make control software prototype this weekend.

So I have 2 possibilities:

First is use ready-to-use hardware. It needs modifications for the RepRap software. Fairly big modifications, as far as I can understand. I don't know for now how modular RepRap code is.

Second is using a ready-to-use RepRap software. It needs new motors - steppers - for the robot.