[Gariep]

Hi everyone.
I want to build a rotary positioner for my welding robot. I have a low budget and i have little knowledge on the subject.

I need a minimum torque of 1600oz/in on the positionner. Bigger torque would be welcome.
I was thinking using a timing belt and gear kit similart to this one here
I can't use direct drive as i don't have enough place behind the positionner to set up a motor.

I was looking at a nema 34 step motor kit may be this one here

What i want to do is to be able to rotate 45-90-135-180-225-270-315-360 degree rotation. It don't have to be fast.
And i might need to do continuous rotation at different speed.

i have digital output on my robot from which i can send pulse from 0.1 sec to as much as i want. I don't want it to be pulgged on a computer to be running. I'm looking for a solution i can program and execute "routine" depending on either the i/o activated or the amount of time an i/o is activated.

would you use a timing belt like the one in the ebay link of another solution?
I'm i better to go with a integrated Step Motor + Driver + Encoder + Controller?

Thanks you for your help

David

[RomanLini]

A stepper motor might not be ideal. I would look at some large DC motors or gearmotors, and a final drive belt or chain.

For positioning you could use 8 limit switches, for the 8 desired positions.

Of course if you have 1:8 gearing you only need 1 limit switch. Or 1:4 gearing and 2 limit switches etc.

Then you use a relay to rotate the motor until the switch is detected. It's avery common commercial setup as DC motors have better power and are cheaper than steppers, and the drive system is much cheaper. If they need positioning accuracy the usualy solution is to use a mechanical detent catch (something like a ballbearing and spring that catches in a hole) or a solenoid activated locking pin if it subjected to force.