What is the best stepper for precision

[Ashb82]

I’ve been using centroid controllers to grind parts, what is the most accurate stepper and fine adjustment because I most of the time work in .0001

[suntravel]

Acorn Six with closed loop with scales or Hickory with servo and scales.

Uwe

[jhnmdahl]

If you're locked to stepper (i.e., step and direction) control, the Clearpath SDSK motors have -ELN variants that have 1/6400 of a turn resolution instead of their standard 1/800 of a turn resolution. The standard 1/800 turn models would typically need to be set to 1/1600 input resolution to work right with Acorn controllers, which you can do easily with software and a USB cable.

Since the difference between models is in the software and these motors get paired with Acorn controllers all the time, it would be great if Teknic modified the base models to resolve 1/1600 of a turn rather than just accept it as input for 1/800 of a turn resolution motors (hint hint, Teknic).

Edit - to clarify, the resolvable resolution is always 1/800 turn or 1/6400 turn, depending on the RLN or ELN model, but you can adjust the addressable resolution to be different things, e.g. 1/1600 turn and the motor will skip input steps or skip turning the motor as needed to make them match up.

[ShawnM]

The best stepper is a SERVO.

[ShawnM]

If you're locked to stepper (i.e., step and direction) control, the Clearpath SDSK motors have -ELN variants that have 1/6400 of a turn resolution instead of their standard 1/800 of a turn resolution. The standard 1/800 turn models would typically need to be set to 1/1600 input resolution to work right with Acorn controllers, which you can do easily with software and a USB cable.

Since the difference between models is in the software and these motors get paired with Acorn controllers all the time, it would be great if Teknic modified the base models to resolve 1/1600 of a turn rather than just accept it as input for 1/800 of a turn resolution motors (hint hint, Teknic).

For the record, you can set either of the Teknic RLN or the ELN to 1600, 3200 or 6400 pulses per rev. I have the ELN servo on my plasma Z axis set to 1600 and I have all 3 of the RLN series servos on my small router set to 3200. You are not limited by the RLN or ELN variation. Just make sure you set the motor and Acorn to the same number.

[centroid467]

I think you are going to need to consider the whole mechanical system if you want to achieve 0.0001" accuracy. High resolution is easy to get but accuracy and repeatability down in that range and further requires some effort.

If you are only able to use step and direction then I recommend Delta ASDA-B3-xxxx-L or ASDA-B3A-xxxx-L model servo systems because the standard encoder resolutions are 17 bits (65,335 counts / rev) or 24 bits (16,777,216 counts per revolution) and they are relatively easy to tune within a small number of those encoder counts. Slightly pricier and slightly easier tuning would be Yaskawa Sigma7. Reduction from the motor would also give resolution at the cost of speed and will still be limited by the reduction mechanism's accuracy and backlash.

However, the high resolution encoders on these servos will only be accurate down to their accuracy specification. Seems obvious but it can be overlooked very easily and is not often published. The higher resolution encoders will help by giving finer control over the position but that is moot if the rest of the mechanical system is not capable of positioning that finely.

You will need to know and understand the various accuracy and backlash specifications of all of the components to know which is the limiting factor.

That's a whole lot of words just to say: what are you trying to achieve with what hardware?

[suntravel]

I think you are going to need to consider the whole mechanical system if you want to achieve 0.0001" accuracy. High resolution is easy to get but accuracy and repeatability down in that range and further requires some effort.

If you are only able to use step and direction then I recommend Delta ASDA-B3-xxxx-L or ASDA-B3A-xxxx-L model servo systems because the standard encoder resolutions are 17 bits (65,335 counts / rev) or 24 bits (16,777,216 counts per revolution) and they are relatively easy to tune within a small number of those encoder counts. Slightly pricier and slightly easier tuning would be Yaskawa Sigma7. Reduction from the motor would also give resolution at the cost of speed and will still be limited by the reduction mechanism's accuracy and backlash.

However, the high resolution encoders on these servos will only be accurate down to their accuracy specification. Seems obvious but it can be overlooked very easily and is not often published. The higher resolution encoders will help by giving finer control over the position but that is moot if the rest of the mechanical system is not capable of positioning that finely.

You will need to know and understand the various accuracy and backlash specifications of all of the components to know which is the limiting factor.

That's a whole lot of words just to say: what are you trying to achieve with what hardware?

true words, 0.0001" accuracy is 0.00254 mm. For this you have to set up the whole system right. Axis drives with enough power to do such small steps, take an eye on the thermal expansion of the machine and part and use scales with factor 10 better resolution to get the process under control without baby sitting...

Uwe

[ShawnM]

I didn't want to just come out and say it either but .0001" will be VERY, VERY difficult unless you are in a climate controlled room with the very best equipment. A slight rise or fall in the room temp can shrink or expand the machine that much.