5 Phase steppers (0.72 Deg.) using a SCARA system and Duet 6XD.

[dogboy]

Hello everyone,

I am currently looking into upgrading a machine I have to use a DUET 3 6XD board.

My existing old machine (Versatronis RV4S pick and place assembly machine), is based on a SCARA system and has 0.72 Deg. 5 phase stepper motors, made by Sanyo Denki. The Stepper drivers (also SanyoDenki) has various micro step settings from 1 to 250. (1, 2, 2.5, 4, 5, 8, 10, 20, 25, 40, 50, 80, 100, 125, 200 & 250).

I am new to the world of Duet and have a question.
Using the Duet config tool, initially setting the motion type to Cartesian (followed by setting up for a SCARA system manually), is their anyway I can configure the Duet 6XD board to support the 0.72 deg. steppers with with any of the micro step options.

The initial cartesian settings only offer 0.9, 1.8 or 7.5 Deg. steps.
How can I setup 6XD board for the 0.72 Deg. 5 phase steppers and drivers I have?

Any ideas or perhaps documents pointing me in the right direction would be really appreciated.

Thanks
Paul

[jay_s_uk]

@dogboy I'm assuming the steppers have their own drivers?
In which case the 6XD doesn't care about the microstepping set. All it cares about are the steps per mm

[dogboy]

@jay_s_uk Thanks for your reply.
Ah, yes, it did click after I posted this message, but my confusion is how does this relate to a SCARA setup.
Maybe I am missing something here (more than likely) but if each SCARA axis is rotational, how do you measure steps /mm?

Obviously, I am new to all this, but I have just realised of course with external drivers, it does not matter about the micro stepping.
I am just confused about the setup for a SCARA system.

Can you recommend any links or docs that may explain this in more detail for a SCARA setup with a DUET 3 board.

Thanks
Paul

[jay_s_uk]

@dogboy I've never setup a scara but there are a couple of pages on the duet docs depending on the type of scara.
https://docs.duet3d.com/User_manual/Machine_configuration/Configuration_SCARA
That's for a serial Scara
https://docs.duet3d.com/User_manual/Machine_configuration/Configuration_five_bar_parallel_scara
And that's for a 5 bar parallel scara

[dogboy]

@jay_s_uk

After reading a lot of documents, it would seem that once the Duet board is setup as a cartesian machine, I need to use the M669 command in the config file to tell it that a SCARA system is used. I also need to use the M92 command to set the the steps / degree of the two SCARA joints, these being Xnnn and Ynnn which relate to the proximal joint and the distal joint.

My next question, is how can I use the M92 command to set the steps/degree if one degree of rotation on the joint does not give a whole number of steps?
Of course that comes down the the rotational accuracy and I assume that I would have to measure the angle of the rotation against a certain number of steps moved. Or calculate this, but it would be hard to measure all the required parts to work this out.
Hopefully, with the gearing ratio of the motors / large drive wheels & belt setup, along with any micro steeping, this could be pretty accurate.
Sounds like it will be a bit if an experiment more than anything else to get it right.

Time to fire up my Duet 3, 6XD!

Thanks
Paul

[droftarts]

@dogboy said in 5 Phase steppers (0.72 Deg.) using a SCARA system and Duet 6XD.:

My next question, is how can I use the M92 command to set the steps/degree if one degree of rotation on the joint does not give a whole number of steps?

Steps per mm don't need to be integers, you can use decimal points. See the example in https://docs.duet3d.com/User_manual/Machine_configuration/Configuration_SCARA#example

M92 X28.6738351 Y28.6738351 Z2560

Ian

[dogboy]

@droftarts Hi Ian,
That's perfect. Thank you.
I did think about this but assumed that it had to be an integer and never spotted that in the example!
That makes things much better all round.
I just need to work out the gear ratio, then I should know the Steps/Deg.

Cheers
Paul

[o_lampe]

@dogboy If you really need high accuracy, you can add positional sensors on the motor shaft(s) and the joint(s).
Closed loop is still pretty new in RRF, but once tuned in seems to iron out all accuracy problems.
Homing the arm once in a while will have a similar effect.