Rotary axis

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Rotary axis

Postby naijin » Tue Oct 09, 2018 10:19 am

Hi there, I am half way through building a rotary axis for my cnc router, I am using uc100 and I have a 4 axis break out board, I need to know how to set the axis up in uccnc, are there any plug ins or wizards available in uccnc?
at present I have no idea how to configure the rotary axis, do I use Y axis to rotate the rotary axis or can I utilise the fourth available axis on the break out board and have all four axis working? if anyone can explain how it could be done
I would very much appreciate it( and have a lot less sleepless nights.)

Nick :?: :?: :shock:
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Re: Rotary axis

Postby Robertspark » Tue Oct 09, 2018 7:57 pm

20 views and no comments....

UCCNC does not have a rotary axis function, all axis wthin uccnc are treated as linear axis.

That being said, some people tend to use the 4th axis as an indexing axis and then its contol becomes a little simpler to consider with regards to operation, or as a spindle in the case of a lathe, then the incremental motion tends to be less of a concern.

No, there are no plugins / wizards within uccnc for 4th axis motion.

The 4th axis is normally the "A" axis, or "B" or "C" depending upon the orientation to the other axis.


You normally don't use X,Y or Z as they are (nearly always) linear {I don't know when X,YorZ are not linear.... but I'm sure some clever bod will point out the error of my ways}

Depending upon your machine setup, you may have X X' Y and Z axis, where X' will be a slave to X

I've also heard of the slaved axis being called UVW.... but I don't think this is quite right as they are "normally" secondary axis additional to the primary XYZ axis such as the image below.

:roll: I digress.....

What is it you "really" want to do (what sort of motion)?

I have a 4th axis on my plasma, it's treated as a linear axis with sheetcam so uccnc not having a rotary axis option makes no difference to me.
Hoever, it uses a 200 step/ revolution stepper, which operates on 10 micro steps and have a 6:1 gear reduction drive.

Which gives me 12,000 steps per revolution

Now you have an option...... you can set it up as 12,000 steps per unit (with the unit being 1 revolution.... the problem with that is if you wanted to increment say 10 degrees would be 0.027777r units )
Or you could set it up as 33.3333r steps per unit (with the unit being 1 degree {you'll probably suffer some rounding error issues and would suggest choosing another uStep increment .... like 12 or 6 micro steps..... that way it would be 40 steps per unit or 20)
You could also set it up in radians or any other unit that takes your fancy and serves your purpose.

You also need to consider that the object you are machining will have an outer diameter which in turn provides a circumference which translates to a "linear" distance relative to the diameter of the 4th axis. Machining a 100mm (4") object at 200mm/min will give a totally different 4th axis rotational speed than a 50mm (2") object. It is possible to correct for this but not via changing the step on the fly..... you have to change the feedrate..... and also consider that a 100mm metal bar spinning at 4000rpm could become quite a projectile if it came loose..... but you probably won't be getting that out of your 4th axis with a stepper motor though.
I had a go at creating a constant surface speed macro a while ago. Have a read of this post, you'll need to modify the macroloop as per the suggestions in the post.
Einstein ― “If you can't explain it to a six year old, you don't understand it yourself”
...working my way through the 1000+ ways things don't work to find the one that does
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Re: Rotary axis

Postby naijin » Thu Oct 11, 2018 8:42 am

Thanks for the reply Robert, looks like not many people are using rotary axis with uccnc, Its is great software but the lack of rotary axis is a very big limitation, just as well I still
have Mach 3, may have to go back to it just to operate the rotary, or I may just stop building it and wait for uccnc to add rotary axis to their soft ware ( If ... and When ?).
Nick :?
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Re: Rotary axis

Postby cncdrive » Thu Oct 11, 2018 10:20 am

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Re: Rotary axis

Postby Greolt » Thu Oct 11, 2018 9:56 pm

For all 3 axis work I use UCCNC but for rotary axis work I revert to Mach3.

If UCCNC interpreted G93 (Inverse time mode) then it would be a big step forward IMO.
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Re: Rotary axis

Postby naijin » Sat Oct 13, 2018 10:07 am

Now you have interested again, I will finish building my rotary axis, but where can I get some assistance as to how to set it up in uccnc?, how to calibrate it , if some one can explain it in very basic
way I would greatly appreciate it.

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Re: Rotary axis

Postby ger21 » Sat Oct 13, 2018 10:37 am

Just set it up as the A or B axis, and set the steps/unit to be steps/degree of rotation.

You'll likely have issues with the feedrate, though, without G93 or some other method of properly controlling the feedrate at different depths of cut.
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