How turn off servo loop for one axis?

Hello there. We have a machine with 5 axes, one of these axes is for turning the part. It has the ability to spin endlessly in any direction. Is it possible to disable the tracking of this axis and set an analog signal to move this axis? So that the system does not count degrees and simply returns it infinitely. Like an ordinary lathe spindle. Thanks for the help.

Yes, this is possible.  Closest analogy would be a "C-axis" lathe spindle, which needs to switch between spindle mode and positioning mode.

The positioning part can be done in a couple ways:

• Using M19 to orient the spindle, or
• Creating a separate axis, and switching between spindle mode and axis mode as needed.

Option #1 is easier to set up as there is no separate axis to manage.
Option #2 is more flexible, as the movement can be synchronized with other axes and the speed/feedrate can be managed like a normal axis in gcode.  In addition, the display backplot can be made to track the axis movement.

There are examples of both - admittedly a little hard to find - throughout the forum.

Which use case is better for your machine?  An 'indexer' or an axis?

Thanks for the help. I will better describe my task to you so that you can suggest what you think will be better.
First, the part must be ground with a diamond wheel into a perfect cylinder. Then the "spindle" stops, is indexed and is already used as a normal rotary axis. The last stage, a hexagon is formed on the part. All this must be done in one installation. And preferably with one program.
Therefore, most likely, the idea of ​​using M19 is better. This is in my opinion. Thank you.

First thing to keep in mind is that the hardware is the same for both control methods - no need to worry about picking one and having to change anything serious if you find you prefer one over the other.

Both methods can be commanded via gcode, within a single program.  If I wasn't clear before, the difference - to the programmer/operator - is that with M19 orient you cannot orient while another axis is moving.  Think of it like an indexer and not a continuous axis:

• spindle rotates, part is ground
• spindle stops
• spindle postions and is held in place
• machine/grind one hex face
• index spindle
• repeat 5 more times
•  

But if you need one or more additional axes to move while rotating the part (to grind the hex shapes) - perhaps grinding a fillet at the edge intersections - you will likely want to pursue the 'axis' postioning scheme instead of the spindle-orient method.

It sounds like you've already got the machine and aren't building something from scratch.  Is this the case?  And are you already familiar or experienced with LinuxCNC and just need some help with this particular spindle/positioning feature?

Or are you very new to LCNC and are just trying to figure out if what you want is possible?

Thanks for the answer. Yes, I already have 5 axes implemented on a Strausak machine using LinuxCNC. Axis A rotates the part. But anyway, I'm a newbie and trying to learn LCNC. That is why I asked the question whether the system will be able to do this task.
The main thing is that it should be done in one program and one installation of the part. Thank you.

I have uploaded all my files to the forum. Maybe this will help. It's just that I don't even know how to implement switching between the axis and the spindle. Tell me where to start. Thank you.

Maybe I didn't express myself correctly. I have 5 axes and a spindle. Can I configure the system so that I have 2 spindles at the same time? Will one of them switch to M19 mode or switch to axis mode? Can someone tell me how to implement this correctly?

You've expressed yourself clearly, no worries there.

What your're contemplating is possible, but a bit complicated.  The lack of responses likely isn't due to disinterest or miscommunication - it's that there aren't a ton of people who frequent the forum with an identical situation who can just post a working example for you to copy-paste.  And remember that LCNC community is a group of people with no obligation to get involved with anyone else - other than what interests them.

On the bright side, there are some very helpful, shockingly bright people that frequent this forum.  You aren't completely up the creek.

I don't have a known-working config to give you, although the lathe I'm working on will have a very similar feature (axis + spindle) when finished.

Rather than posting your files, I think the most productive thing is for you to research similar configurations posted on the forum.  That's not the answer you likely want, but it'll help in the long run as you start to digest the logic.

Here's a series of posts where Andy Pugh helped a nice gent get his lathe working as a C-axis as well as a normal spindle.  He was kind enough to post his entire config recently when I pestered him for it.
forum.linuxcnc.org/10-advanced-configura...stop-command?start=0

Here's some links to more recent discussions regarding spindle-as-axis

forum.linuxcnc.org/10-advanced-configura...is-from-inside-gcode

forum.linuxcnc.org/10-advanced-configura...-challenges?start=10

Download any attached config files you find, have a bit of a read, and when something doesn't make sense, post back here and I or someone can try to help you get some context.
 

... and maybe this should not be here in 'Forum Questions'. I mean isn't this place for questions about the forum itself???

IMHO a better place would be in 'Advanced Configuration'. Maybe a mod could move it there