Acorn suitability for small 4 axis lathe.

[martyscncgarage]

I'm confused, page 192 of the CNC12 manual indicates that the M51 command to enable C-Axis is a feature.

https://www.centroidcnc.com/centroid_di ... -v4.14.pdf

It is. You can assign an axis to be a C axis.
But how you mechanically implement that is up to you.
I believe the original poster wanted to use the same motor to be a spindle and a C axis. That means that the control would have to stream step signals to drive the axis motor as well a spindle motor (The RPM limitation could also be the pulse stream the drive would accept along with max voltage the drive could accept) but then TURN it into a C axis when commanded.

At this time, and I confirmed this with Centroid. ACORN can not do this. It is on their list of things to do.
But remember, its not just as simple as taking a servo motor and driving a spindle. You also need to lock that spindle in position and NOT rely on the axis motor to hold position against tool cutting pressure.

Right now, the user has to use a drive/axis motor to position the spindle (along with a brake mechanism) and a SEPARATE spindle motor to utilize the C-Axis feature

Marty

[vtcnc]

I'm confused, page 192 of the CNC12 manual indicates that the M51 command to enable C-Axis is a feature.

https://www.centroidcnc.com/centroid_di ... -v4.14.pdf

It is. You can assign an axis to be a C axis.
But how you mechanically implement that is up to you.

Marty

I see. OK, thanks for the explanation.

[JoNo]

I'm confused, page 192 of the CNC12 manual indicates that the M51 command to enable C-Axis is a feature.

https://www.centroidcnc.com/centroid_di ... -v4.14.pdf

It is. You can assign an axis to be a C axis.
But how you mechanically implement that is up to you.
I believe the original poster wanted to use the same motor to be a spindle and a C axis. That means that the control would have to stream step signals to drive the axis motor as well a spindle motor (The RPM limitation could also be the pulse stream the drive would accept along with max voltage the drive could accept) but then TURN it into a C axis when commanded.

At this time, and I confirmed this with Centroid. ACORN can not do this. It is on their list of things to do.
But remember, its not just as simple as taking a servo motor and driving a spindle. You also need to lock that spindle in position and NOT rely on the axis motor to hold position against tool cutting pressure.

Right now, the user has to use a drive/axis motor to position the spindle (along with a brake mechanism) and a SEPARATE spindle motor to utilize the C-Axis feature

Marty

To be clear on the spindle / C axis combo switchover :

Marty, I would read your sentence revised as follows-
That means that the control would have to stream step signals to drive THE SAME PHYSICAL MOTOR as a spindle motor in 'plain' turning mode, and as a Rotary Axis in C Axis mode.

Note that the use of a brake on the 'now' C axis is not necessarily as you state - first, it depends on the holding torque capability of the 'servo', and second, in lieu of a Y axis, many, if not most, part milling operations require coordinated motion between C axis and X/Z axis - eg, milling a HEX onto the end of a shaft in the C axis chuck , with the mill cutter axis in the same plain as the C axis - milling a course pitch thread or helix, etc.

I am trying to see if LinuxCNC may do what I wish - it does have all the hooks and functions to do so, but requires deep linux knowledge, ability to modify and add routines yourself, etc, etc..and THAT is a BIG journey and I am suffering! - I am close to just procuring the Acorn and getting the lathe going to the extent the Acorn permits, and hope Centroid adds the extra features later! The Acorn is a very polished package, and my project is about the lathe, NOT about making a controller!

Thanks to all who commented.
Regards
Joe

[vtcnc]

Hi Joe,

I'm keenly interested in your project as I'm researching to do the same thing you are. I have access to a Hardinge HC headstock and bed and plan to fit up an XY stage with Clearpath SD units. I'm kind of stuck on this same spindle motor selection problem as you.

I guess I'm fundamentally misunderstanding what Marty is saying. I read his explanation as you interpreted it. Acorn cannot do plane switching using the same spindle motor that serves dual duty (plain/C-axis). But the Acorn documentation suggests it can in the marketing literature and Marty suggests that the C-Axis can be utilized if using seperate motors.

So my misunderstanding in WHY this is the case is apparently in not grasping why a servo motor timed to the spindle can't be utilized as the C-axis. I THINK/GUESS that it is because the M spindle commands in the g-code are not telling the C-axis to take step and direction which is what the Acorn can do, at least according to the documentation and how I interpreted Marty's answers.

[tblough]

Looks like a small microcontroller project. 0-10V analog in along with spinFwd and spinRev and generate a step and direction pulse train. Use some isolation relays to switch this circuit in when spinEnable is on, and switch in axis4 pulse and dir when spinEnable is off.

[martyscncgarage]

Acorn can't drive a servo motor in position and analog spindle mode...YET (On Centroid's laundry list of feature enhancements)
You can assign any axis motor as a C axis. But YOU have to devise a way to couple it to the spindle.
If you need to home the spindle, add a sensor to it perhaps. You could write a G code program to home it before using the C axis...

[Navanod]

Dont shoot me but was the feature to use the step/dir as both an x drive and spindle ever implemented?

[cnckeith]

Dont shoot me but was the feature to use the step/dir as both an x drive and spindle ever implemented?

sorry, its still on the list. we've been concentrating on Plasma with a few Mill,Lathe,Router small improvements and fixes tossed in there for the last months now.