Rotary Axis speed control

[srracer]

The help manual has this twisted sister paragraph about this issue. It is about as clear as mud. Furthermore, if a user is in fact setting up a rotary axis and a check box says "Axis is Rotary" then that checkbox should be checked. Period. Full Stop.

That is not the case here, instead, checking that box results in the axis not running correctly for the vast majority of people running a rotary axis. Some of them never notice it because they primarily cut along the linear axis and do not see that the rotary is not rotating under feed rate control.

Like I have posted elsewhere, this miserably labeled checkbox cost me 2.5 days and $400. And yea, I read that stupid paragraph in the manual a dozen times, it is so twisted it is virtually incomprehensible.

I thought about this 'work around' (hack around?) but to me this completely screws up the feedrate calculations. I suppose you could still use G93 acceptably, but if you forget, you are going to get some very weird behavior if you have setup your rotary pulses such that your units are in degrees. And if you setup the axis so that they are not in degrees but in inches/mm, then what diameter are you supposed to assume your part is? That is why I am reluctant to take this approach. I'd rather introduce a .0001" offset in X/Y/Z when I am using the A axis so that I can control feedrate the way I expect AND have the units behave correctly. But this is also a frustrating workaround.

[Greolt]

Yes I think I have a good grasp of G93 and its advantages.
I was one that was urging Cncdrive to include it in UCCNC.
Doesn't feel like that was very long ago, but I guess it has been a few years.
I used to have to revert back to Mach3 for rotary jobs.
And prior to Vectric adding G93 I used a program that someone wrote that would convert code to G93.
My apologies to that someone, I can't remember his name.

[TReischl]

In case some of you missed this. . .

If you want your rotary to move at something other than rapid when it is told to move at a feedrate (G1) then

TURN OFF THAT AXIS IS ROTARY checkbox!!!!!

What that checkbox should say is probably AXIS IS INDEXER

[TReischl]

For rotary, G1 is tough (impossible) because the speed of the bit along the material depends upon the radius of the material where the tool is. So I sympathize with anybody who has to write a controller to interpret what is meant by the G-code.

That's why G93 does make a LOT of sense to me for any moves that utilize a rotary axis. That said, it should work when the rotary axis is the only axis to move. Currently UCCNC does not do that. Any rotary only movement is only at max rapid speed. And I agree, this should be fixed.

No, G1 is not tough or impossible. Remember we are talking about software. I wrote this type of software for a lot of years, anyone who writes this stuff has several variables that are usually global in nature X, Y, Z, A etc. Those are the current positions the machine has been commanded to. The machine does not make any move without the software knowing exactly where it went. So it does "know" where the tool is in relation to the center line of the rotary axis.

If you turn off "Axis is Rotary" and put the machine in G93 the rotary axis will move at feed rate rather than rapid.

In my humble opinion that checkbox is mislabeled, it should probably read "Axis is Indexer". Because that is how the rotary acts when the box is checked, like an indexer, full rapid to commanded position.

[Greolt]

Just to finish off my post above. I was unable to remember the author of this very handy tool.

Shawn Gano is his name and here is a link to his G93 code convert software.

If your CAM software does not include "Inverse time mode" capability then take a look at Shawn's site.

This can really improve your 4th axis performance.

https://www.ganotechnologies.com/cnc/rapidrotary/

[srracer]

No, G1 is not tough or impossible. Remember we are talking about software. I wrote this type of software for a lot of years, anyone who writes this stuff has several variables that are usually global in nature X, Y, Z, A etc. Those are the current positions the machine has been commanded to. The machine does not make any move without the software knowing exactly where it went. So it does "know" where the tool is in relation to the center line of the rotary axis.

If you turn off "Axis is Rotary" and put the machine in G93 the rotary axis will move at feed rate rather than rapid.[/quote]

You are missing my point. I manage 20+ software engineers - I have a pretty good idea of the complexity. The point is if you uncheck rotary, now you have 2 axes that have DIFFERENT units (one is in inches/mm one is in radians/degrees) and you are trying to control the feedrate with a single value (inches/mm). You could *try* to setup your rotary axis so that its units are close to the same as what you are using for the rest of your axes, but that will only be accurate for a single radius of part in your A axis.

So to uncheck "Rotary axis" is going to create far more problems for most G-code programs in my opinion. The reality is, G94 G1 F? is not intended to be used for rotary axes.

[Greolt]

The point is if you uncheck rotary, now you have 2 axes that have DIFFERENT units (one is in inches/mm one is in radians/degrees) and you are trying to control the feedrate with a single value (inches/mm).
You could *try* to setup your rotary axis so that its units are close to the same as what you are using for the rest of your axes, but that will only be accurate for a single radius of part in your A axis.

That is pretty much the whole point of "Inverse time mode" where it relates to a rotary axis. It eliminates the issues of mixed units. Eg. mm and degrees.

[TReischl]

:::::sigh::::::

I am just going to go out to my shop and run my rotary not understanding the point, whatever that may be.

[Greolt]

LOL
USA, UK, Australia, we all use English but there are some funny differences.

[cncdrive]

We checked the issue and the rotary axis moved with full speed with G1 because the feedrate is calculated on the linear axes the rotary axis just follows.
The feedrate is programmed in units per min, the unit is inches or mm, and the rotary axis unit is degree (angle).
Now if only the rotaty axis is programmed then the rotary axis runs with max. velocity, because there is no linear axis movement to calculate the feedrate for.
So, now we modified the working that when in G94 mode and the rotary axis is programmed with G94 then it will rotate with the programmed degree/min velocity.
In G93 it will reach the target in the programmed time even if only rotary axis is programmed.
It will work like how described in 1.2117.