Varying rotational axis max speed?

[MRob]

OK so I'm pretty sure the answer to this will be a "lol no", but hey I'll ask anyway...

So I am doing 4th axis carving, in a slow spiral up the length of the piece, and the first issue I ran up against is the feedrate. Z axis is moving up and down to create the profile, as A axis rotates, and Y slowly progresses along the length of the spindle. If feedrate is set for Y then the Z motion is stupid slow, if I set feed to Z then Y (and A) is crazy fast. The workaround is to set the A axis maximum speed in axis settings, to make this the limiting factor for speed of cut, and the feedrate setting itself then applies only to Z. This works pretty well, but obviously gives me no fine control, with a constant speed of cut irrespective of the distance of the cutting head from the centre of rotation of the piece, and no ability to vary feed rate. So! I was thinking, if I had a piece of code that let me vary the maximum speed of the A axis, I could then run a script in the background that was constantly checking the distance from centre of rotation, and adjusting A axis speed accordingly. I am pretty sure there is no way to do this at present? If not, it would be a super helpful feature!! But perhaps it would be a bit difficult to implement.... and likely a bit niche. Still, raising just in case, as properly implemented this would be a decent solution to rotational axis feedrate issues.

On a different topic, is there any code I can use to create a feedrate button? I have made a reset feedrate button, but it would be helpful for me to be able to create a button that took me straight to 20% feedrate.

Loving UCCNC in general by the way, big improvement over mach.

[MRob]

Any chance of a reply? Even if just to answer the feedrate code question. Aside, having feedrate apply to A axis max speed would be another solution, but obviously I have no idea how this would work with the main code base.

[ger21]

The answer is to use G93, inverse time mode, which was added to UCCNC to specifically address this issue.

[MRob]

Oh I see, much more elegant, very nice. Any answer to my other question re code to create an x% feedrate button?

[ger21]

Add a button, number it 20555.
Create a macro with the following code, name it M20555.txt. Make sure it's in the macro_yourprofilename folder.

Code: Select all

AS3.Setfield(20, 232); // Set Feedrate Override to 20%
AS3.Validatefield(232);

This will set the Feedrate override to 20%.

[MRob]

Awesome, thanks for the code. I really appreciate being able to easily mod the screen and add buttons.

Now I just need to modify my fusion post to produce G93 moves, which is unfortunately not as simple as I had hoped. The mach3 post has this built in already, I've tried copying over large chunks but I've obviously missed something. Checked the latest updated UCCNC and stepcraft UCCNC posts on fusion site, and neither of them have this functionality in them either. Tricky. I'm wondering if it might just be easier to mod the mach post to remove the G28 style moves and replace with G53.

[ger21]

You could just use this converter.

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

[MRob]

Interesting, unfortunately my gcode is outputting as G1 moves, no G94's in there. Also the files are 10+mb each, and I am regularly changing them around. Maybe I could find a way to use this as a workaround, but would really like to get the post outputting properly! Thanks for linking though, I do appreciate your taking the time to try and help me out. It might just be easier for me to downgrade to mach3 though, unless I can find a way to get proper G93 moves coded in. Have posted to the autodesk post processors forum, maybe someone there will be able to help me.

[ger21]

G94 is just standard feedrate mode.
As long as there is a G94 at the start of your code, it should convert just fine.

If I had more time at the moment, I'd look into the Fusion post, but I'm too busy right now.

[MRob]

OK, not familiar with G94, although it is not there in the code, all G90 movements.