I would be interested in knowing how the attached NC file runs. Note*** There aren't any A axis moves, this file is meant to be ran in tangential mode. Run it in the air first (as always) to check extents and what not.

Currently I don't have the A axis setup as a rotational axis on the config page.  I'm treating it as a normal linear motion axis and have just set it up on the motor tuning page such that 1 unit of travel = 1 degree of rotation.  Then each G1 code must contain the A parameter to keep the wheel tangent to the line being traveled.  This works ok, except for the problem previously mentioned where the angle lags the curve unless A command is broken out onto a separate line that comes before the next X Y command.

So in order to run the WINDOW.nc file using tangential mode built into Mach3, is the only thing I need to do is specify the A axis as rotational on the config page and maybe also set the "Use radius as federate" option on the toolpath settings page?

No, that is not the way to run tangential mode.

OK, I got the WINDOWS.nc file to work great, this is exactly how I need my own files to run.  The feed rate is constant, the wheel stays tangent to the curve and there is no jerky motion.  If I specify the A axis as rotational the file generates an error when it loads, so I have to leave the A axis as not rotational.  Just clicking the tangential button on the settings page is apparently all I need to do.  The only problem is that when I run my own files with the A commands removed, I don't get the smooth motion like the windows.nc file has.  With a series of G1 X Y commands, I get a stop on each point when the wheel angle changes, so the motion is very jerky.  It only appears to work smoothly with G2 commands.

I am afraid your files are not going to run like this  . You need to change your code so it is like the example.

 

OK.  I've tested it on both G2 and G3 codes and it works.  I had a diamond shaped panel I was trying to do using my old method and it just wasn't working, but this new method with the arc commands works good.

When converting poly-lines to arcs in Cam-Bam it will still insert G1 statements for portions of the curve that are straight lines, so I still get stops on that.  I may be able to convert the G1 commands to G2 and G3 in my post processor, but at least there's not that many of them so if I have to put up with an occasional jolt during the run that is fine.  It would be good if the tangential mode was fixed for G1 commands in Mach4 though.  I realize development on Mach3 has probably stopped in order to avoid dual maintenance issues with the old and new versions.  I'm a software developer myself, so I know what a nightmare that can be. 

Anyway, I have a working solution now so thanks a lot for the help!

I can post a picture of my upcoming 8 foot diameter flying saucer here when I get it done if you want.  I'm putting quad controller boards on these things and actually making them fly

  

No problem, glad you have a solution. Mach3 is what it is as you said. The developers are working on tangential in 4 right now though and I think you guys are gong to love it.

By all means, post the pics. We like pictures.

Brett

The only other thing I need to figure out is how to turn the tangential mode on and off from within the G-code script.  I tried creating a file for an arbitrary M code of 1800 called M1800.m1s which has the following line of code in it:

DoOEMButton( 241 )

and then copy that file into  Mach3\macros\MachStdMill\Mill.  My understanding is that you can then run the macro by just including M1800 in the G-code, but this does not seem to toggle the mode (or the on screen button in the Settings section).   I should also be able to type M1800 from the MDI input field and toggle the tangential mode that way too right?  I've tried copying the macro file to several different directories also, including Mach3, Mach3\macros and Mach3\macros\Mach3Mill but still can't get it to work.

The thing is that I have three tool heads and one of them is just a pen or a hot knife which is not tangential, so I want to get out of tangential mode when switching to that tool during the script.