Mach4 CV Tuning Wizard

About a month ago I was troubleshooting an issue of losing steps on a 3d toolpath. Through this forum, I realized it was the tolerance setting in Fusion 360 causing the problem. Setting Fusion 360 tolerance to .001" and turning smoothing on fixed the problem of losing steps.

Before figuring out the problem, I did run the CV Tuning Wizard in Mach4. I used the one label “mcCvTuning”. At that time, I didn’t notice that my movements (or change of direction) wasn’t as smooth as it was in the past. After running few more jobs, it dawn on me that it looked like it was slowing down when doing arc moves. It almost looked like it was in exact stop mode instead of CV mode. It was in CV mode.

I made sure my motor tuning was back to AVID’s default and reran the “mcCvTuning” wizard with no change. I wasn’t sure if that was the problem. After checking a lot more things and having it not fix the problem, I returned back to the CV tuning I did previously. Looking at the generated CV feed rate table wizard, I saw over 800 feedrate and dramatically slower feed rates for the listed angles. I reran it many times with different axis turned off/on and only saw minor changes in the table generated.

I looked closer at all of the wizards, and I noticed one label: “mcCvTuningWizard.” It is very different from the other one. This one has two sliders, one for max feedrate and the other for stopping CV at an angle. Setting the max feedrate to 300 and the stop angle at 179 seemed to fix the jerkiness of the toolpath.

Does anyone here have any experience with the built-in Mach4 tuning wizards?

There have been at least 3 different tuning wizards from NFS over the years, and at least two of them were in some of AVID’s builds at times (I haven’t checked the lastest to see if more that one are there now).

The latest one is mcCvTuning. I haven’t compared results in the tables from the different wizards, but thats the one NFS recommends. This one calculates the table for the axis(s) you chose, based on the tolerance you provide, and the acceleration settings that are in your motor settings, so make sure you have the acceleration settings where you want before running the calculations.
I played with this a bunch last year and didn’t really see much effect from it unless I was running VERY low acceleration values (like around 5 i/s^2). I think its more usefull for other kinds of machines other than cnc routers.

mcCvTuning is the one that is giving the non-smooth running toolpaths. I have the motor tuning set to AVID’s defaults and tried many different combination of axis with the same result. The “mcCvTuningWizard” gives me the smooth toolpaths I remember.

AVID never asks us to run any of the CV tuning wizards included in Mach4, and I never did prior to the problem with losing steps. I’m curios what AVID has for CV_Feedrate table by default.

If anyone notices that their AVID isn’t running smoothly through curves and they ran the “mcCvTuning” wizard previously, they should try the “mcCvTuningWizard” and see if they get better results.

Thats interesting. The CV stuff is not well documented by NFS for sure. They also have been making a lot of changes to the CV stuff in the 5k series of M4 releases and I haven’t had time to look into any side effects. I have notices some concerning toolpath traces in the toolpath display that don’t follow the actual toolpath, and don’t seem to represent the actual path the machine takes. Need to do some investigation one of these days.

I’m curious what feed rate you run normally? The number in the CV table is supposed to be the max value allowed, so if 300ipm smoothed it out significantly vs the 800, that would imply you are running a lot faster than 300ipm.

My feedrate varies but the smoothness of the slower toolpath wasn’t really smooth either unless i was going really slow.

Now that i use the other CV tuning wizard, it appears to be running as i expected at a constant velocity into curves. I haven’t seen anything so far that look like it coming out wrong because of what i did.

Thats weird because you said the only difference was at 179 and that is almost a straight line. I wouldn’t expect it to matter than much.
I really wish NFS had some tutorials on CV mode, but they like to keep things a mystery a lot of times.
Now I’m gonna have to go back and dig into this again :slight_smile:

Here is a link to wizard that I used.

Reply #2 explains it best.
When I’m back in the shop, I will use all three wizards and compare the CV_feedrate table generated to see what is different. Using the wizard linked above, I am getting better curve motion (i.e., constant velocity).

BTW, I think the lower angle number (ex. Angle 0) is closer to a straight line and gets the max feedrate. Angle 179 would be almost going back the other way and get slowest feedrate and would need to stop to change direction.

Cool, I’m definitely interested in hearing what you see in your comparisons.