Slow or Jerky G02 / G3 moves

[ronateah]

I am having some trouble getting smooth motion out of my router. I am under the impression, i can not recall why, that cv does not work well with arcs. I actually have two systems. A plasma system where I had to change the posts in sheet cam from mach with arcs to mach with out arcs. Seemed to be necessary to get smooth motion out of plasma table. The router on the other hand is still aproblem. It seem to speed up and low down between each G2/3. The posts in Artcam do not offfer a Mach post with out arcs. I should mention I have limited exposure to gcodes. I just know the problem is associated with G2/3. Anyone had any insite to this work be greatly appreciated

Simple 30 by 15 inch oval I am having trouble with.

(test3)
G90
G20
G49
G0Z0.2500
M3 S15000
G0 X0.2501 Y15.4937 Z0.2500
G1 Z0.0400 F50
X0.2866 Y16.9981 Z-0.0036
X0.3998 Y18.4996 Z-0.0473
X0.5892 Y19.9924 Z-0.0909
X0.6717 Y20.4699 Z-0.1050
X0.5892 Y19.9924 Z-0.1191
X0.3998 Y18.4996 Z-0.1627
X0.2866 Y16.9981 Z-0.2064
X0.2501 Y15.4937 Z-0.2500
G2 X0.5892 Y19.9924 I29.5410 J0.0351 F100
G2 X3.0103 Y27.1952 I19.7952 J-2.6453
G2 X5.6221 Y30.0274 I7.3153 J-4.1258
G2 X8.7920 Y30.6713 I2.3823 J-3.6032
G2 X11.7484 Y28.8696 I-1.2736 J-5.4164
G2 X14.4533 Y23.9742 I-10.3456 J-8.9113
G2 X15.4108 Y11.0076 I-26.8353 J-8.5002
G2 X12.9897 Y3.8048 I-19.7952 J2.6453
G2 X10.3779 Y0.9726 I-7.3153 J4.1258
G2 X7.2080 Y0.3287 I-2.3823 J3.6032
G2 X4.2516 Y2.1304 I1.2736 J5.4164
G2 X1.9850 Y5.8552 I9.4055 J8.2753
G2 X0.2501 Y15.4937 I24.2326 J9.3373
G1 X0.2501 Y15.4937 Z-0.2500 F50
X0.2866 Y16.9981 Z-0.2876
X0.3998 Y18.4996 Z-0.3253
X0.5892 Y19.9924 Z-0.3629
X0.6717 Y20.4699 Z-0.3750
X0.5892 Y19.9924 Z-0.3871
X0.3998 Y18.4996 Z-0.4247
X0.2866 Y16.9981 Z-0.4624
X0.2501 Y15.4937 Z-0.5000
G2 X0.5892 Y19.9924 I29.5410 J0.0351 F100
G2 X3.0103 Y27.1952 I19.7952 J-2.6453
G2 X5.6221 Y30.0274 I7.3153 J-4.1258
G2 X8.7920 Y30.6713 I2.3823 J-3.6032
G2 X11.7484 Y28.8696 I-1.2736 J-5.4164
G2 X14.4533 Y23.9742 I-10.3456 J-8.9113
G2 X15.4108 Y11.0076 I-26.8353 J-8.5002
G2 X12.9897 Y3.8048 I-19.7952 J2.6453
G2 X10.3779 Y0.9726 I-7.3153 J4.1258
G2 X7.2080 Y0.3287 I-2.3823 J3.6032
G2 X4.2516 Y2.1304 I1.2736 J5.4164
G2 X1.9850 Y5.8552 I9.4055 J8.2753
G2 X0.2501 Y15.4937 I24.2326 J9.3373
G0 Z0.2500
G0 X0.0000 Y0.0000
G0Z0.2500
G0X0.0000Y0.0000
M5
M30

[neilw20]

I have always found G2/G3 to be perfect.
If your motor tuning, acceleration and pulsing rate setup are not optimal this is the first place you will notice lack of smoothness.

If the PC speed is inadequate, or KHz speed too high, or DMA access is interrupting the CPU, smoothness of motion will deteriorate.

Read the attached, and this will give a better understanding of why it even works at all under windows.
First, get rid of ALL un-necessary background tasks, especially anti-virus stuff, automatic updates, and have at least 500MB memory.
If CPU is below 1 GHZ the attached will also give the reasons for special requirements.
If it is on a laptop, you MUST disable any battery saving setup.

Apologies if necessary to Art Fenerty, for including file. I could not find a link to it. Does anyone know the link?

[ger21]

I am under the impression, i can not recall why, that cv does not work well with arcs.

False. Turn on CV mode and it should fix this. One thing you should do, though, is turn off all the CV options. Uncheck everything in the General Config, and turn off CV distance and Feedrate on the settings page. Once it's working with the settings off, then you can read this and start playing with them if you want to fine tune CV mode.
http://www.machsupport.com/docs/Mach3_CVSettings_v2.pdf

[ronateah]

Thanks all I have partially solved this. I found my self play the cv settings on settings page in mach3. Changing cv feedrate and enabling / disabling cv while it was a running some test code and it just started to work. Artcam cam back with the suggestion of adding a g64 to the code which I suspect would have curred the issue. So i can not put a finger on the the exact fix pbut all is well now.

Thanks Much

[ger21]

G64 turns on CV mode, G61 turns it off.

As I said, you'll be better off turning off CV Feedrate and all other CV options, until you know exactly what they do. The wrong CV Feedrate can cause it to not work properly.