Mach 3 / CS Labs Smoothing

[Chaz]

On my concrete mill (Thor) I run CS Labs IPA with Panasonic servos. Ive always noticed that on circles and similar I get jerky movement, specifically where there are I and J type G Code involved.

I did a test last night, took the same code, ran it on my Bridgeport, running on Centroid Acorn, same Panasonic setup but in Step / Direction (Position mode) versus Speed move as per Thor. The same code was smooth.

Ive seen a lot of complaints about Mach 3's smoothness.

Is my issue a limitation with Mach 3 (or badly configured), related to not having good PID on the servos or something else?

I might try the new SimCNC software from CS Labs to see if its Mach 3 or not. A newer PC might also help.

Thoughts?

[Clive S]

On my concrete mill (Thor) I run CS Labs IPA with Panasonic servos. Ive always noticed that on circles and similar I get jerky movement, specifically where there are I and J type G Code involved.

I did a test last night, took the same code, ran it on my Bridgeport, running on Centroid Acorn, same Panasonic setup but in Step / Direction (Position mode) versus Speed move as per Thor. The same code was smooth.

Ive seen a lot of complaints about Mach 3's smoothness.

Is my issue a limitation with Mach 3 (or badly configured), related to not having good PID on the servos or something else?

I might try the new SimCNC software from CS Labs to see if its Mach 3 or not. A newer PC might also help.

Thoughts?

I think there is a setting tick box in Mach3 to use arcs CV mode

[Chaz]

I think there is a setting tick box in Mach3 to use arcs CV mode

Thanks. Ill check. I was actually surprised the code worked as standard on the Bridgeport. Suppose its feasible despite different post processors.

[Chaz]

I'm looking at a screenshot of the General settings page, I dont see it. Any idea where it is?

https://www.machsupport.com/wp-content/uploads/2013/02/Mach3Mill_Install_Config.pdf - page 5-35 is the General Settings Page.

[Neale]

I use Mach3 and an IP/M on my router and have never noticed any jerkiness on curves. Don't know if that is luck or the right settings! I've been using F360 with various cutting strategies recently, some of which use a large number of short straight line segments which Mach3 seems to handle ok. So it seems ok whether or not G2/3 or straight line segments are used. I am using steppers rather than servos and it does seem possible that servo tuning would have an effect here.

[Chaz]

I use Mach3 and an IP/M on my router and have never noticed any jerkiness on curves. Don't know if that is luck or the right settings! I've been using F360 with various cutting strategies recently, some of which use a large number of short straight line segments which Mach3 seems to handle ok. So it seems ok whether or not G2/3 or straight line segments are used. I am using steppers rather than servos and it does seem possible that servo tuning would have an effect here.

Thanks. I have no issues with straight lines, its when arcs / circles are involved.

[Neale]

I was thinking of the case where F360 is approximating non-circular curves (e.g. adaptive clearing strategies) using many very short straight line segments so there are a lot of rapid direction changes. Mach3 is supposed to smooth these, as I understand it. This kind of tool path is bad news if Mach3 is configured to "exact stop" mode but in constant velocity mode it's fine.

On reflection, though, probably not very relevant as you are using analogue servo controls which introduces a whole bunch of other variables. Good luck!

[Chaz]

I was thinking of the case where F360 is approximating non-circular curves (e.g. adaptive clearing strategies) using many very short straight line segments so there are a lot of rapid direction changes. Mach3 is supposed to smooth these, as I understand it. This kind of tool path is bad news if Mach3 is configured to "exact stop" mode but in constant velocity mode it's fine.

On reflection, though, probably not very relevant as you are using analogue servo controls which introduces a whole bunch of other variables. Good luck!

Yep and the same code runs without an issue on Centroid.

[phill05]

I'm looking at a screenshot of the General settings page, I dont see it. Any idea where it is?

https://www.machsupport.com/wp-content/uploads/2013/02/Mach3Mill_Install_Config.pdf - page 5-35 is the General Settings Page.

Have a look at 5.6.6.2, I/J Mode: You can set the interpretation to be placed on I & J in arc moves. This is provided for compatibility
with different CAM post-processors and to emulate other machine controllers. In Inc IJ
mode, I and J (the center point) are interpreted as relative to the starting point of a center format arc.
This is compatible with NIST EMC. In Absolute IJ mode, I and J are the coordinates of the center in
the current coordinate system (i.e. after application of work, tool and G92 offsets). If circles always
fail to display or to cut properly (especially obvious by them being too big if they are far from the origin),
then the IJ mode is not compatible with your part program. An error in this setting is the most
frequent cause of questions from users when trying to cut circles.

Phill

[Chaz]

Have a look at 5.6.6.2, I/J Mode: You can set the interpretation to be placed on I & J in arc moves. This is provided for compatibility
with different CAM post-processors and to emulate other machine controllers. In Inc IJ
mode, I and J (the center point) are interpreted as relative to the starting point of a center format arc.
This is compatible with NIST EMC. In Absolute IJ mode, I and J are the coordinates of the center in
the current coordinate system (i.e. after application of work, tool and G92 offsets). If circles always
fail to display or to cut properly (especially obvious by them being too big if they are far from the origin),
then the IJ mode is not compatible with your part program. An error in this setting is the most
frequent cause of questions from users when trying to cut circles.

Phill

Thanks. Ive messed with this before. Normally when its wrong, it doesnt cut the right tool path at all. I dont think that's the issue here.

[Clive S]

I'm looking at a screenshot of the General settings page, I dont see it. Any idea where it is?

https://www.machsupport.com/wp-content/uploads/2013/02/Mach3Mill_Install_Config.pdf - page 5-35 is the General Settings Page.

Ok there is a setting on that page radio button "motion mode" it should be on constant vel. I think there is a light on the main screen that should go green when G64 is on in the code. If G61 is in the code that will cause the stopping