Problem cutting a circle..servo setup

[powerfade]

Hi there...So I just got my machine up and runnning. Servos running Mach 2 right now. When I try to cut a circle or as pic below will show a "C", the arc does not cut in a fluid motion. Actually it goes about a quarter of the cut stops, moves a bit and then proceeds leaving little jagged marks. There are no breaks in the gcode or anything. Its almost like its adjusting after a certain amount of time. I am pretty new to this servo stuff, so I am trying to learn as I go along. I was hoping someone could give me some insight as to what might be causing this. Tuning??? Backlash??? Maybe a setting I missed in Mach 2? I am using the Rutex 2020 drives. Thank you in advance for your input....

[ger21]

If it's backlash it's pretty severe. Is backlash comp turned on? Are you in exact stop mode or constant velocity? Can I see the code?

[powerfade]

Hi...Thanks for your quick reply.. Backlash comp is turned on, it is in constant velocity mode. I have attached a pic of the settings screen and the gcode that was run. Thanks..

[lakeside]

Your code looks good ran it thru bobcad and the moves don't appear you controller may be trying to catch up to your table try dropping feed and see if you get the same path

[powerfade]

I dropped it down to 25ipm and still the same thing. It's almost as if it is correcting itself. Maybe getting off track and then hitting an error limit somewhere that says, "get back to where you are supposed to be". Still confused....

[lakeside]

the cutter could be correcting it postion from the last move can you run the code in a single block mode and see where the cutter end up from last move to program position and see where the cutter next move should start from here is a portion of your code to inside of top "C"
G1 X6.5400 Y8.0400
G1 X6.5170 Y8.0660
G1 X6.4950 Y8.0930
G1 X6.4720 Y8.1190
G1 X6.4480 Y8.1440
G1 X6.4240 Y8.1690
G1 X6.3980 Y8.1930
G1 X6.3730 Y8.2170
G1 X6.3470 Y8.2400
G1 X6.3200 Y8.2630
G1 X6.2920 Y8.2850
G1 X6.2650 Y8.3070
G1 X6.2370 Y8.3280
G1 X6.2080 Y8.3480
G1 X6.1790 Y8.3680
G1 X6.1510 Y8.3870
G1 X6.1210 Y8.4050
G1 X6.0910 Y8.4220
G1 X6.0600 Y8.4390
G1 X6.0300 Y8.4550
G1 X5.9990 Y8.4710
G1 X5.9670 Y8.4860
G1 X5.9360 Y8.5000
G1 X5.9030 Y8.5130
G1 X5.8710 Y8.5260
G1 X5.8380 Y8.5380
G1 X5.8050 Y8.5490

[powerfade]

I stepped through the code and the digital readout of the current position is equivalent to the last move. It looks like the cutter is being corrected, but not sure why. On a circle, the correction is in the exact same place on each quadrant of the circle. At least its consistent..argh...

[lakeside]

try this file needs command line to first move and look at end

[powerfade]

Still does the same thing...Goes and then does a funny little jag move..

[ger21]

Backlash and constant velocity usually don't work well together, and it's recommended that you don't use both. Try it with either one turned on, but not both together.

[lakeside]

run a 4" and cut a 8" cicle and see if your tool jumps. you don't need a cutter in the tool holder your table may have an alignment issue also here a file of a C about the same size and in the area of the first path see if it works the radis are tighter so you may not see any movement or you may bindup

[powerfade]

Gerry....That was it.....I turned off the backlash and just left the constant velocity and it runs smooth as silk. Thank you soo much.......I really appreciate it....

Lakeside....Thank you very much for taking the time and effort to help me try and find a solution... I appreciate it.

What would one do without this site???? Time to start cutting stuff...

In case you are curious here is my machine....

Thanks again to you both..

Chris