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Z stalling issues.
« on: May 03, 2009, 11:18:10 PM »
I have a cnc plasma table running a CandCnc mp1000c THC, Mach3 2.63 and I am having problems with the Z stalling. After the first cut it lifts up and rapids to the next spot fine but on the second cut on a part the Z stalls when it tries to lift up before it rapids to the next cut. It only happens when the torch has been on. I can dry run everything with the torch off and it does not stall. I normally run the Z at 75ipm for velocity and 15 for accel. The problem goes away if I lower the Velocity to 30 and accel to 1. Version 2.63 makes my computer freeze a lot so I loaded 3.042.020 and the freezing goes away but no mater what velocity and accel I try the Z still stalls so I went back to 2.63 and just deal with the computer freezing all the time. Any Ideas?

Ryan
Re: Z stalling issues.
« Reply #1 on: May 04, 2009, 12:11:02 AM »
In the past, I had the same problem but on a router table, my problem was power supply not strong enough to drive all 3 axes at the same time so my Z axis was not working very well.

Maybe you could verify for current capability.

Just my idea, Jeff
Re: Z stalling issues.
« Reply #2 on: May 04, 2009, 12:19:43 AM »
In the past, I had the same problem but on a router table, my problem was power supply not strong enough to drive all 3 axes at the same time so my Z axis was not working very well.

Maybe you could verify for current capability.

Just my idea, Jeff

When it does it only the Z is moving. None of the other axis are moving.

Offline Hood

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Re: Z stalling issues.
« Reply #3 on: May 04, 2009, 02:37:34 AM »
Sounds like its either heat from the cutting that is binding the axis or noise that is interfering with it.

Can you remove the torch from the axis and just hold it away a bit and run, that way it should eliminate heat.

Hood

Offline simpson36

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Re: Z stalling issues.
« Reply #4 on: May 04, 2009, 07:21:13 AM »


A thread not long ago was titled something like "Mach does not honor accelleration [in blah blah situation]"

I'm going to throw out some very sketchy info here, but it is all I know at this point. I just tripped over this yesterday and have not had a chance to look up the thread on it, but since the beahvior you describe is exactly what I was getting, there may be a connection.

I'm still looking into this, but basically, it seems that under certain conditions, which I think *may* be related to CV being active or not, Mach will not honor the accell setting and instantly moves a stepper from zero to commanded speed.

The result of this was immediate stalling of my servo motor whenever the stepper slammed into motion.

As in your case, lowering the axis speed setting to stupidly low levels cured the probem, but I found a change in the program also remedied the issue, indicating it is likely a Mach bug.

In my case I had the A axis rotating fast (servo motor) and the X axis (stepper) stationary. At a point, I began the X and A moving together and WHAM. Very obviously the accell setting on the stepper was ingored by Mach.

Changing the program to eliminate the initial A only rotation completely eliminated the problem. The command G1 X.5 A1800 that was causing the stalling was unchanged. I simply had eliminated the immediately preceeding G1 A360

 

Things you might look for:

Is there an extremely sudden movement (or attempt at same) from the attempted motion causing the stall.

Turn off CV and see if there is any effect.

If you can edit the G-code, you might try adding another axis move to the Z move.

-or-

If the Z move is G0, change it to G1.


I'll try to post back as I learn more about this bug.






Re: Z stalling issues.
« Reply #5 on: May 04, 2009, 10:22:42 AM »


A thread not long ago was titled something like "Mach does not honor accelleration [in blah blah situation]"

I'm going to throw out some very sketchy info here, but it is all I know at this point. I just tripped over this yesterday and have not had a chance to look up the thread on it, but since the beahvior you describe is exactly what I was getting, there may be a connection.

I'm still looking into this, but basically, it seems that under certain conditions, which I think *may* be related to CV being active or not, Mach will not honor the accell setting and instantly moves a stepper from zero to commanded speed.

The result of this was immediate stalling of my servo motor whenever the stepper slammed into motion.

As in your case, lowering the axis speed setting to stupidly low levels cured the probem, but I found a change in the program also remedied the issue, indicating it is likely a Mach bug.

In my case I had the A axis rotating fast (servo motor) and the X axis (stepper) stationary. At a point, I began the X and A moving together and WHAM. Very obviously the accell setting on the stepper was ingored by Mach.

Changing the program to eliminate the initial A only rotation completely eliminated the problem. The command G1 X.5 A1800 that was causing the stalling was unchanged. I simply had eliminated the immediately preceeding G1 A360

 

Things you might look for:

Is there an extremely sudden movement (or attempt at same) from the attempted motion causing the stall.

Turn off CV and see if there is any effect.

If you can edit the G-code, you might try adding another axis move to the Z move.

-or-

If the Z move is G0, change it to G1.


I'll try to post back as I learn more about this bug.








I am using G00 to retract the Z. I will post my code after I get home from work. What I don't understand is with the torch off everything is fine but after the thc takes over control of the Z mach ignores accel even after the m05 command. When the cut is active mach is supposed to ignore accel because there are to many quick moves on the Z, but after the m05 command it should switch back.
Re: Z stalling issues.
« Reply #6 on: May 04, 2009, 10:25:06 PM »
Here is a sample of my code.

N0000 (Filename: squareholes.tap)
N0010 (Post processor: 5 MP1000-THC-Fan on  piercecount.post)
N0020 (Date: 12/21/2008)
N0030 G20 (Units: Inches)
N0040 M8
N0050 G53 G90 G40
N0060 F1
N0070 (Part: squareholes)
N0080 (Process: Plasma,  0, Plasma, 0.055 inch kerf)
N0090 M06 T2 F120  (Plasma, 0.055 inch kerf)
N0100 G00 Z0.5000
N0110 X0.6225 Y1.5000
N0120 G28.1 Z0.12
N0130 G92 Z0.0
N0140 G00 Z0.0968
N0150 G92 Z0.0
N0160 G00 Z0.0600
N0170 M03
N0180 G01 X0.6825 Z0.0400 F75
N0190 X0.7225 F120
N0200 G03 X0.5000 Y1.7225 I-0.2225 J0.0000
N0210 X0.2775 Y1.5000 I0.0000 J-0.2225
N0220 X0.5000 Y1.2775 I0.2225 J0.0000
N0230 X0.7225 Y1.5000 I0.0000 J0.2225
N0240 M05
N0250 G00 Z0.500
N0260 G00 X1.6225
N0270 G28.1 Z0.12
N0280 G92 Z0.0
N0290 G00 Z0.0968
N0300 G92 Z0.0
N0310 G00 Z0.0800
N0320 M03
N0330 G01 X1.6825 Z0.0600 F75
N0340 X1.7225 F120
N0350 G03 X1.5000 Y1.7225 I-0.2225 J0.0000
N0360 X1.2775 Y1.5000 I0.0000 J-0.2225
N0370 X1.5000 Y1.2775 I0.2225 J0.0000
N0380 X1.7225 Y1.5000 I0.0000 J0.2225
N0390 M05
N0400 G00 Z0.500
N0410 G00 X1.6225 Y0.5000
N0420 G28.1 Z0.12
N0430 G92 Z0.0
N0440 G00 Z0.0968
N0450 G92 Z0.0
N0460 G00 Z0.0800
N0470 M03
N0480 G01 X1.6825 Z0.0600 F75
N0490 X1.7225 F120
N0500 G03 X1.5000 Y0.7225 I-0.2225 J0.0000
N0510 X1.2775 Y0.5000 I0.0000 J-0.2225
N0520 X1.5000 Y0.2775 I0.2225 J0.0000
N0530 X1.7225 Y0.5000 I0.0000 J0.2225
N0540 M05
N0550 G00 Z0.500
N0560 G00 X0.6225
N0570 G28.1 Z0.12
N0580 G92 Z0.0
N0590 G00 Z0.0968
N0600 G92 Z0.0
N0610 G00 Z0.0800
N0620 M03
N0630 G01 X0.6825 Z0.0600 F75
N0640 X0.7225 F120
N0650 G03 X0.5000 Y0.7225 I-0.2225 J0.0000
N0660 X0.2775 Y0.5000 I0.0000 J-0.2225
N0670 X0.5000 Y0.2775 I0.2225 J0.0000
N0680 X0.7225 Y0.5000 I0.0000 J0.2225
N0690 M05
N0700 G00 Z0.500
N0710 G00 X2.1275 Y0.0000
N0720 G28.1 Z0.12
N0730 G92 Z0.0
N0740 G00 Z0.0968
N0750 G92 Z0.0
N0760 G00 Z0.0800
N0770 M03
N0780 G01 X2.0675 Z0.0400 F75
N0790 X2.0275 F120
N0800 G02 X2.0000 Y-0.0275 I-0.0275 J0.0000
N0810 G01 X0.0000
N0820 G02 X-0.0275 Y0.0000 I0.0000 J0.0275
N0830 G01 Y2.0000
N0840 G02 X0.0000 Y2.0275 I0.0275 J0.0000
N0850 G01 X2.0000
N0860 G02 X2.0275 Y2.0000 I0.0000 J-0.0275
N0870 G01 Y0.0000
N0880 M05
N0890 G00 Z.5000
N0910 M9
N0920 M05 M30
Re: Z stalling issues.
« Reply #7 on: May 05, 2009, 10:13:56 PM »
I got it all figured out today. I had the box checked in the options to allow up/down on the z during cutting. I unchecked it and the Z does not stall anymore.