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  #1  
Old Sun 12 October 2008, 03:36
liaoh75
Just call me: David
 
Taibao
Taiwan
Runs out of steam? Machine freezes during cutting - controlling PC's performance

Last weekend, my computer wouldn't boot up. I took it in and they said nothing was wrong so I brought it back and the same problem occured. It freezes in the middle of a cut and the screen gets all blocky and patchy colors. The motherboard was an ASUS with integrated graphics. I did some research and read somewhere that integrated M/Bs are not good for running Mach3. So, I bought a new motherboard, memory, and reloaded everything thinking everything was going to be just like before. Was I in for a shock!!

Everything appeared ok until I started jogging the X and y axis. What's happening is so strange that it's hard to describe. If I hold down the left or right arrow keys to jog the gantry from one end of the table to the other, it seizes up after a few seconds and makes a strange whining noise. Initially I thought it was the pinion getting stuck so I removed the springs and let the motors hang and tried it again. Again I get the same noise. It seams as if the pulse stream is getting interupted but the strange thing is, it's not just one motor. If I hold down the arrow keys, X1 and X2 seizes up at the same time under absolutely no load. Now get this, the problem doesn't show up when I'm cutting something. It only shows when doing jogs on X and Y axis. Z axis seems fine at the moment. If I set the jog speed to 20% of full speed, it doesn't happen. Is there something going on with the pulse stream?? Does anyone think trying a PCI based parallel port would help?

My motors are tuned according to instructions, I'm fairly sure everything is grounded.

Any assistance on this would be greatly appreciated. I remember reading about a similar situation many months ago on this forum but, I can't find it. Please Help!!
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  #2  
Old Sun 12 October 2008, 06:14
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
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David my guess is it's in the motor tuning setup. It sounds like you are over driving the motors and missing a lot of steps thus the "strange whining noise". We need more info. What type of motors, are they geared, what's the setup in motor tuning, how fast are you jogging when it happens. etc. etc. etc.
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  #3  
Old Sun 12 October 2008, 06:23
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Have you tried another PC?
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  #4  
Old Sun 12 October 2008, 08:18
Roadkill_321
Just call me: John #7
 
Wiseton, Saskatchewan
Canada
Hi David, I think it was Doug's thread where he had a similar problem.

I also had this problem and it turned out that I was running the motors too fast.

Try this link http://www.mechmate.com/forums/showt...&postcount=140
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  #5  
Old Sun 12 October 2008, 19:35
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
You've got a good memory John.

David,

Same thing happened to me. I tinkered with the settings in Mach3 and if I recall correctly, once I slowed down the acceleration rate, it started acting right. Or maybe it was when I slowed down the jog speed. That was so long ago, I can't remember for sure. But I'd bet a six pack that it's just one of the speed settings in Mach3. Good luck.
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  #6  
Old Sun 12 October 2008, 23:46
liaoh75
Just call me: David
 
Taibao
Taiwan
Thanks to all who have made suggestions

Gerald, my intention is to try another PC tomorrow.

JR, Here is the detailed info on my machine:

Motor OM PK296A2A-SG7.2 geared motor
Motor Drives: Gecko G203V X4
B.O.B.: PMDX-122
Power Supply: Antek 35VDC 500VA

Mach Settings:

Metric Mode
Velocity: 17,000 units/min ~ 283mm/sec ~11.15 Inches/sec
Acceleration: 700

When I changed the computer, I didn’t change any settings. I just copied the configuration file over to the new computer. Just a note though, this problem did occur on the old computer as well, but once in a blue moon. The whining noises I mentioned earlier only occur when the motor seizes up.

Another observation: When I had the motors disengaged from the rack as I was doing slow jogging, I noticed that the sound of the motors is not smooth. It almost seems as if the pulse stream is getting interrupted somehow. Also when the motors seize up, they seize up at the same time. It doesn’t seize up one motor at a time.

I read somewhere a while back (not on this forum) that the parallel port that comes with the motherboard is inferior to PCI based add on boards. I remember reading about the fact that dedicated PCI parallel cards pulse smoother and takes some of the processing away from the CPU. Has anyone heard of this?
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  #7  
Old Mon 13 October 2008, 06:59
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
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JR has been using one that is integrated for about 7-8 months with no such problems. His motherboard is the Intel "Little Valley" mini ITX.
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  #8  
Old Mon 13 October 2008, 07:24
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
I'm betting that the problem is being caused by Mach 3 settings. The PMDX-122 break out board should "buffer" any substandard signals being generated by your computer's parallel port.

In your Mach 3 settings, reduce the top speed by 25% and see what happens. If that cures the problem, then play with some numbers between your current settings and the lower settings until you find a number that always works.

You may find that the acceleration needs to be reduced. The ideal acceleration for a stepper motor is not linear. If you plotted an acceleration curve, it would have a steep, almost straight portion, followed by a long curve that allowed the motor to get to its highest speed without missed steps; however, that kind of curve does not work in most CNC environments because you need to move various axes at various speeds. That means that linear acceleration is required. That also means that the acceleration "ramp" needs to be longer than optimum.

There is the possibility that you have electronic noise, but if the problem is repeatable, then electrical noise can usually be ruled out. Noise tends to be random.
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  #9  
Old Mon 13 October 2008, 08:00
DMS
Just call me: Sharma #9 India
 
Rajasthan
India
Nice setup David,
Quote:
that the parallel port that comes with the motherboard is inferior to PCI based add on boards.
Have to disagree with that, as most of MM are running on onboard parallel card. Besides all printers are running fine on that port.

I took photo of my TFT with stone age voltage and current detectors - Red- current detector, black - voltage detector.
shows presence of voltage and strong current fields.
Do you have screen between monitor and motherboard ? I can't deduce whether this is the reason of your problem.May be other members may through some light on it.

ps - oops, while I was typing and loading image, Richard posted. Anyway this can be taken as information.
Attached Images
File Type: jpg voltamp detector.JPG (157.3 KB, 84 views)
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  #10  
Old Mon 13 October 2008, 09:39
javeria
Just call me: Irfan #33
 
Bangalore
India
Hi Sharma, that might bee the cause - but usually not - manjeet on one of his plasma cutter had a problem where the problem was a parallel port cable with really thin wires inside and that caused a lot of problem for him - it was solved when thicker wired cable was use for the PP.

RGDS
Irfan
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  #11  
Old Wed 22 October 2008, 07:39
javeria
Just call me: Irfan #33
 
Bangalore
India
David did you solve your problem - if so can you share what had happened.
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  #12  
Old Thu 23 October 2008, 22:34
liaoh75
Just call me: David
 
Taibao
Taiwan
I finally solved the problem. It had something to do with the computer. I changed it out to another motherboard with INTEGRATED video and everything is back to the way it was before I changed out the first time. I wish I had a better technical answer for those that have been tracking this problem.

Interesting observations:

1) The problem still rears it's head once in a blue moon when jogging, but usually for the first few minutes of powering on. It almost seems as if powering on is producing some ultra strong pulse of EMI that has an effect on the control system. Then as I get going, the problem goes away. It's almost like a capacitor that charges and discharges and after the (EMI "charge") fades away, the problem goes away. I will be moving the PMDX and Geckos to the other control box on the left (see pics above) and all high voltage stuff will be in one box and the low voltage stuff will be in the other.

2) I've lowered my settings in mach to 15,000 pulses per min from 17,000 and that has helped and my acceleration setting is now at 550 vs 700.

Any other suggestions would be more than welcomed.
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