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Re: Motors stalling, losing steps
« Reply #30 on: February 08, 2009, 10:25:15 PM »
I am having almost the exact same problem. Here is what I posted to the Mechmate forum. Some additional things, I am running Oriental PK296A2A motors and using Gecko 203Vs. This is also being driven by an IBM 6221, which has an onboard parallel port. Is there something about the IBM parallel ports that MACH and/or the BOB doesn't like?

I'm stumped. I thought I had a grounding problem, but I've rechecked all the grounds and everything looks good. The symptoms are:

1) If I go very slow, there seem to be no problems, although I do notice an occasional "tick" from the motors.

2) Operating at 300 in/min and anywhere from 5-20 in/sec/sec acceleration, all motors will run smooth, with the normal high pitch whine.

3) They do not get hot, nor do the geckos

4) After traveling for anywhere from 20 - 100 inches, the motors will what I would describe as gear grinding sound and quit spinning. If I stop and start again, it runs smooth again.

5) All of the motors seem to be doing this. At first I noticed it on the X-axis only, so thought it might be a binding problem. I have dropped all motors and still get the behavior even under no load.

I'm guessing software setting or tuning problem, just not sure what exactly would cause this?

Under Mach 3 Config + Motor Tuning, there are two boxes labeled Step Pulse and Dir Pulse with units of micro-seconds? What should these values be?

Thanks

Offline simpson36

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Re: Motors stalling, losing steps
« Reply #31 on: February 09, 2009, 05:40:24 AM »
The correct settings for the 203v (which are opposite of all other Gecko drives) are found on www.geckodrive.com along with a bunch of other useful info about CNC mechanics in general. Definitely worth a read.

Two thoughts:

I wonder if one possible cause of a regularly spaced 'tick' might be the system adding or subtracting an extra step to correct for rounding if the drive ratio is something odd that slowly gets off-step.

Is there anyone who has used a third party add-in parallel port that is known to work with Mach3? That would be great info to post.

I have experienced the motors skipping/stalling/grinding in two instances:

A wireless network adapter very definitely caused the issue. Unplugging it from the USB port instantly stopped the problem.

The computer reaching 100% CPU utilization also caused the symptom. It is likely that any process that interrupts the CPU with polling or 'wait' type operations could also cause this. In my research on steppers, it seems to me that they cannot recover from  receiving a step command that is out of sequence with the previous command, so in addition to the obvious timing sensitivity, any lost or out-of-order-step commands are going to stall the motor.

I suggest as a general rule to go into the task manager (right click on task bar) and set the mach3 process to 'real time' which is the highest level of priority. (right click on the process) This *should* prevent other processes from suspending Mach3 long enough to cause a problem.

Make sure the PP is set in the bios to the correct communication type as required by your BOB . . presumably the highest setting.







« Last Edit: February 09, 2009, 05:44:47 AM by simpson36 »
Re: Motors stalling, losing steps
« Reply #32 on: February 09, 2009, 06:56:46 AM »
Thanks for the suggestions. Your statement, "I wonder if one possible cause of a regularly spaced 'tick' might be the system adding or subtracting an extra step to correct for rounding if the drive ratio is something odd that slowly gets off-step.", has me wondering because the "tick" does seemed regularly spaced. Can you elaborate on what might cause the system to add or subtract an extra step?  Thanks.

Offline simpson36

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Re: Motors stalling, losing steps
« Reply #33 on: February 09, 2009, 05:52:59 PM »
Comments on the 'tick' from motors:

Something I noticed about Mach3 is that manual jogging behaves differently than running Gcode. This was explained by others on this forum as a Mach 'rounding' process.

I can only speculate on this issue as the programmers did not weigh in on that thread, so anybody's guess is as good as the next.

The behavior though is not speculative as it is observable. If I set the jog distance to 1", the jog will be a few thou short and then make it up on the next jog, then be short again, then make it up again later. Yet if I enter Gcode to go to sequential coord's 1" apart, the error is not present and the movement is dead accurate.

So it would seem that Mach uses different methods with jogging and with Gcode moves.

This is only speculation on my part, but if Mach jogs my stringing short moves together, it would have to make up the shortfalls as it goes along . . which at certain speeds might manifest as a 'tick'.



« Last Edit: February 09, 2009, 05:57:41 PM by simpson36 »

Offline Zaae

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Re: Motors stalling, losing steps
« Reply #34 on: February 10, 2009, 02:23:43 PM »
Hello again guys :)

First of all a GIGANTIC thank you for all your help and support.

I'm back to tell you that after several long, difficult cuts at top speed, I FINALLY have no missed steps.

My problem was all related to the computers I was using. If you're having a very similar problem, save yourself some headache, and try a computer with no less than 1.6ghz processor, with a separate video card (not on board), and use a fresh install of windows, or whatever OS you're using.

I still don't know what exactly was causing it, but after stripping xp down to the bare minimums, and following the optimization suggestions from the support section of this site, two of my machines have the exact same problem. I have read nearly every post on this forum, and several others that discuss skipping or stalling motors, and have tried every suggestion I've read, but in the end what finally cured my problem was a completely different computer. I went to the local surplus store, picked up a 2.6ghz 512mb ram pentium 4  desktop for $75.00, and even before the optimizing, the problem was gone.

A 333mhz pc would run smoothly, but it was too slow, it can't pulse fast enough for 10x microstepping drives and motors with 10tpi screws, so it didn't really answer any questions for me.

As for the little 'ticking' sound while jogging, this seems to be something about the keyboard polling or something, because it only does it for me on the slower machines, and only when using key jogging. The ticking sound didn't happen when it was just code running the motors.

Right now the rapids on the machine are ridiculously fast, I can jog at over 177ipm with fairly low acceleration numbers, or 145 with quick acceleration. Of course, cutting that fast isn't realistic, but when it comes to programs with lots of jogging, it saves a HUGE amount of time.

So, thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you all very much!

 

Offline Hood

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Re: Motors stalling, losing steps
« Reply #35 on: February 10, 2009, 02:36:41 PM »
You need to get yourself a new keyboard, it seems to be repeating certain combinations of k, t, n, a etc ;D

Great you are sorted now :)
Hood
Re: Motors stalling, losing steps
« Reply #36 on: March 24, 2009, 04:03:04 PM »
Hello,

I have to agree with Zaaephod. I bought a CNC lathe from a vendor who offered a PC with it. I turned it down because we had a computer not being used that had W2K on it. I hooked it all up and proceeded try and learn. After clearing up a few things I always had a nagging intermittent problem with the steppers going crazy. Turns out the PC was a 550Mhz machine. The manual clearly says 1Ghz processor which I either missed or ignored. The frustrating part was things would run great for weeks sometimes then go crazy. I hooked up a machine with WXP and 1.2 Ghz what a difference.

To help convince me I was using the three finger salute to task manager and looking at processor performance, I was hitting 100% just running Gcode without running the steppers. The pulse frequency would drop out. The driver test would always look good.

Thanks for everyones help and I look forward to working with Mach3 now instead of dreading it. :D

What surplus store did find the $75 computer at? You might want to work on that keyboard.

B.E.N.