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Author Topic: About ready to throw in the towel!!! Help Please.  (Read 3284 times)

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About ready to throw in the towel!!! Help Please.
« on: February 01, 2013, 10:29:45 AM »
Hello all,

I've been reading through the forums here for a month and I found problems similar to mine, but it seems the root cause of my problem is different.

My Z axis will move from zero in the + or - direction depending on the type of cut.

I've been using my CNC for about 6 months.  Mostly playing, but I've made a few signs for neighbors.  They would turn out OK, but I always noticed the bottom of a V cut would be a little rough.  About a month ago I was making some cribbage boards for a friend and while cutting the holes, spiral cut with 1/8" end mill to .5 deep, I noticed end mill getting closer and closer to the wood.  You couldn't notice a difference from hole to hole, but after lets say 20 holes, you would definitely see a difference.  I would stop the machine and check Z zero and sure enough it would be .020 to .030 in the minus direction(closer to the wood).
I figured I was missing steps, so I tuned the stepper slower and tried again.  Same results.  Bumper up the torque on the stepper.  Same results. Different ramping. Same results.
Then I thought maybe it's something to do with using the spiral ramp feature in V-Carve, so I changed it to plunging .100 at a time.  Here's the weird part.  Now the bit after 20 or so hole would be .020 to .030 off in the plus direction(getting farther away from the wood).

Gave up making saw dust and started troubleshooting my machine.

I checked the Z axis slide for binding.  Smooth as silk.  I can easily spin the stepper by hand to make it go up and down.
Then I was touching the stepper when I was jogging it.  I noticed it had a random hiccup I could feel.  I was feeling the missing steps.
I removed the stepper, so I could run it by it's self.  Still got the missing step hiccup. So I know it's not my slide.
Tried a different stepper.  Same hiccup.
I was thinking noise, but I am not having any problems with X or Y.  I got out my oscilloscope and checked the waveform coming out of my parallel port, then out of my BOB, then at the step input of the IMS483 stepper driver.  All the step pulses looked good.  Looked clean. Had a little freq variation, but nothing bad. So not noise.
Next I tried different outputs from the parallel port. Same problem.  Then I tried swapping Z and Y.  Now Y had the missing step hiccup.  So that means the funky steps was following the Z output from the computer, because swapping Z and Y made it so I was using a different IMS driver and different output.  Weird huh?
I swapped out drivers, made short stepper cables for testing right next to control box, tried every output I had, and the missing pulse always follows the Z axis output.
I even remapped what keyboard keys I was using.  Didn't help.

I ran Drivertest and it said "System Excellent".

So I uninstalled Mach, then reinstalled.  Set everything up again and tried, same problem.  Tried the Windows optimization.  Same problem. I even tried a new motherboard. Same problem.

The only thing I can think of that I didn't try is getting a priest to perform a exorcism!

It now seems to me that it's coming from Mach3.  Like it's the pulse engine itself screwing up the Z steps.
I'm going to hook up the oscilloscope again this weekend and take a 2 second sample of the pulse train, then zoom in to see if I can see the missing pulse(s)

Do you guys have any ideas I should try?

My hardware is
2Ghz Celeron, 1 gig ram, Windows XP sp3
IMS 483 stepper drivers turning 425 oz In steppers
Mach3 latest version
KL-DB25 breakout board from Keling

Thank you,
Loogie






Re: About ready to throw in the towel!!! Help Please.
« Reply #1 on: February 01, 2013, 10:45:31 AM »
have you tried another computer.
Re: About ready to throw in the towel!!! Help Please.
« Reply #2 on: February 01, 2013, 10:52:42 AM »
have you tried another computer.

I replaced the motherboard in my computer with an identical motherboard I had in stock.  I will see if I can scrape up a different computer and try it this weekend.

Thanks,
Loogie
Re: About ready to throw in the towel!!! Help Please.
« Reply #3 on: February 01, 2013, 10:57:14 AM »
i've found problems on certain ibm models
Re: About ready to throw in the towel!!! Help Please.
« Reply #4 on: February 05, 2013, 10:50:04 AM »
Do you have backlash compensation turned on?  I think, if it is turned on and the amount is not aligned with the actual backlash, it will introduce a progressive error depending on the cutting sequence.
Re: About ready to throw in the towel!!! Help Please.
« Reply #5 on: February 08, 2013, 03:56:07 PM »
I´m having exactly the same problem. Please let me know if you find any solution.

Offline Chaoticone

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Re: About ready to throw in the towel!!! Help Please.
« Reply #6 on: February 08, 2013, 04:51:35 PM »
What version of Mach are you guys running?

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

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Re: About ready to throw in the towel!!! Help Please.
« Reply #7 on: February 12, 2013, 06:53:10 AM »
This is also happening to me. I am running the latest version of Mach, but it is happening on my x axis. Doesn't happen all the time, but it usually "Clunks" at leats once when jogging from one end of the machine to the other. Somtimes it causes one of my motors to stall, throwing my two motor gantry WAY off. When running a job, I notice that it often will be off about a half an inch after a while of cutting in the X axis. I have read about others with simular problems, but yet to read of a cure. Thanks.