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Author Topic: Losing steps on the run. . .  (Read 4808 times)

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Losing steps on the run. . .
« on: February 19, 2008, 12:26:27 AM »
Hi All,

I am two weeks new into this CNC stuff and I need a little help from my new friends.  My motors in all three axes are missing steps as I am moving along at 10 in/min.  I hear random chirps or step skips as I move along; sorry if I am not being clear with the proper vernacular.  And once in a while I get a burp and the motor stops turning as the counter on the Mach3 screen continues to go and then I’m off position by as much as ¼ inch. I discounted the motors so there is no load on them and I tuned and tuned and tuned with no avail.  I changed the pulse widths all the way up to +15. 

Here is some background information on my setup:
I am running MachX (2 on 3) on an IBM laptop with all the recommendations called out in the Art’s optimization file. When I run the driver test I see pure perfection at 25, 35, 45 . . . 100kHz.  BTW, I am plugged-in, not running off the battery; however I did try both setups.

I have a quality printer cable 3ft long running to my Gecko’s G201 with no BOB.  I have three AC/DC switcher power supplies made by GlobTec RT-3S150-24 each at 24V 6A. I am running little steppers made by Superior Electric Type MO62-CS-513 DCV 1.65, 4.7 amps. 200 steps/rev.  I built a Vicor AC 120V /DC 120V To DC/DC 5V with a 660 mF holdup capacitor to feed power to the Gecko’s opto’s and LPT ground.  Speaking of ground, I have tried many different configurations of grounding, the outputs of the power supplies, the Geckos, but not Gecko common to AC ground; I hear that could be costly.

Do you have any ideas guys and gals?  Gals as in girls not a unit of acceleration in the centimeter-gram-second system equal to 1 cm per second per second.  Sorry the geek in my just spilled out. 

Rick

Offline Chaoticone

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Re: Losing steps on the run. . .
« Reply #1 on: February 19, 2008, 05:31:16 AM »
Hey Rick,
   Sounds like you are picking up some random noise to me. Can you post some pics of your controls for clues?

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

My guard dog is not what you need to worry about!

Offline Tweakie.CNC

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Re: Losing steps on the run. . .
« Reply #2 on: February 20, 2008, 11:11:18 AM »
Hi Rick,

I had similar problems when using a laptop / switch mode power supply combination - my driver test was not too good though. When I switched to using an old PC everything was perfect. Could you perhaps try a PC and see if the situation improves ?.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Losing steps on the run. . .
« Reply #3 on: February 20, 2008, 11:19:52 AM »
Hi Tweakie,

I think you are right!  I am building a PC for this application and I will post my results.  Thanks for the conformation that laptops may not be up to the task.  However, they are so much more convenient.

Rick
Re: Losing steps on the run. . .
« Reply #4 on: February 20, 2008, 11:24:25 AM »
Hi Brett,

I have not forgotten about your request.  Pictures – I must make time for the pictures.  :-)
Re: Losing steps on the run. . .
« Reply #5 on: February 21, 2008, 12:56:38 AM »
Hi,

A little update:  I have been able to make my mill stop translating - missing steps for a second, at will.  I am still using a laptop and I think that is where the problem (noise) is coming from.  While the cutter is moving along, if I change from one screen page to another in Mach3 the condition occurs.

Rick

Offline Tweakie.CNC

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Re: Losing steps on the run. . .
« Reply #6 on: February 21, 2008, 02:51:35 AM »
Hi Rick,

My initial problems with missing / extra steps were with noise generated on the earth return / screening circuits. I changed to a single point earth, metal control box and of course screened cables for everything, which were only screen terminated at one end (except mains input). Although this improved the situation, as said earlier it was only fully solved by changing to a PC. Thinking back on the problem it may well have been the CNC interfering with correct operation of the the laptop which is not that well screened.

Good luck,

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Losing steps on the run. . .
« Reply #7 on: February 22, 2008, 12:06:49 AM »
It was the laptop!  All better now with a desktop computer.  Thanks for the help.  I'm so happy now I think I am going to breakout in song.

Offline Chaoticone

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Re: Losing steps on the run. . .
« Reply #8 on: February 22, 2008, 06:22:52 AM »
 :)

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

My guard dog is not what you need to worry about!