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servo following error problems
« on: March 25, 2007, 11:45:27 AM »

My main problem is trying to get a close following error to
maintain accurate part machining. The Rogers Interface card has
software settings that allows a maxium following error before the
system is hauled.
Just today I had some strange results. The first time I started the
machine the following error DRO for the X axis was paging
between .005 and .00055. Twenty minutes latter the axis was
reading .0153 to .0253. It seemed even when the machine was not
cutting a part its following error was increasing. For awhile now I
had the following error set to .020 just to get a few jobs done. Any
following error less then .020 would cause the interface card to
stop the machine.
Latter in the day I shut down the machine and Mach3. I changed the
following error to .003. I decided to run some code at 100 ipm and
on a 45 degree cut plane.
To my surprise the machine cut the part without a fault. Normally in
the past with a .003 following error set, the machine would fault
and stop just as soon as I pressed the RUN button. I`m starting to
think its a grounding issue. I purchased a pre- made encoder cable
from US Digital. I just looked at it and it seems its unshielded.
I`m not certain whats going on with my system but its very

Regards barry

Offline Chaoticone

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Re: servo following error problems
« Reply #1 on: March 25, 2007, 09:54:59 PM »
Hi Barry,
    How long was the machine off before you tried the second test at .003? Are your components well ventalated? Fans across drives? Any machine I have ever been around chages gradually as mechanical components change temp. It shouldn't be that much though I wouldn't think. What kind of machine is it? What is the frame made of?

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

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Re: servo following error problems
« Reply #2 on: March 25, 2007, 10:44:22 PM »
Here`s what my DIY machine looks like: http://www.cnczone.com/gallery/showgallery.php/cat/500/ppuser/5962/sl/b
The components are cooled with fans and the machine frame is aluminum I-beams
Re: servo following error problems
« Reply #3 on: April 01, 2007, 10:31:12 PM »
 Any good findings to sort out the problem?
Re: servo following error problems
« Reply #4 on: April 02, 2007, 08:32:48 AM »

Art mentioned that I should try using the sherline mode in Mach3. That solved
the noise issue I was having on the encoders. At the time, I didn`t know it
was necessary to have shielded wires for the encoder. I will be replacing the
wires sometime soon.
The strange vibration problem on was x axis was also resolved. I had too much
gain and not enough damping. Before these changes were made I was lucky if
I could run a 3D part at 40 ipm without servo errors. I`ve tested speeds up to
120 ipm without errors. I am now happy again. :)
Re: servo following error problems
« Reply #5 on: April 05, 2007, 10:46:38 PM »
Do you have servos or steppers on you machine?  In the pictures you have steppers.  So now the encoder board is tracking the machine like it should?  I'm thinking of getting one also in a day or two.

Re: servo following error problems
« Reply #6 on: April 06, 2007, 02:09:12 PM »
Do you have a Scope to look at the pules? I think you have a noise problem :(
Fixing problems one post at a time ;)

Re: servo following error problems
« Reply #7 on: April 06, 2007, 06:40:51 PM »

I converted two of my three steppers to servos. I`d recommend the Roger`s Machine interface card.
The support is first-class and the addition of the board to a DIY CnC is great for fine-tuning your
system and also for saving a part from the trash can. :)
Re: servo following error problems
« Reply #8 on: April 06, 2007, 07:44:38 PM »
^^ Then Ron has another customer!