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x axis loosing current position
« on: July 02, 2009, 08:28:41 PM »
I have a 3 axis home built machine using Camtronics Stepper Motors with the MACH 3 (version 3.041) software in the controller.  I use this machine to drive a 3 HP router to shape wood parts - the cutter table size is 4 feet by 8 feet. 

I have over the years occasionally  had a problem with the X axis loosing steps,  that I have corrected by just reinstalling a "golden XML file" that I keep stored on the hard drive.  Last night while making a relatively square part - the machine was moving in the negative x direction in a  40 inches move when it lost about 10 inches in current position register.  The result of this error is the cutter head  changed direction about 10 inches before it should have and ruined the part.  When I saw this performance I reloaded the XML  file - but the problem persists.

It appears that if I let the machine run - it would follow the same path (X Axis  being 10  inches from original datum).    I am convinced that it is not a hardware problem with the machine - the motors did not growl or sound like it was under undo load.  I believe that something in computer is being corrupted or that the processor is being interrupted and is loosing count this way.  When originally setting up the machine I used the instruction "Mach 3 Optimization" - shuts off screen saver,  no auto updates ...that kind of stuff.  The machine has worked flawlessly for a year - and now is corrupted. A year ago - when I saw this problem - I decided to reformat the hard drive and having done so have had no problem since - that was a lot of work - if there is a simple fix I would like to avoid having to rebuild a hard drive.

One final note : the method I transfer  G code files from my design computer to the shop computers is through a thumb drive.  Virus's is an issue (that was the root cause  problem a year ago)  but I scanned the thumb drive - no virus found and I run a virus / malware protection problem regularly pn my design computer - since it is connected to the internet with all the filters and firewalls ... so I don't think I have a virus,  but  I am doing some checking into that now.

Thanks in advance for any help.

Krug

Offline jimpinder

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Re: x axis loosing current position
« Reply #1 on: July 11, 2009, 05:13:19 AM »
You do not say what the readouts are on the DRO's when this happens. I realise that, unless you watch these all the time, that would be difficult, but if it is 10 inches out in 40 inches, the problem should be quite apparent before the axis changes direction.

If you are in fact, loosing steps, then one would think this would be a regular loss along the axis (and if you mark the job in pencil every foot, you will see that it is 3/4 short each foot). If it is something sudden i.e. Mach has suddenly lost interest in one line and gone onto the next, for no apparent reason, then the DRO's should bear no relation to the program when the move occurs.

It must be one, or the other. If your machine was loosing steps intermittently, then I am sure you would hear or "pick this up" immediately.

I don't know if it is possible for Mach to keep a log of it's movements, I've never heard so.
Not me driving the engine - I'm better looking.

Offline RICH

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Re: x axis loosing current position
« Reply #2 on: July 11, 2009, 09:03:10 AM »
Hmm...
If the loss was intermittent and not consistant, could be that the steppers are getting hot, and
when that happens, they start to behave weird. But you would not get some consistent error
in movement. Don't think it is a noise issue.

As far as occasionally loosing steps, you may want to just drop your velocity and acceleration down a bit
as you may be boarderline when routing out a harder wood.

I don't ever remember needing to reload / reuse an XML because it got corrupted. But that's just my experience.

I am wondering if you don't have some work offset that is throwing things off that you are not aware of??

Is it consistently 10" off"
RICH
Re: x axis loosing current position
« Reply #3 on: July 17, 2009, 03:19:53 PM »
Jimpinder, RICH

Thank you for the reply.  I apologize for not getting back sooner - been away - I have not had access to the internet until just now. 

I thought about the heat concern - because it is middle of summer here and that is an issue.  I have also spoke with Dan Maunch from Camtronics (he has been so good to do business with) and together we decided that we needed to tune the motors differently.  So I have sent them off - he will make the adjustments -  test and return.   I hope to have them back in couple weeks ... will let you know how it turns out.  BTW I wrote a test program that executes a series of moves repeatably and then comes back to x,y=0.  I ran this test and it repeatably had errors - easy to duplicate. 
I'm convinced it will have something to do with the Gecko drivers.  Thanks for you input ...  Krug

Offline RICH

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Re: x axis loosing current position
« Reply #4 on: July 17, 2009, 05:38:38 PM »
Krug,
Let us know how you make out and more importantly what was wrong.
RICH
Re: x axis loosing current position
« Reply #5 on: July 17, 2009, 08:01:15 PM »
I will - it will be a few weeks since I am going on travel, and will not have a chance to work this.

Krug