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Author Topic: servos not traveling proper distance, new install of 2.0  (Read 7783 times)

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servos not traveling proper distance, new install of 2.0
« on: May 07, 2007, 06:43:24 PM »
Ive been running tests all day and im at a loss to figure out whats wrong.
I just installed v2.0 and am having trouble figuring this out
Here are the symptoms.
1. The z axis when traveling down 1" only goes down .995  . When I cycle it up and down, it always comes back to perfect 0 but never goes down below .995  .
     This exact .005 error is happening with each Axis. It always arrives .005 short of the mark, but always returns to zero.
2. No matter how much adjusting I do with backlash compensation all my circles are all slightly round boxes. When I de energize the servos and roll them back and fourth by hand, there is zero play.
3. When I run a 350 line gcode file, that has a final depth cut of .225, the actual depth is .350  .

If anyone has any ideas, please let me know.
Rob
« Last Edit: May 07, 2007, 07:15:38 PM by replicaprops »
Re: servos not traveling proper distance, new install of 2.0
« Reply #1 on: May 07, 2007, 10:39:52 PM »
sounds to me like you have some PID loop tuning that you need to do :(
Fixing problems one post at a time ;)

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Re: servos not traveling proper distance, new install of 2.0
« Reply #2 on: May 07, 2007, 11:51:30 PM »
what is that?
Re: servos not traveling proper distance, new install of 2.0
« Reply #3 on: May 08, 2007, 10:11:12 AM »
what are you running for servo drives?
Fixing problems one post at a time ;)

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Re: servos not traveling proper distance, new install of 2.0
« Reply #4 on: May 08, 2007, 12:04:54 PM »
geckos
Re: servos not traveling proper distance, new install of 2.0
« Reply #5 on: May 08, 2007, 12:37:24 PM »
Read your docs about setting your Gain and Dampen pots on the back side of the drives...

Also can you turn the shaft by hand with the servo on?
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Offline fdos

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Re: servos not traveling proper distance, new install of 2.0
« Reply #6 on: May 08, 2007, 12:59:45 PM »
If you're DRO's in mach are saying -1" and the job is ending up 5 thou short of 1" then I agree with Brian your servo tuning is off.  Or you are losing some steps somehow.   

If your DRO's read .995" then there's something else wrong.

Wayne....
Re: servos not traveling proper distance, new install of 2.0
« Reply #7 on: May 08, 2007, 02:41:49 PM »
So even though the drives have been running fine for over a year, you thing I need to tune the drives again?

Offline fdos

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Re: servos not traveling proper distance, new install of 2.0
« Reply #8 on: May 08, 2007, 02:56:21 PM »
Well who knows!    If you tell mach to move say 1"  what do the DRO's in mach say?

If it's been working ok for a year and not now then something has changed surely?

In one of the cases you gave above the distance fell short, in the other it gained?

Wayne....
Re: servos not traveling proper distance, new install of 2.0
« Reply #9 on: May 08, 2007, 04:25:43 PM »
I was running a file and I noticed the z was droppng, so I sat and watched the servo and the servo was slowly lowering the Z. The DRO in mach 3 was remaining constant at a set level even though the servo was moving. I had an extra servo, so I swapped them out and it did the same thing. So I think the servos and the encoders are ok. With the servo turning and mach 3 not compensating, what does that mean?