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I could really use some help.
« on: January 05, 2009, 12:56:08 PM »
Howdy all,
             last year I built myself a small (26" x 13" x 2") CNC Router. I set it up with Mach 3 on an older computer running windows 2000 Pro and it seemed to run fine. I would have a problem with the "Z" axis not repeating when I changed bits but all in all it was something I could live with.

Now however it is becoming very annoying. Not only is the "Z" not repeating but now the "Y" is out as well. I just tried to do some 3D work and the paths are not lining up at all. I have checked my rate of travel and it seems okay. Is there any setting in the control panel that I may have missed or that has changed on me somehow that would account for this?

I am ruining more material than I am keeping.

Offline Glenn

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Re: I could really use some help.
« Reply #1 on: January 05, 2009, 02:43:12 PM »
Hi Marwellca,

   If you haven't checked already, double check to see if your issue is
mechanical--maybe some play in the nut on your allthread, or even where you attach the nut to the y and z carriage.
Please forgive me if this seems too obvious , but mine is homebrew, and I need to tighten things up every once
in a while to keep the z x and y running true.!
   Please tell us more about it's symptoms; can you draw a perfectly round circle in x and y, or is it oblong?
    Glenn :)
Don't assume anything.....it'll make a Manager out of U and Me!
Re: I could really use some help.
« Reply #2 on: January 05, 2009, 03:18:14 PM »
Hi Glenn,
            I checked the connections and all seems good. I cut a circle yesterday approximately .060" deep and the start and finish points did not line up. I was using a 90 degree V tip cutter and the finish point was out by approximately .030". Not much but enough to be noticeable.

When I am cutting a pocket, say .500" deep, I can see on the Mach screen that my cutter has entered the workpiece by .090, when I actually measure the depth of cut it is out, sometimes by .050".

I cut a project yesterday, the material is pine and is the top of a plate. When I did the rough cut it looked good, when I did the finish cut it did not line up with the rough cut by almost .125". I the did another project and cut a Harley Davidson emblem into another plate you can see the result, the emblem is supposed to be centred in the plate but is way off to one side.

Martyn.

Offline Hood

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Re: I could really use some help.
« Reply #3 on: January 05, 2009, 05:19:51 PM »
What hardware do you have (drives breakout etc) ?
Hood
Re: I could really use some help.
« Reply #4 on: January 05, 2009, 06:14:46 PM »
Hi Hood,
          I purchased a 3 axis controller package from Mike Beck, www.mikebeck.org way back in September 2007 and put my machine together in 2008. There is no breakout board with this system. The reason I bought it was that it was basic plug and play.

Martyn.

Offline Hood

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Re: I could really use some help.
« Reply #5 on: January 05, 2009, 06:32:14 PM »
Just had a look and its not the most user friendly site I have seen so docs may be there, however I couldnt find them. Do you have docs in pdf or similar format that you could attach so I can take a look?
 By the looks of it you have all the drives on one PCB so no realy option to switch things around for testing purposes. The only thing you could do is swap axis pins in Mach config and see if the problem moves or swap motor and see if the problem moves.
Hood
Re: I could really use some help.
« Reply #6 on: January 05, 2009, 06:38:23 PM »
Here is another shot of the same problem. I started to cut the top of a plate out of Maple. I ran the roughing, changed the tooling re zeroed the machine and then started to run the finish toolpath. The path was fine until a short time into the run. I hope you can see in the photo, kind of blurry, sorry, that all of a sudden the co-ordinates shifted and now the tooling is cutting the material off centre of the original cut.

Martyn.

Offline Hood

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Re: I could really use some help.
« Reply #7 on: January 05, 2009, 06:57:01 PM »
Well that is a classic example of an axis stalling for a second or so, drop the acell a bit and see if it helps, same with velocity. Have a look on the general configs page and see whether Enhanced pulsing is enabled or not.
Hood
Re: I could really use some help.
« Reply #8 on: January 05, 2009, 07:04:57 PM »
Hood,
     I just looked and Enhanced pulsing has a checkmark beside it. Is this correct?

Martyn.

Offline Hood

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Re: I could really use some help.
« Reply #9 on: January 05, 2009, 07:14:10 PM »
yes, well for 99.9999999999% its the best option :) If you have not knowingly altered it then it is almost certain it has always been set that way so it wont be your problem.

Hood