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  1. #1
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    Z DRO moving, axis not moving

    I know I've seen this question asked before, but searching yielded no results.

    I can jog all three axis with no problem. (And the Z is probably the smoothest running axis out of the 3 on my machine.) When I home, the z axis DRO shows movement, but the motor doesn't rotate. I can change the rate of movement ( in Config/Home&Limits from the default of 20% up to 50%) and then the axis will home correctly. But the next time I try to home, I may or may not get the same problem. I'm now up to 70%.

    Also, when I manually type in G-code, the axis does not move at all, but again, the DRO shows movement. X and Y respond correctly, Z doesn't.

    I just got this system up and running today, and I'm still in the testing and calibration stages. One thing I'm not sure about is the soft min and soft max for the Z axis. I presently have it set up with home being 0 (or soft max) and when it goes down toward cutting depth, it goes in a negative direction (or soft min of -6.25).

    Need advice on if I have it set up correctly and why the Z axis is acting strangely.

  2. #2
    Community Moderator ger21's Avatar
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    Could be an issue with the parallel port not providing enough voltage.

    What kind of drives are you using? And what are the pulse widths set at i nMotor Tuning.

    Usually you'd set the soft limit max slightly below the switch, so it wouldn't hit the switch. The min is correct, at the lowest point, which is negative.
    Gerry

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  3. #3
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    When I had a similar problem it was the parallel port not supplying enough current causing the voltage to drop. It worked fine most of the time but as I slowed down the Z axis it would start to be flaky - stuttering or not moving at all even though the DRO was changing. I have no idea how it worked at all to be honest.

    What is your motor driver and breakout board setup?
    CNC mill build thread: http://www.cnczone.com/forums/vertical_mill_lathe_project_log/110305-gantry_mill.html

  4. #4
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    I bought a Keling bundle of a Gecko 540, 387 oz motors and the PSU they put in the bundle. The PSU is running at 48 volts. I built basically this same machine a couple of years ago, but finally gave up because the computer I was using was not up to par. I have just rebuilt it using a different design and a different computer, but I'm using the same electronics now that I used then and didn't have this issue on the first machine.

    It's really not a big deal, because homing is not a big thing (and I can work around it) and I will rarely run manual G-Code. I'm going to cut some basic squares and circles tomorrow, and hopefully everything will be OK when I load and run a G-Code file.

    Not to question the responses, but if it's a parallel port problem, why does the X and Y axis work correctly, but the Z doesn't. Would it be feasible to hook the Z axis up to the A axis connector on the Gecko, do the re-configurations, and try that. Don't know if the Gecko requires the first three connectors (X, Y & Z) to be working for the A to work.

  5. #5
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    Forgot to mention

    As I just got this thing spinning motors today, I haven't (yet) done the trimpot adjustments on the Gecko. (According to the Gecko manual, this is done to adjust low speed smoothness). Don't know if that matters or will help, but just wanted to include all info I could.

  6. #6
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    I don't know why, but my machine was doing the same thing (x, a and y working fine, just z not). Like I said, I'm not even sure how my Z axis was working at all, but it was most of the time. It's worth looking into, but other than using an oscilloscope I'm not sure how you'd do that other than putting in an outboard card. And card I put in also had a few pins without enough current capacity, so I had to make a new cable that used pins from two ports to drive the G540.

    I'd say it's not something to ignore. That's what I did, and it eventually came back to bite me while I was cutting parts. It ate into a sheet of parts when the z axis failed to retract and then it ate into the frame of my machine before the router stalled and tripped the breaker the machine was on. It had run without incident for months before that. Of course having limit switches would have prevented some of this.
    CNC mill build thread: http://www.cnczone.com/forums/vertical_mill_lathe_project_log/110305-gantry_mill.html

  7. #7
    Community Moderator ger21's Avatar
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    Set the pulse widths in Motor tuning to about 15, and it should get it working. If not, try using Sherline Mode.
    Gerry

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    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  8. #8
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    If the problem is the parallel port current, changing the pulse width is not a solution - just a bandaid. That's what got mine working for a long time but eventually it still messed up again.
    CNC mill build thread: http://www.cnczone.com/forums/vertical_mill_lathe_project_log/110305-gantry_mill.html

  9. #9
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    Also depending on when you bought your G540, there was an issue with bad chips. You could check out the Gecko forum for info on that. I posted some scope pics in a thread there where that was being discussed, so you could search for my user name in that forum.
    CNC mill build thread: http://www.cnczone.com/forums/vertical_mill_lathe_project_log/110305-gantry_mill.html

  10. #10
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    I also have another PCI parallel port board that I can and will try. I may also need to do a continuity check on my printer cable and just make sure that it is a straight through. Like I say, I just started testing today, so I've got a world of things to adjust, troubleshoot and learn before I cut my first masterpiece (whatever that turns out to be )

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