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Z axis problems

Discussion in 'Trouble Shooting - Support - Help Section' started by rcav8r, Feb 10, 2010.

  1. rcav8r

    rcav8r Moderator Staff Member

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    Hi All;

    I am having a weird Z axis issue. Not sure if it is the hardware/software or....

    A little history.
    Had the original 1/4x20 rod and "stock" stepper. Got about 10ipm on the Z. While doing a mod, I took the Z axis apart and found a lot of binding. I removed that, and also replaced the 1/4x20 rod w/ a 3/8x8 ACME rod and nut. Also replaced the Dremel w/a rotozip flex shaft so there is less weight.

    I can spin the nut from one end of the rod to the other so I know there is no binding there.
    The Z gantry now is as smooth as a new born's behind. No binding at all.
    I put it all together, re-tuned, and still get a whopping 10ipm on the Z.
    It was suggested the stock stepper was not up to the task, so I ordered a stepper from Trish and Mark and installed it last night.
    Same 10ipm.

    I then took the rods out of the Z gantry to eliminate that. Still 10ipm before it skips steps.
    I then took the Z gantry all the way out, and ran the stepper with no load. I could easily stop the stepper by hand. I barely squeeze the shaft and it skips.
    I then swapped the Z and Y axis physically at the board. Same issue with the Z stepper.

    After reading through some posts here, I see that some guys had problems with the wire for the Z axis. Not the same issues as I was having, but problems non-the less. I will try changing that tonight when / (if due to blizzard out there) I get home tonight.

    But should that not fix it... any ideas what else it might be?

    Also what is the value for the steps when using a 12pitch rod? I copied my settings down from when I had a 12pitch for the Y axis, but I MAY have copied wrong. I tried to calibrate, and I think I'm close, but it is hard to do on the Z.

    THANKS
    Dave
     
    rcav8r, Feb 10, 2010
    #1
  2. Jnida63

    Jnida63 Member

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    Sounds likie the board voltage is off to me
     
    Jnida63, Feb 10, 2010
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  3. Anonymous

    Anonymous New Member

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    Yeah, it sounds like the V-ref is cranked down to "barely working" on the Z-axis. Is that the Easy-CNC board?
     
    Anonymous, Feb 10, 2010
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  4. rcav8r

    rcav8r Moderator Staff Member

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    Hummm. I will have to check that when I get home. Never thought of re-checking...
    Yes it is the Easy-CNC board. I forget the exact voltage, but it should be the same as the stock steppers, right?


    THANKS
     
    rcav8r, Feb 10, 2010
    #4
  5. Anonymous

    Anonymous New Member

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    If you look here, http://www.phlatboyz.com/phlatstore/#ec ... uct=369613 , the Phlatstore says 3.6V, 2A.
    If you have an Ohm-meter, read the resistance through the coil on one phase, (say 1.8 Ohms) and double that number (1.8 X 2 = 3.6), then set V-Ref to that number in volts. That would give you 3.6V, 2A with a 1.8 ohm coil. If your coil resistance is different, adjust your voltage accordingly.
     
    Anonymous, Feb 10, 2010
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  6. kyyu

    kyyu Active Member

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    The amp rating also depends on if it unipolar or bipolar. So I wouldn't necessarily use the 2A rating. I thought someone had the skinny on this. Was it Crash? You might want to pm him, 1st. I found this old post of his: viewtopic.php?f=135&t=894&p=11964#p11964 If it's 1.4A for bipolar, the max setting of vref should be 2.8V?

    -Kwok
     
    kyyu, Feb 10, 2010
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  7. Anonymous

    Anonymous New Member

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    Kwok, you are absolutely correct, the final voltage depends on whether the system is wired unipolar or bipolar. Vextra has a complete spec sheet on their website, iirc.
     
    Anonymous, Feb 10, 2010
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  8. rcav8r

    rcav8r Moderator Staff Member

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    Yep this was it. :D THANKS!!! So simple I missed the obvious.
    It was set to .3V Yikes was it low. Set to 1.3 (just to be on the safe side) and I get 40ipm easy. I backed off to 25 just to be sure I don't miss any steps, and when it's traveling so little, it really won't make that much of a difference.

    THANKS Again to all who helped
    Dave
     
    rcav8r, Feb 10, 2010
    #8

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