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Thread: x stepper motor

  1. #1
    Join Date
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    Default x stepper motor

    I do primarily 3-d and even for a hobbyist i have lots of hours on my buddy. There is a tick when you move the table back and forth. i changed pinion gears and pretty much got the same thing. my carvings are ok but could be better. If it is the x stepper motor what should i see in my carvings.

  2. #2
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    Hey Cowboy,

    Is it a continuous tick tick as it moves in one direction or just a tick tick you can hear by manually push/pull on the carriage/table or when it's changing direction (a lot of this in 3D files if that's your axis of raster)? If it's the latter and not showing up as poor cuts, it's likely just gearbox backlash. Check it with a dial indicator to see how much it is. Make sure the motor/pinion are adjusted into the rack properly as well.

    Beautiful piece in your other post, as always!
    Scott




  3. #3
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    Default

    you can hear it, and also with the table removed. but it is so small that you cant see the movement to determine if it is the pinion or stepper. one of my pinions was fairly new and other has a gazillion hours on it just like the stepper motor. thanks for the comment. maybe it is just me being anal. here is a blow up and again maybe it is just me being to critical.
    Attached Images Attached Images

  4. #4
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    Drop the motor out of the rack and see how smooth it is without it. You also can swap x and y motors and see if the tick follows.
    Kenneth

  5. #5
    Join Date
    Jan 2004
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    iBILD Solutions - Southern NJ
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    Unfortunately ALL of the SB gearbox motors wear out over time - especially when they are either under heavy load or long repetitious cycles. Early on I built a scanning machine based on a SB that rastered back and forth using the 7.2TH motors...after several hundred million cycles, the gearbox had about 3/8" backlash in it...This is an extreme case, and you can adjust them if you are prepared to mis-adjust and chuck it into the trash...However, if it ain't good and broke, don't go fixin it. These gearbox motors have .002 + backlash in them when new. I've verified this with a dial indicator.

    The BT tools are tough to truly get 'tight' on the moving table axis. That motor is doing a lot of work compared to the others. I'd suggest, rather than feeling blindly in the dark that you turn on the control box and wiggle each axis against its line of travel - using a dial indicator. Then you'll know if anything can be adjusted out since you've quantified the slop as a baseline.

    Looking at the surface finish of your work, it is clear that you did an offset strategy (unless my eyes deceive me) - in my world, this is a no-no unless you are machining a half sphere or some other spherical relief in the round - which is rare. The issue here is that you get the little bit of slop/lash from every axis because you are doing 3 axis moves. This causes compound hysteresis - in any and ALL axes - and is the absolute worst quality result when 3D machining on any tool with some miles on it.

    If you truly are going after quality, raster along the most stable axis on the machine - the beam - and only have the 2 axes moving instead of 3. When the raster changes direction, the backlash is taken up in the first .01" of movement in the opposite direction. While doing an offset, it is never taken up. The bit is free to act like a gyroscope and waller around...combine this with microstepping and it 'ain't real good'...Try rastering parallel with the beam. Lower your stepover if you're worried about compound geometry creating moire lines.

    Let us know if it helps...
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  6. #6
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    thanks, that gives me a lot to think about

  7. #7
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    Oct 2009
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    Elgin Illinois
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    That was interesting reading Brady! Again, more things I had never realized. Thanks, Chuck
    Chuck Keysor (circa 1956)
    PRT Alpha 60" x 144" (circa 2004)
    Columbo 5HP spindle
    Aspire 9.0, Rhino 5

  8. #8
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    Marietta, Ga.
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    My Buddy BT has the same little tick in it from the X axis also. I have tried to adjust this out from talking to ShopBot and information gotten from the Forum. But, as Brady says, there is a good chance you can cause it to run too tight and ruin it. Finally, I left it as it was and made sure all else was OK and all has been well. Beautiful work as always...joe

  9. #9
    Join Date
    Apr 1999
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    Rock Hill SC
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    I thought that I had put these on the forum but now I can not find them.
    I have two steppers from my buddy for sale. They are $125 each plus shipping. Will go in a large USPS one rate box I believe.
    Lightly used since I spend about 50% or my time travelling and have for many years. These were on a 2008 machine.
    Attached Images Attached Images

  10. #10
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    Thanks for the comments and i will keep those used motors in mind.

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