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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better fix
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  1. #1
    Join Date
    Jun 2013
    Posts
    52

    Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better fix

    Hi,

    After some minutes into the program run I heard a bad squeak and saw how the Y axis had drifted about an inch. I checked the motor pulley as this has already come loose a couple of times in the X axis, but it was firm there. I checked the pulley on the ballscrew and while it was firmly attached to this I could still move the ballscrew because when this pulley doesn't push against the bearing, the bearing somehow comes out of the housing and thus the ballscrew moves. I'm really disappointed with the Optimum cnc kit due to all these problems and also the fact that they're lacking the necessary parts to be able to keep using the mill manually also.

    Anyways, I'm wondering if there's a better way to have the Y axis pulley push against the bearing other than tightening the nut, because then if you make it too tight it also takes a toll on how smooth the crosstable slides on the Y axis...

    Thanks

  2. #2
    Join Date
    Jun 2013
    Posts
    52

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    Alright, it was actually the motor pulley. Those little set screws that came with the CNC kit are pissing me off. Apparently you gotta tighten them as much as possible, yet if you go too far the allen socket will deform. Anyways when I removed the motor support to tighten the nut on the ballscrew and pulley end, I noticed the dang thing fell off and the motor pulley had been holding onto the motor shaft by the grace of some divinity. I did tighten the other part a lot more, just in case. Anyways, I'll eventually have to replace those set screws by its stainless counterparts. They're just so annoying.

  3. #3

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    I use loctite threadlocker on all screws on the machine so the vibrations won't make them loosen up.
    Hoss
    http://www.hossmachine.info - Gosh, you've... really got some nice toys here. - Roy Batty -- http://www.g0704.com - http://www.bf20.com - http://www.g0602.com

  4. #4
    Join Date
    Jan 2005
    Posts
    1943

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    As Hoss said, use loctite (blue in this case), and I also either file a flat on the shaft, or put a drill dimple on the shaft, and then put one of the set screws on the flat/dimple.

    Also, the black oxide set screws are actually much stronger than a stainless screw would be. About 3x stronger in both tensile and yield. You need the strength for tip flattening and for more durable hex socket. The stainless will strip the socket a lot easier.

  5. #5
    Join Date
    Jun 2013
    Posts
    52

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    Hey, thanks for the advice guys. I'm gonna get me this loctite ASAP. The shafts have a flat but I'm considering drilling a little and threading. I think I get what you mean 109jb. They're more plastic so that the tip can deform against the shaft and adapt better, if I didn't get you wrong. Oh and for the record I had to tighten the Z axis one shortly after.

  6. #6
    Join Date
    Jan 2005
    Posts
    1943

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    Quote Originally Posted by oxi View Post
    Hey, thanks for the advice guys. I'm gonna get me this loctite ASAP. The shafts have a flat but I'm considering drilling a little and threading.
    Threading what? The motor shaft? Don't do that. Just put loctite on the screws and tighten them.

    Quote Originally Posted by oxi View Post
    I think I get what you mean 109jb. They're more plastic so that the tip can deform against the shaft and adapt better, if I didn't get you wrong. Oh and for the record I had to tighten the Z axis one shortly after.
    You got me wrong. You don't want the set screws to deform. The black ones are much stronger and tougher than stainless. Going to stainless set screws would be a mistake.

  7. #7
    Join Date
    Jun 2013
    Posts
    52

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    Oh all right I'll stick to the loctite Just curious, why not thread the shafts? Just a little you know and put longer set screws so that they hold both pieces together better.

    I thought these were common 8.8 quality steel

  8. #8
    Join Date
    Dec 2009
    Posts
    1416

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    Threading the dimples won't solve the underlying issue of the screw backing out and your removing material from the shaft far in excess of what's needed for a small flat to have a chance of getting even a turn or two of full thread. The flat will do the job quite acceptably without the hassle of threading a hole provided a little blue Loctite is added.
    CNC: Making incorrect parts and breaking stuff, faster and with greater precision.

  9. #9
    Join Date
    Jun 2013
    Posts
    52

    Re: Y axis drifting on BF20L (G0704). Source of problem spotted. Looking for better f

    Thank you!

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