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Thread: Fadal Z-axis ball screw or thrust bearing concerns.

  1. #1
    Christopher is offline Aluminum
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    Default Fadal Z-axis ball screw or thrust bearing concerns.

    Howdy all,

    We are running a Fadal VMC40 (aka 2216) and have a feature that is bored to a shoulder. The bore is 1.851" diameter and roughed out with a 1.75" Ingersoll "quad drill", then finished with a pair of boring operations (roughing/finishing); the last 0.007-9" diameter with a Criterion "tenthset" head. I am getting varying depths on the bore, to the tune of 0.010"!!! I assume our machine has bad thrust bearings on the Z, but the ball screw may be partially to blame as well. As a newcomer to the world of "NC" machinery, I have considered using a screw jack and thick rubber matting, to CAREFULLY apply measurable upward load on the Z axis and measure the change. Do any of you more experienced folks have any thoughts on this? It seems impractical to try and separate ball screw wear from thrust bearing wear; with my rudimentary method, and I am not sure if there is a way to do this without taking the ball screw out. Thankfully, the depth variation is not a closely held value on the job; however, the variation in depth IS causing the finishing tool to work harder at the bottom of the holes than desirable for maintaining the bore diameter values needed!!! I also hear a noticeable "bump" in the Z axis during peck drilling operation that have moderate load; this does not make me feel like everything is at "factory tolerances". Any insight from the PM community would be coveted!

    Best regards,

    Christopher

  2. #2
    Bobw's Avatar
    Bobw is offline Diamond
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    Odds are its thrust bearings, its almost always thrust bearings.

    You should be able to pop off the cover over the ball screw, put an indicator on the end of the screw, and then jack the head, if it moves,
    its thrust bearings, you can also jog up and down and see what happens.

    Also while you are in there, make sure your screw is getting oil.
    scadvice likes this.

  3. #3
    Christopher is offline Aluminum
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    Bob,

    Thanks for the reply; I suspected this was the issue from previous reading. I will likely get a bearing and seal kit while I'm "in there"; I will also examine the lube system as well!

    Christopher

  4. #4
    Speedie's Avatar
    Speedie is offline Hot Rolled
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    A bump or thump while peck drilling only means one thing on the small fadals and that is nut damage. The smaller ballscrews aren't able to take a huge crash without damaging the nut. You get maybe 4 crashes in Z before your nut will need work.

  5. #5
    Ccarrigan is offline Plastic
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    It's the nut, thrust bearings AND ball screw !! The repair has been made simple by the suggestions I have found here. Thanks for all the advice!!

  6. #6
    scadvice's Avatar
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    Most Fadals will have a "mild" bump sound when peck drilling. the splash guards will also have a shuttering sound (again mild) and the side panels will rattle some. A 'Knocking" or even banging is not normal. As Bob says, it's 90% of the time, the thrust bearings.

    Errors in z depth like you've described suggest also the thrust bearing. In very, very rare cases...maybe the ball nut is loose in its mounting...

    Ccarrigan, I'm not sure where your coming from, I assume your just being sarcastic???

    Steve

  7. #7
    Ccarrigan is offline Plastic
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    Actually I am working on the machine, it was EVERYTHING !!

  8. #8
    Ccarrigan is offline Plastic
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    Good afternoon everyone. Would just like to update this thread with something that I learned doing the work on this machine. When you are in the re-assembly stage when you are putting the ball screw in the machine I found out there is a process. You need to loosely put your bolts in with the spindle moved as far to the top as you can and still work on it. Tighten the ball nut bolts first then tighten the bolts at the top mounting block. This insures correct alignment of the ball screw. We did not do this to start with and we had alignment issues which led to error code 18. After a call to the tech at cnc pros we had everything working well. The machine sounds like new again. Thanks again for all the great advice.

  9. #9
    scadvice's Avatar
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    Ahhh... pulled the 'ole switcharhoooney' on me!

    Thanks for the feedback.

    Steve

    Hummm...I bet it was really banging!

  10. #10
    Ccarrigan is offline Plastic
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    I am a different Chris, same shop, different Chris. The machine sounds great now!

  11. #11
    Bobw's Avatar
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    Quote Originally Posted by Ccarrigan View Post
    I am a different Chris, same shop, different Chris. The machine sounds great now!
    Odd but OK, Did you Chrises make sure that the new screw is getting oil? So that doesn't happen again?
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  12. #12
    Ccarrigan is offline Plastic
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    It is getting oil. Checked the line as we disassembled and reassembled.

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