power-off table pushing tests in X. should it move? Tens backlash w/ power-on
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  1. #1
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    Default power-off table pushing tests in X. should it move? Tens backlash w/ power-on

    Having a brain freeze.... We are dealing w/ some vibration issues in X and been rooting around. The power-on backlash text is a ten. It seems really tights. We had completed the thrust bearing cartridge and end bearing last Winter.
    Now, With power OFF, the Son pushes on the table in X and can get it to move.. and move.. and move. A thou to a few thou as he pushes hard. He thinks that's really bad? I wonder as it's just putting force to the screws and converting to rotation and movement? Nothing in the manual says to do this w/ power-off I can see. Are we having a problem or not?

    Y will not budge w/ power off. but we did not do the thrust and end bearings either.

    Wondering if we are onto something here or not?
    TIA

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    Hi Countryguy the X and Y axis do not have brakes on them and if you push hard enough they will move with the power off, I just did it on a 2001 VF-0 in the Y axis. It takes a lot to get it moving but it can move.
    If you push on it with the power on does it move? It might move a few tenths but should move back as the servos are holding it.
    I hope this helps.

    Joe

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    Call Haas and ask them. Move the saddle down to the ends of X travel and see if he can get the same movement. If not the ball screw is probably worn in the middle. If the travel or backlash is the same, then the thrust bearings are probably loose. Ask Haas how to adjust them. Better then guessing here.

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    Ball screws? Without servo motor holding torque, pushing on an axis will cause things to move and keep moving.

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    thanks... We were slogging off A-36 steel. 60 Thou at 100IPM Flying thru large parts for the first 2 of 8. Finally had the mill running like it was made to do.
    Then it hit a wall and started vibrating and ruining cutters. Howling so loud you could hear it thru the entire house. PArt is 10" x 12" x 2.5" thick.
    It got worse and worse thru a single day. On a Circle 5" round and 1" deep, it'll scream and chatter at 2 spots on the circle. On long X cuts, it'll scream around the back side of the part on X+ cuts. (table moving to left). Otherwise it sounds super till it hits those key sections and blows up a cutter. Or chatters a mess into the steel and then blows up the cutter. slowing it WAAAAaaayyyyyy down lets you dance thru it but it's taking 18hours for a part. Not gonna make any money that way.

    The thrust bearings were replaced last year on X. Under power the backlash is minimal... at a ten or two. That's it. Same for Y. 2 tens. So we think it's a worn screw in a few posts possibly? A busted bolt? We'll take anyone's input.

    To pull this table off a VF/4 is going to be a journey for sure. Not sure what else to do for now. Have the PN's and costs for X and Y screws/nuts. Not looking forward to that w/o proving its the cause. (X screw at least)...

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    It is losing position? Sounds like something came loose.

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    It is not loosing position.
    We're going to pull the covers and possibly the table. inspect the screw and such. Never had to diagnose the screw and trucks. Not sure how to and I'll get into the manual. Was going to call CA and see what they may say.

    Quote Originally Posted by mhajicek View Post
    It is losing position? Sounds like something came loose.

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    Pull stud still tight in the holder? Drawbar tension?

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    Quote Originally Posted by mhajicek View Post
    Pull stud still tight in the holder? Drawbar tension?
    Pull stud is solid, we recently did a spindle re-grind. (less than a year) We did a tool-taper bluing test the other day too in checking this issue. It's good. better than good actually.

    We replaced the drawbar less than a year ago as well. Could be a few broken washers, but should be in good shape there.

    I wish we had a spindle and drawbar to just pop in there to isolate. When it's a $5K tag for screws you really want to prove that will fix it.

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    Could try the screwdriver pry test for drawbar tension.

    When the cutter was screaming, did it make any marks on the holder taper?

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    It's prolly the screw.............just had the Y screw, carriers, thrust bearings replaced in my VF2.................no more issues. I figgered just replace it all and then I don't have to fiddle with one part at a time and not getting the problem resolved..................

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    I'll ask the kid on marks, I'm pretty sure he checked for the fretting marks on the holders. This is a good thread to pull and check.

    What's the screwdriver test? I get it.. but how does one do the bend-over test on this w/ the screwdriver :-)
    Quote Originally Posted by mhajicek View Post
    Could try the screwdriver pry test for drawbar tension.
    When the cutter was screaming, did it make any marks on the holder taper?

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    Close to doing/saying the same thing. Are the carriers the 'trucks'? but on X and Y. and we would try to do it ourselves... did everything else. may as well do this too .

    Quote Originally Posted by david n View Post
    It's prolly the screw.............just had the Y screw, carriers, thrust bearings replaced in my VF2.................no more issues. I figgered just replace it all and then I don't have to fiddle with one part at a time and not getting the problem resolved..................

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    Quote Originally Posted by countryguy View Post
    I'll ask the kid on marks, I'm pretty sure he checked for the fretting marks on the holders. This is a good thread to pull and check.

    What's the screwdriver test? I get it.. but how does one do the bend-over test on this w/ the screwdriver :-)
    Take a large flathead screwdriver, put it in the gap between the spindle nose and the holder flange, and try to pry the holder out. From what I've read, you shouldn't be able to make it move.

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    Hi folks- An update (of sorts) The person he was doing the job for allowed him to use one of their machines to finish the last 6 parts. Super guys there and really swell of them to allow this. He's on a 2007 VF2 SS says' it's night and day to our VF/4 in the cutting rigidity. OF course he's asking me to get the screws on order. I'm of the 'open the patient up' first before I put in new hips. Seems it's time to pull the covers off and get the table hoisted. If anyone has some threads or knows of getting it in the air, appreciate any tips!

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    If'n your just swappin out the screw, you don't need to lift the table................................

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    David thanks.... how in the heck does one get in to undo the screws holding it to the saddle/table. WE wanted to check if they were tight some time ago but could not see how on earth you get to the screws at the nut and saddle. TRying to read up on the Haas manuals tonight....

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    found a good doc on the removal... not too bad!
    VMC - Ballscrew - 32mm - Horizontal Plane - Replacement

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    Anyone know if the replacement screws from Haas are rolled or ground? getting close to making an order. Wondered if there are other sources as well. Not interested in screw repairing but I would assume there are some quality screw/nut Co's that must sell these.

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    They're ground. Even with comp, a rolled screw has no place in a proper CNC machine.

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