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  1. #1
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    Nov 2003
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    108

    Leaving lines on material

    Hi,

    I have a mini mill self converted to CNC.

    Last night and I noticed that when cutting a largish flat surface with a .5 inch end mill I am leaving lines on the work. The lines are parallel to the X axis indicating the Y axis is out of tram.

    The lines are deeper towards me (if that makes sense) and are maybe 1-2 thou deep. They are noticeable and can be felt with the ball of your finger.

    Has anyone experienced this?
    Is there are way to correct this?

    Thanks
    phil

  2. #2
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    Mar 2006
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    hi beerfizz
    it has been my experience when this happens your z axis is out of plumb and you need to trammel the head

  3. #3
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    Thanks for the response Dar,

    The head has an adjustment from side to side, if you were standing in front of the mill. Adjusting this would take out any lines which are parallel to the Y axis.

    The lines I have are parallel to the X axis, and in my case seems to indicate that the head is leaning forward.

    I am looking for a way to correct this?

    Ideas?

  4. #4
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    Mar 2006
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    with a bp you can adjust the head both ways. but i have a bp2 so if i have that problem i have to shim tha head BIG JOB. you are going to have to do the same good luck
    Dar

  5. #5
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    I'm not sure which machine it is that you have, but i was just thinking, if its built like mine, the griz x3, there is the potential for slack in the z axis ways, so, in my mind, if theres slack in the z you might tighten the jibs a little and see if that changes anything...

    if the head is pretty solid with the column, then it sounds like the column is not plumb..
    .002" over .500" is an angle of .23deg. so its not much.. way smaller than anything than i can measure.

    ok, so i'm going to ask this next question, cause its something that poped in my head, and i havent had my coffee yet... is it possible for the work peice to not be flat down against the table, could that cause this angle gouging?
    Grizzly X3, CNC Fusion Ballscrew kit, 3 500oz-in bipolar steppers, 3 203v Gecko's, Linear power supply from Hubbard CNC, Mach 3, BOBcad Pro Art V22, Rhino.

  6. #6
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    Nov 2003
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    Hi Project,

    Thanks for the reply.

    I have my mill in pieces at the moment, so I can't test much, perhaps in a few hours.

    I have a X2 Mini Mill, the X3's baby brother. Yes, there is the potential for some slop in the Z especially if the Gibs are not tightened correctly. When I have everything back together I think I will tighten the gibs, starting at the top and work my way down. If there is an issue, perhaps that will pull the top in first and cause the head to be straight instead of leaning forward. This all seems to be somewhat of an Art.

    Best
    Phil

  7. #7
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    Jul 2004
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    How about adding this kit?
    http://littlemachineshop.com/product...gory=879658189

    I have the same problem with my X2.

  8. #8
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    Nov 2003
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    Hi Dang,

    Thanks for the response.

    Have you tried adding the Air Spring yet? That could be a good idea.

    As I mentioned in an earlier post, I thought I would try tightening the Gibs from the top, to see if that would pull the head back a little. Interestingly it worked some, but not entirely, I think I reduced the line by half or maybe more. Its almost not noticeable, but you can feel a slight raise.

    When I compare it to the X Tramming on the head, I have that set to less than a thou over about 10 inches. The half inch end mill leaves a perfectly flat surface in that direction.

    So, there is still a little room for improvement. I would hate to go through the process of taking off the head shimming, trying and perhaps having to shim again.

    The Air Spring might be a good idea?

    Also, its clearly a good idea to tighten the Z gibs often. (for me, from the top down, if that makes a difference at all).

    Anyone any other ideas?

    Thanks
    Phil

    Edit: I should add, that I currently have no additional support on the Z other than the servo and ball screw.

  9. #9
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    Feb 2007
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    Hi Phil
    I'm experiencing this right now as we speak with my X1, little brother to the X2.

    I've spent almost 10 hours now trying to figure out my Z axis issues, but only got a little bit of improvement. I can't go all the way up without the motors stalling, not unless I loosen the gib screws a little more. The problems is when I loosen them too much the head starts to make a funny deep sloppy vibrating sound when jogging down and while jogging down if I push up on the head the dovetail comes off the track. It's a PIA to get them perfect and having figure it out yet.


    Now I had an idea with adding a longer gib plate to the Z head. This would extend a little more on the top and bottom, allowing maybe a little more support, but haven't tested it yet.




    Here's the part and if you look closely inside the ring, you'll see a layered looking surface (not the way it is suppose to look at all).

    I wish they made something like that compression spring for the X1, I feel like I own the red headed step child. I'm most likely going to make my own to hold me over until I decide on my new mill (looking into the Tormach).
    Attached Thumbnails Attached Thumbnails mail.jpg  

  10. #10
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    Feb 2007
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    Phil,

    I had this on my X2, also. I just fixed it, yesterday. Mine was off by about 5 thou from the front of the table to the back. I loosened the three screws that hold the column pivot-plate to the base, tilted the the column back and put a shim under the pivot-plate. I used a 0.002" feeler gauge for a shim and got lucky the first time. Now, it's under half a thou, front-to-back.

    - Don

  11. #11
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    Feb 2007
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    "I used a 0.002" feeler gauge for a shim and got lucky the first time."

    Do you have any pictures of what you used ? Kind of new to machines and tooling.


    Yea I think mine is somewhere around .010 or so. I've taken apart my machine and fixed everything but the head. (chair)

    I'm going to take it apart from the base tonight and hope to figure out the problem!

  12. #12
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    Quote Originally Posted by twocik View Post
    Hi Phil
    I'm experiencing this right now as we speak with my X1, little brother to the X2.

    I've spent almost 10 hours now trying to figure out my Z axis issues, but only got a little bit of improvement. I can't go all the way up without the motors stalling, not unless I loosen the gib screws a little more. The problems is when I loosen them too much the head starts to make a funny deep sloppy vibrating sound when jogging down and while jogging down if I push up on the head the dovetail comes off the track.
    Hi twocik,

    This particular issue sounds like the "mill head" and the "column mount for the ball screw" are out of alignment. This is evidenced by the fact that as the head gets closer to the top, it gets tighter and harder to move.

    Perhaps you can try something like this. Move the head as high as possible either under power or manually. Then loosen the bolts which hold the mount attached to the column (the mount that holds the ball screw -- I'm assuming that your system is designed like this ) Then, if there is enough clearance in the bolt holes, wiggle the mount around so the head moves more freely than before. If there is not enough clearance in the holes can you drill them out a bit?

    Hope this helps
    Phil

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