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Sherline CNC Mill leadscrew backlash and end play help

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  • Dan Putman
    I have been using my Sherline packaged CNC for about 6 months. I have made the usual number goof ups, but at last think I know which end is up. I started
    Message 1 of 5 , Apr 1, 2009
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      I have been using my "Sherline packaged CNC" for about 6 months.
      I have made the usual number goof ups, but at last think I know which end is up.
      I started chasing a backlash issue as a tune up before my next planned parts run. I had noticed that the backlash in X was about .005". Not bad, but half that much would be better. My previous experience in setting the X backlash was something of a chore since I half to demount the Mill Bed from its bookshelf base. Just to get a feel for how things were going to go I decided to check the Y backlash. To my surprise it measured in at .009". Something was a miss.I backed off the hold down screw on the backlash star wheel and worked the table, leadscrew, and backlash until it felt right. I measured again and still .009". I lock the backlash down tighter until the stepper motor was stalling on moves of .001. The play was still .009". then it came to me I grabbed the X table and pulled it towards me. There was movement, and a click. The click was coming from the endplay nut behind the outer leadscrew thrust bearing on the stepper motor housing. By trail and accidental success, I discovered that I could adjust out the end play by snugging up the end play nut against the thrust bearing. With the end play fixed I can now adjust the Y backlash down to about .005". AFAIK Sherline does not mention adjusting the lead screw end play anywhere in their manuals.


      My questions to those wiser than I.
      Can I do better than .005 backlash or is that about what I can expect in the real world?

      I know about the setscrew that holds the coupling nut that couples the lead screw to the saddle. What else should I check to reduce the backlash?

      N.T. My Y stage moans at about the mid point of its travel on the bed.
      I have cleaned and lubed everything I can get at (Lead screw, ways, bed. Is this just another life with Sherline thing or can I make this noise go away?

      Thanks to all.
      Dan
    • Phil M
      I had a Sherline mill for about 10 years and was never able to get the backlash below about .004 on either axis. Those star nuts are not very snug in their
      Message 2 of 5 , Apr 1, 2009
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        I had a Sherline mill for about 10 years and was never able to get the
        backlash below about .004 on either axis. Those star nuts are not very snug
        in their seats, they don't mesh very well, and it is nearly impossible to
        tighten the holding screw without affecting the adjustment, so you end up
        leaving in more backlash than you might otherwise. Don't forget that you
        will have more backlast near the center of travel as the lead screw/nut
        wears. So you end up setting the backlash at one end of the travel, and
        settling for whatever you get at the center.
        --
        Phil Mattison


        ----- Original Message -----
        From: Dan Putman <dan@...>
        To: <SherlineCNC@yahoogroups.com>
        Sent: Wednesday, April 01, 2009 12:43 AM
        Subject: [SherlineCNC] Sherline CNC Mill leadscrew backlash and end play
        help


        >
        > I have been using my "Sherline packaged CNC" for about 6 months.
        > I have made the usual number goof ups, but at last think I know which end
        is up.
        > I started chasing a backlash issue as a tune up before my next planned
        parts run. I had noticed that the backlash in X was about .005". Not bad,
        but half that much would be better. My previous experience in setting the X
        backlash was something of a chore since I half to demount the Mill Bed from
        its bookshelf base. Just to get a feel for how things were going to go I
        decided to check the Y backlash. To my surprise it measured in at .009".
        Something was a miss.I backed off the hold down screw on the backlash star
        wheel and worked the table, leadscrew, and backlash until it felt right. I
        measured again and still .009". I lock the backlash down tighter until the
        stepper motor was stalling on moves of .001. The play was still .009". then
        it came to me I grabbed the X table and pulled it towards me. There was
        movement, and a click. The click was coming from the endplay nut behind the
        outer leadscrew thrust bearing on the stepper motor housing. By trail and
        accidental success, I discovered that I could adjust out the end play by
        snugging up the end play nut against the thrust bearing. With the end play
        fixed I can now adjust the Y backlash down to about .005". AFAIK Sherline
        does not mention adjusting the lead screw end play anywhere in their
        manuals.
        >
        >
        > My questions to those wiser than I.
        > Can I do better than .005 backlash or is that about what I can expect in
        the real world?
        >
        > I know about the setscrew that holds the coupling nut that couples the
        lead screw to the saddle. What else should I check to reduce the backlash?
        >
        > N.T. My Y stage moans at about the mid point of its travel on the bed.
        > I have cleaned and lubed everything I can get at (Lead screw, ways, bed.
        Is this just another life with Sherline thing or can I make this noise go
        away?
        >
        > Thanks to all.
        > Dan
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
        >
        >
      • timgoldstein
        Dan, Not the only way to get the lash lower, but a great way to do it is upgrade to our precision leadscrew set and extended travel Z column. We use Kerk
        Message 3 of 5 , Apr 14, 2009
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          Dan,

          Not the only way to get the lash lower, but a great way to do it is upgrade to our precision leadscrew set and extended travel Z column. We use Kerk Motion precision leadscrews that are far more accurate than stock along with their NTBF anti-lash self compensating nuts. Heck, throw in our extended X and Y and people describe it as an entirely new and more capable machine.

          Pictures and video at http://www.a2zcnc.com/a2zcncmonstermill.htm

          While people may tell you they do better than .005" on the stock setup it is hard to achieve and almost impossible to keep due to the rapid wear of the little brass adjusters when run on CNC.

          Tim
          A2Z Corp
          A2Z CNC division
          1530 W Tufts Ave Unit B
          Englewood CO 80110
          720 833-9300

          www.A2ZCorp.us/store
        • dnldkempton
          I will concur with Tim s statements on the Kerk leadscrews, and the anti backlash nuts from A2Z. The single best upgrade to my mill since I started machining.
          Message 4 of 5 , Apr 14, 2009
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            I will concur with Tim's statements on the Kerk leadscrews, and the anti backlash nuts from A2Z.

            The single best upgrade to my mill since I started machining. The factory lead screws and adjustments are OK for manual machining, but cannot hold true for long CNC intervals.

            I cannot say how many times I began a project, just to have something un-adjust, slip, or collide due to the old setup. Now, it runs so smoothly, at nearly double the feed.. all while running the motors at lower RPM's (much more torque).

            My machine has been running all night, and is still going out in the shed. The performance just can't be matched, and the up side is that I've got so many upgrades to the Sherline, I only need a couple more parts to make another manual mill for a backup.
          • Chuck
            Another option on backlash: I was trying to mill a PC board for some .65 mm surface mount chips. Backlash was killing me. I measured it to be .004, .005, and
            Message 5 of 5 , Apr 14, 2009
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              Another option on backlash:

              I was trying to mill a PC board for some .65 mm surface mount chips.
              Backlash was killing me. I measured it to be .004, .005, and .006.
              After reading a lot of stuff, I decided that trying to adjust that out
              would just lead to further wear. So I tightened it up a bit, but not
              much. Then I added the BACKLASH= for each axis to the EMC2 config file
              (I am not sure if EMC1 has this). With these backlash compensation
              values set, I then measured the backlash again. then I tuned the
              backlash values again measured with the compensation. Using this, I was
              able to get .0005 repeatable values in direction changes because EMC2
              would "take up the slack". I know that this may not help on deeper cuts
              if the cut moves the board, but EMC will make up for it.

              Perhaps a combination of the precision lead screws along with emc2's
              backlash compensation would be the best plan. But if you do not want to
              upgrade the leadscrews right now (maybe in the future for me, at the
              moment I have more pressing upgrade requirements), the backlash
              compensation is a good choice and helps lot! -Chuck-

              >
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