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Re: [mach1mach2cnc] Re: does that allow for any conclusions?

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  • Bill Kichman
    You said I am not sure how close to zero one can get mechanically You can get ZERO backlash with ballscrews. Not a question. I set up my new installation
    Message 1 of 3 , Sep 30, 2003
      You said "> I am not sure how close to zero one can get mechanically"

      You can get ZERO backlash with ballscrews. Not a question. I set up my new
      installation this week, and checked it using a dial indicator just as others
      had described. On my x and y axes, with preloaded ballscrews, I have
      absolutely ZERO backlash. Ran it many many times, amazed to see that
      pointer return to absolute zero each time it traveled back and forth.
      My mill Z axis (existing acme screw with heavy knee) has only 4 thou
      backlash, as I was able to press the bevel gear closer for less slop. I am
      very happy with the setup. The only thing I want to change is to revise the
      fixed preload to a belleville spring (washer) preload to account for future
      wear on both screws. Then it wil be darn near perfect.

      It sounds like you have a single ballnut installation by the amount of
      backlash you are seeing. You might consider reviewing the previous messages
      about a month to 6 weeks back related to preloaded screws using 2 identical,
      inexpensive ballnuts threaded against one another in a threaded body
      attached to the table.

      happy camper here...

      R. William Kichman, P.E.
      Kichman Engineering Associates
      103 Old Furnace Road
      Cornwall, PA 17016-0643
      tel/fax 717/270-0714
      ----- Original Message -----
      From: "jocowa2111" <jwagner@...>
      To: <mach1mach2cnc@yahoogroups.com>
      Sent: Tuesday, September 30, 2003 12:07 PM
      Subject: [mach1mach2cnc] Re: does that allow for any conclusions?

      > Bob,
      > I took measurements last night.
      > On each the y and x axis I I moved "in-line" and in reverse, whereby
      > in-line means I traveled in minus direction, then took measurement
      > trvelling further in minus direction. Reverse means, I traveled in
      > plus direction, the took measurement travelling in minus direction.
      > On 4 measurements of each I noted the differnce between the computer
      > travel distance and my caliper reading. These were the averages:
      > X Inline travel .0012 Reverse travel .0068
      > Y Inline travel .0015 Reverse travel .0036
      > So it looks to me that I have backlash of about .0056 on X and .0021
      > on Y
      > I am not sure how close to zero one can get mechanically. My
      > machine has 5/8" dia ball screws with 5tpi. The Y axis has double
      > ball nuts, the x axis only a single. My sense is that for the X
      > axis at least the most play is right in the ball nut, not in the
      > shaft bearings. Any idea whether one can adjust thsoe ball nuts for
      > less play?
      > JW
      > --- In mach1mach2cnc@yahoogroups.com, "Robert Hansberger"
      > <rhansberger@c...> wrote:
      > > Perhaps, But until you take actual measurements you don't really
      > know.
      > > If it does have some B/L it can be entered into the software.
      > >
      > > I don't mean to be a hard a--, but I do believe in following the
      > > basic procedure step by step. Never any question that way.
      > >
      > > Be well
      > > Bob
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