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Poor man's DRO revisited!

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  • Poor man's DRO revisited!

    Way back in 2009 I wrote about my Poor Man's DRO on the Mad Modder site...



    http://madmodder.net/index.php?topic=781.0

    It worked 'quite well', but not perfect. Less than optimum accuracy due to the use of flexible cables and eventually almost total failure due to the plastic covering of the steel fishing lines getting rubbed off and jamming in the cable sleeves.

    There had to be a better way....


    DRO in cross slide by aardvark_akubra, on Flickr


    ... and they dont come much easier than this!

    I had a cheap DRO scale with a remote display, I drilled a hole in the end of the scale and tapped a 3mm thread in the side of the cross slide feed nut. There is just enough room for the scale under there. A simple bracket was made to hold the sensor head at the rear of the cross slide and it was ready for testing.

    Of course using a scale like this reads in radius rather than diameter and it remains to be seen if the scale is adequately protected under there, I think it will be especially as I do not use flood coolant and the oil on the dovetails and feed screw is not exactly being thrown around.

    It needs something fixed to the rear of the cross slide to protect the sensor and the exposed end of the scale but I will give the scale a bit of a trial before drilling holes in the cross slide.

  • #2
    good idea - gonna try it next week when i buy my dro. Might not work on the 10x20 lathes

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    • #3
      Another older DRO idea, input through an old DOS PC Parallel port.
      http://www.lindsayengraving.com/othe...rests/dro.html
      I have found scales and encoders work as long as 5v quadrature output, also the buffer transistors are often not needed.
      Might be neater now with LCD screens.
      Max.

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      • #4
        Would love to get a DRO on both the mill and lathe, and while I am good with electronics and software, I haven't a clue about the actual pick up scales or how they even work. Going to see if I can research it a bit, as making a processor based DRO control unit would not be that hard for me, but without a clue about the scales I have only looked at pre made DRO units (which are not that cheap, even the cheap ones lol).

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        • #5
          Originally posted by Stern View Post
          I haven't a clue about the actual pick up scales or how they even work.
          One of the common methods is the read head is decoded into two TTL dual or RS420 differential square wave pulses, 90° apart (quadrature) one is used for pulse count and the other for direction.
          Some manufactures use the basic sine wave before squaring up and use the arc tangent function to obtain an even higher resolution.
          The four edges of the TTL version is often used to increase the resolution x4.
          If you Google quadrature detection you should find more.
          Max.

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          • #6
            Originally posted by Elninio View Post
            good idea - gonna try it next week when i buy my dro. Might not work on the 10x20 lathes
            There is very little room under the cross slide, but there is enough on this 12x36 CQ6230-A.

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            • #7
              Look at the linear magnetic encoders from Austria Microsystems. High accuracy and very high resolution. If I ever DIY'ed a DRO that's where I'd start.

              Originally posted by Stern View Post
              Would love to get a DRO on both the mill and lathe, and while I am good with electronics and software, I haven't a clue about the actual pick up scales or how they even work. Going to see if I can research it a bit, as making a processor based DRO control unit would not be that hard for me, but without a clue about the scales I have only looked at pre made DRO units (which are not that cheap, even the cheap ones lol).

              Comment


              • #8
                Pretty clever Artful Bodger, never thought about going under the cross slide like that.
                ~ What was once an Opinion, became a Fact, to be later proven Wrong ~
                http://site.thisisjusthowidoit.com
                https://www.youtube.com/user/thisisjusthowidoit

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                • #9
                  Originally posted by iMisspell View Post
                  Pretty clever Artful Bodger, never thought about going under the cross slide like that.
                  I am not really the clever, I made a mistake and put the scale end-for-end through the sensor head which lead to very strange operation of the display!

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