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Using a DRO - working to zero - absolute and incremental

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  • Using a DRO - working to zero - absolute and incremental

    A while back I built a shumatech DRO550 for my lathe and mill. They seem to work OK. I really use them for preset and diameter. I dont use any of the other features.

    Although I completely understand the concept of absolute and incremental, the way this DRO implements them baffles me - especially when trying to do an ABS preset.

    So I figure I would read the manual (what an idea!) and search the net. The information is scarce. But when explaining how the DRO works, it says is is designed around the concept of "working to zero". I understand this in principle, But dont really understand how I would set up a job and use the DRO to "work to zero"...or why.

    So here is what I think. Lets say I have a job on the lathe. OD has a couple of shoulders. Single diameter blind bore. So I set some point to be my absolute zero. Perhaps the axis of the part closest to the chuck? Then when I am ready to machine to the first shoulder I move the X to the desired depth in ABS mode, flip to INCR and zero. The move the carriage out, move the Z to the desired ABS location, flip to INCR and zero. RInse and repeat.

    Is this the way "work to zero" should work - why is this better than any other way?

    thanks for the help.

  • #2
    There are several ways to go about this and some of it depends on the features that your DRO system has.

    When I start turning something I'll take a cut, measure the dia. and I can either set my DRO to "0" or the actual dia. of the part. If I need two settings for some reason I can switch between incremental and absolute. Same goes for the carriage positioning. I don't think that there is really any right way or wrong way to go about this. You can do this any way you want as long as "you" know what your doing. Most of the time you have to keep mental notes of what your doing.
    Keep in mind that every time you change tooling all those setting are lost.



    • #3
      doesnt that have a memory for tools?


      • #4
        My DRO 200T has 10 tool offsets. Try and keep track of which one is which when all you have to go by is a designation number.
        By the time you set all this up in most cases you could have the job done. again, even if you change the insert in the tool holder to a different chip breaker edge that setting could be lost.
        If you move your tool post, the setting are lost. I move my tool post quite often depending on what I'm doing.

        Here is the manual for my DRO. Page 13 explains the tool offset set up. The set up is pretty simple, keeping track of all this not so.



        • #5
          [QUOTE=JW1942;n1864053...........the concept of "working to zero". I understand this in principle, But dont really understand how I would set up a job and use the DRO to "work to zero"...or why.
          .......................................Is this the way "work to zero" should work - why is this better than any other way? ....[/QUOTE]

          Are you over thinking the instruction ?
          Working to zero can also mean --Positive numbers !
          Say you are facing a 4 inch rod end. If you set your tool on the OD and then zero, all face moves are negative (in reading).
          If you center the tool on the axis and set zero, all indications are positive, so when the tool moves to the OD it will be +4.000

          Green Bay, WI


          • #6
            No I am not overthinking it - this is from the instructions.

            I typically do it the way you guys described. However the DRO wants to be used a certain way that ,might be more efficient, just trying to figure out how. Always good to learn something new!


            • #7
              From your manual

              The main operation to master on the DRO is setting zeros. OpenDRO uses a "work to zero" philosophy where you set a zero and then machine towards that zero. There are two kinds of zeros - absolute and incremental. Absolute zeros are usually set once when starting on a work piece and correspond to the origin for the work. Incremental zeros are set for each movement you make. For example, assume you are at absolute position -1 and you set an incremental zero at absolute position -3. The display will show 2 in incremental mode indicating that you are 2 units to the positive side of the incremental zero. If you switch back to absolute mode, you are still at position -1. If you then set an incremental zero at an incremental preset of 5, then the incremental zero moves 5 to the right to absolute position 2 and the display shows -3 in incremental mode and still -1 in absolute mode. The picture below shows this example visually with the incremental zeros depicted as half black and half white arrows and the current position as a solid black arrow.

              The sections below will detail how to set each type of zero and how to enter and modify numeric data. "

              I could be mistaken , but believe most all DRO's program the Incremental move position "0" from the current position .
              This DRO has 2 functions -you can set the Incremental position "0" without being there ( one function) and still program the expected incremental position for that move ( second function)


              Green Bay, WI