Cylinder Alignment Problem

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  • Cylinder Alignment Problem

    We have a job on now, it's a housing with an internal cylinder as the only datum on the drawing. I need to check the perpendicularity of all the machined faces to this cylinder, also all the other bores for concentricity.

    I measured the cylinder using 8 points, I measured two rows of four with the second row twisted 45 degrees for an even spread. I levelled it in Z, then set it as the origin in X and Y. I measured a plane further up on the part and set this as the origin in Z.

    When I check for concentricity, I get completely random dimensions, ranging from 0.35 to 1.45! Also the perpendiculrity od the planes to the cylinder is way out, I have checked it on a height gauge.

    Am i doing something wrong here? Is there a better way of measuring the cylinder and setting it as the datum? We took a part over to the customer and they checked it on their zeiss machine, and embarrassingly for me, it came out consistently correct...
    sigpicIt's a crazy idea Captain, but it might just work!

  • #2
    Try three levels (3 circles) for the cylinder? Make sure you don't get any shank hits (shanked out?) when measuring.
    PC-DMIS CAD++ 2o19 R1 SP11

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    • #3
      1/ while you were there , did they set it up/check it in the same way as you did ?
      2/you ought to post a drawing of what your on about, if possible.
      3/ was the same version of software used ?
      sigpicRichie the Villian!!

      V4.2 MR1 CAD++/MISTRAL 10-07-07 DCC/XP

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      • #4
        3 rows, and throw in some sample hits if possible.
        Ver.2009
        B&S Global

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        • #5
          Originally posted by RCW52 View Post
          3/ was the same version of software used ?
          Unless the customer were running PC-DMIS on their Zeiss, it wouldn't matter?
          PC-DMIS CAD++ 2o19 R1 SP11

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          • #6
            Align the z axis around the x axis then align the z axis around the y axis then origin the cylinder for x and y

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            • #7
              Their Zeiss has a scanning probe, so I'mnot too bothered how they checked it.

              I'll try three rows of hits for the cylinder, then try and align it as JohnR advises, see how we get on...
              sigpicIt's a crazy idea Captain, but it might just work!

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              • #8
                Originally posted by vpt.se View Post
                Unless the customer were running PC-DMIS on their Zeiss, it wouldn't matter?
                Oh..................really ...............thanks for that.
                sigpicRichie the Villian!!

                V4.2 MR1 CAD++/MISTRAL 10-07-07 DCC/XP

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                • #9
                  Originally posted by vpt.se View Post
                  Unless the customer were running PC-DMIS on their Zeiss, it wouldn't matter?
                  Differences in software will not give you much of a difference in results providing the alignment, measurement techniques and algorithms are the same.
                  Xcel & MicroVal Pfx & Global 37mr4 thru 2012mr1sp3
                  Contura Calypso 5.4

                  Lord, keep Your arm around my shoulder and Your hand over my mouth. Amen.

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                  • #10
                    along with 3 rows of hits, you should move up to 5 or 7 or 9 hit per row, a 4 hit circle is one of the worst to use. The software like a odd number of hits in its calculations
                    sigpic

                    B&S Global 544
                    Using 3.7mr3


                    Peace
                    Greg


                    Nothin left ta dew but :) :) :) !

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                    • #11
                      Originally posted by John R View Post
                      Align the z axis around the x axis then align the z axis around the y axis then origin the cylinder for x and y


                      I don't understand this. Too early I need more coffe
                      sigpicIt's corona time!
                      737 Xcel Cad++ v2009MR1....SE HABLA ESPAƑOL

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                      • #12
                        An 8-hit cylinder in an invitation to disaster. A 6-hit would be better. If you are a good and careful operator, there will be an "unlimited" number of possible cylinders that can be made from an 8-hit, 2-level cylinder with the second level '45 degrees off', especially if the distance between the levels is close to or the same as the diameter of the cylinder. 3 levels and use a different number of hits per adjacent levels. I will generally do 5-3-4. Never had a bad cylinder from that yet.
                        sigpic
                        Originally posted by AndersI
                        I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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                        • #13
                          Concentricity is going to give you problems.
                          Are you sure that is the design intent and not coaxiality?
                          Lately, it occurs to me
                          What a long, strange trip it's been.

                          2017 R1 (Offline programming)

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