Symmetry

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  • Symmetry

    Hello.

    I am trying to evaluate the symmetry of 2 holes to a cylinder (datum A). I have created a point at each hole with COLPTS and then created a midpoint with SYMPNT. I believe I now need 2 constructed planes or axes, offset equally from the cylinder origin.

    How do I create offset theoretical planes or axes?

    Also on the symmetry input form, there are inputs for "Axis" and "Projection plane". Do I need to specify something in these as my datum is a cylinder?

    Thanks.

  • #2
    Quindos will allow you to programmatically create an Element and then populate a result. You can do this and enter the nominal values as the result thereby creating a theoretical plane. If you double click on an existing Element in the object browser pane, you will see "Element Data" including the "Actual Element" on the "Element" tab. If you probe a feature, for example, then doing a "Calculate" will populate this info with a result computed from the actual measured data (APT's=actual points). You can also use PUTVALS to populate this yourself. Simply use PUTVALS and populate the result with the nominal values to create a theoretical Element:

    CREATOBJ (NAM=PLANE1, TYP=ELE)
    CREATOBJ (NAM=PLANE2, TYP=ELE)

    PUTVALS (OBJ=PLANE1, TYP=ELE, RDS=(^X,^Y,^Z,^U,^V,^W), VAL=(5,0,0,1,0,0), CDS=$T, STR=PLA)
    PUTVALS (OBJ=PLANE2, TYP=ELE, RDS=(^X,^Y,^Z,^U,^V,^W), VAL=(-5,0,0,-1,0,0), CDS=$T, STR=PLA)

    In this example, 2 elements are created with one being in +X direction at X=5 and the other in the -X direction at X=-5. If necessary, you could transform these Elements or create in a different coordinate system. I did not specify a coordinate system so the result is automatically populated with REFR$CSY in the Coordinate System field (field descriptor = "$H($I)").

    As a note, Field Descriptors allow one to programmatically get or put values to any number of fields. If you mouse over the Coordinate System field in the Element Data, for example, a popup/mouse tip will display the field descriptor. If you want to put or get values in a points buffer (e.g., APT actual points or add/read a row of info from an Evaluation), each column of info has a field descriptor and the syntax of the GETVALS/PUTVALS changes slightly to also identify the row to/from which you would like to put/get info. The method to get the field descriptor is also different than that described above.




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    • #3
      You can also use the GEN** commands to generate an element with NPT, then use the EXCHNG command to copy NPT to APT and then BLD** to calculate.

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