Entire Program is Vector Points

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Entire Program is Vector Points

    I am looking at a program someone else wrote, and it is done entirely with vector points. Cylinders, planes, circles, all constructed from vector points. In his constructions, he is using BF, not BFRE. Please give me your thoughts on this. Is this a good way to program? What is better in this case, BF or BFRE?
    sigpic
    Global Advantage 12-22-10
    TESASTAR M SP25 4.3mr2

  • #2
    Sounds like a product of the beginner training class to me. If it's not a point or a circle you don't learn it. It's doable but clunky way to program. The BF not BFRE could be an issue I would think depending on how the previous person wrote the program. If they used CAD and the vectors for all of the points are normal to the surfaces they hit your error will be minimized, if they SWAG'd it I would think that it's questionable.
    Saving the world, one bad part at a time.

    Comment


    • #3
      If correct nominals and vectors used on all the points I don't see an issue with constructing cylinders, planes, circles...etc
      sigpicIt's corona time!
      737 Xcel Cad++ v2009MR1....SE HABLA ESPAÑOL

      Comment


      • #4
        The worse the part is, the worse the error will be if they don't use re-comp.
        sigpic
        Originally posted by AndersI
        I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

        Comment


        • #5
          Yeah, he did not use a cad model, that's why I'm questioning the re-comp. Thanks guys.
          sigpic
          Global Advantage 12-22-10
          TESASTAR M SP25 4.3mr2

          Comment


          • #6
            It can be usefull to construct BF circle from vector points on a cone, for example, if vectors are perp to the surface. In this case, BFRE will give a bad result for diameter.

            Comment


            • #7
              Originally posted by JEFMAN View Post
              It can be usefull to construct BF circle from vector points on a cone, for example, if vectors are perp to the surface. In this case, BFRE will give a bad result for diameter.
              Sorry Jeff, but I have to disagree with you on this one, vector points on a cone are 3D and when you’re constructing a circle the software sees it as 2D vector points if you know what I mean, you may get away with it if the cone total angle is very small and also the measured points must be on the same elevation of the cone which is hard to accomplish due to machine drift. Besides that who would want to use measured points from a cone to construct a circle, I don’t see any practical application for that.
              Last edited by lambo; 07-21-2010, 12:42 PM.

              Comment


              • #8
                Using a cad model will make no difference.. the actual part is not where the cad model is anyway. Shouldnt you always use BFRE?

                This would not be my preferred method to inspect a part, but my only real concern(beyond the BF or BFRE) is where the datums done properly before all the single hits were taken.
                Links to my utilities for PCDMIS

                Comment


                • #9
                  Originally posted by cmmguy View Post
                  Using a cad model will make no difference.. the actual part is not where the cad model is anyway. Shouldnt you always use BFRE?

                  This would not be my preferred method to inspect a part, but my only real concern(beyond the BF or BFRE) is where the datums done properly before all the single hits were taken.
                  wtf do you mean by that... are you suggesting the parts and the models aren't the same? This is my argument against iterative alignments unless necessary.

                  Comment


                  • #10
                    Originally posted by Ironhoe View Post
                    wtf do you mean by that... are you suggesting the parts and the models aren't the same? This is my argument against iterative alignments unless necessary.
                    Im sorry, I forgot to add this caveat for you... except in cases where your parts are made to perfect nominal in size and location.
                    Links to my utilities for PCDMIS

                    Comment


                    • #11
                      Originally posted by cmmguy View Post
                      Using a cad model will make no difference.. the actual part is not where the cad model is anyway. Shouldnt you always use BFRE?

                      This would not be my preferred method to inspect a part, but my only real concern(beyond the BF or BFRE) is where the datums done properly before all the single hits were taken.
                      I would always use the recomp option.

                      TK
                      sigpicHave a homebrew

                      Comment


                      • #12
                        Originally posted by lambo View Post
                        Sorry Jeff, but I have to disagree with you on this one, vector points on a cone are 3D and when you’re constructing a circle the software sees it as 2D vector points if you know what I mean, you may get away with it if the cone total angle is very small and also the measured points must be on the same elevation of the cone which is hard to accomplish due to machine drift. Besides that who would want to use measured points from a cone to construct a circle, I don’t see any practical application for that.
                        Hi Lambo ! Itook a cone for example to explain difference between a circle constructed from compensated points (vector point + BF) and a circle constructed from ball center (vector point + BFRE).There's a big difference on diameter value and height of center. I agree with you, the machine drift (I learn a new word today !) doesn't help for an accurate measurement in this case. I had to measure a diameter on a sphere, not a the center level, the problem is the same. You can estimate accuracy by dimensioning the flatness of circle hits...

                        Comment


                        • #13
                          Originally posted by cmmguy View Post
                          Using a cad model will make no difference.. the actual part is not where the cad model is anyway. Shouldnt you always use BFRE?

                          This would not be my preferred method to inspect a part, but my only real concern(beyond the BF or BFRE) is where the datums done properly before all the single hits were taken.

                          If they had CAD available when they programmed it and we assume that they used the CAD to generate the vectors then the vectors would be closer than if they programmed it by hand or guessed at what the vectors were supposed to be. The error would be minimized but not eliminated so the CAD would make a difference but not enough to get it perfect, no.
                          Saving the world, one bad part at a time.

                          Comment


                          • #14
                            Originally posted by EHines View Post
                            If they had CAD available when they programmed it and we assume that they used the CAD to generate the vectors then the vectors would be closer than if they programmed it by hand or guessed at what the vectors were supposed to be. The error would be minimized but not eliminated so the CAD would make a difference but not enough to get it perfect, no.
                            If you are using BFRE(as you probably should), why would the vector make a difference? Is it not going to recomp the features anyway? (btw, I am talking prismatic features not shapes)
                            Links to my utilities for PCDMIS

                            Comment


                            • #15
                              Originally posted by JEFMAN View Post
                              Hi Lambo ! Itook a cone for example to explain difference between a circle constructed from compensated points (vector point + BF) and a circle constructed from ball center (vector point + BFRE).There's a big difference on diameter value and height of center. I agree with you, the machine drift (I learn a new word today !) doesn't help for an accurate measurement in this case. I had to measure a diameter on a sphere, not a the center level, the problem is the same. You can estimate accuracy by dimensioning the flatness of circle hits...
                              Bonjour Jefman.

                              OK- I see what you're saying...
                              Why didn’t you construct a circle with plane/sphere instead? Were you checking the runout of a gage diameter or something?

                              Comment

                              Related Topics

                              Collapse

                              Working...
                              X