Transforming the trihedron

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  • Transforming the trihedron

    Hello, I am still very new to programming on PC-DMIS and programming in general. I have only been doing it for about 5 months now. Almost every new part I have programmed since I started has had a circle of some kind. So, my mentor taught me how to use read points to start a program in DCC. I have just received a new part and there is no circle. My mentor my not have been the best teacher, because he never taught me what to do if this situation came up. So... I have transformed the trihedron on the part to where I want it, but now i don't know how to align the trihedron to my part, or vise versa, whichever it is.

    How do I find out how much I need to rotate the trihedron on X, Y, or Z?

    I apologize that my terminology isn't great yet.

  • #2
    I use read point only when I program. I find that the best start point if you do not have any circular features to begin with is to use a corner of the part. When you say you transformed the trihedron, not sure what exactly you mean by this. My approach is to rotate the cad model to how it will sit on the cmm first. If the model is a standard import where only the x,y,z coordinates need adjusting it is quite simple. Looking at your trihedron after having rotated the model to how it will sit for measurement,simply note where the vectors are facing. I usually find the z upside down and the x and y going in the wrong directions. I simply rotate the x by 90 degrees and the z by 90 or maybe 180 if needed. When all on the trihedron is facing the correct vector directions, i.e. z arrow facing up, y to the back, and x facing to the right, simply go into program mode and take a hit on the surface for z, one on each corner side for the x and y. Then look at your translate box and enter the exact opposite value of what you see in the edit window for each coordinate. For example if the z surface hit is .03. ,1, 4.5 then you would translate the z to -4.5. Look at the hit on the x surface and likewise enter the opposite sign in the box. Same for y. Once done your trihedron should jump to your model just where you want it to be. Delete the hits you took since they are of no use anymore and save the program. Close it and open it again and insert your read point and it will be right where you need it to be. If you have angles involved that need rotation, the best approach is to create a plane or line and analyze its angle to any normal axis. Rotate that amount of degrees. Hope this helps.

    I should add that when you open the transform dialogue menu you have both translation and rotation options. I find it best to do all the rotations first so that all the axes line up to how you would see them when sitting in front of the cmm. Follow this with your translation values. Makes life much easier than doing it the other way and dealing with odd translation values.
    Last edited by Jim Poehler; 01-25-2020, 07:47 AM. Reason: Added information.


    • ThePudds
      ThePudds commented
      Editing a comment
      Thanks a whole lot Jim! Hopefully I won't need help with this anymore. What I meant by "transforming the trihedron", when you go into the operations tab, under graphic display, you see the transform tab. "you know this of course". I just assumed it was called transforming the trihedron because that seems like what you are doing. It seems like you are moving the trihedron around. So, now i'm assuming you are actually moving the part around the trihedron rather than vise versa?

      P.S. Like i said, i apologize about my terminology. It is still not the greatest.

    • Jim Poehler
      Jim Poehler commented
      Editing a comment
      No problem. Actually you can look at it either way. If you move the part around you will notice that the trihedron moves as well. If you move the trihedron itself, then the part moves. The key is to get the part looking the orientation you want it to sit with the trihedron also sitting the same way. Then your all set to start programming.

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