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True Position in 3 axis???

1CMM4ME
Ok, I have read the post regarding this so called argument that my boss and I got into today. He told me that you cannot measure true position in 3 axis, as I told him he was wrong. I know it depends on the way the FCF calls it out, but I tried to explain to him that it is possible to measure TP in 3 axis.
I have seen the formulas, so I know it's possible. I just wish I could get one of you gurus to reply back explaining that it is possible and why. I see the picture but he does not. I do not like to get into pissing matches with upper management, but I have learned a h**ll of alot from you guys, and I know this is possible. So if one of you fine gentleman can back me up on this, I would very much appreciate it. Thank you very much.
Now I am going to get a cold beer.Smiley
  • As far as I know there is no such thing as spherical TP. There is however, such a thing as a spherical cut which can be controled by true position using more than 2 axis. That spherical cut must qualify as a feature of size, a spherical radius does not qualify as a feature of size though.
  • As far as I know there is no such thing as spherical TP. There is however, such a thing as a spherical cut which can be controled by true position using more than 2 axis. That spherical cut must qualify as a feature of size, a spherical radius does not qualify as a feature of size though.
    NOT to disagree, BUT, since B&S makes TP work in spherical mode when reporting 3 axis UNLESS you select PERP to CL, then there MUST be psherical TP, I mean, they wouldn't make THAT kind of a mistake, would they?
  • I'm not familiar with "spherical mode". What is that? I suppose the target zone for a spherical radius would be sherical but that is not to say that all TPs with 3 axis callouts would be a spherical target zone. I am curious if it is legal to TP a saw cut as long as it is a FOS. If you could I suppose that too would be a spherical target zone.
  • ok, so in what cases do you use xy and z? only when the callout to 3 datums?
  • I'm not familiar with "spherical mode". What is that? I suppose the target zone for a spherical radius would be sherical but that is not to say that all TPs with 3 axis callouts would be a spherical target zone. I am curious if it is legal to TP a saw cut as long as it is a FOS. If you could I suppose that too would be a spherical target zone.
    Well, if you are measuring a hole, WITH surface sample hits, and report XYZ axis for the hole, the TP results will be 3-D TP, unless you tall it to use PERP to CL for the TP dimension. I can 'see' where this would be needed. OK, take a sheet metal part, automotive, if you will, that has a hole in it. Also imagine a rod that needs to go through that hole, but that is not in any direct way attached to that part. So, you have a 'perfect' rod in space, then a sheet metal part (assembly) that has to allow this rod to pass, if the rod/hole or on funky angles to body axis (not 'square' to any body axis), then you would need to know the 3-D, or spherical TP of that hole to ensure that the rod would passs through it. Where-as if this rod is actually a bolt that has to pass through 2 parts, 2 parts that are assembled and this bolt ties them together, then the surface deviation does not matter, just the perp-to-cl does for BOTH holes to ensure that the bolt will go through them.
  • ok, so in what cases do you use xy and z? only when the callout to 3 datums?

    We have a part here with a spherical cut and in order to locate it you have to have more than 2 axis. I'm not sure I am folowing your question in regards to datums.
  • Well, if you are measuring a hole, WITH surface sample hits, and report XYZ axis for the hole, the TP results will be 3-D TP, unless you tall it to use PERP to CL for the TP dimension. I can 'see' where this would be needed. OK, take a sheet metal part, automotive, if you will, that has a hole in it. Also imagine a rod that needs to go through that hole, but that is not in any direct way attached to that part. So, you have a 'perfect' rod in space, then a sheet metal part (assembly) that has to allow this rod to pass, if the rod/hole or on funky angles to body axis (not 'square' to any body axis), then you would need to know the 3-D, or spherical TP of that hole to ensure that the rod would passs through it. Where-as if this rod is actually a bolt that has to pass through 2 parts, 2 parts that are assembled and this bolt ties them together, then the surface deviation does not matter, just the perp-to-cl does for BOTH holes to ensure that the bolt will go through them.

    Yes we have TP callouts here that locate a hole with basic dimensions to the intersection of that hole and a surface. However, the target zone is still cylindrical not spherical as the TP for the hole is controlling the axis not the intersection point of that hole and the surface. In other words the point you are talking about simply locates the target zone but is not the actual target zone if I am making sense here.
  • We have a part here with a spherical cut and in order to locate it you have to have more than 2 axis. I'm not sure I am folowing your question in regards to datums.
    It SHOULD be called out to 3 datums in a VAST majority of cases. IF you need to use 3-D or 2-D (perp-to-cl) will depend on the application, if you don't know, you need to ask. 99.95234% of the time in auto motive sheet-metal, it will be perp-to-cl (or 2-D TP).
  • As far as I know there is no such thing as spherical TP. There is however, such a thing as a spherical cut which can be controled by true position using more than 2 axis. That spherical cut must qualify as a feature of size, a spherical radius does not qualify as a feature of size though.

    How about a tooling ball controlled with three basic dims and Tp callout.
    Curious, how would you measure that?
  • How about a tooling ball controlled with three basic dims and Tp callout.
    Curious, how would you measure that?

    Measure and align to the datum reference frame and measure the tooling bal. TP it on 3 basic dims. A tooling ball is a FOS so I don't believe there is an issue with that scheme. Perhaps I am missing something in regards to the questions here.
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