Projecting a point from SPC Bushing

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  • Projecting a point from SPC Bushing

    If I were needing to know if a SPC bushing was in the right place (50mm from parts), How would I go about it?

    I have tried several things but I am not sure it is giving me the right answer. I have tried measuring the bushing as a cylinder and making a plane on the part an projecting it to the part but it doesn't seem right.

    What is the proper way without gage data? I don't know exactly how to word things. I have noticed that there are some sharp fellows on here.


    We do injection molding in my plant and we have a hundred or so gages that we certify. I want to make sure I am doing it the right way. I have had allot of trouble getting the programs for our gage sources so I have to do them from scratch.


    Like the preacher says "Bare with me a little while" because my responsibilities change weekly and I have to learn allot fast.


    I just hope I can understand what you are telling me. I am a country boy from Alabama you know. Thanks and Have a wonderful Day!
    REVERSE, REVERSE, REVERSE

  • #2
    Reverse your thinking

    If the SPC points are called out on cad or the print, I'll pick the point out on cad in my program, change the feature to a circle, and set the material thickness to the required distance (the height of the zero block). If the points are not called out any where, I'll blue up an indicator and find out exactly where the points are being taken. Then I'll pick them out cad in my program, , change the feature to a circle, and set the material thickness to the required distance (the height of the zero block).

    Make sure you're taking three prehits to measure the surface the indicator sits on.

    For the dimension I'll output 2D True Position (error perpendicular to centerline) and output the surface error.
    28 Years, 8 Months, 0 weeks and 1 Days until retirement...

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    • #3
      What I do is measure a cylinder in the bushing. I will then create but DO NOT measure, 3 points on the cad data 'around' the shaft of the cylinder. I construct a plane. I intersect the cylinder and the plane. I use those XYZ values to create a vector point (DO NOT MESAURE) by typing in the values, then finding the cad nominals. I will then measure a plane on the face of the bushing and do a 3-D distance from the measured plane to the point.
      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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      • #4
        Baylor,

        Here is the way I do it. If you have the nominal, open the auto features and choose SURFACE POINT. Key in the nominal location and hit find. Keep doing this until the numbers that come up match your nominals. Uncheck MEASURE and create the point. Create a generic plane using the nominals and IJK vectors of the point you just created. Now delete that point you created or when you run the program it will try to measure it. Now measure a plane at the bushing head. Now measure your bushing cylinder. Intersect the bushing head plane with the cylinder (top_cir) and now intersect the generic plane with the cylinder (srf_cir). Create an alignment leveled to the cylinder and origin X,Y, and Z at the srf_cir. Now dimension the top_cir in Z only. It should be 50 MM. Recall your primary alignment and do it again and again for all the rest of your SPCs.

        Bill

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        • #5
          With out nominals, I pick up the bushing head as a plane. Then I measure the Cylinder. I setup an alignment to the cylinder, Level to the cylinder and origin X,Y, and Z to the Cylinder. Open AUTO FEATURES Surface Point. Set X and Y to zero, click the little box next to z and hit find. Create this point but don't measure it. Recall your primary alignment and dimension the point you created. This is the CAD nominal location that the Cylinder IS going to hit. Now you have your nominal location and you can delete all the junk and proceed as above.

          Bill

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          • #6
            To keep it simple I'll setup an example. Assume the table of the CMM was the correct plane to level to and a pin gage stuck in one of the clamping holes in the table was your bushing. We want to know where the bushing is at gage point, say 50mm from the top of our gage pin. Probe the table and level to it. Probe a point on top of the pin and origin your Z axis on it, then translate 50mm in the Z axis. Construct a plane at alignment, you'll get one parallel to the table and 50mm from the top of the pin. Probe the pin as a cylinder. Set your X and Y axes to origin at the correct feature, machine origin would work for this example. Now construct a point or a circle by piercing the constructed plane with the cylinder. Make sense? Or did I not understand the question?

            TK
            sigpicHave a homebrew

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            • #7
              Thank you guys. Most of our SPC ports were just put in areas and not to print or any kind of call out. We do have a few that were actually called out I will have to find what they were. I will have to try your ideas and see if I can make them work. I have spent the better part of three years learning as I go and trying to give the best data possible. I wish I would have found you guys earlier. Thanks again.
              REVERSE, REVERSE, REVERSE

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              • #8
                Old thread, but I don't care...this has been an issue of mine for, oh, let's see...about 6 or 7 years! LOL

                I think plugging in the target for the SPC bushing, changing the material thickness to the offset of the master (usually 31mm in my case) and measuring as a circle is the way to go!

                That freakin' material thickness option...always wondered what that "T" was in the auto feature window...now I know! ha HA! Goes to show that even after years of experience, once can still learn...thanks a lot fellas.
                sigpic

                "Some people spend an entire lifetime wondering if they made a difference in the world.
                But, the Marines don't have that problem."

                Ronald Reagan

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