Trigger force

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  • Trigger force

    I am measuring a flexible part that I can't support. I'd like to reduce the trigger force to get accurate result and to make sure the part doesn't move. What force should I reduce? I see there are several different force such as max, low etc...
    Thank you very much.
    Nguyen

  • #2
    What type of touch trigger probe are you using?

    Comment


    • #3
      We have TP200 running on PC-DMIS 3.5

      Comment


      • #4
        If you have a TP20 probe, you will want to use the low force module if possible.

        Other things that can help:

        Don't take hits where the vector is in line with the probe. A hit with a vector of 0,0,1 and probe angle A0B0 is an example of this. The probes typically have a higher trigger force in this direction than in the side to side direction.

        Use longer probe builds. While this can affect accuracy, lengthing the probe essentially gives the probe more leverage to trigger the probe with. Now, I'm not talking put all your extensions together and use a probe 200mm long. What I am suggesting is instead of using a 2X10mm probe, use a 2X20 or a 2X30. You will have to evaluate how much you think this may affect your results and whether it is acceptable.

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        • #5
          I would say if its flexible & cannot be supported then your screwed...
          sigpic.....Its called golf because all the other 4 letter words were taken

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          • #6
            Originally posted by Goodluck View Post
            If you have a TP20 probe, you will want to use the low force module if possible.

            Other things that can help:

            Don't take hits where the vector is in line with the probe. A hit with a vector of 0,0,1 and probe angle A0B0 is an example of this. The probes typically have a higher trigger force in this direction than in the side to side direction.

            Use longer probe builds. While this can affect accuracy, lengthing the probe essentially gives the probe more leverage to trigger the probe with. Now, I'm not talking put all your extensions together and use a probe 200mm long. What I am suggesting is instead of using a 2X10mm probe, use a 2X20 or a 2X30. You will have to evaluate how much you think this may affect your results and whether it is acceptable.
            Thank you for your help. By the way is it the same for TP200? And can you explain more about "low force module"?

            Comment


            • #7
              Originally posted by Nguyen View Post
              Thank you for your help. By the way is it the same for TP200? And can you explain more about "low force module"?
              The TP200 is a different probe from the TP20. The TP20 uses an electrical contact system to trigger the probe. The TP200 uses strain gauges. Both of them have interchangeable modules to which the tips are attached. These modules come in several different force ranges for use with different probe builds. It looks like the TP200 can use three different force modules (standard force, low force, and extended overtravel).

              Have a look at the renishaw website for more info on the TP200 modules. They are near the bottom of the page.

              http://www.renishaw.com/en/6671.aspx

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              • #8
                Nguyen,

                The force values you are referencing are for analog scanning probes, such as SP25 and SP600 systems. They don't affect TP20 or TP200 devices, so changing these settings won't affect the touch trigger probe. Your best bet is to obtain a low force module as others have suggested. I'm not sure what nature of flexible part you are attempting to probe. If it will work, you can considering using some reprorubber putty (www.flexbar.com) to make a custom 'fixture' to better support the subject

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                • #9
                  One more tip:

                  I've been asked before to measure rubber gaskets. I've explained to the engineers that any measurements will not be repeatable as it will depend on how the part 'sits' on any given day. I was able to use double face tape and just drop the gasket onto it so it is as natural as possible. The double face tape stuck it well enough and made it stiff enough that I could probe it. In the end, very few features were within tolerance and they decided to put a note on that said "Use as is". Why did I measure it then!

                  Along the same lines... I've sandwiched gaskets in between two pieces of plexiglass to keep them stiff while standing up on the optical comparator.

                  Comment


                  • #10
                    Originally posted by Goodluck View Post
                    One more tip:

                    I've been asked before to measure rubber gaskets. .
                    You got to be kidding!!

                    Don't do it, tell them CMM has limitations.
                    sigpicIt's corona time!
                    737 Xcel Cad++ v2009MR1....SE HABLA ESPAƑOL

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                    • #11
                      Originally posted by Roberto View Post
                      You got to be kidding!!

                      Don't do it, tell them CMM has limitations.
                      They don't care. They just want a report showing that we tried and then they can put on it "Use as is" or some such nonsense. I've told them the only way to accurately measure them would be to measure the die that cuts them. Even then, you won't get a true measurement of the final piece.

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                      • #12
                        Thank you all for your help.

                        Comment


                        • #13
                          Originally posted by Goodluck View Post
                          One more tip:

                          I've been asked before to measure rubber gaskets. I've explained to the engineers that any measurements will not be repeatable as it will depend on how the part 'sits' on any given day. I was able to use double face tape and just drop the gasket onto it so it is as natural as possible. The double face tape stuck it well enough and made it stiff enough that I could probe it. In the end, very few features were within tolerance and they decided to put a note on that said "Use as is". Why did I measure it then!

                          Along the same lines... I've sandwiched gaskets in between two pieces of plexiglass to keep them stiff while standing up on the optical comparator.
                          Originally posted by Roberto View Post
                          You got to be kidding!!

                          Don't do it, tell them CMM has limitations.
                          Heck, that's NOTHING! No kidding, we once had a guy come in here wanted the diameter of a ROPE checked. Yeah, that's what I said, the diameter of a rope! Something he bought off EBAY, wasn't 'as advertised' and he wanted a 'certified' report showing that it was not what was advertised.
                          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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                          • #14
                            There is a special probe you can buy that will check extremely flexible parts it works on a harmonic frequency rather than pressure.
                            http://www.cmmtouchprobe.com/
                            I was thinking of getting one of these for the very thin stuff they sometimes ask me to check.
                            Tolerance challenged ... Living in the world of unseen lines.

                            This software isn't buggy its an infestation

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                            • #15
                              Originally posted by Matthew D. Hoedeman View Post
                              Heck, that's NOTHING! No kidding, we once had a guy come in here wanted the diameter of a ROPE checked. Yeah, that's what I said, the diameter of a rope! Something he bought off EBAY, wasn't 'as advertised' and he wanted a 'certified' report showing that it was not what was advertised.
                              Who buys rope on e-bay!?

                              Comment

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