[Wi...] Posted April 15, 2019 Share Posted April 15, 2019 I wrote a program to check true position of 4 diameters with Calypso and got them out of tolerance.... I then wrote a PC Dmis program practically just like the Zeiss prog and got good results.....got me scratching my head I seen a you tube video the other day where the guy in the video said the form dat(in the measurement settings) should be set different from the way my cmm is setup.....i just need to make sure i have it setup right....please if someone could look at the attached pic and let me know i would greatly appreciate it. ThanksFORM1.JPG Link to comment Share on other sites More sharing options...
[Br...] Posted April 15, 2019 Share Posted April 15, 2019 Yes you want that "Ref Calculation as per ISO 5459" check-box Ticked, and the Outer Tangential Element button ticked. When you program any GD&T characteristics, it will automatically set the proper constraints and evaluation method that best reflect a datum reference frame as described in ASME Y14.5 and ISO standards. Unfortunately for you, this wont effect a measurement plan that has already been written. You can go into all your Datum reference frames, select one of your datum features being referenced, click the constraints button, and press the button that says "Form Datum as per ISO 5459" and it will add these parameters to your DRF. You will still have to set the evaluation method to Outer Tangential. All that being said, there are alot of other factors that can come into play between two different CMM software and how they calculate. Are the strategies hitting the same spot on the measured features? Are they both scanning? Is the filtering set the same on both?(That's probably close to impossible) Are the fitting evaluations the same? Are they being run on two different brand CMM's? e.g. Zeiss and Hexagon? All these factors can bring inconsistencies to your measurement. Link to comment Share on other sites More sharing options...
[De...] Posted April 15, 2019 Share Posted April 15, 2019 To check parts correctly, it should be set to outer tangential and the checkbox should be checked for "Ref Calculation as per ISO 5459" That said, in some cases you may find that even though outer tangential is the technically correct method, you might not get results that make sense in the real world due to form error in your datum features. In these cases you might find you need to evaluate the form error on a case by case basis and make a determination if LSQ might provide results that are more representitive of reality. Link to comment Share on other sites More sharing options...
[Wi...] Posted April 15, 2019 Author Share Posted April 15, 2019 I really appreciate the help guys. My other cmm is a hexagon machine that is (non scanning) points only... I figured if anything my results would be worse but they was way better. I am going to switch my setting over now and just do a quick rewrite and see if that is the fix..... Thank You very much for the help Link to comment Share on other sites More sharing options...
[Br...] Posted April 15, 2019 Share Posted April 15, 2019 Please sign in to view this quote. Just to elaborate on what Derek said here, Outer Tangential is very susceptible to Outliers, especially when there is a substantial amount of form error. So make sure you are using filtering and outlier elimination. Link to comment Share on other sites More sharing options...
[Wi...] Posted April 16, 2019 Author Share Posted April 16, 2019 That did the trick 🙂 Got my settings correct now. I was also using a cylinder for my origin and i was getting a big difference in my actuals to nominal.....what should have been zero was showing like .004"-.005" ..... I switched to a 3d line and got it stable... Thanks again Guys I should sleep better tonight...lol Link to comment Share on other sites More sharing options...
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