Should I be doing more allignments

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  • Should I be doing more allignments

    Hi guys,

    I have a part im measuring, which on the drawing states different datum's for each hole set. The part gets up to 'R' in the alphabet for datums so theres a few.

    Should I be creating a new alignment for each hole set using the required different datums or is it just the case of measuring the points and creating a feature out of them and using them as a datum?

  • #2
    Typically, I use one alignment for measuring. Most of the time, they are my primary datums on the print, but that is not always the case.

    It is a lot easier if you are using a model (so long as it is correct) because it should pull the nominal values from that. If not, you may have to back-figure numbers to be able to type in your nominal values.

    It doesn't matter what you use to measure, so long as the machine knows where the part is and you make sure that all the features you need to use for other alignments are measured. Then, I create and change to whatever alignment I need when it comes to the dimensioning and reporting part.

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    • #3
      It depends - if you're using Xact measure (FCF builder dialog thingy) you should be fine.

      Personally I usually prefer to create the datum structure as an alignment anyway (I'll usually program/measure the features in the datum ref frame they're called out in).

      I prefer to do it this was as it's easy to check the feature theo's (basic dims) against the print (if using CAD) or without CAD they're easier to program in the correct alignment).
      Automettech - Automated Metrology Technology

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      • #4
        So basically I should run through the part as normal using datums A,B and C for the manual and DCC alignment.

        Then just construct the features from lets say datum F to create a plane and then dimension from that feature?

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        • #5
          Depends on what the FCF calls for. I would measure to the print, if the print has a position called out to |D|M|R| I would measure to that FCF.
          Jesse Krook

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          • #6
            Originally posted by YGOLORTEM View Post
            Depends on what the FCF calls for. I would measure to the print, if the print has a position called out to |D|M|R| I would measure to that FCF.
            OK, so how would I go about doing that,

            create main alignment of part to A,B,C
            Then measure features which relate to those datums
            then creat alignment to say A,D,E
            then measure those features etc. and so on?

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            • #7
              "So basically I should run through the part as normal using datums A,B and C for the manual and DCC alignment.
              Then just construct the features from lets say datum F to create a plane and then dimension from that feature?"

              That is how I do it. For me, I find it much easier not changing during a program. Then as I am going through deciphering the print, I just change the alignment, or recall one that I have already created depending on what the print is calling out for that feature.

              I do understand what NinjaBadger is saying though that it may be easier to do it as you go along. You will get the correct nominal when you do it that way. Then in the dimensioning, you only need to recall what you have already created.
              Last edited by JenWasch; 03-30-2015, 11:56 AM.

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              • #8
                I originally started out doing it in the manner the badger ninja described.

                Then as I got older I migrated to Jen's method and prefer it that way because I use a lot of marked sets. If you know what you're about this won't be a problem.
                Last edited by TheyCallMeWoody; 03-30-2015, 12:44 PM.

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                • #9
                  Another way to look at this is, I try to pick three features on the same side of the part also. Some FCF jump from side to side of the part. That takes more time to measure, rotate, measure, rotate. If you have all day to run a program, great! I don't so, I try to streamline things as much a s possible. I will measure everything on one side of the part and then move on to the next.

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                  • #10
                    Originally posted by JenWasch View Post
                    "So basically I should run through the part as normal using datums A,B and C for the manual and DCC alignment.
                    Then just construct the features from lets say datum F to create a plane and then dimension from that feature?"

                    That is how I do it. For me, I find it much easier not changing during a program. Then as I am going through deciphering the print, I just change the alignment, or recall one that I have already created depending on what the print is calling out for that feature.

                    I do understand what NinjaBadger is saying though that it may be easier to do it as you go along. You will get the correct nominal when you do it that way. Then in the dimensioning, you only need to recall what you have already created.

                    This or align and measure as you go, either way you will still be aligned to the same features. It's all a matter of personal preference I guess.
                    Jesse Krook

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                    • #11
                      Perform your own personal test using different methods, compare the reported results. Sometimes they are the same (at least no significant difference), but sometimes . . . That's the only way you will know. Programming methodology can directly impact dimensional results.
                      sigpic

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                      • #12
                        i believe with positions of features it probably doesn't make too much of a difference unless possibly the feature is not in a hard plane. However I think it is very important to measure in the correct FCF when measuring and reporting profiles.

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                        • #13
                          Originally posted by ir a programmer View Post
                          Perform your own personal test using different methods, compare the reported results. Sometimes they are the same (at least no significant difference), but sometimes . . . That's the only way you will know. Programming methodology can directly impact dimensional results.
                          I think I will have to do this, at least to prove to myself what way is best but also if anyone upstairs asks any questions about my method.

                          i believe with positions of features it probably doesn't make too much of a difference unless possibly the feature is not in a hard plane. However I think it is very important to measure in the correct FCF when measuring and reporting profiles.
                          theres a fair few profiles in this part, well actually they all are on the drawing but the engineer just wants positions for some of them.

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                          • #14
                            A picture worth a thousand words. Hard to say, but likel you have to create a new Align.
                            B&S One
                            PC-DMIS CAD v2014

                            Romer Infinity

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                            • #15
                              I always create my initial alignment, example abc... then measure everything on the entire part... labeling everything as it is.... example measuring and label datum -d- and so on... then when it comes time to dimension my features I will change my alignment per the callout. example -DBC- I would only level DBC before I did my dimensioning and then instantly recall my primary alignment -ABC- after the dimensioning is done. I found that the less alignments during the creation of all of the features is less stress on Dmis and also makes editing a lot easier.

                              So my programs always look like this... manual initial alignment, DCC alignment.... ALL of the parts features (with labeling being one of the most important things) and then at the bottom of my program would be all of the comments/dimensioning and other alignments.

                              All preference though.
                              I will find a center in you...

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