Read Point

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  • Read Point

    Good Day everyone! I'm fairly new to PC-DMIS and was introduced to the read point alignment. I can get it to work with minimal issues - It seems that the feature directly after this alignment is greatly affected by how close the operator sets the probe to the read point location - sometimes it misses the feature, as an OD Ø for example - any help on this is appreciated.

  • #2
    One option is to increase your prehit and retract values to allow more room for operator error.

    Comment


    • #3
      Originally posted by MetsoMetrology View Post
      One option is to increase your prehit and retract values to allow more room for operator error.
      I second this. I run my programs at .1" prehit/retract/check distances but I increase it to between .2" to .3" on read point alignment programs. I drop it back to .1" after the DCC alignment though. No need to run that much through the whole program unless you have a specific need for it.
      Remembering my beautiful wife Taz who's life was lost on 6-13-2020. I love you and I miss you.

      Comment


      • #4
        PREHIT, RETRACT, CHECK are the three values you want to manipulate as you're "finding" your part. CHECK is the distance PC DMIS will search for material once it goes past the prehit zone and realizes that it hasn't touched anything.

        My nominal TOUCHSPEED is 5. However, you'll see that on the larger ID I made my touchspeed fast to speed things up (this cir also has larger prehit and retract) and once I find the initial large circle I go back in and measure the same circle again with correct touch parameters.

        A3 would be my "finding" alignment. From there, I would find datums all in order & go to town.

        Code:
        LOADPROBE/7107_Y_3X40
        TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
        MODE/DCC
        COMMENT/OPER,NO,FULL SCREEN=YES,AUTO-CONTINUE=NO,
        Drive probe to readpoint.
        
        Ball is central to hole shown.
        
        Ball is coplanar with Datum -A-.
        
        Press OK once complete.
        COMMENT/OPER,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,
        Press OK for CNC Measurement
        PLN_THEO_ZP=GENERIC/PLANE,DEPENDENT,CARTESIAN,$
        NOM/XYZ,<0*1,0*1,0*1>,$
        MEAS/XYZ,<0*1,0*1,0*1>,$
        NOM/IJK,<0*1,0*1,1*1>,$
        MEAS/IJK,<0*1,0*1,1*1>
        PLN_THEO_XP=GENERIC/PLANE,DEPENDENT,CARTESIAN,$
        NOM/XYZ,<0*1,0*1,0*1>,$
        MEAS/XYZ,<0*1,0*1,0*1>,$
        NOM/IJK,<1*1,0*1,0*1>,$
        MEAS/IJK,<1*1,0*1,0*1>
        READPOINT =FEAT/POINT,CARTESIAN
        THEO/<2.0082,1.2208,0>,<0,0,1>
        ACTL/<2.0082,1.2208,0>,<0,0,1>
        READPOINT/
        A1 =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
        ALIGNMENT/LEVEL,ZPLUS,PLN_THEO_ZP
        ALIGNMENT/ROTATE,XPLUS,TO,PLN_THEO_XP,ABOUT,ZPLUS
        ALIGNMENT/TRANS,XAXIS,READPOINT
        ALIGNMENT/TRANS,YAXIS,READPOINT
        ALIGNMENT/TRANS,ZAXIS,READPOINT
        ALIGNMENT/END
        FLY/ON
        MOVESPEED/ 270
        TOUCHSPEED/ 5
        PREHIT/0.3
        RETRACT/0.3
        CHECK/0.3,1
        PNTZ1 =FEAT/CONTACT/VECTOR POINT/DEFAULT,POLAR
        THEO/<0.5,135,0>,<0,0,1>
        ACTL/<0.5,135,0>,<0,0,1>
        TARG/<0.5,135,0>,<0,0,1>
        SNAP=NO
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=NO
        CLEARP/ZPLUS,PNTZ1.Z+1,ZPLUS,PNTZ1.Z+1,ON
        MOVE/CLEARPLANE
        CIRXY1 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
        THEO/<0,0,-0.2>,<0,0,1>,0.6457
        ACTL/<0,0,-0.2>,<0,0,1>,0.6457
        TARG/<0,0,PNTZ1.Z-0.2>,<0,0,1>
        START ANG=0,END ANG=360
        ANGLE VEC=<1,0,0>
        DIRECTION=CCW
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=NO
        FLY/ON
        MOVESPEED/ 270
        TOUCHSPEED/ 15
        PREHIT/1.5
        RETRACT/1.5
        CHECK/1.5,1
        MOVE/CLEARPLANE
        CIRXY2 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
        THEO/<1.1414,1.1414,-0.2>,<0,0,1>,2.3622
        ACTL/<1.1414,1.1414,-0.2>,<0,0,1>,2.3622
        TARG/<CIRXY1.X+1.1414,CIRXY1.Y+1.1414,PNTZ1.Z-0.2>,<0,0,1>
        START ANG=0,END ANG=360
        ANGLE VEC=<1,0,0>
        DIRECTION=CCW
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=NO
        FLY/ON
        MOVESPEED/ 270
        TOUCHSPEED/ 5
        PREHIT/0.125
        RETRACT/0.125
        CHECK/0.125,1
        CIRXY3 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
        THEO/<1.1414,1.1414,-0.2>,<0,0,1>,2.3622
        ACTL/<1.1414,1.1414,-0.2>,<0,0,1>,2.3622
        TARG/<CIRXY2.X,CIRXY2.Y,PNTZ1.Z-0.2>,<0,0,1>
        START ANG=-120,END ANG=240
        ANGLE VEC=<1,0,0>
        DIRECTION=CCW
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=NO
        MOVE/CLEARPLANE
        PLNZ1 =FEAT/CONTACT/PLANE/DEFAULT,CARTESIAN,NONE,LEAST_SQR
        THEO/<1.1414,1.1414,0>,<0,0,1>
        ACTL/<1.1414,1.1414,0>,<0,0,1>
        TARG/<CIRXY3.X,CIRXY3.Y,PNTZ1.Z>,<0,0,1>
        ANGLE VEC=<-0.9284767,0.3713907,0>,RADIAL
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=NO
        A2 =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
        ALIGNMENT/LEVEL,ZPLUS,PLNZ1
        ALIGNMENT/ROTATE_CIRCLE,YMINUS,TO,CIRXY3,AND,CIRXY1,ABOUT,ZP LUS
        ALIGNMENT/ROTATE_OFFSET,45,ABOUT,ZPLUS
        ALIGNMENT/TRANS,XAXIS,CIRXY3
        ALIGNMENT/TRANS,YAXIS,CIRXY3
        ALIGNMENT/TRANS,ZAXIS,PLNZ1
        ALIGNMENT/END
        Capture.JPG
        Last edited by DAN_M; 03-11-2021, 12:55 PM.
        SF7107(PCD), SF454(PCD), 152614(Quindos), 9159(Quindos), 7107(Quindos), B&S Manual, M&M Gear Checker

        Comment


        • #5
          DAN_M What does the second number in the "check" line control? It's always 1...

          Comment


          • #6
            Originally posted by MetsoMetrology View Post
            DAN_M What does the second number in the "check" line control? It's always 1...
            The first number is the actual amount you want. The second number is for use with find hole command.
            Last edited by DAN_M; 03-11-2021, 08:10 AM.
            SF7107(PCD), SF454(PCD), 152614(Quindos), 9159(Quindos), 7107(Quindos), B&S Manual, M&M Gear Checker

            Comment


            • DAN_M
              DAN_M commented
              Editing a comment
              Unless I'm missing something my friend thats what I said but you just used different words
              Last edited by DAN_M; 03-11-2021, 08:02 AM.

            • Matthew D. Hoedeman
              Matthew D. Hoedeman commented
              Editing a comment
              You said nothing about 'find hole' function, making it seem that for EVERYTHING the second value (percent) controls the check value distance.

            • DAN_M
              DAN_M commented
              Editing a comment
              Wow s#it I totally did miss that, thanks for that !!! I have been misinterpreting the whole time!

          • #7
            MetsoMetrology Sorry friend I gave you incorrect information. I just found out I have been misinterpreting the CHECK command, Matthew D. Hoedeman steered me in the right direction, please see his comment #6.1. I will amend my comment #6 so nobody gets messed up in the future if they stumble across this thread
            SF7107(PCD), SF454(PCD), 152614(Quindos), 9159(Quindos), 7107(Quindos), B&S Manual, M&M Gear Checker

            Comment


            • Matthew D. Hoedeman
              Matthew D. Hoedeman commented
              Editing a comment
              took me some time to get it through my head as well, and pretty much when I have to use it, I double check the hep-me-file to make sure.

              I use 5mm prehit/retract values all the time, and there have been times when I've had a (big) fixture that was crowding the limits of the machine, and for features close to the limits, I've had to use a tiny check value due to the DOUBLE amount of 'travel-past' Pcdmis normally uses based on the prehit value, to keep from getting an out-of-bounds error (limit error) when I knew d-well that it wasn't going to hit the limit.

          • #8
            DAN_M Not a problem I was following along. All good info. Thanks!

            Comment


            • #9
              Read Point programs try to make them all the same (if possible) let's say you do use a hole for your starting point. How high to I place the probe above that hole? Make it easy on yourself and anyone else, because sometimes you might be to high on the hole or even to low I used to dedicate a 123 block to keep at the CMM, I would set my read point 1 inch above the hole and set my block on the part and kinda eyeball the height, so I'm not to high and not to low, now the 123 block is ok on big parts but when your parts are smaller than the block, not so good, so at this point I found a .250 gage block and changed my Read Points to be .250 above the hole and used this instead, 2nd what about that darned ol hole? how do I know it's center? Who cares, Let's say your hole is a .250 hole. I always change the hole size to .010 under, So Even though I know it's .250, I don't have to be center and I don't have to wait for it to center the hole choice. But If, and only if the hole is not very deep, I will use the sample hit or hits, That's only if I'm limited on my choice for a hole. and of course, my check distance found in F10, in here this is normally set at 0, this is so it will travel a little further in search of the material for your feature, I have my set to .250, <<< you would think I don't know any other number, but when you change the numbers to your liking, Then click on the Default button to the right, and it will hold those numbers from here on out. <<< or it's suppose to. Same goes with Prehit and Retract. Those Prehit and Retract, of course like others said bump them up a bit, but not really needed to bump it up to high if you do it right.
              (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
              They say "Nobody's Perfect." I must be Nobody.

              Comment


              • #10
                Some of my read point alignments are getting kind-of advanced. On larger parts or parts that do not have a true outer edge to line up with the holes in the table, I will put 2 rotate points with the start circle (that's what I call the first circle after the read point) so my start circle alignment starts with a rotate then my translation to the start circle. I have a few parts that are really long with datum B and C both being circles so I will do a double read point, rotate using the two points, then translate to one of the points. Hasn't failed me yet!
                Remembering my beautiful wife Taz who's life was lost on 6-13-2020. I love you and I miss you.

                Comment


                • #11
                  The Find hole parameter settings was not well described in PC-DMIS and should have been corrected years ago for better clarity of the meaning for the setting.
                  With Summary mode in 2019R1 will show that the second parameter is for the Find Hole. (This view feature in Summary Mode is no longer available in the newer versions.)

                  Within the Settings dialog window the only value for Check is for distance not for the Find Hole.

                  Then the Parameter Settings will show Check percent with no description. Leave one thinking that this could be for the Check distance.
                  As an example Check percentage should have been described as (Check Find Hole percent)



                  CHECK/1,0.1 (First parameter is for Check Distance and Second parameter is for Check Percent for Find Hole.)

                  Help Menu:
                  The Check Distance box defines the distance past the theoretical hit location that the machine continues to search or check for the surface of the part. This distance is after it traverses the Prehit Distance value. The default value is zero.
                  The Check Percent value determines the percent of the total distance moved when performing a Find Hole operation. Be aware that if you type 1, the value is equal to 100 percent. Thus, 100% would be entered as 1, 25% would be entered as .25, and 10% would be .10.

                  Added this to the Idea Center (Suggested Features)
                  https://hexagonmi.userecho.com/en/co...eck-percentage

                  Comment


                  • #12
                    For my read point alignments I always take a manual hit on the surface before positioning it in the center of the hole. By taking the manual touch the CMM will retract after the manual hit which sets my height from the surface. Then the only thing I need to worry about is getting close to the center of the hole. Find hole does the rest. This eliminates any kind of depth error in positioning the probe.

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