Question about IRCalibration Frame Shift

  • Hi everyone,

    New to the forum here. I have recently started programming for a Fanuc robot with a R-30iB controller.

    It uses a laser to do a frame calibration every time a thermal formed hot tub is loaded onto the fixture.

    My question, does the Frame Shift calibration program simply adjust the tilt and shift of a Cartesian frame, or does it also account for the wrapping and shrinkage of the tub as well.

    From the controller manual, it seems to indicate some level of compensations for dimensional changes,. I am just trying to understand how it works behind the scene.

    Thanks in advance.

    Frank

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  • I run CellFinder (later updated to CellCal, then Frame Shift) on my RJ3iB on thermoformed/FRP reinforced bathtubs. So keeping in mind that I'm a few generations of software older than you: It uses some sort of best fit algorithm to match the found points against the mastered points and adjusts the frame XYZWPR, not the individual points of your toolpath. I found that 13 search points with an allowable convergence of 4 keeps me well within my tolerances of +/- 1/8."


    Not sure if that answered your question, but hope it helps. I spent a while trying to figure out what's going on behind the scenes once and all I was able to deduce was that Fanuc's engineers are a lot smarter than I am.

  • Thank you for sharing the insight. I am currently using 7 points, 4Z, 2Y, and 1X on the lip portion of the tub. It is working reasonably well, but some points on the opposite side of the X are slightly off (1/8). May I ask what do you mean by "allowable convergence of 4"? Do you mind sharing your search point selection strategies?

  • In the cellfinder menu, go to schedules. There's two options for offset type, "3 Planes" and "Volume." 3 planes works great if you have three flat orthogonal planes you can measure off of, you can get a pretty decent reading using 6 points (3 on one plane, 2 on another, and 1 on the third). Unfortunately we don't make cube shaped product so I'm stuck with using the volume method. The attached picture shows more or less how one of my search programs is set up. My methodology changes depending on tub geometry, but I typically to 4 Z- searches on the deck (as close to the bathing well as possible gives the best results), 6 split between Y+ and Y-, and 4 on X+ and X-. With a tub like the one pictured with no real flat surfaces, I'll need all those points. On a mostly rectangular tub I'll usually do 4 Z-, 3 X+, and 3 Y+ and that will be plenty sufficient.


    My schedule is

    Frame Type: UFRAME

    Offset Type: Volume

    Max XYZ Change: 30.000 mm

    Max Ort Change: 5.000 deg

    Convergence Tol: 4.000 mm

    Auto Update: True

    Register Number:2


    Convergence Tolerance (as I understand it) is a measure of how confident the robot is that it put the new UFrame in the right place. The smaller the number, the more accurate the new frame is.


    We're more or less a job shop, so we don't batch anything which means I don't have changeable fixturing. Our fixturing consists of a hold down screw through the drain hole and a pair of 24" C-Clamp vise grips; and my cellfinder search is required on every single tub that we run. The tub's main program will contain a section like this (edited for clarity):



    Cellcall is my program to call the appropriate search program:



    Hopefully something here is helpful to you.


  • Thank you so much for the additional details sir. I will have to study it a little bit. I am in the process of convincing my client to digitize their hand made thermal forming molds as well. Do you have any experience with 3D scanners? or are your molds are digitally designed to begin with?

  • Our molds are all hand made; I used a cheap i-pad based 3d scanner to create a surface, imported the surface to Inventor, and essentially manually traced the surface in 3d and took measurements of critical dimensions from the physical molds to create my parametric model. It was/is a real pain; if you go this route don't buy the cheapest scanner that you can find.

  • Thank you Titus, that does sound like a real pain. I have experience using photogrammetry for smaller parts. Maybe I will try the same route for the tubs and mount the camera onto the robotic arm. Will need to get some dotted stickers for the tub.


    I check the frame shift schedule, and it seems like there is no longer an option to set the offset type. I am going to have to do some trials to see if adding additional points would compensate for minor dimensional changes. I greatly appreciate your help TitusLepic

  • Hi Everyone! I am using iRCalibration Frame Shift feature to find not a perfect rectangle part that doesn't have a locating mechanism. I was able to set this feature up with 6 points (3in Z, 2 in X, and 1 in Y - using 321 example in FANUC's manual. But since the part is so large (1.5 meters width and 2 meters length), 3 points in Z aren't enough to capture the roll and pitch part has, so I am trying to teach more points in Z essentially just one more point in z to cover all the foUr corners. But I keep getting this error
    ACAL-055 Too many parallel searches

    The error manual shows remedy of either adding more searches than 7 or change the search direction. I added 2 more search points, but no luck. Does anyone have the same issue, if so what did you do get through this and how were you able to add more than 3 points in one direction.

  • Hi schittampalli ,

    1. As long as you set the search points as far apart as possible, you may not need to add more points to capture the roll and pitch of the part.

    2. You can mix different search frames. For example, you can mix UTOOL[-Z] with UFRAME[X,Y,Z] for additional search points.


    Hope it helps.

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