Milling in Aluminium, wich robot?

    I'am planning to use a Kuka robot for milling in aluminium profiles.

    I have read a lot about accuracy and backslash in this forum but I would like your opinion about which robot to choose.

    We mill square and round holes from 10 to 40 mm in standard aluminum 6063 of 2.5 mm wallthickness (in one pass) with a cutter of 5mm.

    Required working range of 5-6m

    The options are:

    - KR60 HA on a lineair track

    - KR120 R2700 extra HA on a lineair track

    - KR90 R3100 extra HA without a track


    1. Is it better to chose a smaller robot like KR60 HA or a more robust one like the KR120 R2700 HA or even the KR500?

    The larger the robot, the fewer milling forces will have an effect, but a small robot has fewer backlash problems?

    2. Is a HA (High Accuracy robot) really better for this job?

    3. I read something here about tilting the robot 10 ° to minimize the backslash of axis 1, but what about Kuka's gravity compensation?

    Can you enter this angle in the settings? KRC4

    1. In My opinion a bigger more robust robot is better for problems like this. Backlash is not your only problem, you will have a lot of problems with rigidity as well. What kind of tolerances are you expecting?

    Also in your case i would advise a linear track. With these distances it will be very hard to get the same accuracy at the end of the reach of robot as to near its base.

    2.Depends on your tolerances.

    3.Tilting your robot is a trick i heard about as well. It could help eliminate backlash on A1, but if you don't have to do it then don't. I also would not do it with a HA robot as the are measured when they are level.

    i my self only mill in plastics and i have milled round holes from 30mm to 500mm without too much backlash issues. General repeatability is around 0.2 mm with a KR150 and a KR210. The thing to read here is the word repeatability not accuracy. It normally takes me several times to get a milling program fine-tuned to be accurate enough.

    Every problem has a solution, that isn't the problem. The problem is the solution.

    1. feed rate will have an effect

    2. is this supposed to be parametric or hardcoded? i am guessing parametric and in that case there is no way around positionally accurate robot (either HA or ABS)

    3. that is what $ROBROOT is for. does not matter if KRC4 or not.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

    Quote from panic mode

    1. feed rate will have an effect

    2. is this supposed to be parametric or hardcoded? i am guessing parametric and in that case there is no way around positionally accurate robot (either HA or ABS)

    3. that is what $ROBROOT is for. does not matter if KRC4 or not.

    1. Feed rate of 15mm/sec would be nice

    2.It is parametric but only in the length of the profile.

    So I always cut the same hole, shifted along the length of the profile (5-6m). X and Z coordinate remain the same, Y coordinate changes.

    My idea is to mill a test hole at every position so that I can adjust the absolute deviation by software. Repeat accuracy is therefore more important to me but absolute accuracy makes it easier.

    Quote from Leon

    1. In My opinion a bigger more robust robot is better for problems like this. Backlash is not your only problem, you will have a lot of problems with rigidity as well. What kind of tolerances are you expecting?

    Also in your case i would advise a linear track. With these distances it will be very hard to get the same accuracy at the end of the reach of robot as to near its base.

    2.Depends on your tolerances.

    3.Tilting your robot is a trick i heard about as well. It could help eliminate backlash on A1, but if you don't have to do it then don't. I also would not do it with a HA robot as the are measured when they are level.

    i my self only mill in plastics and i have milled round holes from 30mm to 500mm without too much backlash issues. General repeatability is around 0.2 mm with a KR150 and a KR210. The thing to read here is the word repeatability not accuracy. It normally takes me several times to get a milling program fine-tuned to be accurate enough.

    1. Repeatability of +-0,1mm in x-direction and +-0,3 in the y-direction

    3. I thought an HA robot only had different gears? Or is this also / only absolutely calibrated?

    Kuka advised me to do an absolute calibration on site with the spindle mounted, but I am not sure if I have understood this correctly

    with KUKA there are three grades of robots:

    STD - standard ($$$)

    ABS - absolute ($$$ + $2.5k)

    HA - high accuracy ($$$ + $10k)

    STD is robot made from stock parts. that is some 99% of robots out there. parts (link arm, arm, carousel etc.) have machining tolerances so bunch of STD robots will all be slightly different even though they are same model and same batch.

    ABS is like STD but also it is calibrated with laser (could of data points for automatic corrections) this can be done on site too, after robot is delivered.

    HA is robot made from best parts (tightest tolerances). So even without extra calibration closer matches software model. But it also gets laser calibration like ABS. HA is the ultimate in precision but - it only comes from factory and it has longer lead time (it takes time to gather parts with really tight tolerances).

    both ABS and HA are considered "positionally accurate" as both are using PID file.

    if you want ABS or HA robot on a linear rail, they should be measured together (with robot on the rail).

    if you get positionally accurate robot but decide to mount it on an angle, it will need to be recalibrated again. and of course same applies to robots that are mounted on wall or ceiling.

    there is company not far from me that specializes in waterjet cutting. they are both integrator and manufacturing facility using their own products. all of their robots are mounted slightly tilted (10deg) and then calibrated in field.

    when everything goes well, robot can be calibrated in maybe 4h so if you have several robots, it pays to do them at once.

    KUKA gave you good advice, have robot mounted, dressed and fitted with tool (could be STD robot). then get it calibrated to upgrade it to ABS.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

    Thanks for the info man!!

    Quote from panic mode

    there is company not far from me that specializes in waterjet cutting. they are both integrator and manufacturing facility using their own products. all of their robots are mounted slightly tilted (10deg) and then calibrated in field.

    Which robots are they using?

    Do you know which software are they using? KUKA.CNC ?

    I read somewhere that KUKA.CNC is more accurate then normal KRL because it uses path interpolation in the background. Does anyone have experience with this? Or is it the same as doing a path interpolation in KRL?

    Quote from Leon

    i my self only mill in plastics and i have milled round holes from 30mm to 500mm without too much backlash issues. General repeatability is around 0.2 mm with a KR150 and a KR210. The thing to read here is the word repeatability not accuracy. It normally takes me several times to get a milling program fine-tuned to be accurate enough.

    Why didn't you use an HA robot?

    What software are you using?

    Quote from AluMill

    Why didn't you use an HA robot?

    Well, that is very simple i did not have the budget for one. When we started with robotics we bought a used vkrc2 with a kr150 and figured the rest out as we went. Also i think that in our case i would not make sense to spent money on a HA robot when generally accuracy is needed between +-0.5 and 1 mm. So this is not a problem. There have been exceptions where tighter tolerances where needed but that only means that i have to spend more time fine tuning. We do a lot of serie production so spending extra time on the first 5 or 10 product of a serie of 200 is fine.

    As of now i am not using any software for programming (other then what is running in my brain :winking_face_with_tongue:). But i am looking to buy mastercam or sprutcam. Programs are getting more complex and my brain has a hard time keeping up.

    Every problem has a solution, that isn't the problem. The problem is the solution.

    Quote from panic mode

    ABS is like STD but also it is calibrated with laser (could of data points for automatic corrections) this can be done on site too, after robot is delivered.

    there is company not far from me that specializes in waterjet cutting. they areboth integrator and manufacturing facility using their own products. all of their robots are mounted slightly tilted (10deg) and then calibrated in field.

    I have an abs robot without it's paired krc2 only the robot

    can i use it with a simple krc2?

    abs calibration stored in rdw2 or in krc2 ?

    Which axis is tilted 10 degrees ? Have you a photo to understand ?

    A simple kr150 can work as waterjet?

    I mean have enough protection against rust-corrosion from water ?

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