KUKA.RoboTeam KRC4

  • Hello. I have application with 4 welding robots KR 5-2 arc HW(KRC4, KSS 8.3.17) and they will weld very close together. Welding equipment is from FRONIUS. I would like to use RoboTeam because robots would have to be in sync(if $OV_PRO is changed on one robot, others must adjust and viceversa in order to avoid collision). Also ArcTech.Basic package will be installed on them. Did anyone experienced some problems using RoboTeam and ArcTech together? Is this right approach to use RoboTeam for this application?

    Thank you?

    Edited once, last by DannyDJ ().

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  • If all you need is speed coordination, RoboTeam is probably overkill. Plus, RoboTeam limits you to a single shared teach pendant, which I've always found to be more trouble than it's worth, except for robots that have to move precisely together as if they were a single physical device.

    You can probably just output $OV_PRO from one robot to the other over Fieldbus signals (8 bits will be enough), and designate one robot as the "master", so that the other robot's $OV_PRO follows it.

  • Thank you for your answer. I also thought of this doing $ov_pro sync in sps. I have already managed this in Kuka.Sim pro. Forgot to mentioned that there will be also 2 external axes added, one axis on one robot, second axis on other robot(like 2 turn tables), but robots don't have to weld while external axis is moving(just to position the part.)I already have the Roboteam package(also one teach pendant for all 4 robot is prefered option from customer). If we go with Roboteam, i dont need load sharing or anything else just sync option that during movent they don't hit each other.

    Do i need for this sync option to be operational, calibrate robots beetween to each other also like for load sharing, etc...?

    also what if one robot welds with different speed than others and $OV_PRO can be 100, they still can crash to each other regardlles if i match $OV_PRO in sps.

  • If the robots are that close together, the Sync commands may not be enough. Or they might cause one robot to pause mid-weld, which I can't think would be good for the weld.

    The issue with using RoboTeam to keep the two robots moving in sync is that (unless I've missed something), they have to move in full 6-DOF and speed sync, or not at all. So if the two robots are welding seams that are not perfectly parallel, at exactly the same speed, you can't have them motion-synchronized.

    If your welding process can tolerate mild changes in robot speed, you might be able to set up a realtime distance-measurement between the TCPs, and have the following robot slow down as the distance between the TCPs drops. That could be a bit involved, but I've been able to make it work in other circumstances in the past.

  • There are several ways to use Roboteam and weld. Last year, we completed a mig welding system using 2 robots and Roboteam. We employed the simplest way to use Roboteam; we used the PROGSYNC command. The way this works is that you program each robot separately at whatever speed they need to run. Since I understood you to say that the external positioner will NOT be moving while welding, each robot is therefore free to weld at whatever speed is needed for the joints each is welding.

    When you come to a place in either robot's program where you want to verify where the other robot physically is in space before continuing, you use a PROGSYNC command. Basically, this command uses a uniquely named position that each robot knows about and must both be at before either robot can continue moving.

    Using this approach, it is important to understand that the robots are NOT speed synchronized and they also do NOT know where the other is in space (that's up to the programmer to know). However, using the PROGSYNC command, you can verify where each robot is in the program it is running. If one robot gets to a particular PROGSYNC command before the other, then that robot will sit and wait (not move) until the other robot catches up.

    In the end, we found that even using Roboteam in this fashion was probably overkill. We probably could have used a series of digital I/O signals between the 2 robots to establish "communication" and allow the programmer to know where each is in the programs that are running.

    Hope this helps.

    Building robotic welding systems.

  • Thank both of you for your answers. This info will help for sure. Basically then i did this already in Kuka.SimPro where i programmed robots so that the fastest robot(which can be any of them 4) always after finished weld WAITS for other three to finish, then they move to second weld together again fastest robot waits again for all others to finish and so on and from simulation they looked like in sync :). Yes external axis will be use just for positioning the workpiece and i was thinking to be async.

    I have another question. If we use RoboTeam and one robot in team doesn't work anymore due to some error, others can still working and executing their programs?

    Edited once, last by DannyDJ ().

  • Yes, if one of the robots stops for some reason (i.e. arc start failure), the others will continue to run their own programs. Only when a PROGSYNC command is reached, will all of the robots need to be at the correct locations. If the arc start failure robot is still not running, then the others will wind up waiting forever.

    So this brings up an interesting point, only use a PROGSYNC command when you need to (to say, avoid robot to robot collisions).

    So here's a question for you: Will there be an operator at all times supervising the robots (to take care of arc start failures for example) or will you be using stack lights to show the shop floor supervisor the status of the robots?

    Building robotic welding systems.

  • Hello. Thank you. They will be also able to work if one of the robot controllers has some electrical error inside the cabinet(faulty KPP,KSP)?. For safety will use ProfiSafe. There will be operator and the stack lights.

  • Yes, the robots actually work independently of each other. It is only the PROGSYNC commands that force the robots all to be at a pre-programmed spot.

    Building robotic welding systems.

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