Turntable setup with Linear axis

[Hyperbot]

Hi there,

I am trying to setup a turntable in combination to a KUKA KR240 L210-2 2000 on a KL1500/2 track.
I followed the tutorial to it on youtube by Karl Singline.
Unfortunately it doesen't work for some reason.
On the simulation it works totally fine but when I check the generated code, the robot wrist rotates around the workpiece in A.
When I send it to the robot, the turntable rotates synchronized with the robot, but it doesn't keep the given vector and rotates around the table.
I checked the settings of the table, so I rotate it manually 360° is does a full circle. So the gear ratio is ok.
Can anyone help me with this ? I would really appreciate it !

Best,
Oliver

[Johannes @ Robots in Architecture]

Hello,

That sounds about right, because you are rotating around the workpiece, it's just that your turntable-coordinate system is rotating in the opposite direction, so that the robot isn't moving that much.
My guess is that your turntable is not configured as a synchronous axis, or that you didn't calibrate your base as an Offset Base (Startup, calibrate, External kinematic system, Offset). If you calibrate it as a normal base, it won't rotate.
When using a turntable, KUKA|prc automatically assumes that you're using an offset base.
You can check if you're using an offset base by looking at the XYZABC values of the base. By default the origin is the origin of the robot, but with an offset base it's linked to the turntable. So in your case it will be rather low values.

Best,
Johannes

[Hyperbot]

Hi Johannes,

Thank you for your very quick reply.
I checked the external axis settings and it seems to be configured as synchronous axis. $EX_AX_ASYNC is set to =0 (see attachment)
Now i try to calibrate the offset base, but it said "Die externe Maschine muss zuerst kalibriert werden."
And when I try to set the rootpoint of the table, the message: "Kinematikzuweisung" appears. I chose ext. Kinematik Nr. 2 since it is the second external axis E2.

But I think the problem starts already earlier, because when I check the code in the editor before I load it to the robot, I see that it rotates +- almost 180° in A.

Best,

Oliver

[Johannes @ Robots in Architecture]

Hello,

Have you been able to calibrate the Offset base then?
Without it, it won't work.
I don't see a fundamental problem in A +- 180 - there is no "degree limit" and depending on what B and C are, +- 180 can basically be any direction.

For more details on the setup see the KUKA manual on external axes (for KRC2, which you seem to be using), which I found online at https://www.kinematics.com/ftp/SA/Install/Driver%20Downloads/Robots/SARobotDriver%20Kuka%20Deployment%202014.08.13/KUKA%20KRC2%20Configuration/Important%20Docs/KSS_55_external%20axis%20setup%20and%20programming.pdf

Before you go into PRC I would make sure that everything is properly set up: So calibrate the Offset Base, go into the Base-specific Cartesian movement mode and then move the turntable. If everything is set up correctly, the robot will keep its relative position to the turntable, i.e. it will rotate with it. While e.g. in axis movement mode only the turntable would rotate while the robot stays at its position.

Best,
Johannes

[Hyperbot]

Hi,

Unfortunately not.
The message "the external machine has to be calibrated first." comes up.
So what is the step before, that is missing ? I also can't set the rootpoint.
Thank you for the link. I will read it and hopefully figure out where the problem comes from.

Best,
Oliver

[Johannes @ Robots in Architecture]

Sorry, I haven't encountered that particular message before. Is the axis maybe just not mastered?

For those basic "does not work" problems I usually recommend calling the KUKA hotline, they are very good at solving those issues.

Best,
Johannes