Posts by aka

I continue to try Y and Z Calibration with Rotating Z Axis.
However, result is not better than I expected.

My Procudure is
1)Tune Z TCP value while dial gauge indicates +/-0.02mm while Z Axis rotating 180 degrees
2)Then, tune Y TCP value while dial gauge indicates +/-0.02mm while Z Axis rotating 180 degrees

Robot Moved as I posted before.

Procedure 1) was completed.
After I fixed Procedure 2) , I checked Procedure 1) again.
I found that more deviation occured at Procedure 1).

I tried over and over but I couldn't fix Y nad Z TCP value yet.

Does Anyone have ideas or opinions about this issue?

If you want more information, tell me please!
I will try.

Thank you.

Thank you for advises and questions, SkyeFire.

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KRC2 or KRC4? KSS version?
I have KRC4(KSS version : 8.3.82).
In terms of accuracy of robots, are there any differences between 8.3.2 and other version?

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Absolute Accuracy or not?

I don't know about absolute accuracy robot model at all.
I heard "HA" is the best option for milling application.
Is there any defference between HA type and Absolute Accuracy type?

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Is is possible to tune a TCP using a dial gauge. It will require iterative alignment , and careful location. The ideal scenario would be to use a "tool" with a precision machined spherical tip, but if you are less concerned about the axial dimension of the tool, then using a good machined cylinder can serve.

Now I have only good machined cylinder. But I bought machined spherical tip an hour ago.

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Assuming that the Z axis of the TCP is aligned with the axis of the spindle, you will want a way to align the dial gauge with the X and Y axes of the TCP, without major reorientation of the robot. This could be two dial gauges mounted 90deg apart, or a good jig for swapping positions of the gauge. TCP tuning should be done in a pose very similar to the working pose.

The X and Y values of the TCP can be tuned by rotating around the Z axis of the TCP and iteratively correcting the TCP along its own X and Y values (using the Geometric Operator) until the gauges show minimal drift. Then iteratively correct the B and C angles (again, around their own vectors) while moving the tool up and down along the Z axis, until the gauges show minimal drift. You will probably find that correcting one axis causes increased error on the other, so in the end you will have to find some average medium.

I carried out Calibration test as you adevised.

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Load data should be as accurate as possible. At minimum, the Mass value needs to be correct, and the CoG values need to be as accurate as you can manage. If the robot has Absolute Accuracy (The "HA" suggests is does), you will have to carry out the correct No-load and With-load Mastering procedures.

I used LoadDataDetermination.
But I found I forgot to input values about Loads on A3.
Without values loads on A3 during LDD, do you think this cause huge effects accuracy?

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Optimizing for backlash... there's no simple answer. Try to avoid reversing the direction of an axis during the milling program, even if that means holding to only Conventional or Climb milling. For tight tolerances, expect to leave material during roughing and then incrementally "walk in" on the correct final dimensions. Do NOT expect to cut perfect circles -- every time one of the robot axes reverses direction, that backlash of that axis has complex effects on the motion of the TCP. And the robot has 6 axes, which multiply each others' errors in ways that are extremely hard to model.Feed rates depend on your material, but in general, robots are very "floppy" compared to CNC machines -- optimize your paths to minimize the forces on the tool. You have to treat the robot the way you would a very light-duty CNC, like the Carbide3D Shapeoko.

I agree your opinions and advises.
Other people who does not work on Robotic milling often think Robots can mill better and faster than CNC machines
I try to convince them Robots are defferent from CNC machines, but I never make it clear.
Anyway, thank you for your opinon about backlash issue.

Hello,There!
I'm working on Robotic milling projects with KUKA.CNC.
However, I found it is not easy to mill in high accuracy.
I'm trying to solve problems but I don't have any colleagues or friends to discuss about these problems.
So I want to share and discuss about my problems and your problem.

My problems and questions are...

1)There is diviation after millling with TCP Rotation.
2)Is it Possible to optimize TCP only with dial gauge?
3)How much is effect of load data on Robotic milling?
4)How can I optimize robot axes backlash? If I could do, how can I calibrate and evaluate?
5)Should I set feed rate low while milling with KUKA robots?

Now I 'm testing and checking TCP withdial gauge.
Procedures can be seen these videos.
1)

Move Robot to Z direction 130mm and chack what happen during moving.

My equipment are..
Robot : KR120 R2700 extra HA
Option Software : KUKA.CNC(2.1.2 to 2.1.7)
LoadDataDetermination
Multiprog 5-35
CAM : MasterCAM
Simulation Software: RobotMaster

What's your problems?
Let's Share and discuss to solve problems!

I can test your idea for Calibration.
If you want test, leave comment and details of your idea.

Thank you

Hi, there.

After KSS updating(8.3.4 to 8.3.32) in Office.lite, some error occurred when booting KSS.
Error dialog says like "Cannot establish to KRC. Robot Control impossible"
I also got error log .txt file(attached)

Does anyone know about this problem?

Hello, There

Now I'm trying configrate Multiprog for getting KUKA.CNC error signal.

When NC program error occur, ERR red sign can be seen on CNC-HMI.
I just want to send it as signal to external device via Devicenet(Beckhoff EL6752-0010).

I dont have much information about Software PLC like Multiprog.

Does anyone know about Multiprog Configration for KUKA.CNC?

Thank you.

aka