TCP precision trouble, fanuc welding robot

Hello everyone, I'm new to the forum.

I'm working with two fanuc robot for welding task. Model 120ic and controler R-30ia. The TCP was never great on either one, it move around at least 5mm. It wasn't a problem since we could weld pretty straight anyway. They have runned like that for at least 5 years.

But now we need to have them certified by the Canadian Welding Bureau. The certification process include to "configurate and adjust the TCP".

I didn't find any method to define the tool that worked, so we figured out it must be the Masering. We tried to redo it, but we got two problem; we don't find the align mark on the 5th and 6th axis and I don't think using that method alone is precise enough? Surely there is a more precise way to do it no?

So to resume;

1: Anybody has certified fanuc robot with CWB?

2: Where are the mark on the 5th and 6th axis?

3: Are there any method more precise than to align the mark?

Oh and before I forget; english isn't my first language and 95% of my knowledge is self-learned. Although I explored these robot far and wide for five years, I know I can be considered a rookie and I'm more than happy to learn new/real technique/procedure.

I'll look for that, meanwhile is there a way to adjust the 5th and 6th axis without it? I'm not sure we can get the jig in time. The test is 16 march.

For the 5th I tried to rotate both the 4th and 6th axis by 180, I belive the tip of tge tool should stay at the same place?

Quote from Lemster68

That stands to reason, and good thinking.

I tried it, it worked great. I also made something similar with the 4th and 6th axis.

For the 4th, I put robot it that position:

J1:0

J2:30

J3:-75

J4:90

J5:-90

J6:0

I mesured from a fixed part of the tool to a centered machined part at the base of the robot. Rotated J4 by 180° until both mesure were the same.

For the 6th I put the robot in that position:

J1:0

J2:45

J3:0

J4:180

J5:-90

J6:90

Then again I mesured from a fixed part of the tool to a centered machined part between the 3rd and 4th axis. Rotated J6 by 180° until both mesure were the same.

One robot went from +/- 8mm to +/-4mm and the other from +/-5mm to +/-2mm

The difference is barely visible when looking at the mark. I'm currently working on a similar process for the 3 first joint, but I'm not sure I will find something.