tool calibrating error

[farzaneh.eskandari]

Hi,
I have a serious problem with calibrating the tool of Kuka KR210. I use a manual dial gauge for mastering the axis. However, after calibrating the tool using the 4points method, I got a maximum error of 5mm. we have an HSD spindle on the flange. This big error causes problems when I want to cut an object from the top of the block and the sides of the block.
Do you think the dial gauge would cause the error or there might be something wrong with the robot?

[Johannes @ Robots in Architecture]

Hello,

Personally I would unmount the spindle, master the robot without load and then just place a very light object with a sharp tip on the flange and try to calibrate it.
Regarding the gauge: If the gauge is pressing vertically onto the pin, I don't see much that can go wrong as the values of the gauge are all "relative", i.e. there is no need to calibrate it as you are just looking for the deepest value in the V-shaped groove.
Theoretically there is a wide range of things that could be wrong, like e.g. some looseness in the gears or a dented mastering pin. But let's assume that it's the weight for now.

Best,
Johannes

[farzaneh.eskandari]

Thanks Johannes,
Should I add the load data after mastering the robot without the spindle?

[Johannes @ Robots in Architecture]

Hello,
It seems that the load correction can only be used with the EMD/EMT and not the dial gauge, if I understood that correctly. In any case, I would first do the steps from my initial post and if the XYZ calibration turns out fine, mount the spindle and then try again if there is a change in accuracy due to the load.
As far as I know - but I might be wrong! - the load data in the tool (unless you use the load data correction with the EMD/EMT) is mostly used in the pathplanning, so that e.g. with a heavy item a more gentle acceleration curve is used. I don't think that it will have an effect on a robot that is standing still (as is the case when you get the coordinates for 4-point calibration).
Best,
Johannes