I had asked a question in this thread:
Load Data Determination - "no identification of load data"
And as I am reading this one, I think that what I had asked about ABB armload is what Kuka calls supplemental loads?
Yep, Lemster.
KUKA Supplementary Load Data is analog to ABB Armload.
here are examples of dumbbell in KUKA robot gym (from fence test videos).
also note the blue brick on A3 (supplementary load). both payload and A3 supplementary load are measured from flange when robot arm is in the "cannon" position (0,-90,90,0,0,0). other supplementary payloads (A1 and A2) are measured from foot of the robot (robroot).
and this is why Z value for A3 load is negative and some good meter away from flange. Setting this value to zero places this load at the flange, not at shoulder.
so.... when it comes to laods... all values are wrong except when they ARE correct.
service case story about loads from years ago:
company X purchased large robot to do arc welding. did not care for any consulting or training since they can read the manual and figure things out. so second hand KRC2 system with KR150 was chosen. this is a big arm, better suited for spot welding than arc welding but they said it was a hard to beat deal and that it worked. they did not need this high payload unit but did want long reach to weld some really long welds. it turned out they were filling deep V-slots between huge parts requiring multiple layers and weaving. after a year or so of production one of the motors failed. X wanted production back on track but also to know why did this happen. so archive was shared and did not take long to see logs and that loads were way off.
note that factory default payloads are not for some "typical user payloads". they are for very specific type of payload (deadweight / dumbbell) used in a factory. in case of KUKA robots they are chosen to be at ... or above... robot rated load so that short factory stress-test can guarantee that everything works. but this meant as a stress test, not years of operation. so for this particular robot, rated load was 150kg but the factory default load was 175kg and some 30cm from the center of the flange (about 230mm in Z, and 210mm in X direction). as mentioned, in this cse, actually attached payload was just an arc welding torch so... more like 0.5kg for tool and holder. logs also revealed TONS of recurring messages complaing about wrong load, overheating, overcurrent etc. but all of this was ignored, operators just kept on acknowledging messages and running production no matter what. that poor beast was killing itself trying to weave with the heavy arm and imaginary 175kg payload, doing multi-pass of very long welds without any notable idle time.
so, motor was replaced... this time supposedly correct load data was entered and production resumed... and about year later the exact same problem happened. same axis, same errors... someone really upset was screaming over the phone, they wanted it fixed NOW and they are not paying for it since previous diagnose was crap and replacement motor was only 1 year old. no way they will be paying for another motor when this big robot should handle this puny load with ease.
so another archive was shared and it confirmed what was mentioned in the phone call - logs with same messages as before. tool #1 was still the only tool used. also this time tool 1 did have correct load data (although this could have been edited in, even after motor failed since logs matched previous ones). but comparison with previous archive revelaed dramatically different code. robot was still doing same kind of work with multi layer welding, weaving etc but no ILF instructions are used. everything was coded by hand in KRL. so tool and base were specified using direct variable assignments. except...there was nothing in the program to tell robot what load to use. single ILF motion like PTP HOME would have assigned load.
... they paid for repair.
EDIT ----
ILFs take care of many things. this is for a reason. but when you login as an Expert and write code in KRL... you are the Expert and you need to take care of everything yourself - training wheels are off. wrong configiration or code can destroy robot - no collision necessary. there is a reason certain things are password protected. so make sure to follow commissioning steps per System Integrator manual.
and in case of programming.... ILF motion instructions don't ask for load, they allways assign load based on selected tool. when writing code in KRL, loads need to be specified explicitly:
$BASE = base_data[1..32] ; ok
$TOOL = tool_data[1..16] ; ok
$LOAD = load_data[1..16] ; needed but - often missing
