On a KUKA KR 210-2 with a KR C2 controller, almost every major item in the maintenance plan falls due by hours or by years, whichever comes first. Part of the plan also depends on the build date shown on the robot's rating plate. If you only look at the hour counter, the plan runs late.
KUKA documents maintenance jointly for the KR 150-2 to KR 270-2 family and splits it into two documents: «Maintenance - Manipulator without Wrist» and «Maintenance In-line Wrist 150/180/210/240/270». In our technical database we work from modules Ro/Me/05/33.01 and Ro/Me/05/33.02 of the manipulator manual, and from the KR C2 ed05 operating instructions for the cabinet.
Watch the scope. The -2 family was also supplied with a KR C4. If your KR 210-2 has that controller, the manipulator plan is the same but the cabinet plan is different. QUANTEC robots have their own manual with different greasing intervals and are not covered here.
What to gather before planning a KR 210-2
Many of these robots left the factory between 2005 and 2010 and are still in production, often with a lighter workload than when they were new. That is exactly where the counter misleads you: thousands of hours remain before the next change, yet the oil and grease are already past their time limit. Before deciding what is due, we collect the following:
- The current hour-counter reading of each robot.
- The date of the last oil change on each axis and of the last greasing, taken from the maintenance log or the CMMS, not from memory.
- The build date on the robot's rating plate. Whether it is before or after 08/2004 and 07/2007 changes the plan.
- The robot's actual application: press linking, highly dynamic handling, or cycles with short, repeated axis 2 movements.
- The wrist variant fitted, because some greasing tasks do not apply to every variant.
Without the date of the last change, the counter tells you nothing about the jobs that also fall due by years. If that date is missing, our rule is to treat the job as overdue.
Gear oil: 20,000 h or 5 years, no fixed quantity
The gear units on axes 1 to 6 all take the same oil, Optigear Synthetic RO 150. It is changed at 20,000 hours or 5 years, whichever comes first. The time limit is there because oil ages even when the robot runs little.
Refilling is where most mistakes happen. On a KUKA you do not drain and fill to the nominal quantity: you put back the amount you drained. And if what comes out is less than 70 % of the fill quantity, the gear unit must be flushed before refilling.
The reasoning is simple. The nominal quantity assumes an empty gear unit, and after draining it never is. Pour the nominal quantity on top of the oil left inside and the gear unit ends up overfilled, which makes life harder for the seals.
If far less comes out than expected, there are two possible explanations. Either the gear unit has been losing oil and you need to find where it went, or old oil is still trapped inside and refilling without flushing mixes it with the new. That is why we record what comes out of each axis: it tells you something about the gear unit's condition, it is not a formality. There is more background in our article on lubrication and oil changes.
Greasing and anchoring: by hours, capped at 5 years
Greasing on the manipulator runs on an hours cycle. Even so, the manual requires it at least every 5 years, whether or not the hours have been reached.
- Counterbalancing system bearings (link arm, axis 2): every 10,000 h with LGEP 2 grease. You pump until clean grease comes out, so there is no fixed quantity here either. If axis 2 makes short, repeated movements, the interval drops to 3,000 h. Check this against the cell's actual program, not the robot's purchase spec.
- O-rings on axes 4 and 5 (wrist): every 10,000 h. They are taken out of their groove, the old grease is removed and they are greased with Optigear Olit CLS. This does not apply to every wrist variant, so check which one your robot has.
- Robot anchor bolts: tightening torque check every 10,000 h. An anchor that has loosened usually shows up as vibration or lost accuracy well before it raises an alarm.
What the rating plate decides: cardan shafts and the axis 1 gearing
Two jobs on the KR 210-2 depend on the build date. In a fleet of robots from different years, two machines that look identical can need different plans.
Wrist cardan shafts
On robots built from 08/2004 onwards, the first inspection is due at 15,000 h or 6 years. On earlier robots it is due at 10,000 h or 4 years. After that, the inspection is yearly. The replacement criterion is clear: if the cardan shaft has axial play, it is replaced.
Gearing between the axis 1 motor and gear unit
This only applies to robots built before 07/2007 that work in press linking or highly dynamic handling. On those robots the gearing is inspected and regreased every 7,500 h with Microlube GL 261. It is not a small job: the axis 1 motor has to come off, and the axis has to be zero-adjusted (mastered) afterwards. Plan it as a stoppage with its own time slot rather than squeezing it into another intervention.
Yearly manipulator inspection: where we look
On top of the hour-based items, our practice is to give the manipulator one inspection a year. Among other things, we check the pneumatic circuit and wiring at the axis 1 base, the cable harness and buffers on axes 2 and 3, the wrist belts and the mechanical stops. We also test axes and brakes for abnormal play. This inspection catches what has no counter: chafing, play that is just starting, and parts that suffer more from the cell environment than from use.
KR C2 cabinet: what falls due and when
On the controller, intervals are mostly time-based.
- Accumulators (cabinet backup batteries): the manufacturer calls for replacement every 2 years, always both blocks together. We replace them every 24 months, in line with KUKA. Spares stored at 20 °C or below must be recharged every 9 months. An accumulator that has sat on the shelf for years without recharging is not a reliable spare.
- Control PC mainboard battery (CR2032): the manufacturer specifies 5 years. Our rule is shorter: we replace it every 24 months, together with the accumulators.
- Internal and external cabinet fans and control PC fan: replacement every 5 years on three-shift operation, according to the manufacturer. Fans, heat exchanger and heat sink must be cleaned at least every 2 years; we clean them at every yearly inspection.
- Cabinet pressure compensation plug: replaced on condition, when the white filter changes colour. In very dusty or dirty plants we replace it at every yearly inspection.
- System check: at every inspection we check the software version and take a backup.
With this data, the plan for a KR 210-2 stops being «the yearly service is due». It becomes a list of due dates per robot: what falls due by hours, what falls due by time, and what applies only because of its build date. That is how we approach KUKA robot maintenance and our preventive maintenance work.