KUKA KR CYBERTECH CR maintenance troubleshooting

KUKA KR CYBERTECH CR maintenance troubleshooting

KUKA KR CYBERTECH CR is a high-precision six axis robot designed for cleanroom applications, with the typical model being KR 20 R1810 CR. It uses stainless steel components and screws to enhance corrosion resistance, with a rated load of 20 kg, a maximum load of 23.9 kg, a maximum arm span of 1813 mm, a repeat positioning accuracy of about ± 0.04 mm, a body weight of about 250 kg, a protection level of IP65, and is usually paired with KR C5 S6/S7 or KR C4 controllers. The cleanroom level can reach ISO Class 4 at 40% procedural magnification and Class 5 at 80% procedural magnification. For on-site engineers, the real tricky problem is often not "replacing a component", but how to determine the root cause of the fault under clean room conditions and complete the replacement, calibration, and testing according to specifications. Below, we will discuss several aspects including safe shutdown, common faults, maintenance and oil change, motor disassembly and assembly, and zero point calibration.

First, check the safety and shutdown distance

The danger zone of KR 20 R1810 CR consists of both workspace and stopping distance. The stopping distance is not a fixed value, it is affected by program magnification, load, extension distance, and brake wear. Taking STOP 0 as an example, A1 stops at a distance of about 16.27 °, A2 stops at a distance of about 17.61 °, and A3 stops at a distance of about 27.24 °; The corresponding stop times are approximately 0.23 s, 0.19 s, and 0.26 s. STOP 1 varies with program magnification and mass, and the corresponding curve needs to be checked. If it is found on site that the robot's sliding after braking has significantly increased, there is abnormal braking noise, and there is repeated positioning drift, the first reaction should not be to change the program, but to check the brake wear and stopping distance. It is recommended to retest the stopping distance at least once a year, especially under frequent triggering of STOP 0, high cycle, and high load conditions.

Strict habits must be formed for safe operation: switch T1 before entering the danger zone, press emergency stop, cut off the main switch and lock it; If it is necessary to debug in the powered on state, it can only run at low speed T1 and ensure emergency stop at any time. After the robot loses power, the power components may still be charged for a short period of time. Wait for at least 5 minutes and verify the power. The motor and brake will generate electromagnetic fields, and personnel wearing active implants such as pacemakers should maintain a distance of at least 300 mm. The surface temperature of the motor is high, and protective gloves must be worn when replacing or inspecting it. When it comes to electrical operations, strictly follow the five safety rules: power off, prevent accidental restart, confirm no power, ground short circuit, and block adjacent live parts; After the work is completed, restore in reverse order.

Common fault one: abnormal stopping distance and brake wear

Performance: Stop position deviation, increased collision risk, and abnormal braking sound in automatic mode.

Reason: Brake wear, incorrect input of load data, high program magnification, external axis stacking motion.

Processing: Verify the load data in the controller, including mass, center of gravity Lx/Ly/Lz, moment of inertia Ix/Iy/Iz, and A/B/C directions; Verify with KUKA Load; Check the brake system; Retest the stopping distance. If there is a change in load or supplementary load, it must be re inputted, not based solely on experience. For cleanroom robots, attention should also be paid to the relationship between cleanroom level and program magnification: if the working range A1 exceeds ± 170 °, it may no longer meet the cleanroom level requirements when contact stops. Therefore, stopping distance anomalies is not only a safety issue, but may also pose a risk of particle contamination.

Common Fault 2: Wear of Involute Teeth and Motor Disassembly and Assembly

The involute teeth are a critical transmission component between the motor and the input shaft of the gearbox. The document stipulates that the involute teeth of A1 to A6 need to be regularly inspected and greased. The typical cycle is 2000 hours (please refer to the latest information from KUKA Xpert). During inspection, it is necessary to remove the motor, clean the teeth, and check for wear and tear; If the teeth are damaged, the input shaft of the motor or gearbox must be replaced, and the replacement of the gearbox input shaft requires contacting KUKA Service.

Operation points:

A1: Remove 4 M8x22-8.8-A2K hex socket screws, take out the motor, be careful not to tilt it; Clean the sealing groove and sealing surface, apply Drei Bond 5204HV, and replace the sealing strip; Apply Microlube GL 261 to the teeth, thin and continuous; Check the O-ring.

A2: First, fix the connecting rod arm with a sling to prevent the arm from falling down after disassembling the motor; Remove 4 M8x22-8.8-A2K pieces; The rest are the same as A1.

A3: First, fix the robot arm with a sling; Remove 4 M8x20-A4-80 pieces; Apply Drei Bond 5204HV to the sealing surface; Apply Microlube GL 261 to the teeth.