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.

A4/A5: Disassemble 4 M5x14-A4-80 pieces; Pay attention to the connecting shaft and compression spring; If there is a back up ring on the old motor shaft, it must be discarded and cannot be reused; Apply Microlube GL 261 to the connecting shaft teeth; After installation, the connecting shaft should have a slight axial clearance.

A6: A4, A5, and inline writer need to be disassembled first; The inline hoist weighs approximately 23 kg and must be reliably lifted; Remove 4 M3x12-10.9 pieces; Apply Microlube GL 261 to the teeth.

After replacing the motor, it is necessary to perform Mastering on the corresponding shaft and test the program in T1 mode. After replacing A4/A5/A6, it is usually necessary to master A4, A5, and A6 simultaneously.

Common Fault 3: Gear Oil Leakage and Oil Change Specification

Performance: There are oil stains near A1, A2, A3, A4, A5/A6, and the temperature is high during operation.

Reason: seal aging, screw plug not tightened according to torque, incorrect oil quantity, installation angle leading to incomplete oil discharge.

Solution: Replace the gear oil according to the shaft. The recommended oil is Cassida Fluid GL150. First filling amount: A1 is about 1.20 L, A2 is about 0.80 L, A3 is about 0.32 L, A4 is about 0.32 L, A5/A6 is about 0.37 L. The replacement cycle is according to the maintenance table, usually 2000 hours (based on KUKA Xpert). Oil discharge must be carried out at operating temperature and the discharge volume measured. If the discharge volume is less than 70% of the specified amount, it should be rinsed once; If it is less than 50%, rinse twice. The filling amount shall be based on the actual discharge amount. Be aware that the oil chamber may be under pressure, and release the pressure before opening the drain plug. The torque of M18x1.5 magnetic plug is about 20 Nm, M10x1 plug is about 7.5 Nm, and A1 union nut is about 45 Nm. After changing the oil, check for leaks and observe abnormalities during T1 operation.

Common Fault 4: Cable group wear and A1 lubrication

The A1 cable group moves with axis 1 inside the base, and long-term operation may result in hose wear and dust accumulation. The document requires regular inspection and lubrication of cable group A1. Before operation, remove the base cover: remove 2 M4 hex nuts and 5 M5x10-10.9 round head screws, and remove the cover and brush strip. Apply PETAMO GHY 133 N grease to the outer surface of the hose, the contact surface with the base, and the inner side of the cover with a brush, approximately 0.3 kg. If damage is found to the hose, the cable assembly must be replaced. After reassembly, wipe off excess grease and move A1 to evenly distribute the grease. For cleanroom applications, excessive lubricating grease may adsorb particles, so it is necessary to control the amount and clean the overflow.

Common fault five: Zero point loss and Mastering

Performance: teaching point offset, program unable to reproduce, abnormal axis angle display.

Reason: Replacement of motor, manual release of brake, loss of encoder data, collision.

Solution: Prioritize using EMD or a dial gauge for standard Mastering. Mastering positions for KR 20 R1810 CR: A1 27 °, A2 90 °, A3 90 °, A4 0 °, A5 0 °, A6 0 °. After replacing the motor, checking the involute teeth, and replacing the connecting shaft, the Mastering must be redone. If the release device is used to manually move the motor, the shaft will lose its zero point and must be re Mastered. The accuracy of emergency Mastering is relatively low, and standard methods should be used to recalibrate as soon as possible afterwards.

Common Fault 6: Connector, Grounding, and Cable Layout

Performance: The controller reports motor/data line faults, intermittent shutdowns, and abnormal shielding.

Solution: Check the motor cables, data cables, and grounding conductors. KR C4 uses X20-X30, X21-X31; KR C5 uses XD20.1... XD20.6-XD30, XD10.1/XD10.2-XD30, XF21-XF31. The cross-sectional area of the grounding conductor is 16 mm ², and the torque of the M8 nut is about 23 Nm. When the cable bending radius is fixed and laid, the motor cable should not be less than 150 mm, and the data cable should not be less than 60 mm. The maximum length is 50 m, and it can be extended up to once. The cable shall not bear tensile force and shall be laid separately from the power line. For cleanroom robots, cable layout should also avoid generating particles, and zip ties or accessories should not be installed arbitrarily.

Installation, transportation, and foundation load

Transportation location: A1 0 °, A2-138 °, A3 139 °, A4 0 °, A5 90 °, A6 0 °. Use slings or forklifts, unauthorized lifting is prohibited. Install base S31 weighing approximately 25.4 kg, using 4 M20x55-8.8 bolts and 6 chemical anchor bolts; Machine frame installation 0000-268-113 weighs approximately 1.05 kg and uses 4 M20x55-8.8 bolts. Tighten the base bolts again after 100 hours. Basic load: floor Fv normal 4038 N、max 4443 N，Fh 2336/2988 N，Mk 3334/4177 Nm，Mr 1965/2361 Nm； Ceiling Fv 4104/4535 N, Fh 2272/2793 N, Mk 3642/4553 Nm, Mr 2017/2314 Nm; Wall Fv 4265/4661 N, Fh 1464/2268 N, Mk 4603/5124 Nm, Mr 1739/2368 Nm. Flange load: operating at F (a) 970 N, F (r) 960 N, M (k) 249 Nm, M (g) 107 Nm; Emergency stop F (a) 1115 N, F (r) 1280 N, M (k) 326 Nm, M (g) 164 Nm. The tool must be able to withstand these loads.

Maintenance Plan and Troubleshooting Checklist

Maintain the core nodes of the table:

100 hours: Check the torque of the fixing bolts on the installation base.

2000 hours: Check A1-A6 involute teeth and grease them; Replace A1, A2, A3, A4, A5/A6 gear oil.

Lubricate cable group A1 according to the document requirements.

Check the stopping distance every year.

Troubleshooting checklist:

Emergency stop, power off, padlock, and power check first.

Check the alarm: motor, brake RDC、 Data cables and safety circuits.

Mechanical inspection: oil level, oil leakage, involute teeth, O-ring, connecting shaft, cable assembly.

Check parameters: load, center of gravity, inertia, installation angle, program magnification.

After replacement: Mastering, T1 testing, stop distance retest.

Record: Fault time, frequency, axle number, temperature, load, maintenance content.

The reliability of KUKA KR CYBERTECH CR is based on standardized maintenance. By controlling the stopping distance, involute teeth, gear oil, cable assembly, zero point calibration, and base bolts, most on-site faults can be detected in advance. For engineers, the true idea of "replacing discontinued modules" is not to wait until they break before replacing them, but to use verifiable parameters and standard steps to turn every maintenance into a traceable quality record.