KUKA KR 20 R1820-2 E Maintenance Troubleshooting and Replacement Practice

KUKA KR 20 R1820-2 E Maintenance Troubleshooting and Replacement Practice

At industrial robot sites, the faults of KUKA KR 20 R1820-2 E are often not a single electrical issue, but the result of the combined effects of mechanical wear, lubrication status, load parameters, brake performance, and zero calibration. This model belongs to a six axis articulated arm robot, with a rated load of 20 kg, a maximum load of 23.9 kg, a maximum arm span of 1820 mm, a repeat positioning accuracy of about ± 0.04 mm, a body weight of about 240 kg, a protection level of IP54, and an IP67 wrist part. It is usually used with KR C5 S6/S7 controllers. It can be installed on the ground, ceiling, walls, and at any angle, with a workspace of approximately 23.24 m ³. For engineers, what is truly valuable is not remembering parameters, but establishing a maintenance logic of "safety first, diagnosis later, replacement later, and final calibration".

Before troubleshooting, check the safety and shutdown distance first

The danger zone of KR 20 R1820-2 E 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 45.00 °, A2 stops at a distance of about 24.73 °, and A3 stops at a distance of about 9.06 °; The corresponding stop times are approximately 0.41 s, 0.29 s, and 0.12 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.

Common faults and troubleshooting ideas

Increased stopping distance or abnormal braking

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.

Gearbox oil leakage or abnormal oil level

Performance: There are oil stains near A1, A2, A3, and A4, metal shavings are attached to the magnetic plug, 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 Optigear Synt. ALR 150. First filling amount: A1 is about 0.77 L, A2 is about 0.70 L, A3 is about 0.25 L, A4 is about 0.05 L. Oil discharge must be carried out at operating temperature and the discharge amount must be 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. The torque of M18x1.5 magnetic plug is about 20 Nm, M10x1 is about 7.5 Nm, and A4 Rc1/8 plug is about 3.3 Nm. Check the seal and replace it if it is damaged.

A5 toothed belt slipping, noise or positioning error

Performance: A5 movement has abnormal noise, increased reverse clearance, and frequency deviation.

Reason: Aging of the toothed belt, insufficient tension, poor engagement of the pulley, and loose adjustment screws.

Solution: After replacing the A5 toothed belt, measure with a frequency meter. The target frequency is 130 ± 5 Hz. When adjusting, first pre tighten the right pulley, and then tighten the three M4X16-10.9 hexagon socket screws, with a final torque of about 3.8 Nm. Be careful not to remove all three screws at the same time, otherwise the A5 motor may fall off. Before reinstalling the belt side cover, check the sealing gasket and apply Drei Bond 5204HV. A4 toothed belt is also a planned replacement item, usually inspected after 5000 hours or 1 year, and if necessary, contact KUKA Service for replacement.