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.

Motor overheating, brake failure, or wear of involute teeth

Performance: High motor temperature, difficult release of brake, A1/A2 motion shaking.

Reason: Load exceeding limit, high ambient temperature, insufficient lubrication of involute teeth, aging of O-ring, improper installation of motor.

Solution: Check the involute teeth, clean and apply PETAMO GHY 133 N, thin and continuous. O-ring coated with Drei Bond 5204HV. When installing the motor, tighten the four M8x22-8.8-A2K screws diagonally and step by step to the specified torque. Before replacing A2, the connecting rod arm must be fixed with a sling to prevent the arm from falling down after disassembling the motor.

Zero point loss or Mastering abnormality

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. If there are only emergency Mastering marks on site, they can be aligned according to the marks and adjusted according to the reference angles: A1-0.8 °, A2-1.2 °, A3-1.5 °, A4-1.5 °, A5-2 °, A6-2.2 °. The accuracy of emergency methods is low, and standard methods should be used for re calibration as soon as possible afterwards. After moving the axis without driving energy, it is necessary to re master it.

Connector, cable, and grounding faults

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

Solution: Check motor cable XD30, data cable XF31, and grounding conductor. The cross-sectional area of the grounding conductor is 16 mm ², and the torque of the M8 nut is about 15 Nm. The connector must be locked, and the motor connector should have a "click" sound, and the red locking ring is not visible. When the cable bending radius is fixed for laying, the motor cable should not be less than 75 mm, the control cable should not be less than 45 mm, the maximum length is 35 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.

Planned maintenance: Block faults before they occur

The core nodes for maintaining a table are as follows:

After 100 hours: Check the torque of the anchor nuts and compression bolts.

5000 hours or 1 year: Check for visible hose damage; Replace the A5 toothed belt; Check the A4 toothed belt.

10000 hours: Lubricate the A1 cable group using Optitemp RB2 for approximately 0.3 kg.

20000 hours or 5 years: Replace A1, A2, A3, A4 gear oil; Check the involute teeth of A1 and A2 and grease them.

Before maintenance, the maintenance point must be accessible and any obstructing tools and accessories must be removed. If the oil temperature exceeds 60 ° C for a long time, the maintenance interval should be shortened and KUKA should be consulted. All accessories must use approved products, otherwise it may lead to early wear and tear.

Practical points for replacing A1/A2 motors

A1 motor replacement: power-off, locking, power verification; Remove XM1 and XP1; Remove 4 M8x22-8.8-A2K pieces; Carefully remove the motor and avoid tilting it; Cover the installation port to prevent contamination. Check the involute teeth of the new motor, clean and apply PETAMO GHY 133 N; Check the O-ring and apply Drei Bond 5204HV; Insert the motor and tighten the screws diagonally; Insert the connector back, pay attention to coding and prevent accidental insertion; Finally Mastering A1 and testing at T1.

A2 motor replacement: First, fix the connecting rod arm, such as pre tightening it with a sling and a crane, to ensure that the arm will not move after removing the motor. The remaining steps are similar to A1. After installation, Master A2 and test the program in T1 mode. If there is still shaking after replacement, check the load data, brake, gearbox, and installation surface.

Start up, transportation, and storage

During transportation, it is necessary to enter the transportation position: A1 0 °, A2-140 °, A3 140 °, A4 0 °, A5 90 °, A6 0 °. Use forklift slots or M12 lifting rings, and unauthorized lifting is prohibited. During installation, a mounting base or machine frame can be used to ensure the safe transmission of foot loads. After connecting the cable, enter the installation location in WorkVisual, which defaults to the ground. If used for walls or ceilings, the tilt angle must be entered correctly, otherwise unexpected movement or overload may occur.

Fault Handling 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, toothed belt, involute teeth, O-ring.

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 KR 20 R1820-2 E is based on standardized maintenance. By controlling the stopping distance, oil quality, frequency of the toothed belt, motor installation, and zero point calibration, 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.