KUKA KR8 R2100-2 arc HW maintenance troubleshooting

KUKA KR8 R2100-2 arc HW maintenance troubleshooting

KUKA KR 8 R2100-2 arc HW is a hollow wrist arc welding robot in the KR CYBERTECH-2 arc series. It has a rated load of 8 kg, a maximum load of 9.3 kg, a maximum arm span of 2101 mm, a repeat positioning accuracy of approximately ± 0.04 mm, a body weight of approximately 260 kg, and a workspace of approximately 36.58 m ³. It adopts a three-axis hollow wrist, and wire feeding, gas, and cable can pass through the inside of the wrist to reach the welding gun, reducing external pipeline interference. It is suitable for scenarios such as arc welding, laser welding, cutting, and handling. This model is usually equipped with a KR C4 controller, with a protection level of IP65, an IP54 wrist section, and noise levels below 65 dB (A). For on-site engineers, the real challenge is not "replacing parts", but how to determine the root cause of the fault and complete standardized maintenance within a narrow hollow wrist and compact base. Below, we will discuss several aspects including stopping distance, common faults, toothed belts, involute teeth, oil change, cable lubrication, zero point calibration, and electrical interfaces.

First, consider safety and stopping distance

The danger zone of this model is composed 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 18.78 °, A2 stops at a distance of about 17.87 °, and A3 stops at a distance of about 16.71 °; The corresponding stop times are approximately 0.19 s, 0.19 s, and 0.15 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: A5/A6 toothed belt abnormality

The hollow wrist is driven by a toothed belt inside, and the A5 and A6 toothed belts must be replaced in pairs, not just one. Common manifestations include A5 or A6 motion noise, increased reverse clearance, positioning drift, and unstable welding gun posture. The reasons are usually due to aging of the toothed belt, insufficient tension, poor meshing of the pulley, loose adjustment screws, or welding spatter or dust entering the wrist.

The replacement steps are crucial: first place the arm in a horizontal position, return the wrist axis to zero, and do not install tools on A6; Remove 6 M4x25-10.9 hex screws and tapered spring washers, and take off the wrist cover; Remove the 4 M4x12-10.9 hex screws and tapered spring washers from each motor, move the pulley, and take out two old toothed belts. When installing a new belt, it is necessary to ensure that the toothed belt is correctly engaged with the belt teeth, and cannot tilt or have any foreign objects. Tighten slightly first, then measure the frequency. The specification of the A5 toothed belt is 510 HTD-5M/500 HP, with a target frequency of 110 ± 5 Hz; the specification of the A6 toothed belt is 610 HTD-5M/860 HP, with a target frequency of 60 ± 5 Hz. When measuring, move the sensor in the middle of the toothed belt, about 5 mm away from the vibration belt, and read the frequency count value. If the frequency does not meet the standard, adjust the tension slightly and repeat the measurement until it falls within the tolerance. Finally, tighten the 4 M4x12-10.9 screws, reinstall the cover, re master A5 and A6, and conduct a trial run in T1 mode.

Common fault 2: Wear of involute teeth and motor replacement

The A1, A2, and A3 motors are connected to the input shaft of the gearbox using involute teeth. Typical fault manifestations include motion shaking, increased reverse clearance, high motor temperature, and abnormal noise. The inspection cycle is usually 20000 hours or 5 years, but if there is high load, high cycle, and frequent start stop, the cycle should be shortened. During inspection, it is necessary to remove the motor, clean the teeth, and check for wear. 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.