KUKA KR 700 PA maintenance troubleshooting

Practical Maintenance and Troubleshooting of KUKA KR 700 PA Stacking Robot

KUKA KR 700 PA is a 4-axis industrial robot designed for heavy-duty palletizing, handling, and workpiece transportation scenarios. It has a rated load of 700 kg, a maximum total load of 750 kg, a working range of 3320 mm, a repeatability of ± 0.08 mm, a total weight of approximately 2850 kg, a protection level of IP65, and a noise level of less than 72 dB (A). For engineers in the "search for solutions" stage, the real factors that affect equipment availability are often not basic parameters, but installation, maintenance, oil change, motor replacement, balance weight inspection, and electrical connection failures. This article focuses on KR 700 PA and KR 700 PA arc, and outlines a practical maintenance and troubleshooting approach.

Check the core parameters first to avoid exceeding the limit of operation

The KR 700 PA adopts a 4-axis parallelogram motion system, with main axes A1, A2, A3, and A6. The axis motion range is limited by software: A1 is ± 185 °, A2 is+10 ° to -120 °, A3 is+150 ° to -10 °, and A6 is ± 350 °. In terms of speed, A1 and A2 are about 76 °/s, A3 is about 67 °/s, and A6 can reach 168 °/s. The workspace volume is about 73 m ³, and the reference point is the intersection point between A6 and the connecting flange plane.

The load capacity must be checked against two values simultaneously: load mass and mass moment of inertia. The rated load on the wrist is 700 kg, the distance between the center of gravity of the load Lz is 300 mm, Lxy is 350 mm, and the allowable moment of inertia is 350 kgm ². The small arm allows an additional load of 50 kg, while the large arm and turntable have an additional load of 0 kg. The connecting flange is similar to DIN/ISO 9409-1-A200, using M12 bolts with 23 fastening threaded holes, with a minimum depth of 15 mm and a maximum depth of 19.5 mm, and a through-hole of ø 60 mm. If the center of gravity, moment of inertia, or additional load of the tool exceeds the load diagram, it will cause motor and gearbox overload, and must be negotiated with KUKA.

Environmental conditions are equally critical. The standard operating temperature is from 0 ℃ to+55 ℃, with Safe RDW operating from 0 ℃ to+50 ℃, and storage and transportation from -40 ℃ to+60 ℃. KR 700 PA arc operates at temperatures ranging from -30 ℃ to+10 ℃ and is suitable for low-temperature environments. Humidity requirements shall comply with DIN EN 60721-3-3, 3K3 level. If operating under conditions such as temperature limits, corrosive environments, high speeds, frequent short stroke movements, or long-term vertical rest of the wrist axis, the maintenance cycle should be shortened.

Safe shutdown and hazardous area control

The hazardous areas of KR 700 PA include the working area, the stopping stroke of the robotic arm, and the stopping stroke of the additional shaft. The stopping stroke is equal to the reaction stroke plus the braking stroke. This model defines STOP0, STOP1, and STOP2: STOP0 is used to immediately turn off the drive and brake, while the robotic arm guides the brake along the path; STOP1 is braking along the trajectory, T1 mode robot stops or shuts off the drive at the latest 680 ms, T2/AUT mode shuts off after 1.5 seconds; STOP2 means that the drive does not turn off, the brake does not brake, and the slope brake is applied according to the trajectory.

In manual operation, T1 is for slow testing ≤ 250 mm/s, and T2 is for fast testing>250 mm/s. After debugging a new program or changing a program, it must be tested under T1 first. If it is necessary to debug within the protective isolation area, the operator should choose a location where the hazardous area can be observed. The personnel should maintain a reference distance of at least 50 cm from the robotic arm and tools, and the actual distance should be determined by risk assessment.

The power-off operation must be carried out by turning off the main switch and preventing restart. Even if the controller is turned off, some components may still be charged up to 780 V and last for several minutes. Before starting the homework, it is necessary to confirm the power outage, notify relevant personnel, and hang signs. The controller with a transformer needs to turn off the transformer first. Follow ESD regulations when operating components. Active implant personnel must maintain a distance of at least 300 mm from the motor, applicable in both powered and powered off states. High temperature motors pose a risk of burns, and protective gloves must be worn. KCP or smartPAD must be clearly assigned to the corresponding robot, and disconnected smartPAD/KCP should be immediately removed from the system.

Installation, transportation, and re-entry into operation

Ground installation can use 175mm or 200mm foundation fixing devices, or rack fixing devices. The recommended concrete strength is C20/25. The foundation surface should be smooth and flat, and there should be no insulation or mortar layer between the foundation slab and the concrete. If the bottom plate is not completely flat, it can be filled with filling mortar, but there should be no filling mortar under the fixing bolts. The horizontal deviation should be less than 3 °. Robot installation typically uses 8 M24x70-8.8 hex bolts and disc washers, which are tightened diagonally in stages to 640 Nm. After 100 hours of operation, they must be tightened again.

Before transportation, the robot must be placed in the transportation position: A1 45 °, A2-120 °, A3 150 °, A6 0 °. If the minimum transportation height is required, the A2 buffer can be removed, with A2 at -130 °. The A2 buffer must be reinstalled after transportation and before being put into operation. When transporting with a forklift, the turntable needs to be equipped with a forklift socket, and the forklift load capacity should be greater than 3500 kg. The weight of the transport frame is 212 kg, including the transport frame but without additional equipment, about 3062 kg. The transport lifting equipment should be hung at three positions: the turntable perforation, the upper arm perforation, and the rear ring head bolt of the turntable. Avoid vibration and collision during transportation, otherwise it may cause subtle damage, especially to the motor and balance weight.

Before resuming operation, check if the robot is properly secured; Is there any external damage, dents, or paint abrasion; Whether the motor and balance weight are damaged; Are there any foreign objects or loose parts; Whether the protective device is intact; Whether the power supply voltage matches the grid system; Whether the grounding wire and potential balance wire are connected correctly; Is the cable plug locked. The length of the connecting cable can be selected as 15 m, 25 m, 35 m, or 50 m, with a maximum of 50 m and a maximum extension of 1 time. When fixed laying, the bending radius of the motor cable shall not be less than 150 mm, and the data cable shall not be less than 60 mm. If it exceeds 25 m, an additional grounding wire is required, and an optional grounding wire is always required on KR C4.

Maintenance cycle and practical operation of lubrication and oil change

The KR 700 PA maintenance schedule is mainly based on 100 hours, 2500 hours, 5000 hours, 20000 hours, and 10 years. After 100 hours of operation, check the bolts and tighten them to a torque of 640 Nm. After 2500 hours or at the latest 6 months, lubricate the A3 bearings and lubricate the 4 oil nozzles at a 30 ° offset position for a total of 12 times, each time with 1.5 cm ³, using LGEP 2 grease for a total of 18 cm ³. Lubricate multiple points for 5000 hours, with approximately 10 cm ³ LGEP 2 per lubrication. Replace A1, A2, A3, A6 gearbox oil after 20000 hours or at the latest 5 years, using Optigear Synt.ALR 150. First filling amount: A1 is about 13.00 L, A2 is about 11.00 L, A3 is about 8.20 L, A6 is about 1.70 L. Replace the balance weight in 10 years and conduct internal inspection of the pressure vessel according to regulations.

When changing oil, the amount of oil discharged depends on the discharge time and oil temperature. The re added amount should be the actual discharge amount. If the discharge volume is less than 70% of the specified oil volume, the gearbox should be flushed; If it is less than 50%, it needs to be rinsed again. Move the shaft at manual speed throughout the entire shaft range during flushing. The tightening torque of A1 magnetic plug is 25 Nm; A2 and A3 are both 25 Nm; A6 lower magnetic plug is 25 Nm, and upper magnetic plug is 10 Nm. If the oil temperature exceeds 60 ℃ during operation, the maintenance cycle should be shortened. Before all maintenance operations, if tools or auxiliary devices hinder operation, they should be removed first.

Motor replacement and zero calibration

Motor replacement is a high-frequency operation in KR 700 PA maintenance. A1, A2, and A3 motors typically use four M12x30-8.8 hexagon socket bolts, which are tightened diagonally in stages to 78 Nm. A6 motor uses four M10x25-8.8 hexagon socket bolts, which are also tightened to 78 Nm. Before disassembly, the corresponding shaft must be locked: A1 prevents rotation around shaft 1, A2 uses a sling to fix the upper arm, A3 needs to fix the lower arm, and A6 needs to ensure that the tool has been removed or locked. During disassembly and assembly, it is not allowed to tilt to avoid crushing injuries, and protective gloves must be worn.

Before installing a new motor, clean the motor and gearbox of rodents and apply a small amount of Microlube GL261, but apply it completely. Check the O-ring of the motor shaft. The connection plugs XM1/XP1, XM2/XP2, XM3/XP3, XM6/XP6 must be arranged according to the diagram. After installation, the corresponding axis zero point must be calibrated. If the robot axis has been moved using a free rotating device or an electric screwdriver with torque support, all axes must be recalibrated for zero point.

The free rotation device is only allowed for emergency situations, such as rescuing trapped individuals. After use, the corresponding motor must be replaced as the motor brake may be damaged. When moving a robotic arm without driving energy, it should not be used as a routine operation.

Balance weight inspection and replacement

The KR 700 PA adopts a hydraulic pneumatic balance weight to reduce the torque around shaft 2. The system includes a diaphragm accumulator, hydraulic cylinder, pressure gauge, and safety valve, with the accumulator filled with nitrogen gas. The balance weight is approximately 95 kg and is under pressure. During inspection, the boom should be in the -90 ° position and the hydraulic oil pressure should be 138 bar; At the -45 ° position, the pressure should be 151 bar. At 20 ℃, a deviation of ± 15 bar is allowed. If the values do not match, a dedicated pressure measuring instrument should be used to measure and negotiate with KUKA.

Check whether the lead seal of the safety valve is intact, whether the accessories are damaged, clean and sealed, and whether the leather bowl is damaged or dirty. Pressure vessels should undergo internal inspection in accordance with national regulations after 10 years of use of balance weights. Before disassembling the balance weight, it is necessary to lock the piston rod with a clamping sleeve, fix the boom and balance weight with a sling, and remove the pin and cover plate after unloading. Use anti loosening agent Drei Bond 1342 during installation and replace with new bolts. If the balance weight of the robot may form a pressure pad after storage, a safe distance should be maintained when removing the exhaust valve cover, and A2 should be moved ± 30 ° before reinstalling the cover.

Electrical connections and common troubleshooting

KR C2 electrical equipment consists of cable kits, junction boxes, and RDC boxes; KR C4 consists of cable kit, multifunctional junction box MFG, and RDC box. The motor cable is usually X30, the data cable is X31, and the control cabinet side corresponds to X8, X21, etc. The total cable cross-section of the grounding protection system is 10 mm ². Common faults include: loose plug, poor shielding, excessive grounding resistance, RDC box failure, abnormal motor temperature, brake wear, zero point loss, gearbox oil leakage, abnormal balance weight pressure, and increased stopping stroke.

If the robot experiences unexpected movement or sinking, it should immediately stop running and check the brakes, balance weights, overload, and collision damage. If the robotic arm or additional shaft collides with obstacles, mechanical end stops, or shaft limiting devices, it must stop running and contact KUKA. External forces may cause subtle damage, such as slow loss of motor power transmission, and the motor and balance weight must be carefully inspected. It is recommended to check the itinerary once a year. STOP0 reference values: A1 has a stopping stroke of approximately 87.12 ° and a stopping time of 2.13 seconds; A2 has a stopping stroke of approximately 6.76 ° and 1.86 seconds; A3 has a stopping stroke of approximately 77.61 ° and 1.43 seconds. Actual values may vary depending on brake wear, load, and speed.

Stop operation, storage, and disposal of waste

Before stopping operation, move the robot to the transport position, remove tools and accessories, loosen peripheral device interfaces, motor cables, and data cables, remove grounding wires, and use transport lifting equipment or forklifts. The storage location should be dry, dust-free, avoid temperature fluctuations, wind blowing, ventilation, and condensation, and avoid direct sunlight. Clean and dry the robot, remove rust spots, seal electrical interfaces and hose joints, cover with film and seal on the base, and add desiccant if necessary.

When disposing of waste, materials are classified as cast iron parts, copper cables, light metal castings, steel gearboxes and bolts, motors, electrical components, plastic parts, etc. Hydraulic and pneumatic balance weights must be professionally depressurized in advance and are only allowed to be disposed of in a non pressurized state. Gear oil, hydraulic oil, lubricating grease, and adhesives should be handled in accordance with the manufacturer's safety data page requirements.

For heavy-duty palletizing robots like KR 700 PA, the key to stable operation lies in not exceeding the limit, not disassembling randomly, maintaining regularly, adding oil according to the discharge amount, calibrating the zero point after motor replacement, regularly checking the balance weight pressure, and ensuring reliable electrical plugs and grounding. As long as these basic tasks are done solidly, most faults can be detected early and unplanned downtime can be reduced.