Troubleshooting of KUKA KR FORTEC-2

Troubleshooting of KUKA KR FORTEC-2

KUKA KR FORTEC-2 is a six axis articulated robot designed for heavy-duty handling, machine loading and unloading, casting, and high cycle automation, covering KR 240 R3400-2、KR 240 R3700-2、KR 280 R3100-2、KR 340 R3400-2、KR 340 R3400-2 F、KR 360 R2800-2、KR 420 R3100-2、KR 420 R3100-2 F、KR 420 R3100-2 HI、KR 500 R2800-2、KR 500 R2800-2 F、KR 500 R2800-2 HI  Waiting for the model. For on-site engineers, the real challenge is not programming, but how to quickly locate the robot according to the system hierarchy and restore operation without compromising safety integrity when the robot experiences abnormal pressure in the balance system, abnormal wrist noise, worn connecting shafts, gear oil leakage, motor overheating, or safety circuit shutdown.

Product positioning and core structure

KR FORTEC-2 adopts a six axis articulated arm structure, with main components including a linear wrist, arm, connecting rod, rotating column, base, balance system, electrical installation, and connecting cables. The shaft is driven by an AC servo motor. The balance system is used to balance the A2 axis load torque, using a closed hydraulic pneumatic system consisting of three accumulators, hydraulic cylinders, hoses, and rupture discs, and belongs to the category of pressure equipment instructions. The F variant is designed for harsh environments such as casting, while the HI variant is designed for high inertia applications.

The straight wrist includes three axes: A4, A5, and A6. A6 motor is directly installed in the wrist to drive the wrist; A4 and A5 are driven by the rear of the arm through a connecting shaft. The arm is connected to a straight wrist and a connecting rod, with A4 and A5 motors installed internally, and A3 motor driving the arm. The connecting rod is located between the arm and the rotating column. Install A1 and A2 motors inside the rotating column and support the connecting rod. The base is connected to the installation base, and the internal layout includes electrical installation and interface A1. The electrical installation includes cable groups, RDC boxes, and connectors, with interface A1 located at the rear of the base.

Technical data and load foundation

KR 240 R3400-2 has a rated load of 240 kg, a maximum load of 310 kg, a maximum arm span of 3400 mm, a body weight of approximately 1597 kg, a workspace of approximately 111.8 m ³, a repeatability accuracy of ± 0.08 mm, a protection level of IP65, wrist IP65/IP67, and controller KR C5 L6/L7. KR 240 R3700-2 has a rated load of 240 kg, maximum load of 300 kg, arm span of 3750 mm, and weight of approximately 1620 kg. KR 280 R3100-2 has a rated load of 280 kg, maximum load of 360 kg, arm span of 3100 mm, and weight of approximately 1687 kg. KR 340 R3400-2 has a rated load of 340 kg, maximum load of 426 kg, arm span of 3400 mm, and weight of approximately 1728 kg. KR 360 R2800-2 has a rated load of 360 kg, maximum load of 474 kg, arm span of 2800 mm, and weight of approximately 1660 kg. KR 420 R3100-2 has a rated load of 420 kg, maximum load of 527 kg, arm span of 3100 mm, and weight of approximately 1704 kg. KR 500 R2800-2 has a rated load of 500 kg, maximum load of 611 kg, and arm span of 2800 mm. The weight is approximately 1671 kg.

Axis motion range: A1 ± 185 °, A2-130 °/5 °, A3-110 °/162 °, A4 ± 350 °, A5 ± 120 ° or ± 122.5 °, A6 ± 350 °. The speed varies according to the model, A1 is about 100-103 °/s, A2 is about 80-97 °/s, A3 is about 90-104 °/s, A4 is about 80-120 °/s, A5 is about 90-125 °/s, A6 is about 140-210 °/s. The flange standard is ISO 9409-1, IW 300-2 hole circle 160 mm, M10, IW 500 hole circle 200 mm, M12. The foundation load varies depending on the model, for example, KR 240 R3400-2 has a normal vertical force of 28500 N, with a maximum of 34500 N; a normal horizontal force of 11000 N, with a maximum of 23500 N; a normal tilting moment of 45000 Nm, with a maximum of 68500 Nm; and a normal moment around A1 of 15000 Nm, with a maximum of 28500 Nm. The foundation must withstand these loads for a long time. The supplementary loads on A1 and A2 are not included in the calculation of foundation loads and must be taken into account as vertical forces.

Installation foundation and transportation

The installation methods mainly include a 200mm mounting base, a 175mm optional base, and machine frame installation. The 200mm base weighs approximately 131 kg and consists of 4 bed plates, 16 chemical anchor bolts, 8 M24x65-8.8-A2K hex bolts, and locating pins. The 175mm base weighs approximately 306 kg and consists of a bed plate, 20 chemical anchor bolts, 8 M24x65 bolts, and locating pins. Machine frame installation weighs approximately 3.52 kg and is used for steel structures, foundations, or linear units. The concrete strength should be at least C20/25, and there should be no insulation layer or mortar layer. The diameter of the chemical anchor bolt drilling hole is 18 mm. Diamond tools or coring drills must not be used, and setting tools approved by the anchor bolt manufacturer must be used. The installation surface must be flat, and the leveling material must not cover the fastening bolt area.

When installing the robot, first clean the foundation, install the positioning pin, lift the robot with a forklift, install the bed board, tighten the M24 bolts in diagonal order, check the flatness of the foundation, fill in leveling materials if necessary, drill anchor bolt holes, and cure. When connecting the cable, use an M8 nut with a torque of 23 Nm for the grounding conductor; connect the data cable XF31 to ensure that the lock is closed; Connect motor cables XD30.1 and XD30.4; Check the equipotential. The transportation positions are A1 0 °, A2-130 °, A3 130 °, A4 0 °, A5 90 °, A6 0 °. When transporting by forklift, each of the four fork slots is fixed with 3 M16x50-8.8-A2K Allen screws, and the minimum load of the forklift is 2.5 t. During lifting, 3 M20 eyebolts are used, and the ropes are arranged according to the diagram. The transport protection strap should be located on the transport protection device and gearbox A2, and should not be placed on the motor or other components. The standard length of the connecting cable is 7-50 meters, with a maximum of 50 meters and a maximum of one extension. The bending radius for the fixed laying of motor cables shall not be less than 150 mm, and for data cables shall not be less than 60 mm. Motor cables and data cables shall be laid separately, and EMC measures shall be taken if necessary.

Safety and Debugging Inspection

The danger zone consists of a workspace and a stopping distance. Mechanical end stop is used to protect the machine, and personnel protection can be selected through the Safe Robot function or mechanical axis limitation. Before debugging, it is necessary to check the safety functions, including emergency stop, enable switch, mode selection, safety door, external safety stop, and safety output. T1 is in manual deceleration mode, with a speed not exceeding 250 mm/s; T2 is manual high-speed mode; AUT is in automatic mode; AUT External is in automatic external mode. New or modified programs must be tested under T1 first.

Five safety rules must be followed during maintenance and repair: power off, prevent accidental restart, confirm that the system is out of power, ground and short-circuit, cover or isolate adjacent live parts. After the controller is turned off, some components may still have a voltage of 50 V to 780 V for several minutes. The robot system must be disconnected from the main power supply and cannot rely solely on emergency stop or safe stop. Hot surfaces, oil pressure, nitrogen pressure, and extrusion risks should all be prevented. The motor and brake will generate electromagnetic fields, and personnel wearing implants should maintain a distance of 300 mm from the motor and brake. Unauthorized modifications may render warranty and liability invalid. Before starting, the default password must be changed, and the robot installation, fastening, cable connection, grounding conductor, and equipotential must be checked. If there is a significant difference between the internal temperature of the controller and the ambient temperature, it is necessary to wait for temperature equilibrium to prevent condensation. Functional testing must confirm the correct installation of the robot, no external damage, no debris, complete safety equipment, matching power supply, reliable grounding and equipotential, and locked connection cables. External force damage such as collision may cause invisible damage, and the motor and balance system must be checked. The safety function must be tested, and the braking test must be performed regularly. The system will force it and cannot be turned off. The balancing system belongs to pressure equipment and must be operated by qualified personnel. Before maintenance, the supported components must be fixed and depressurized.

Maintenance cycle and oil management

The maintenance cycle for standard and HI variants is 100 hours to check the torque of fastening bolts and nuts. 5000 hours or up to 1 year, lubricate the balance system bearings, rotating column, and connecting rod with one lubrication point each, using LGEP 2, with each lubrication point approximately 10 cm ³; If A2 frequently short trips less than 40 °, the interval should be shortened to 3000 hours. After 5000 hours or 1 year, check the pressure, leakage, and appearance of the balance system. Replace gear oil after 20000 hours or 5 years: A3 is 2.60 L, A4 IW300-2 is 2.10 L, IW500 is 3.00 L, A5/A6 IW300-2 is 1.90 L, IW500's A5 is 1.50 L, A6 is 1.30 L, A2 is 3.60 L, A1 is 6.40 L, and the oil is Optigear Synt. ALR 150. Lubricate the A1 cable assembly for 20000 hours or 5 years, using Optitemp RB2 for approximately 50 g. Replace the balance system in 10 years. F variant has a shorter maintenance cycle: 100 hours for checking and tightening; Inspect the gearbox and structural components for sedimentation, damage, and corrosion after 2500 hours or 6 months; 2500 hours or 1 year lubrication balance system bearings; Check the balance system pressure after 2500 hours or 6 months; Change oil after 10000 hours or 5 years; 10000 hours or 5-year lubrication cable set; Replace the balance system in 10 years. If the oil temperature exceeds 60 ° C, the maintenance interval must be shortened and KUKA Service consulted.

Oil drainage and filling must be carried out at operating temperature, with pressure relief first. When draining A1 oil, use M22x1.5 magnetic plug to exhaust, remove the sealing cover of the service valve, connect M26x1.5 oil pipe, drain the oil and measure. Fill from below until the lower edge of the inspection hole, with a torque of 25 Nm for M22 plug and 45 Nm for service valve. A2 and A3 are similar. A4 uses upper and lower M18x1.5 screw plugs, and after draining the oil, adds oil with a torque of 20 Nm. A5/A6 share the oil chamber in IW300-2 and need to be added separately: A4 drains oil at+90 °, drains the lower part at 0 °, adds oil at -90 °, A5 adds about one-third, A6 adds excess, and M18 screw plug torque is 20 Nm. In IW500, A5 and A6 are independent oil chambers, drain oil at+90 °, drain the rear part at 0 °/-85 °, add oil at -90 °, and add oil separately. M18 screw plug torque is 20 Nm. If the amount of discharged oil is less than 70% of the specified amount, it needs to be flushed with discharged oil once; Less than 50%, rinse twice and move the entire axis range at a jog speed during the rinsing process.

Balance system inspection and replacement

When checking, manually move A2 to -90 ° and wait for 1 minute. Prepare pressure gauge: Install adapter and sensor, connect CH1, press F4 to turn on the machine. Measure the temperature of the component with a digital thermometer, which should be 20 ° C. Remove the M16x2 protective cover, connect the sensor, wait for 3 minutes, and read the minimum pressure of 152.6 bar (20 ° C). If the value is lower than this or there is a deviation in the application, the balance system must be replaced. Clean the valve, reinstall the protective cover, and check for accessory leaks and bellows.

When replacing, the robot should be in the mechanical zero position, A2 should be movable, and fixed on the ground. The weight of the balance system is about 40 kg. Use two ropes to suspend the connecting rod, loosen the worm clamp, push the bellows, move the connecting rod to the appropriate position, insert the clamping sleeve, and clamp the piston rod. Hang the balance system with ropes, remove 4 M8x20-10.9 Allen screws and retaining plates, remove the plug, insert the pin locator, use an M16 pin puller to pull out the pin by about 25 mm, and remove the balance system. Remove anti-corrosion before installing the new pressure filling balance system, move the connecting rod to about -90 °, insert the connecting rod, install it on the rotating column pin, apply Drei Bond 1342, M12x30-10.9 and M8x20-10.9 and tighten with torque, apply LGEP 2 to the thrust ring, insert the pin, install the retaining plate, M8x20 screw and sealing plug. After replacement, the pressure must be checked and a functional test must be conducted.

Motor and linear wrist replacement

A1 motor replacement: Remove XDM1 and XG1 connectors, remove 4 M12x25-8.8 Allen screws, install Load Lifting Attachment, torque 15 Nm for M8x20 screws, lift the motor and remove. The F variant requires replacement of the seal. Remove the spacer ring. Clean the teeth of the new motor, apply Microlube GL 261, install 30x5 O-ring, and install a new seal for the F variant. Insert the motor, tighten 4 M12x25-8.8 in diagonal order, connect the plug, and perform mastering. A2 motor replacement is similar. First, fix the connecting rod, remove XDM2 and XG2, hang the motor, remove 4 M12x25-8.8, take them out, install a new motor, and connect them, mastering。 A3 motor replacement is similar, requiring a fixed arm. A4/A5 motor replacement: Remove XDM4, XG4 or XDM5, XG5, remove 4 M8x25-8.8 (IW300-2) or M10x25-8.8 (IW500), take out the motor and connecting shaft, remove the connecting shaft and sine spring. Replace the seal with the F variant. Remove the bushings M8x30-8.8 and 17x3 O-rings. Clean the new motor, install the bushing and 17x3 O-ring, use the centering bushing, tighten M8x30, install 21x2 O-ring, and install a new seal for the F variant. Insert the connecting shaft, install the sine spring, insert the motor, tighten the 4 screws in diagonal order, and connect, mastering。 The replacement of A6 motor is more complex, requiring the disassembly of A4/A5, connecting plate, and linear arm before disassembling A6. The installation should be carried out in reverse. Linear wrist replacement: Remove A4/A5, remove the connecting plate, remove 20 or 24 M10x200-10.9, take out the linear wrist, remove A6, prepare a new linear wrist, clean the teeth, apply Microlube GL 261, install, tighten M10x200-10.9 with torque, install the connecting plate, connect the cable, install A4/A5, master. The replacement of connecting shafts must be carried out in pairs. Remove the motor and connecting shaft, replace the O-ring, and install a new connecting shaft. KR 240 R3700-2 still needs to replace the adapter connecting shaft.

Common troubleshooting ideas

Unexpected shutdown or safety stop: Check the emergency stop, enable switch, safety door, mode selection, external safety stop, safety configuration, and brake status.

Low or fluctuating pressure in the balancing system: Check the pressure gauge, accumulator, hoses, fittings, and leaks. The minimum pressure is 152.6 bar (20 ° C), and if it is lower than this value, it should be replaced.

A2 abnormal noise, sinking or vibration: Check the balance system bearings, pressure, mechanical limit and connecting rod fixation.

Wrist abnormal noise or positioning drift: Check the connecting shaft teeth, straight wrist teeth, bearings, and lubrication status; If worn or discolored, replace the connecting shaft or straight wrist.

Gear oil leakage: Check the magnetic plug, oil pipe, service valve, O-ring, and gearbox seal, and tighten according to torque.

Motor overheating: Check the load, duty cycle, ambient temperature, cooling, brake holding, and motor current to confirm that the load data has been input into the controller.

Cable wear or interference: Check the cable group, bending radius, shielding, separate laying, and A1 cable group lubrication.

Zero point loss: Mastering A1 to A6 again.

Abnormal braking: Conduct a braking test to check the parameters of the brake, motor, and controller.

Automatic mode cannot start: check safety door, operate safety signal, external emergency stop, confirm button, and mode selection.

Abnormal noise after replacing the straight wrist: Check if the teeth are damaged, M10x200 torque, A4/A5 are in zero position, and if the mastering is correct.

After replacing the balance system, the pressure is unstable: check the hydraulic oil filling amount, accumulator pre charge pressure, exhaust and leakage.

Abnormal noise after replacing the connecting shaft: Check for damage to the sine spring, O-ring, teeth, and torque.

F variant seal leakage: Replace the seal, use Drei Bond 5204HV, and pay attention to the bonding of the connecting plate.

Insufficient lubrication of cable assembly: Use Optitemp RB2 for approximately 50g at a 20000 hour or 5-year cycle, and move A1 to evenly distribute the grease.

Key points of standards and compliance

KR FORTEC-2 involves the Machinery Directive 2006/42/EC, EMC Directive 2014/30/EU, Pressure Equipment Directive 2014/68/EU, and EN 60204-1、EN ISO 10218-1、EN ISO 12100、EN ISO 13849-1/-2、EN ISO 13850、NFPA 79、UL 1740  Waiting for standards. The F variant has higher dust, lubricant, coolant, and water vapor resistance, while the HI variant is designed for high inertia applications. Industrial robots must be integrated into a complete system and undergo compliance assessment before they can operate. The balance system contains nitrogen and hydraulic oil, and must be depressurized before disposal. Only pressure free balance systems are allowed to be scrapped.

Overall, the reliability of KUKA KR FORTEC-2 depends on the installation foundation, balance system, gear oil, connecting shaft, motor, and safety circuit. Regularly checking pressure, oil level, teeth, clearance, and torque can detect abnormalities in the early stages of faults. When encountering abnormal pressure, abnormal noise, leakage or shutdown, first lock it safely, and then investigate according to the levels of power supply, safety circuit, balance system, connecting shaft, gear oil and motor. This can reduce unplanned downtime and maintain stable operation of heavy-duty robots under harsh working conditions.