KUKA KR C4 Midsize Fault Diagnosis

KUKA KR C4 Midsize Fault Diagnosis

KUKA KR C4 midsize and KR C4 midsize CK are control cabinets in the KUKA robot system designed for medium load, multi axis applications. It can control up to 9 axes, weighs approximately 160 kg, has a protection level of IP54, and has a cabinet size of approximately 1160 mm × 1262.5 mm × 792 mm. It is suitable for industrial robots, linear units, positioners, and motion systems that comply with DIN EN ISO 10218-1. The control cabinet adopts modular design and internal integration KUKA Power Pack、KUKA Servo Pack、Cabinet Control Unit、Safety Interface Board、Resolver Digital Converter、Controller System Panel、 Low voltage power supply, battery, fan, and main filter. For on-site engineers, mastering their fault diagnosis, LED indication, fuse specifications, and module replacement process can significantly reduce downtime and improve equipment availability.

System architecture and key components

The driving power supply for KR C4 midsize is completed by KUKA Power Pack, also known as KPP. KPP rectifies the AC power supply into an intermediate circuit voltage, which is supplied to the internal drive controller and external drive. It has four variants: shaftless amplifier version, single axis 40 A, dual axis 40 A, three-axis 20 A, and single axis 64 A. KPP has a power output of 14 kW under 400 V power supply, rated current of 25 A DC, integrated brake chopper, external brake resistor activation, brake resistor overload monitoring, and synchronous servo motor short-circuit braking. KUKA Servo Pack, also known as KSP, is a drive controller for robotic arm shafts, available in three variants: three-axis 40 A, three-axis 64 A, and three-axis 20 A, with a power range of 11 kW to 14 kW per axis, using magnetic field oriented control.

The Cabinet Control Unit (CCU) is the central power distribution and communication interface of the control cabinet, consisting of the Cabinet Interface Board and Power Management Board. CCU is responsible for safety input and output, main contactor control, mastering testing, smartPAD recognition, rapid measurement input, fan monitoring, and temperature detection. If the main power supply fails, the battery will continue to supply power to the control components until the position data is saved and the controlled shutdown is completed. The Safety Interface Board (SIB) is a component of the safety interface. The standard SIB has 5 safety inputs and 3 safety outputs, while the extended SIB has 8 safety inputs and 8 safety outputs. The Resolver Digital Converter, also known as RDC, is used to detect motor position data and can connect up to 8 rotary transformers to measure motor temperature. Controller System Panel, also known as CSP, is an operational status display component with USB, KSI, and other connections. The control cabinet is also equipped with a low-voltage power supply, a 24V external power interface, a battery, a fan, and a pressure relief plug.

Safety regulations and power-off operation

Before any maintenance or replacement work on KR C4 midsize, five safety rules must be followed: power off, prevent accidental restart, confirm that the system is out of power, ground short circuit, and cover or isolate adjacent live parts. Wait for at least 5 minutes after power failure to allow the intermediate circuit to discharge. KPP、KSP、 The motor connection and intermediate circuit cables may still carry a voltage of 50 V to 780 V, and must be confirmed with a multimeter before operation. When operating, protective gloves should be worn to avoid contact with high-temperature heat sinks, and ESD regulations should be strictly followed to prevent static electricity from damaging electronic components. The main switch of the control cabinet cannot isolate the incoming power supply. The cable connecting power supply X1 to the main switch is always live, and the upper power supply must be disconnected. If it is necessary to work while powered on, it can only be done in T1 mode and additional safety measures should be taken. The safety functions include operation mode selection, operator safety, emergency stop devices, enabling devices, external safety stops, and T1 speed monitoring, in compliance with EN ISO 13849-1 Category 3 and Performance Level d. The emergency stop device must be pressed at least once every 12 months, and the enable switch must also be checked regularly.

LED indicator diagnosis

The LED on CCU is the first-hand information for fault diagnosis. The fuse LED is red, it lights up to indicate that the fuse is damaged, and it goes out to indicate that it is normal. PWRS/3.3 V green, check F17.3 when turned off; If the PWR/3.3 V is on and the PWRS/3.3 V is off, the CCU module may need to be replaced. STAS2 and STAS1 are orange safety node indicator lights, check F17.3 when turned off; 1 Hz flashing indicates normal operation, 10 Hz flashing indicates guidance phase, and when the fault code flashes, check the X309, X310, and X312 cables. FSoE green indicates the status of EtherCAT security protocol, off indicates inactive, constant light indicates running, and flashing indicates internal fault. 27 V, PS1, PS2, and PS3 are green power indicators, corresponding to main power, short-term battery backup, medium battery backup, and long-term battery backup, respectively. L/A green indicates physical connection, flashing indicates data traffic. RUNSION and RUNCIB green indicate the status of EtherCAT nodes. PWR/3.3 V supplies power to CIB, and PWR/5 V supplies power to PMB. STA1 and STA2 are in orange microcontroller status, flashing to indicate normal or fault codes.

The LED of SIB includes L/A, PWR_3V3, RUN, STAS2, FSoE, STAS1, PWRS 3.3 V, and fuse LED. The standard SIB fuse F250 is 4 A, and the extended SIB fuse F260 is 4 A. The LED of RDC includes STA3、RUN、L/A1、L/A2、L/A3、STA4、PWR/3.3 V、FSoE、STA2、STA1、STA0。 CSP's LEDs include LED1 operation, LED2 sleep, LED3 automatic, LED4 to LED6 error. If all LEDs light up for 3 seconds after CSP is powered on, it indicates normal operation. Error states include: LED1 flashing slowly and LED4 on, indicating device or BIOS startup error, checking HDD/SSD, USB or replacing PC; LED5 on, indicating Windows or PMS startup timeout, replacing hard disk or reloading image; LED6 lights up to indicate waiting for RTS RUNNING timeout, reloading the image or running setup.

Fuses and error codes

The specifications of CCU fuses are as follows: F17.1 for contactor output 1 to 4, 5 A; F17.2 for CCU input, 2 A; F17.4 for CCU safety input, 2 A; F17.3 for CCU logic, 2 A; F306 for smartPAD power supply, 2 A; F302 for SIB power supply, 5 A; F3.2 for KPP1 logic, 7.5 A; F3.1 for KPP1 brake, 15 A; F5.2 for KPP2 logic, 7.5 A; F5.1 for KPP2 brake, 15 A; F22 for option power supply, 7.5 A; F4.1 for KPC, 10 A; F4.2 is a KPC fan, 2 A; F307 is a CSP power supply, 2 A; F21 is an RDC power supply, 2 A; F305 is battery fed, 15 A; F6 is a 24 V battery free backup US1, 7.5 A; F301 is a 24V battery free backup US2, 10A; F15 is an internal fan, 2 A; F14 is an external fan, 7.5 A; F308 is an internal power supply, 7.5 A. The same specifications must be used when replacing fuses.

In the error messages of KPP and KSP,% 1 represents the device type,% 2 represents the driver or power supply number, and% 3 represents the error code. Common errors include: 26031 internal error, reinitializing the driver bus and checking the KPP LED; 26032 IxT overload, check program load, machine, temperature, current trajectory, adjust speed; 26033 grounding fault, check the motor cable and motor; 26034 overcurrent, check the current trajectory, motor, and cable; 26035 Intermediate circuit overvoltage, check the trajectory of the intermediate circuit, main power supply, and braking resistor to reduce the braking load; 26036 intermediate circuit undervoltage, check the main power supply and intermediate circuit cables; 26037 logic power supply overvoltage, check 27 V power supply; 26038 logic power supply undervoltage, check 27 V power supply and battery; The temperature of device 26039 is too high. Check the fan inside the cabinet, ambient temperature, program load, cooling circuit, and PC fan; The temperature of the 26040 radiator is too high. Check the installation position, ventilation duct, and gap; 26041 motor phase loss, check motor cable and motor; 26042 communication error, check EtherCAT cable, stack CCU、KPP、KSP； 26045 hardware failure, reinitialize or replace the device; 26046 main power supply phase loss, check the power cord and KPP wiring; 26047 power failure, check if the power supply is below 300 V; 26048 charging overvoltage, check the main power supply voltage and module quantity; 26050 brake resistor fault, check the brake resistor and wiring; 26051 chopping overload, reducing frequent braking overload; 26130 intermediate circuit charging failed, check the intermediate circuit cable; 26132 brake fault, check the brake voltage, motor/brake, and brake cable. Warning messages are similar to error messages, but of lower severity.

Module replacement steps

When replacing the external fan, first unplug the fan connector X14, remove the rear panel, remove the fan bracket and fan, install a new fan and restore the connection. When replacing the internal fan, unplug the fan connector X962, remove the fastening screws of the fan module, install the new module and connect it. When replacing the control PC, unplug the power supply and all connections, loosen the rolling nut, and take out the PC along the guide rail; After installing a new PC, connect the network cable, start the controller, and test it. When replacing the control PC fan, it is necessary to open the PC casing, remove the fan grille, fan, and rivets, install a new fan, and restore it. When replacing HDD/SSD, disconnect the SATA and power connections, remove the knurled screws, install the new hard drive, install the operating system and KSS, and configure the system through WorkVisual. When replacing the LAN Dual NIC network card, open the PC case, unplug the connection, release the network card fixing, insert the new network card and fix it.

When replacing KPP, unplug all connections, unlock and unplug X20 and X21 data cables, loosen Allen screws, and remove KPP from the bracket; When installing the new KPP, hang it into the bracket and tighten the fastening screws with a torque of 4 Nm, then insert it back into the connection according to the label and lock X20 and X21. Replacing KSP is similar. When replacing the CCU, unlock the data cable connector, unplug all connections, remove the fixing plate, and take out the CCU; After installing the new CCU, insert it back according to the label and lock the connector. When replacing the SIB, unlock the data cable connector, unplug all connections, remove the fixing plate, install the new SIB, and insert it back according to the label. When replacing the RDC, disconnect all cables, remove the RDC box cover, unplug the EDS connection, remove the 4 TORX screws, and take out the RDC module; When installing a new RDC, thread the cable through the designated entrance and place it in the RDC box. Tighten the TORX screws in diagonal order to 2.0 Nm, connect the EDS, X15, X17, X18, X20, and rotary transformer cables X1 to X6, cover the box cover and tighten to 3.0 Nm. When replacing the battery, pay attention to the polarity, both battery blocks must be replaced at the same time, and check if the system variable $ACCU_STATE is # CHARGE.OK. When replacing the low-voltage power supply, unplug the connection, remove the rear panel, take out the power supply, install a new power supply, and restore the connection. When replacing the pressure relief plug, remove the foam ring, replace the filter element, and replace the foam ring. When replacing the main filter, remove the main switch and side panel, disconnect them, remove the grounding conductor, install a new filter, and restore it.

Maintenance cycle and inspection

The maintenance work of KR C4 midsize should be carried out on a periodic basis. At least annually, check the relay output of SIB and expand SIB, and clean the external fan protective grille. At least every 2 years, clean the heat exchanger, internal fan, KPP and KSP radiators, and low-voltage power radiator according to the degree of pollution. Replace the motherboard battery, control the PC fan, external fan, and internal fan every 5 years. The battery replacement cycle depends on the battery monitoring indication, and the pressure relief plug filter needs to be replaced when it changes color. After maintenance is completed, a visual inspection should be conducted to confirm that fuses, contactors, plugs, and boards are securely installed, cables are undamaged, PE equipotential connections are reliable, and system components are not worn or damaged. When cleaning the control cabinet, the power must be turned off and wait for 5 minutes. Use solvent-free, water-soluble, non flammable, and non corrosive cleaning agents. Do not use compressed air, spray water, or allow cleaning agents to enter electrical components.