In modern industrial production, KUKA robots are widely used in various fields with their excellent performance and high reliability. However, when the ambient temperature is low, the normal operation of KUKA robots may face some challenges. At this time, the preheating function WARMUP of the KUKA robot is particularly important. This function can not only effectively protect the key components of the robot, but also ensure its stable and efficient operation in a low temperature environment.
The KUKA robot’s WARMUP function is crucial for ensuring optimal performance. Before operation, it pre – heats key components like motors and actuators. The principle lies in gradually raising the temperature to the ideal operating range. This reduces wear and tear and improves mechanical efficiency.
To configure it, access the robot’s control panel. Navigate to the system settings, where you’ll find the WARMUP section. Set the desired warm – up time and temperature thresholds according to the robot model and working environment. Regular calibration of these settings guarantees consistent and reliable performance, maximizing the robot’s lifespan and productivity.
- Principle of the preheating function
When the KUKA robot is started at a low ambient temperature, the lubricating oil in the reducer becomes viscous, resulting in increased friction. This may cause the motor current of one or more axes to reach the maximum value, causing the robot to stop running, and the robot controller will generate an error message “Exceeding the regulator limit “. In order to avoid this situation, the preheating function WARMUP of the KUKA robot came into being.
During the preheating stage, the system monitors the motor current. If the current reaches the pre-set defined value, the robot controller automatically reduces the movement speed, thereby reducing the motor current. This process involves point-to-point motion (PTP motion) and point-to-point approximate positioning (PTP – CP approximate positioning), but does not include continuous path motion (CP motion) and the spline curves therein, and does not reduce its speed. - Configuration and parameters of the warm-up function
To enable the warm-up function WARMUP of the KUKA robot, the relevant files and parameters need to be configured. Before configuration, it is recommended to back up the robot system to prevent system crashes. If you need a system backup and restore USB disk dedicated to the KUKA robot, you can reply to the background to get it. KUKA USB disk. First, open the file R1 Mada $ machine.dat and set the variable $WARMUP_RED_VEL to TRUE to activate the warm-up function. At the same time, other related parameters need to be set according to actual needs. The meanings of each parameter are as follows.
$WARMUP_TIME Warm-up time of the drive unit [min]: The time to monitor the motor current through the warm-up function. If a cold robot is started, the underamplitude value will increase. If the robot is not controlled by the servo, the value will decrease. If the run time is greater than $WARMUP_TIME, the robot is considered to be warmed up and the motor current is no longer monitored. $WARMUP_RED_VEL Warm-up function: checked (TRUE) means the warm-up function is activated, unchecked (FALSE) means the warm-up function is disabled (default) Setting $WARMUP_RED_VEL from FALSE to TRUE sets the robot’s run time to zero. The robot is considered cold, regardless of how long it has previously run under servo control.
$COOLDOWN_TIME Cooling time for the drive [min]: If a heated robot is not under servo control, the stop value is increased. If the robot is under servo control, the value is decreased. If the standard stop time is greater than $COOLDOWN_TIME, the robot is considered cold and the motor current is monitored. (Precondition: $WARMUP_RED_VEL = TRUE.) If the controller of a hot robot has been switched off and restarted with a hot restart, the time the controller was switched off is counted as standstill time.
$WARMUP_CURR_LIMIT Increase rate of the multiplier during preheating [%/s]: Maximum allowable motor current during preheating (relative to the normal maximum allowable motor current), normal maximum allowable motor current = ($CURR_LIM*$CURR_MAX)/ 100$WARMUP_MIN_FAC Maximum motor current during preheating [%]: Minimum value of the multiplier reduction due to the preheating function. The internal multiplier is reduced to the factor of the programmed multiplier defined here at most. $WARMUP_SLEW_RATE Deceleration factor of the multiplier during preheating [%/s]: Increase rate of speed increase. Once the monitoring is no longer triggered, the robot controller will increase the internal multiplier again. The growth rate is defined here.
In addition, it should be noted that after turning on the preheating function, do not adjust the program running speed at will. The program running speed is unified to 100%. This is because after the preheating is turned on, the robot will adjust the speed according to the current situation. Manually adjusting the speed may interfere with the preheating and affect the preheating effect. In severe cases, the robot may deviate from the original trajectory. - Workflow of the preheating function
The preheating function starts working when $WARMUP_RED_VEL is set to TRUE and other relevant conditions are met. The specific process is as follows:
Monitoring the motor current: Within 30 minutes ($WARMUP_TIME) after startup, the system continuously monitors the motor current. If the motor current of the axis exceeds 60% of the maximum allowed motor current ($WARMUP_CURR_LIMIT), the preheating is triggered. At this time, the robot controller generates the message “Preheating active” and reduces the internal override, the robot decelerates accordingly, and the motor current decreases. It should be noted that the program override on the KCP remains unchanged, while the internal override can be reduced to a maximum of 50% of the programmed override ($WARMUP_MIN_FAC) and cannot affect the speed of reducing the internal override. Adjust the override: As soon as the monitoring is no longer triggered, the robot controller will increase the internal override again. Until the minimum $WARMUP_MIN_FAC is reached, the robot will continue to accelerate, increasing the internal override by the growth rate determined by $WARMUP_SLEW_RATE per second, such as 1% per second.
Repeat monitoring and adjustment: If the robot is still not fully heated, the motor current may exceed the maximum $WARMUP_CURR_LIMIT again, and the robot controller reacts the same as the first time, that is, it triggers monitoring, deceleration and adjustment of the magnification again.
Complete preheating: If the robot temperature is high enough to enable the robot controller to increase the internal magnification to the programmed magnification, the robot controller will deactivate the message “Preheating activated”, indicating that the preheating process is complete.
Recording events: All relevant events during the entire preheating process will be recorded in the file “Warmup.LOG” (path “KRC: Roboter Log”), including changes in status such as monitoring effective, invalid, active control and control invalid. - Advantages and significance of the preheating function
Protect robot components: In low temperature environments, the preheating function can effectively avoid the problem of increased friction caused by the viscosity of the lubricating oil, reduce the wear of components such as the gearbox, and extend the service life of the robot.
Improve production efficiency: By properly configuring the preheating function, the impact of the preheating time on the production cycle can be minimized while ensuring the normal operation of the robot. For example, after testing, on a 60JPH body-in-white production line, the time impact is only about 3 minutes per day.
Enhance system stability: The preheating function helps the robot to operate stably in a low-temperature environment, reduce the problems of control system freeze and reduced precision caused by low temperature, and improve the stability of the production process and product quality.
The preheating function WARMUP of the KUKA robot effectively solves the problem of starting and running the robot in a low-temperature environment by monitoring the motor current and adjusting the movement speed. Reasonable configuration and use of this function can not only protect the key components of the robot and extend its service life, but also improve production efficiency, enhance the stability of the system, and provide a more reliable and efficient automation solution for industrial production.