How do you calibrate robots in Automotive Manufacturing?

1 Why calibrate robots?

Calibrating robots means adjusting their parameters to match their actual performance with their expected or desired performance. Calibration can improve the robot's repeatability, precision, and speed, as well as reduce the risk of errors, defects, and collisions. Calibration can also extend the robot's lifespan and optimize its energy consumption.

2 How often to calibrate robots?

The frequency of calibration depends on several factors, such as the type of robot, the complexity of the task, the quality standards, and the operating conditions. Some general guidelines are to calibrate robots at least once a year, after any major maintenance or repair, after any changes in the work environment or the product specifications, and whenever you notice any signs of deterioration or inconsistency in the robot's performance.

3 What tools to use for calibration?

Different tools and techniques exist for calibrating robots, depending on the accuracy and complexity required. For example, laser trackers measure the position and orientation of a target attached to the robot's end-effector with a laser beam and a camera; however, they are expensive and require a clear line of sight between the tracker and the target. Photogrammetry systems use multiple cameras to capture images of the robot's end-effector and calculate its position and orientation with software algorithms; however, they are sensitive to lighting and occlusion conditions. Articulated arms are portable devices with multiple joints and sensors that measure the position and orientation of the robot's end-effector by touching it with a probe, but they have limited reach and accuracy. Lastly, calibration jigs are fixtures that have predefined positions and orientations that the robot's end-effector can touch or align with; although, they have low accuracy and flexibility.

4 How to perform calibration?

Performing calibration involves several steps: preparing the robot and the tool, setting up the calibration device and aligning it with the robot's coordinate system, collecting data from different positions and orientations within the workspace, analyzing the data to identify errors and deviations, and adjusting parameters to minimize errors. Make sure the robot is clean and lubricated before attaching the tool or target to its end-effector. Connect the calibration device to the robot controller or a computer, calibrate it if necessary, and use software tools to compare the data from the device and controller. Finally, modify parameters such as joint angles, tool center point, base frame, and kinematic model until errors are minimized.

5 How to verify calibration?

After calibrating the robot, it is important to verify that the calibration results are satisfactory and consistent. This can be done by performing a repeatability test, an accuracy test, and a functional test. For the repeatability test, move the robot to the same position and orientation multiple times and measure the variation in the end-effector's location and orientation. Compare this variation with the robot's specifications and the quality requirements. For an accuracy test, move the robot to a known position and orientation and measure the difference between the actual and expected values. Lastly, run a functional test by running the robot's normal operation and checking for errors, defects, or collisions. Calibrating robots in automotive manufacturing is a vital and challenging task that requires careful planning, execution, and verification. By following these methods and tools, you can effectively and efficiently calibrate your robots to improve production performance and quality.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?