With the addition of CAPTRON's ORL-OGLW series, the range of products for industrial robots has expanded yet another step further. Besides robot accessories, vacuum grippers and tool changers, BIBUS also helps you calibrate industrial robots.
This article explains CAPTRON's optical sensors for robot calibration. This series offers an accurate and efficient method for optimising robot performance in various industrial applications.
Calibrating robots with tool-centre-point (TCP) measurements
In modern robotics automation, high accuracy is essential. Especially in demanding environments, with tool wear or tool changes, regular checks and recalibrations are necessary to ensure precision and quality. The Tool Centre Point (TCP) plays a crucial role here.
The TCP is a reference point defined relative to the robot arm. When programming an application, the coordinate system of the tool is used. When changing tools, the TCP is easily adjusted. This affects all motion programmes of the robot in which this tool is used.
For applications such as dispensing or welding, where tool changes are frequent, regular TCP calibration is indispensable. BIBUS recommends an automated calibration process to minimise human error, save time and costs and increase quality.
Using TCP measurement tools to improve robot accuracy
CAPTRON offers high-precision TCP measurement instruments that enable customers to perform automatic TCP recalibration of industrial robots. These measurement instruments use two perpendicularly aligned lasers to accurately detect deviations from the robot's tooling.
An example is shown in the picture below.
The laser barriers of the TCP measurement tools are used to automatically recalibrate the TCP, resulting in automatic motion correction of the robot.
When the tool (such as a milling head or gripper) moves through the laser, the laser beam is interrupted. The ‘centre’ of this interruption, defined by the falling and rising edge of the light signal, is used to determine the reference point of the tool (xref and yref).
For accurate calibration, it is recommended to move the robot arm in a circular (or square) horizontal path within the TCP measuring tool. During this movement, each laser beam is interrupted twice, resulting in two reference positions in both the x and y directions. By averaging these positions, calibration accuracy can be significantly increased.
In addition, the midpoint of the TCP measuring instrument, where both laser beams cross, can also be determined. At this point, it can be checked whether the recalibration was performed correctly, as both laser beams are interrupted at the same time.
Optimal accuracy and recalibration
After calibration, the robot's motion sequences are programmed and the robot can perform its work. For recalibration, the tool is again moved through the laser beams of the TCP measuring instrument. Any deviations from the reference positions are detected, after which the tool is automatically corrected in the x and y directions.
To correct a skewed tool, such as a bent weld point, two calibration runs are performed at different heights (e.g. z1 and z2 in the illustration below).
During these runs, the TCP deviation between the two calibration runs is used to calculate and correct the tilt angle relative to the robot flange (α). This process ensures optimal accuracy and consistency, even in case of tool defects or wear.
BIBUS: the specialist for industrial automation
With this unique product from CAPTRON, BIBUS offers not only a practical, but also a reliable solution for improving robot accuracy. This technology can be used in a variety of applications.
CAPTRON's range of optical sensors is part of a larger range of robot accessories. With products like the CoboShift tool changer, BIBUS can optimise the industrial use of robots. Via the BIBUS webshop, you can easily order tool systems, tool changers, swivels, CiRo, hose packages and other robot accessories. For tailor-made advice, please contact our specialists.
