Automated In-Line Gauging

Manufacturing plants in all industries require ongoing inspection of their production parts, to monitor consistency and quality of the production process. Typical part features to measure are the diameter and the location of a hole (circle, slot, etc.), the location of an edge, the distance to a surface, the location and length of studs, etc. Historically, off-line measuring systems, such as CMM’s, have been used to measure random part samples removed from the production line, and brought over to a dedicated metrology room. Then came in-line ‘fixed sensor’ stations, offering the possibility to inspect 100% of the production output and ensure prompt reactivity to the production process control. 

However, such stations inherently suffer from their lack of flexibility, since any new feature along the part one would want to inspect would generally require the installation or re-installation of a fixed sensor within the station. This is obviously time-consuming and expensive, and therefore limits the ability to change the features to inspect over time as the production process evolves. Hence the more prevalent approach nowadays of using a robot right along the production line, and turning it into a measurement robot – the resulting equipment being referred to as Flexible Measurement System (FMS) or as Automated In-Line Gauging.

By mounting a small-range sensor (such as a 3D laser/camera system, a 1D distance sensor, or a touch probe, etc.) at the end of the robot, one has now access to an, in effect, large-range measurement equipment which can be reprogrammed at any time to inspect new features. However, considering the lack of accuracy of an ‘off-the-shelf’ robot, it is imperative to complement this equipment with a robot calibration solution, in order to ensure high enough measurement accuracy within the entire effective measurement area.

The DynaFlex™ system includes an in-line calibration solution specifically developed for Automated In-Line Gauging. Rather than relying on some external measurement device, the same small-range sensor mounted at the end of the robot for inspection purposes is also used for calibration purposes, through the measurement of passive ‘calibration targets’ fixedly located within the robot’s envelope. The calibration process is transparent to the inspection task itself, as it takes place automatically in between the transfer of one part to the next along the production line, thus not impacting cycle time.

The DynaFlex solution also acts as a ‘central hub’ for the FMS (see “Targeted Robot Communication Solutions”), having been integrated and able to communicate with virtually every available standard industrial robot and with a variety of small-range sensors with 1D to full 6DOF capability (standard 3D laser/camera sensors, 1D distance laser sensors, 2D laser line sensors, CMM probes, etc.). This patented solution also provides the ability to perform both Temperature Compensation and Absolute Accuracy calibration, based on the uniquely developed calibration targets (measured with a laser tracker in case of Absolute Accuracy calibration) exhibiting high mechanical resilience, extremely low temperature sensitivity, and a small foot-print.

Any Automated In-Line Gauging station needs at the very least to include Temperature Compensation, so that the measurement data acquired with the FMS’s robot throughout production remain consistent (accurate) relative to the initial set of measurement data (independent of temperature fluctuations and other possible hazards). This initial set of measurement data might in turn require ‘correlation’ (relative to a CMM typically) as part of the installation of the FMS. By performing Absolute Accuracy calibration (instead of just Temperature Compensation), this upfront correlation can be eliminated altogether, therefore turning the FMS into as close as possible to CMM.