JEC COMPOSITES MAGAZINE - Issue #62 - January/February 2011 - 38

testing
Simulation The path definition process was simplified by integrating robotic simulation software that was developed by Applied Computing Engineering (ACE). All three companies – Profile, Adept and ACE – worked together to develop the NDT functions. The NDT laboratories of a number of large industrial groups also participated. Besides the design of the NDT cell and the optimum position of the robot(s), three other objectives of the simulation process were to: - define the scanning paths, - verify that the robot does not collide with the part or the NDT cell, - verify that there are no singular or inaccessible robot positions. Trying out the paths A teach-and-learn mode is used to inspect parts that are not very complex but which are non-adaptive and cannot be broken down into elementary surfaces. The operator uses a joystick to record a number of carefully chosen points on the surface. The file containing these points is exported to CAD format and transferred to the robotic simulation software and processed in the same way as CAD manufacturing files or 3D scan files (see next).

Fig.4: Screen view of robotic simulation Fig.5: Scatter plot obtained with a scanning laser Fig.6: C-Scan amplitude obtained

The proposed solution is to 3D-scan the contour to be inspected. Here, a Konica Minolta VI-910 laser scanner was used for the tests. For a surface roughly a metre square, it only takes a few seconds to generate the images. For larger surfaces, the scanning is done in multiple images. The software assembles these automatically to obtain a scatter diagram that can be transformed, exported to CAD format, and transferred to the simulation software ( figure 5). The operator is in much the same situation as if he had the original data at his disposal, but he also has the exact contour of the part to be inspected. Zero shift Sometimes accurate positioning or repositioning of parts is not possible – with composite parts, for example. In this case, a zero shift is necessary for the part and/or the scan path origins. This is done using the coordinates of three points on the part to be inspected. The operator uses the joystick to position the robot on the three reference points. Once these three positions have been validated, the origins are automatically shifted back to zero. If the parts to be inspected are of different shapes, the zero shift can be achieved by doing a cursory ultrasonic “pre-scan” to define the part surface (by measuring the height of the water column) and determine the new paths. However, the use of zero shift corrections for either position or shape should not be abused, in order to avoid placing the robot and the movements associated with it in singular zones (figure 6). Inspection by pulse-echo ultrasound or by eddy currents The probes are mounted on the end of the robot arm. Several different ultrasonic techniques

CAD manufacturing files For production controls, the CAD data required for manufacturing the part are often available. The simulation software can used these data directly, as long as the proper format is selected (Catia, Step, Iges, etc.). The operator imports the file, positions the part in the defined NDT cell, enters the scanning parameters, e.g. path-following accuracy or the scanning step, verifies inspection feasibility in terms of accessibility, singular zones, etc., then validates the parameters (figure 4).

jec composites magazine / No62 January - February 2011

This stage considerably reduces the risks of faux pas during inspections. As soon as feasible and satisfactory paths have been achieved, the system creates a file that is transmitted to the robot control, which is on standby for the inspection. 3D scanning When inspecting parts with complex but unknown contours (for maintenance, non-CAD-manufactured parts, etc.), the operator has no data available for a simulation or for path definition.

JEC COMPOSITES MAGAZINE - Issue #62 - January/February 2011

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #62 - January/February 2011