The metrology laboratory at Buildings 72 and 100 has recently acquired a new device that has broadened their measurement capabilities. Although it might not be the same scale as other well-known instruments in the lab such as the tomograph, this newly introduced scanner is unique in the sense that it is able to scan the components quickly and with high precision, using the advanced 3D laser technology.
The scanner is spherical and is easy to handle having an inbuilt grip to easily move it. It has targets on its surface which are read by two fixed cameras that are at least 1.5 meters away in front of the component being inspected. First, these cameras record the measurement volume that is defined by the reflective targets as well as the position and orientation of the scanner in a three dimensional space. The scanner then will project blue laser lines in grid pattern over the surface of the component. This grid slowly fills all the surfaces as the operator moves and turns the device. The positions of the reflected laser positions are saved to form a thick cloud of datapoints that are used to form a digital representation of the component. The volumetric accuracy attained in this reconstruction is 64 to 78 microns, depending on the size of the object.
This is then compared using a dedicated software solution to an ideal reference model of the component. In this comparison, any material differences are discovered. The output is given in the form of a color coded map and serves to highlight areas that have too much or too little material. Also, we can get the value of each individual deviation. With this kind of detailed information, clients at CERN can make the necessary adjustments to the component in a workshop, so that it matches as closely as possible to the intended design.
According to Ahmed Cherif, the head of the metrology laboratory, this type of scanner is already widely used in the industry, with the automotive, aviation, and aeronautics sectors being the most active clients in the laboratory. Since its introduction to the laboratory in January 2020, the demand in terms of component inspection has significantly increased, with many clients bringing a wide variety of components to the laboratory.
Already several complex components such as crab cavities, magnet yokes, beam screens, and even the ALICE inner tracker have been studied with this scanner. The system can model an extremely diverse range of materials and also can deal with extremely complicated geometries. In specific narrow areas, a second sensor may be inserted to scan internal areas. The major constraint is the size of the components which must not exceed a volume of 16 cubic meters as this is the maximum range that the cameras can detect at a given position. This can be compensated by adding more camera stations which will extend the range of the measurement but will decrease the overall accuracy a bit.
Those who believe this technology could support their component inspection requirements, or who have further questions related to metrology, are encouraged to contact ahmed.cherif@cern.ch
References:
1. Home Cern
