Calibration of the Tip
Whenever a new probe is fitted at the end of the arm, it must be calibrated to measure and function accurately. The end effector is calibrated through digitization optimization procedure. Once selected and calibrated, the new end effector is assumed to be used in all subsequent measurements up until a different end effector is selected for scanning. Following methods are used for calibration
After calibrating the tip, the next step is scanning of the component to be Reverse Engineered. For scanning the hardware used is FARO arm and as far as software is concerned, it is either AnthroCAM by FARO itself or Imageware's Surfacer. Proper fixtures are designed to hold the part during scanning, since if the part will move or even vibrate, the data scanned will be inaccurate. FARO arm is a contact system scanner i.e. during scanning it touches the object and collects the points.
FARO arm has got a wide variety of probes. Depending upon the type of component to be scanned, the probe is chosen. If the part is hard enough, steel probes are used. In steel probes there are point probes and spherical probes with different diameters. If the part is made of plastic, scratches will be generated on the component surface if steel probes are used. Hence plastic probes should be used. Sometimes the component, which is going to be scanned is made of such a soft material that above mentioned probes may enter into the object then in that case touch probes, should be used.
If the probe can not reach the portion of the component being scanned then multiple scans are required. The multiple scans after cleaning are transformed to a single co-ordinate system, in Surfacer it is known as Registration. For registration at least three common curves are required. During multiple scanning it is ensured that common curves would be there. Special care should be taken during scanning for common curves and boundaries.
Point cloud should be denser on the blends so that during surface fitting
proper care can be taken of this feature. This is also truth that " Denser
is the point cloud, more accurate will be the surface model." While scanning
the sufficiency of data is always ensured. Special care should be taken
during scanning the small features. Before beginning the scanning, the
surface generation on the digitized data must be properly planned, so that
scanning is properly planned. If it is possible then object should be moved
only after surface generation on the data cloud, so that if more point
data is needed in between then also scanning can be done.
