Check out this case study. This is just one example of what computed tomography can do for you.
A computed tomography evaluation always begins with capturing the scanned data. For the scanning procedure, where the part is turned on a rotary table by 360°, the part needs to be secured from shifting. As computed tomography is a non-contact measuring method a simple fixture can be used for this purpose. The fixture can be made of different materials with low density as for example rigid foam.
During the scanning procedure two dimensional x-ray images are captured. These images are called projections. From a multiplicity of these projections, which consists of pixels, a three dimensional volume model is created. Volume models are made of voxels, these are three dimensional pixels. This procedure is fully automated and carried out in the background during the scanning procedure. For metrological evaluations surface data is needed.
This data is automatically created after the scanning procedure is finished. Surface data consist of single triangles which describe the measured object´s surface detailed. It is the basis for all following evaluations and analyses.
The measuring procedure for dimensional evaluations is similar to well-known tactile measuring methods. The difference lies within the object used for probing. Using the tactile method the real part is the measured object, but when using CT for dimensional control the surface data of the scanned part is used for probing. So a virtual probing procedure is applied.
This procedure has the advantages that a deformation of the part caused by probing cannot happen and there are no limitations caused by the probing sphere or shaft. The measurement is carried out in the same way as it is known from tactile measurements. At the beginning the part needs to be aligned. Therefore the elements to be measured are selected in the CAD model and then the measuring points are placed via mouse click on the surface data.
After the first rough alignment the following measuring procedure can be carried out fully automated. According to the drawing all geometrical and free-form elements are measured and evaluated. For this process the complete functionality of the measuring software is available. The results can be reported either in a table or in a graphical report.
The measuring method of virtual probing offers many advantages. On one hand there is unlimited access on the part. Smallest structures can be measured without any limitations caused by the probing sphere. Undercuts and inner structures can dimensionally be evaluated without destructing the part.
Automatic measuring programs can be written and recalled every time a part of the series needs to be measured, just like it is known from tactile measuring machines.
Furthermore a virtually unlimited number of measuring points can be selected without a noticeable increase of measuring time.