|
|
|
|
|
|
|
|
|
|
Directory of Commercial Providers of this Technology ...
RE Technology Comparison Chart ...
|
There are times when more data is required than can be viewed only from the outside of an object or a part. For example, it may be necessary to verify that a part with complicated internal features has been manufactured correctly, or to survey a fossil’s internal features. Touch and light-based systems may be applicable to some portions of the problem, but may require destruction of the object for complete data gathering. This is acceptable in some situations, but certainly not for others where a valuable or irreplaceable object is involved.
There are, however, additional instrumentation choices available which address the problem of internal viewing. Non-destructive systems based on X-ray computed tomography are made by several companies. These work in an analogous fashion to their medical counterparts, beaming an X-ray from many directions and calculating resulting interior point density. Some systems offer resolutions in the few mil range while accommodating objects as large or larger than 16 inches. The instruments can be large, expensive and require specialized knowledge to use, however. An alternative is offered by CGI, Inc. The company produces a destructive system based on a CNC milling machine combined with optical data-gathering using a CCD camera. CGI calls their technology cross-sectional scanning (CSS). A part or other object is embedded in a contrasting color plastic matrix material. Subsequently, this part and matrix combination is then shaved by the miller and scanned layer by layer until data for the complete object has been acquired. The obvious disadvantage is the destruction of the object, but the machinery is straightforward in concept and use, especially for manufacturers who are familiar with machine tools. The technique can also be comparatively fast and very precise. Destruction of a part is often quite acceptable for quality control and similar applications.
|
|
||||
