Today two-point measures are still widely used. They are quick, easy and cheap to assess and are often sufficient to ensure the function of a product or to control a process. Especially in the shop floor two-point measures taken with simple devices like calipers or micrometer screws are still dominant, because of their efficiency and ease of use.
On the other hand it is very tedious or even impossible to check more complex attributes of a workpiece (e.g. volume of a complex shaped cylinder head, curvature of formed sheet metal parts) or to do reverse engineering with the help of independent two-point measurements.
With the propagation of affordable and powerful computers coordinate metrology became more and more important for industrial metrology. Coordinate metrology is the most universal measurement technology in mechanical manufacturing. Coordinate measuring machines (CMMs) acquire points on the surface of the workpiece rather than measuring features directly. From this set of points diverse geometric features may be calculated which are afterwards used to evaluate the compliance of the workpiece with the specification.
Today there exist many different types of coordinate measuring machines with differing sizes to measure small objects like housings of mobile phones as well as large objects like engine blocks for cargo ships or bearings for wind generators. Portable systems with position measurement based on triangulation (set-up e.g. with laser trackers) can be beneficially used for measuring extremely large objects, such as complete ships or aircrafts and miniaturized CMMs are able to measure micro parts with nanometer resolution. Special robust CMMs can be used to measure in the shop floor in harsh environment next to manufacturing machines.
9th INTERNATIONAL SYMPOSIUM ON MEASUREMENT AND QUALITY CONTROL (9th ISMQC)
November 21 – 24, 2007, IIT Madras
MANUFACTURING METROLOGY – STATE OF THE ART AND PROSPECTS
Weckenmann A., Kraemer P., Hoffmann J.