Traditionally, 3-D dimensional inspection was performed in the quiet, stable, spotless, and controlled environment of quality labs. But during the past few decades, manufacturers have been increasingly interested in measuring devices that are both comprehensive in scope and portable. Nowadays, measurement has broken outside the labs, mainly because successful companies need to be able to produce quickly and accurately to keep their competitive advantage. They depend on technologies that allow them to measure parts on site, wherever the part may be: in the design phase, directly on the production line, or even on the supplier’s or customer’s premises.
Portable measurement technology really took off during the 1990s with the launch of the first portable measuring arms. When compared to traditional coordinate measuring machines (CMMs), they offered obvious and unequaled benefits to quality technicians and metrologists. Starting with hard-probing measurement, the arms represented a valuable alternative to the numerous constraints of CMM measurement (with mandatory stability and limited measuring volume heading the list). Attaching laser-scanning heads onto the arms quickly followed, creating even more measurement possibilities by allowing quick surface measurement.
The development of scanning arms was the first step in one of the greatest industry-changing trends in metrology in the last 30 years. The trend has been to get rid of the measuring arm, which serves only as a positioning device for the scanner head. Improved designs now enable a scanner to be its own positioning device, and as a result, portable measurement is beginning to reach its full potential. Self-positioning, portable 3-D scanners have been steadily arriving on the market during the past decade (see figure 1). Compact, accurate, and highly portable 3-D scanners can now go wherever 3-D measurement needs to be performed.
Another improvement on portability developed during the past decade has been the use of optical CMMs instead of measuring arms (see figure 2). Using an optical tracker for positioning a hard probe or 3-D scanner does away with the mechanical link between the measuring arm and its scanner. An optical tracker can use optical reflectors placed directly on the part to lock the coordinate system of the measuring system to the part. This removes a great deal of stress for the user because he no longer has to validate the stability of the setup, or to minimize the effects of the environmental conditions (mainly vibrations). Using optical reflectors has proved a great boon to bringing measurement to unstable environments.
The quest for more portability in 3-D measuring tools continues. During the next few years, we are expecting the new generation of scanners to push the limits of portability even further. Although we can’t predict what the nature of the improvements will be, a good guess is that they will include lighter weight, better connectivity, and improved ease-of-use.