QMT Features: October 2010
Pushing the limits
Improved performances and automated measurement technology slashes inspection time of large volume parts with the Laser Radar MV330/350 from Nikon Metrology.

The Laser Radar MV330/350 large-scale metrology system, from Nikon Metrology, doubles measurement speed and performance. Its  improved signal-to-noise ratio yields better range measurements on composite material.  The new Laser Radar further enhances hole and edge measurement, and offers higher reliability.

Nikon Metrology say that its propriety laser reflection technology obsoletes tedious positioning of targets at difficult-to-access locations, as is the case with laser trackers or photogrammetry systems.  Through accurate non-contact measurements, running manually or fully automatically, Laser Radar multiplies productivity and delivers benefits to manufacturers in aerospace, energy, communication satellites, casting and many other markets.

Although similar from the outside, and with a  similar  measurement accuracy of 0.025mm, a Laser Radar and laser tracker house completely different technology. Incorporated into the first is frequency modulated coherent laser radar technology (FM CLR). The Laser Radar instrument directs a focused laser beam to a point on the part to be measured and recaptures a portion of the reflected light. The single large-aperture optical path maximizes signal strength and stability.

As the laser light travels to and from the target, it also travels through a reference path of calibrated optical fibre in an environmentally controlled module. Heterodyne detection of the return optical signal mixed coherently with the reference signal produces the most sensitive radar possible. The two paths are combined to determine the absolute range to the point. Combined with the measured horizontal and vertical laser beam angles, the 3D coordinates of the acquired points are determined in real time.

Equipped with more powerful electronics, the Laser Radar MV330/350 drastically increases the measurement speed from 500 to 2000 points per second. This means that manufacturers can proceed twice as fast with their large-scale metrology workload, while acquiring higher-quality data. The Laser Radar G3 allows them to double productivity when they align large parts during assembly, certify tooling and then monitor its repeatability during production. It can also measure metal, plastic and composite parts and compare them to their CAD models.

Outperforming laser tracking and photogrammetry
The productivity gains that can be achieved with the new Laser Radar system are impressive, claim Nikon Metrology. A wind turbine blade project encompassed the surface inspection of the 45m blade, which was required to be completed in a single shift. The Laser Radar automatically measured 48,000+ inspection locations with 0.025mm single point uncertainty in the requisite 8 hour time period. Completing the same single-shift inspection assignment using laser tracking technology would require at least 3 laser tracker systems and operators as well as large overlay templates and additional tooling.

The comparison between Laser Radar and photogrammetry was the subject of a recent study by Randy Fratena and Charles Mitchell  in Quality Digest magazine, USA (www.qualitydigest.com). The study, Comparison Between Photogrammetry and Laser Radar, concluded that Laser Radar significantly reduced the recurring labour required to characterize the surface profile of medium sized carbon fibre reflectors. In addition to matching the required accuracy, the Laser Radar system achieved significant cycle time reduction through automated inspection.

Nikon claim that the non-contact and targetless Laser Radar system is a winning product in every aspect. First of all, the metrology system requires only one operator to set it up, and then it runs unattended. It requires no special environment or expensive tooling. The system works indoors or out, in any lighting, and on any material or finish surface with a reflectivity of even less than 1 percent. Laser Radar is capable of measuring both freeform surfaces and geometric features.

Regarding hole inspection, the MV330/350 system further increases inspection speed, accuracy and reliability. To measure critical sharp edges with superior accuracy, MV330/350 has a dedicated edge measurement mode available. Nikon Metrology assert that the major strength of Laser Radar is undoubtedly that it can scan complex geometry that was impossible to scan before -  because it was too large, too hard to reach, too complex, too delicate or too labour-intensive.
Laser Radar’s capability to accurately and efficiently measure supersize parts used in aerospace has garnered interest from many leading manufacturers.

Aircraft fuselage section inspection with Laser Radar systems is three to five times faster compared with laser trackers, and requires up to ten times less personnel. Other aviation metrology applications include fuselage, wing, wing/body connections, landing gear door and jet engine blade and inlet cowl. The integration of Laser Radar into innovative composite manufacturing methods illustrates the impact of metrology assisted production on composite part production quality and throughput

The successful adoption of Laser Radar metrology by the aerospace community has assured acceptance throughout many other industries, including nuclear, solar and wind energy, shipbuilding, large castings and antennae.For example, in the fast-growing solar energy business, Laser Radar is used to check the geometric integrity of parabolic and flat solar mirrors to accurately and efficiently trace incorrect bending and misalignment.l
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