Advanced Dimensional Measurement Systems

Summary

The Advanced Dimensional Measurement Systems (ADMS) project provides the measurement science and infrastructure needed by industry to adopt new dimensional measurement technology. We accomplish this by investigating new measurement systems, characterizing their errors, developing and codifying instrument test methods into documentary standards, designing high accuracy dimensional artifacts, and, as needed, creating new measurement services.

Description

Figure 1. Some of the parameters that are used in the model for spherical coordinate 3D laser scanners.

New dimensional measurement technologies provide significant benefits to industry such as increasing measurement throughput, enabling new manufacturing process (such as additive manufacturing) and providing more detailed part information for manufacturing process improvement. However, before purchasing and using new measurement technology, the user must understand the capabilities and performance of the instrument. This is not a simple task and, for much of U.S. industry, can be sizable barrier to the adoption of advanced measurement systems.

The ADMS has unique assets and capabilities that we apply to these measurement challenges, including

• advanced analysis capabilities to develop sophisticated models of the measuring systems
• high accuracy testing facilities that provide industry innovators practical access to the SI unit of length
• experience developing high accuracy dimensionally stable measurement artifacts for realization of the unit of length in industrial facilities
• advanced mathematical algorithms to perform computationally complex analysis of the dense data sets provided by many advanced measuring systems.

The ADMS regularly partners with U.S. industry to develop tests for new instruments as well as to provide U.S. manufacturers of measurement equipment access to our unique facilities early in the development process, helping them shorten the time to market. Through these industrial contacts, the ADMS exchanges the vital information regarding the measurement technologies and their uncertainly sources that is critical to developing documentary standards.

Mission:

Figure 2. Scale bar, left, for use in field testing of laser trackers, right.

• Advance dimensional metrology by developing new test methods and first principles error correction and analysis techniques and codify these methods and techniques in national and international standards.
• Promote U.S. innovation and industrial competitiveness by developing high accuracy dimensional artifacts and new measurement services to provide measurement traceability and disseminate our institutional knowledge through collaboration on special measurement challenges and educational outreach.

Current and Future Emphasis Areas:

• Develop methods to test performance of optical dimensional measurement systems (stereo vision systems, fringe projection systems, video-based motion capture systems), x-ray computed tomography systems, etc.
• Support the development of national and international documentary standards for optical dimensional measurement systems, x-ray computed tomography systems, etc.
• Provide guidance to industry on metrological traceability of data obtained from optical dimensional measurement systems, x-ray computed tomography systems, etc.

Major Accomplishments

Figure 3. Laser tracker calibration in Tape Tunnel Facility.

• Designed, assembled, tested, and calibrated a prototype calibration artifact that will eventually be used to realize test lengths for an upcoming ASTM E57 standard for the performance evaluation of large volume 3D laser scanners. The artifact is comprised, primarily, of precision matte finish spheres, arranged in a 6 m x 6 m square grid.

• Held laser-scanner runoff and ASTM 57 meeting as part of the effort to complete a draft standard for the volumetric performance of large volume 3D laser scanners. Participating manufacturers, which included all except one of the major manufacturers of this equipment, brought or sent their equipment to our facilities that were designed, assembled, and calibrated specifically for this purpose.  There were three full days of testing across two labs containing multiple structures that were used for a large number of tests. (https://www.nist.gov/news-events/news/2016/05/3d-laser-scanner-runoff-p…)

• Publication of ISO 14253-5:2015 “Geometrical product specifications (GPS) -- Inspection by measurement of workpieces and measuring equipment -- Part 5: Uncertainty in verification testing of indicating measuring instruments” and ISO 1:2016 “Geometrical product specifications (GPS) -- Standard reference temperature for the specification of geometrical and dimensional properties.” The project team did a substantial amount of work, including writing, towards the development of these standards.

• Installation of a new high-accuracy CMM that will be used to improve the accuracy of Big-G measurements.

• Delivered new calibrated body armor artifact to the US Army that will be used to test the measuring instruments which help to ensure the effectiveness of body armor worn by troops.
• Developed 3D laser scanner testing procedures that have been incorporated by Boeing Inc. to evaluate the measuring systems for use on the factory floor. (see Volumetric Performance Evaluation of a Laser Scanner Based on Geometric Error Model)
• Completed development of a new high accuracy portable length standard and field check procedure for field testing of measuring systems used to assemble and inspect large manufactured components under a CRADA with Brunson. (see A Proposed Interim Check for Field Testing a Laser Tracker's 3-D Length Measurement Capability Using a Calibrated Scale Bar as a Reference Artifact)
• Published An improved L1 based algorithm for standardized planar datum establishment, which is now being used as the basis for a new and superior means of defining planar datums in both ASME and ISO drawing standards revisions.
• Developed new measurement technique to calibrate long (>7 km), high accuracy length standards for the fiber-optic cable industry.