Feb 8, 2016 | By Benedict
How does one measure a helicopter? That question may sound like the start of a joke, but actually represents a serious concern for the Weapons Development and Integration (WDI) Directorate Metrology Team of the U.S. Army. Naturally, all military aircraft and their assorted components are designed with extreme precision long before the manufacturing process begins, but sometimes the completed vehicle must be measured to ensure that the initial blueprints have been perfectly realized. So how do they do it? With a measuring tape?
Fortunately for all concerned, technology has evolved to make matters simpler and infinitely more precise. The WDI Directorate Metrology Team, one of six U.S. Army Research, Development, and Engineering Command (AMRDEC) centers, has been using advanced 3D scanning systems to recreate high quality 3D models of U.S. Army aircraft and other objects.
These 3D scans can be captured in a short space of time, and serve to provide the team with detailed 3D images and precise measurements of a particular object. This data can then be used to assist reverse engineering projects and the rigorous quality control processes necessary at every stage of military manufacturing.
"Optical metrology is an important, emergent technology thrust area for AMRDEC," said James Lackey, AMRDEC director. "As the science of measurement, it represents incredible application value in terms of being able to provide highly-accurate dimensional data sets and [the ability to] translate them through advanced analytic techniques to produce three dimensional electronic product data files."
Prior to the introduction of 3D scanning, measurements were in fact obtained using handheld tools such as calipers. This method was effective to a certain degree, but individual points of a surface were often measured inaccurately. The next generation of measurement technology introduced handheld laser scanners—a marked improvement on calipers, but lacking in edge precision and unsuitable for scanning particularly large objects.
"We had to be innovative and find a better way to solve measurement problems," said Tyler Sherrod, AMRDEC mechanical engineer. "This is important because if a program needs a computer aided design [CAD] model of their helicopter, AMRDEC can use optical metrology to scan and recreate [the] CAD of the helicopter.”
The new technology allows for the accurate scanning of complex objects with bends and turns. These scans can then be used to produce new components to perfectly fit existing parts. Furthermore, once a CAD model is generated, the software used by the team makes it easy for users to compare the measurements of the actual object with those of its initial design. And with any discrepancies calculated and highlighted by a computer, potential for error is reduced drastically.
"When you capture a scanned item and match it with its original design, a color comparison is provided and you are able to determine what is and is not acceptable," explained Benjamin Thomason, AMRDEC WDI metrology team lead.
The 3D scanning technology used by the WDI metrology team provides further advantages to the U.S. army besides quality control: ”If there is a problem getting a part to the warfighter in theater because it is no longer manufactured, we can 3D scan the part, reverse engineer a CAD package, manufacture the part, and deliver it to the men and women on the ground,” said Thomason.
In addition to the 3D scanning systems used to obtain measurements and visual data of objects, the metrology team has also implemented photogrammetry processes for projects involving larger objects.
"We use photogrammetry and 3D scanning as two independent measurement technologies," said Andrew Hall, AMRDEC WDI photographic metrology technician. "The structured light system is great for high detail scanning and the photogrammetry keeps the scan data accurate over large projects.”
Structured blue light scanning of a 3D object. Each scan can capture 8 million measurements.
So just how big an object can these 3D scanning systems handle? Later this month, the metrology team will 3D scan a 41-foot long Coast Guard utility boat at AMRDEC's prototype integration facility—a project that would have seemed particularly daunting during the caliper years.
"We have 3D scanned large and small objects including helicopters, vehicles, aircraft and spacecraft," Hall said. "It will take us about two weeks to scan and obtain the interior and exterior data of the boat. Once we are finished, we will have a full model of the boat including any defects that may not be noticeable to the natural eye," Thomason said.
"Optical metrology can additionally shorten production cycles and realize greater cost efficiency," added Lackey. "This comes about by building more accurate production-ready dimensions and tolerances as well as [the] ability to better define material need and thus lower scrap and rework which represents unnecessary sunk cost from a manufacturing perspective.
“Manufacturing technology is a key part of AMRDEC activity. In partnership with the other services, we will help lead the way on defining use of metrology for aviation and missile systems applications across DOD and industry."
If a pending legal review finds in AMRDEC’s favor, the organization could soon embark on a collaboration with NASA: "We like to collaborate with other industries and organizations. Collaboration is a key initiative within AMRDEC leadership," Thomason said. "Working together and leveraging each other's resources is prudent not only from a practicality of saving the taxpayer money but also enables valuable knowledge exchange.
“By sharing within AMRDEC and NASA to provide information and learn from each other, the Redstone metrology community is pushing forward to accelerate the development and implementation of this technology in creative and innovative ways.”
Posted in 3D Scanning
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