DSSP: The Shape of Things to Come
Digital shape sampling and processing digitally captures physical objects and automatically creates accurate 3D models.
When the space shuttle Discovery landed in August 2005 following its 12-day mission, the world shared a collective sense of relief, especially considering the safety concerns before and during the flight. One of the technologies that helped ensure safety for Discovery is called digital shape sampling and processing (DSSP).
DSSP gave NASA the ability for the first time to detect, assess, repair and validate a repair in the unpredictable environment of space. It was tested and validated months before the launch, and NASA placed ultimate trust in it during the flight. As the shuttle neared the space station on the second day, it rolled over to expose its underside. An optical scanner attached to a 50-foot-long extension of the Discovery's robot arm scanned the underside of the shuttle's wings to capture damage. Scan data was transmitted to Houston, where software was used to create 3D models of the damaged tiles from the data. The models were analyzed, and fortunately damage was not consequential enough to require repair.
If review of the results raised questions about the extent of damage, NASA was prepared to use the 3D models to create tool paths for cutting facsimiles of potentially dangerous damage into an array of test tiles. The reproductions of the damaged tiles would have been tested in NASA's ArcJet facility to evaluate their ability to withstand the heat and stress of reentry. If tile damage was considered too extensive for safe reentry and return to Earth, Discovery astronauts would have made repairs during a spacewalk. In this case, the test tiles would have been used by NASA to prepare step-by-step instructions for the astronauts to repair the damage.
What is DSSP?
DSSP is a category name that encompasses multiple technology advances.
It describes the ability to use scanning hardware and processing
software to digitally capture physical objects and automatically create
accurate 3D models with associated structural properties for design,
engineering, inspection, and custom manufacturing. What digital signal
processing (DSP) is to audio, DSSP is to 3D geometry.
DSSP has evolved as a result of several technology areas that have matured over the last decade, including optical 3D scanning, reverse engineering, computer-aided inspection, and geometry processing. Commercial applications for DSSP technology include design and analysis of complex shapes such as turbine blades, transmission housings, and engine blocks; creating digital inventory of legacy parts; historical preservation; and medical applications such as customized hearing aids and precisely fitted orthodontic devices.
The Essential Components
DSSP requires two essential components: scanner hardware to capture
point data, and software to process point data into useful digital
results. Technology advances made by manufacturers of optical scanners
during the last decade were the first steps in making DSSP possible.
Previously, engineers were limited to manually capturing one point at a
time. Optical scanners have made it possible to collect millions of
points in the time it used to take to record a few points. DSSP enables
capturing the entire bounding surface geometry of a physical object,
including product features, colors, and even textures.
Gathering millions of points of data has little or no value unless the data can be processed easily into digital models with the quality needed for downstream use in design, engineering analysis, rapid prototyping, manufacturing, and construction applications. That's where software plays a critical role.
The combination of greater price/performance for desktop computers and innovation in geometry processing algorithms has moved DSSP forward at a breathtaking pace. Point-cloud data that would choke a high-end computing system five years ago is now easily digested by modern PCs. Gaps and noise in scanning data that used to take days to resolve are now corrected automatically in the best DSSP software. Conversion to polygons and NURBS surfaces, once requiring days of tedious work, can now be handled in minutes using a natural, intuitive workflow.
A Complement to CAD/CAM
DSSP has faced misunderstandings in relation to CAD/CAM. Far from being
an overlapping technology, DSSP complements CAD/CAM and is an essential
part of the digital design and manufacturing life cycle. CAD/CAM
software is limited to prescriptive modeling methods where pre-defined
geometry must be prescribed by an expert on a blank screen. With its
roots in imaging, DSSP offers descriptive modeling methods. The
software extracts geometry and topology from measurement data and
describes them to users for archiving and reuse for multiple purposes.
DSSP bridges the gap between the point domain of measurement and the shape domain of design. It aligns the physical and digital worlds, ensuring that the design model is an accurate representation of the as-built product. This alignment is often missing in CAD/CAM, where changes required to adapt a design to manufacturing create differences between the CAD model and the physical product. DSSP closes the physical-digital loop.
Making Differentiation Possible
One of the most promising aspects of DSSP is its ability to enable mass
customization--manufacturing one-of-a-kind products with the same
efficiency and cost-effectiveness as mass production of
one-size-fits-all goods. Mass customization is already a huge market
differentiator in the medical device industry, where fitting a product
to the unique shapes of the human body is increasingly critical to
success.
It doesn't take much to realize the appeal this kind of mass customization holds for consumer products. Apple's iPod is the perfect example--it provides a digital vessel for its users to fill with content that has personal meaning. Design and color options, along with an endless number of skins and peripheral items, help further ensure that iPod owners are making an individual statement.
In addition to establishing strong brand identity, vendors of products defined by unique design and individualization can often shield themselves from the price pressures faced by purveyors of commodity products. In many cases, they can manufacture close to their customer base. Perhaps best of all, they can be nimble--taking consumer input and quickly transforming it into a product that meets market demands.
Delivering What the Customer Wants
DSSP offers an effective new way of processing limitless shapes for
everything that exists. It frees designers, engineers and manufacturers
from two decades of limitations proliferated by the blank-screen design
of CAD systems, providing the ability to go beyond mainly mechanical
shapes to model an endless variety of organic shapes. By making it
faster and simpler to sample and process shape information, DSSP will
enable manufacturers to deliver exactly what consumers want at a
competitive price. Just as mass production was the hallmark of the
Industrial Age in the 20th century, mass customization promises to
dominate the Knowledge Age in the 21st century.
