DSSP: The shape of things to come
by Ping Fu|
Editor's note: This is the first of a two-part article. In this first part, Ping Fu defines digital shape sampling and processing (DSSP), explaining its origins, how it complements CAD/CAM and its impact on speed, costs and quality. The second part, published in the January 2006 issue of Converge, delves into the applications that rely on DSSP and looks at its future as a catalyst for new forms of manufacturing. |
DSSP is a category whose time has come
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.
Interest in the mission was especially high in Research Triangle Park, N.C., where engineers from Geomagic were on call 24x7 to help ensure the safety of Discovery astronauts. The company's digital shape sampling and processing (DSSP) technology gave NASA the ability for the first time to detect, assess, repair and validate a repair in the unpredictable environment of space.
DSSP 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 Geomagic 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. The demands within these areas have led naturally to integrated DSSP solution offerings.
As with bioscience and other fields with large market potential, DSSP has attracted some of the world's leading scientists and major research funding from government agencies. Geomagic, for example, has Dr. Herbert Edelsbrunner and Dr. Tamas Varady, with more than 200 published papers between them, actively involved in research and development. The company has also received millions of dollars in funding from the National Science Foundation and the National Institute of Standards and Technology.
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.
Mechanical data collection methods such as those used by coordinate measurement machines (CMMs) are still important to some inspection applications, but increasingly even that field is moving from contact mechanical to non-contact optical technology.
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.
Accurate repeatability of DSSP software is making it possible, especially in applications such as digital quality inspection, to move analysis and reporting tasks from experts in offsite offices to staff on shop floors. Experts can now spend more time on product development and manufacturing design processes. Automated reporting using 3D graphics in standard formats enables inspection results to be easily understood and shared throughout the enterprise.
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.
With its roots in drawing, CAD/CAM software is limited to prescriptive modeling methods. In other words, pre-defined geometry must be prescribed by an expert to a software tool for the purpose of modeling. CAD/CAM starts in the virtual world with a goal to produce better products in the real world.
As a drawing-based technology, CAD starts with a blank screen, requiring that the user input dimensions, shapes, curves and surfaces that will define an object. It is great for modeling new products, particularly those with simple facets and standard geometric shapes. It is limited when it is faced with describing or representing the complexity of the existing world.
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 starts in the real world with a goal to produce high-quality digital models in the virtual world that can be used by CAD/CAM/CAE applications.
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 creates differences between the CAD model and the physical product. DSSP closes the physical- digital loop.
Accurate alignment between the digital representation and as-built product delivers major benefits, including the following:
- Time and money savings due to faster development cycles and design iterations.
- Better quality through more accurate engineering analysis, resulting in less manufacturing waste, lower rework costs, and reduced product returns and recalls.
- The ability to customize products in mass quantities, creating competitive advantage and distinctive product branding.
- Automated quality inspections that reduce labor costs and staffing requirements.
- Replacement of tedious, manual jobs with automated processes, providing more control, less reliance on outsourcing, and greater employee safety and satisfaction.
- Immediate and continually escalating return on the DSSP investment.
Ping Fu is president and CEO of Geomagic (www.geomagic.com). Geomagic simplifies digital shape sampling and processing (DSSP), enabling customers to accelerate their design-build cycles and ensure quality at every step. More than 4,000 professionals in industries such as automotive, aerospace, medical devices and consumer products depend on Geomagic software.
The author thanks Peter Marks of Design Insight and Grace Ueng of Savvy Marketing Group for their help in defining DSSP and its marketplaces, and Bob Cramblitt of Cramblitt & Company for editing assistance.