By Kenneth Wong
In general, reverse engineering refers to the process of identifying, extracting, and studying the underlying methods involved in the manufacturing of an existing object. Among mechanical engineers who rely on CAD, the term refers more specifically to the use of a hardware-software combination—typically, handheld or automatic scanners to capture the shape of an object and complementary software packages to convert the digital data into an editable set of geometry—to study an existing product’s shape, structure, and integrity. This method has proven to be particularly useful in developing tailor-made items (prosthetics for amputated patients), one-of-a-kind products (piston heads for modified vehicle engines), or discontinued mechanical parts (municipal water pumps whose original manufacturer has gone out of business). In this article, we take a closer look at reverse-engineering solutions from a number of companies, along with examples of how their products were successfully deployed.
By digitizing its piston heads (top view: left and hollow inside view: center), United Engine and Machine is able to verify how its product will fit on the target cylinder head (right) and identify potential problems beforehand.
Head-On Product Development
Scott Sulprizio and his brothers run a family business, United Engine and Machine Company, founded by their grandfather Deuta Sulprizio, Sr. in 1922. During World War II, the firm briefly dabbled in supplying PT boat equipment and small munitions, but it eventually returned to its roots as a piston maker. Since it primarily serves after-market automotive customers, it relies on reverse-engineering to capture its customers’ unique cylinder heads to produce matching piston heads.
“Our goal ]in using reverse engineering] was not only to scan the cylinder head but also to capture the numeric values we can apply to our piston-head making,” says Scott Sulprizio, co-owner. “We use a Faro ]mechanical coordinate measuring machine] to capture the specific points—circular points, dowel points, dowel angles, head-plane dimensions, and everything else associated with a cylinder head. Then we use a laser scanner to capture the form of the cylinder head.” For editing the captured point-cloud data, the company uses Verisurf and Mastercam.
A digital model reconstructed from a combination of the two—specific points on the cylinder head and the overall shape of the head itself—lets United Engine and Machine design and produce a piston head that fits the target cylinder head like a glove.
Reverse engineering tools helped the company not only develop new product lines but keep its product portfolio manageable. Instead of storing plaster or rubber molds of each cylinder head, the company maintains a digital library, easily handled in a computerized document control system. This allows for storage of the entire data capture process, which then can be used for a variety of projects.
For instance, take the Chevrolet Big-Block family,” explains Sulprizio. “All cylinder suppliers offer a slightly tweaked version of Big Block. With reverse engineering, we can study them and see where the variations are, then come up with a piston head that works across three different manufacturers’ cylinder heads.”
One of the many features he likes about Verisurf, Sulprizio says, is the abilitiy to display the collected point clouds from a scanning session in various levels of detail, automatically create a mesh from the point clouds, and convert the mesh model into a surface model that can be imported to Mastercam.
The use of Geomagic software allows Advanced Design Concepts to automatically parse the irregularities in its original scan data of projects (left) to a smoother version (center). This information is later transformed into a shell (right).
Currently, United Engine and Machine is accumulating an entire archive of 3D digital cylinder heads from different manufacturers. This growing library gives the company an advantage over its competitors, allowing it to swiftly design piston heads with great detail as 3D files that can be fed to its CAM system.
Getting a Grip on Point Cloud
Plowing snow with an industrial-size municipal vehicle is no game, but a playful device like a joystick could make the job easier. So FORCE America, which specializes in mobile hydraulic systems, components, and replacement parts, offers its clients a joystick-like device to control the plow blades (see “Advanced Design Uses Geomagic to Halve Prototype Time”). Before the joystick became a reality, it existed merely as a clay prototype.
As the reverse engineering manager of Advanced Design Concepts (ADC), the firm contracted to help design the joystick-style electrical control system, Greg Groth received one of the early clay models.
The shelled housing of the handheld control must incorporate a series of internal mechanisms. So the first thing Groth did was to produce the internal components in physical form. Using the reference drawings supplied by the client, Groth and his team modeled the necessary internal components in CAD, then printed them out as physical prototypes in an Eden 3D printer from Objet Geometries, an investment the firm made a few years ago. (Most of the internal components, such as buttons and circuit boards, were standard parts that could be purchased, so he didn’t need to model every one of them.) This allowed him to determine how the outer shell and the internal parts would fit together.
Using ReverseEngineering.com’s CAD plug in, the company’s clients are able to capture the shape of industrial mechanical parts no longer produced by the original equipment makers. The process allows companies like BMC Industries to find a market reproducing discontinued parts.
When the clay model was ready for digitizing, Groth and his colleagues used an ATOS GOM white-light scanner to capture the general shape. The use of Geomagic point-cloud processing and surfacing software allowed Groth to automatically smooth out the curvature irregularities picked up by the scanner. Afterward, Groth created a shell structure with the desired wall thickness from the 3D geometry. The model was then further refined in PTC’s Pro/ENGINEER. The 3D printer, white light scanner, laser scanner, and Geomagic software are all part of what ADC calls digital shape sampling and processing (DSSP).
A Few Simple Tips
If you’re just starting out in reverse engineering, here are a few tips that you might find useful, straight from long-time practitioners.
“If you have a part with shiny surfaces, like aluminum, you should use a spray-on developer ]a thin coat of white paint] to give the part texture. It makes it easier for the laser to pick up the details. The shinier the material, the harder it is to scan. Dull, gray surfaces seem to work best.”
“A white light scanner cannot penetrate deep into cavities, so we use it in conjunction with a laser scanner.”
“You should really map out your repeatable part-alignment areas ]the scanned areas that you have chosen to deliberately overlap so the software can use the specific points or markings on these areas for subsequent alignment]. If there’s a feature in those areas that cannot easily be replicated in vector lines because of the clipping, you could lose a lot of time.”
“Have your articulated mechanical arm in sync with the laser probing arm. You can use the arm to directly define certain boundary curves, hole locations, and other features that are not easy to define in point clouds.”
Digging into Point Clouds from CAD
If you’re in need of a replacement part for a municipal water-pump system supplied by an original equipment maker that has gone out of business, who do you turn to? One company is the California-headquartered BMC Industries, which takes pride in its ability to “completely reverse engineer, customize, and manufacture parts and systems.”
As part of its bailiwick, BMC will duplicate the creations of original equipment manufacturers that have gone out of business. BMC’s reverse engineering capability is enabled by ReverseEngineering.com, which develops and markets a line of CAD plug-ins that let you scan a physical object, collect the target points, then convert the data into a 3D model—all directly from within your preferred CAD program.
For example, a municipality once called BMC Industries explaining that it was only getting 18,000 cubic feet of water coming out of a pump that should have been supplying 20,000. “The pattern makers who replicated the part from the original manufacturer that has gone out of business was good at what they did,” says Braxton Carter, chief technology officer for ReverseEngineering.com, “but they probably weren’t able to fully examine the tricky surfaces of the impeller, so their ]replacement] part wasn’t able to produce that extra 2,000 cubic feet.”
With ReverseEngineering.com’s software, Carter says, BMC was able to compare the original part and the pattern maker’s replacement part and identify the differences. “Then ]BMC] did a laser scan and a hard probe ]of the original part],” he added. “Within three hours, they had a solid model of the ]corrected] impeller,” ready for reproduction.
ReverseEngineering.com’s dedication to bridging CAD and point cloud data is evident in its lineup of plug-ins, which essentially encompass every major CAD system in the market. It produces point-cloud capturing and processing tools for SolidWorks, Solid Edge, Siemens’ NX, PTC’s Pro/ENGINEER, CNC’s Mastercam, AutoCAD, Autodesk Inventor, Rhino from McNeel North America, and KeyCreator from Kubotek. Its application programming interface (API) for scanning devices accommodates Immersion, Romer, Faro, Polhemus, and 3D Creator from Boulder Innovation.
“We use a proprietary algorithm that lets the software lock on to the true part coordinate system, so when you laser-scan, you see the result as you would in your CAD system’s drawing view,” explains Carter.
Carter says the company is planning to open its device-to-CAD integration API so that scanning machine makers may use this code—called High-res Integrated Point-cloud Processor (HIPP)—to develop plug-ins compatible with supported CAD programs.
“Ultimately, we’d like our API to become known as the standard,” says Carter. The code, however, will remain ReverseEngineering.com’s proprietary technology, not open source.
The critical part of reverse engineering is the software-aided cleanup process to automatically identify, crop, and remove the irregularities and extraneous points collected in a scanning session. Geomagic, which supplies the conversion software used by Advanced Design Concepts, has been around since 1996. Its software now enters its 11th incarnation. Verisurf, used by United Engine and Machine Company, is now in its 10th release, known as version X. ReverseEngineering.com has been refining its algorithm since 1986. As point-cloud processing algorithms mature, extracting meaningful geometry out of scan data gets easier and faster. Once associated with industrial espionage, reverse engineering has earned legitimacy over the years because it’s quickly becoming a standard practice.
Kenneth Wong writes about technology, its innovative use, and its implications. One of DE’s MCAD/PLM experts, he has written for numerous technology magazines and writes DE’s Virtual Desktop blog at deskeng.com/virtual_desktop/. You can follow him on Twitter at KennethWongCAD, or send e-mail to DE-Editors@deskeng.com.