Quality Innovations: Here Comes the Scan

The ComScan 1000 is an automated 3-D scanning system that integrates an independent scanner with a component handling system.

The sun rises in the East and sets in the West and as it travels, its light waves strike the earth at different points, lighting and warming what it touches. While not as celestial, a new three-dimensional scanning system brings that idea to the world of test, measurement and inspection.

The ComScan CSA 1000 is an automated 3-D scanning system that integrates an independent scanner, a multiaxis component handling system and sophisticated software to capture line of sight data. The tool from Gaspardo & Associates (Aurora, IL) features a telescoping arm that moves in a semi-spherical arc from 0 to 90 degrees, and a component table that rotates, moves back and forth, and up and down-each movement presenting the scanner an area in which to capture data. This eliminates much of the material handling and setup time that often occurs using tripod-mounted 3-D scanning systems.

Gaspardo & Associates Inc. is a 10-year-old metrology services company that performs reverse engineering and inspection work. In 1997, the company invested in its first 3-D white light patch scanner, a Steinbichler Comet 250, and has since standardized exclusively on 3-D scanning for inspection and reverse engineering projects. The scanning system uses white light triangulation to capture a dense 3-D point cloud that can be color mapped and studied.

While effective, the system was limited in that it was tripod-mounted, and so it could only capture data from the field-of-view from that setup. Contours, bores and other surface characteristics require multiple patch shots to capture enough data to generate a complete 3-D model of the component. To obtain the next patch, either the part had to be moved or the camera had to be relocated.

And, that could be a lot of movement. The number of patches required depends on the individual patch scanner used. The company’s Steinbichler Comet 250 captures roughly a 250- millimeter spherical volume of data per shot, meaning that each shot can cover nearly a 10-inch sphere of the object per shot. More advanced scanners such as AFI-5000P from Dimensional Photonics International (DPI, Wilmington, MA) can have scanning volumes up to 500 millimeters or more. Depending on the object’s size and geometry, this could mean from 3 or 4 scans up to 20 scans or more for full surface coverage.

While lightweight parts were more easily repositioned-assuming that the parts could be physically moved after being fixtured to a table, some parts needing to remain stable-capturing data on large and heavy parts presents significantly more challenges. For instance, trying to see down the bore of a cylinder on a 500-pound engine block would require the block to be propped up on one side at up to 45 degrees or so, which is a precarious fixturing challenge.

“We have been scanning for more than 10 years,” says Steve Gaspardo, company owner. “We noticed that 80% of the time we spent on an inspection job was either moving a part, moving a camera or stitching patches together.”

After expending this effort to capture the individual patches of data, each of these scans would need to be manually stitched together. Successive scans with overlapping surface areas would be mouse-selected in order to tell the software exactly how to register the scans together.

In nine minutes, a cylinder head from one of the world’s largest companies was completely scanned using the ComScan system. Two color-map analyses show the component from different angles and data relating to separate inspection points. Source: Gaspardo & Associates

A Better Way

Gaspardo knew that there must be a better way and began considering ways to mount a camera on a robotic system. He was stymied by a lack of software that would automatically stitch the individual patches. “There was no sense in developing an automated material handling system without having an automated system for stitching the patches together,” he explains.

That hurdle was overcome when InnovMetric Software Inc. (Quebec City, Canada) released its PolyWorks/Inspector software. No longer would stitching be a manual process; instead, the software could determine like- surface characteristics and automatically register, or stitch, the patches together. This release paved the way for development of the ComScan, Gaspardo says.

Gaspardo, a robotics-manufacturing engineer by trade, began work on what would become a patented “multi-axis robotic object-camera handling system with a semi-spherical line-of-sight scanning envelope.” The design linchpin is its constant radius telescoping arm that moves the scanner from 0 degrees on the side to 90 degrees overhead. The telescoping arm creates an inward- looking semi-spherical scanning envelope that allows data from multiple spots on the component to be inspected.

Unlike a touch-probe coordinate measuring machine (CMM) that has an orthogonal, mathematical relationship between the part and the CMM, patch scanners do not need to be perpendicular to the part. With a patch scanner, or any white-light scanner, “if you can see it, you can shoot it,” Gaspardo says. “You don’t need this mathematical relationship because the computer is pasting the patches together.”

In addition to the arm movement, the table rotates 360 degrees and a scissor lift can move the part up and down 600 millimeters. Source: Gaspardo & Associates

The system uses six separate axes to facilitate the semi-spherical scanning envelope, each fitted with an electric motor for seamless actuation. Motors attached to ball screws allow the table to travel forward and back as well as lateral side-to-side movement. The table rests on a rotational indexer actuated by its own motor and has 360-degree movement. The entire X-Y rotational assembly is mounted on a vertical Z-axis scissors jack that is actuated by another motor and ball screw assembly. This allows for the standoff between the scanner and the object to be inspected.

This motion can be accomplished through the use of a SpaceBall controller made by 3Dconnexion, a Logitech company, based in San Jose, CA. It controls the object table’s X-Y movement, much as a joystick does with a CMM, and it can control the table’s rotation and the vertical movement of the scissors jack under the object table.

Gaspardo says that the SpaceBall controller is commonly used in the engineering world for rotating parts in CAD on a computer screen. “The controller lent itself really well to line of sight,” Gaspardo says. “Think about a CAD system that allows you to rotate a part on a screen. With this system, we can move the camera and the part around in much the same way as a CAD system, so it has a very familiar feel to it.”

The controller not only controls movements, but it also can be used to develop part-inspection routines. When inspecting a part, each scan is memorized and with each scan an inspection routine builds. When finished inspecting the initial part, the ComScan will have remembered each shot and table position, and will have created a part inspection program that can be called up for subsequent jobs.

When determining the capacity of the initial product, the company fell back on all of the jobs that it has worked on in the past 10 years. Gaspardo determined that 80% of most inspection jobs could be accomplished by a scanning system with a table payload of 500 pounds and a 1 cubic-meter envelope. Working on the 80/20 rule, the company plans to introduce a number of scaled sizes in 2007 to 2008.

These new versions will integrate various scanner sizes and their respective scanning volumes. The upgrade will include expanded table-load capacities-one interested customer needs a payload closer to 2,000 pounds. In addition to making larger capacity equipment, the company is working to develop a tabletop version, the CSA-250, for small objects. Future models also may include a 3-D feedback loop for laser scanner head positional verification that would allow for the integration of laser-line scanners.

TECHNOLOGY CONTACT For more information on the ComScan CSA 1000, contact:

Gaspardo & Associates Inc.

32W119 Old Molitor Rd.

Aurora, IL 60504

(630) 761-8800

Fax: (630) 761-8802

E-mail: John Verni, development manager, [email protected]

URL: www.gaspardo.com