White-Light Scanning Captures, Catalogs New Die and Part Surfaces
Whether called on to reverse-engineer a stamping die, digitize and inspect stamped-part surfaces, or capture the measurements of perishable die components to enable speedy machining of replacement parts, Atlas Tool Inc. has come to rely more and more on its white-light scanner. It’s used to inspect, measure and capture part and die dimensional data. Installed in 2006, the scanner, a Cognitens (Hexagon Metrology) Optigo, has proven to be ten-times more efficient than coordinate-measuring machines, according to Atlas quality manager John Watson.
The firm, primarily a designer and manufacturer of medium- to large-sized dies to automotive OEMs and Tier One suppliers, took white-light scanning (WLS) to a new level in 2010 when it retrofitted its scanner with the Cognitens RE (reverse engineering) upgrade.
“The upgrade,” explains Watson, “captures two images with each snapshot and averages out the data to filter out much of the noise. We find that the images are extremely accurate and useful particularly when capturing measurement data at radiuses and complex curved surfaces. It triangulates everything and, rather than scanning and creating a lot of flat spots, it creates nice, continuous surfaces. And, also beneficial: it reduces the time to process cloud data by 30 percent or more.”
The RE model allows Atlas to operate the scanner in two modes—the more traditional dimensional-measurement mode, and the reverse-engineering mode. According to Hexagon Metrology literature, here are the overall benefits of the RE camera upgrade to its Optiva system:
• Offers adaptive point-cloud spacing for improved geometrical tracing in curved areas;
• Provides improved surface-data quality, creating smoother and cleaner 3D surfaces;
• Captures finer details and geometrical shapes on the target objects;
• Integrates measured feature dimensions into the generated 3D model.
Better Scans of Holes and Trim Edges
Along with its RE camera upgrade to its white-light scanner, Watson also notes software updates provided in recent years. “The most obvious benefit to the updated software,” he notes, “has been the system’s ability to process holes and trim edges when we’re scanning stamped parts to check dimensional accuracy. Triangulation during scanning can make it difficult to image features such as holes or trim edges, so oftentimes the WLS system operator would have to capture these features using several shots from different angles to gather enough data. Newer software versions have made this process much more efficient.”
“Cloud data is very accurate, sometimes too accurate,” says Watson. “It picks up every little ripple and lump, too much detail for practical machining. So, our cad operators will manipulate the scan data and smooth it out to create die-machining programs.”
Machining Perishables from Scan Data
Atlas Tool works out of a 250,000-sq.-ft. building in Roseville, MI, and employs 170 people (130 on the shop floor) to turn out dies to 236 in. long that weigh as much as 140,000 lb. Asked to note any new trends in die build, Atlas vice president John Haas points to increased use of steel in new automotive dies, at the expense of iron.
“Subcomponents like posts and pads, which we used to machine from gray cast iron, now often are specified as steel,” Haas says, noting an uptick in the amount of dies being built to tackle advanced high-strength steel stampings. “Steel die components are more robust and easier to weld-repair.”
Many of the subcomponents Haas speaks of are among those typically white-light scanned, their measurement data archived.
WLS is “Game Changing”
The firm first learned of WLS technology in 2005 when it joined a research consortium to investigate springback analysis on advanced high-strength steels. Along with Ford, General Motors and others, Cognitens also participated in the project. “We got to know them and once we took a look at their WLS technology, we knew it was game-changing,” says Haas. “We immediately decided to invest, and now we’re close to purchasing a second system to further expand our scanning capacity.”
While Atlas doesn’t scan every die, the practice is becoming more and more popular. “A few years ago we scanned maybe 30 percent of the dies we either built ourselves or maintained for other stampers,” says Haas. Today we’re scanning more than half of the dies that come through here, and I can imagine that climbing to 80 percent or more in the next few years.”
General Motors started the recent trend toward more white-light scanning of dies, say Haas and Watson, then Chrysler and Ford followed suit. Nearly every day Watson or the four other Atlas technicians trained to operate the scanner will scan stamped panels and dies.
Scanning finished stamped parts allows Atlas to capture design modifications on current programs made to improve fitup on the assembly lines. “Typically for current automobile models, when we need to tweak a die to improve panel fitup,” Watson says, “once we get the panel to spec we’ll run a five-panel CMM study, then create a color map of the panel with the scanner. And we capture the new die surfaces as well.”
We watched Watson run a white-light scan a stamped frame rail. Prior to conducting the scan, he wiped the surface with a nonreflective coating to optimize light absorption by the scanner’s three synchronized 1.3-megapixel cameras. He then applied dozens of magnetic reflective dots to the entire workpiece surface. These serve as reference points so that the accompanying metrology software can stitch together the series of images created. Each scanned image covers a maximum area of 500 by 500 mm of the workpiece surface, comparable to some 400,000 CMM data points.
A New Application
Describing a whole new application for WLS technology, Watson describes how some customers have begun to ask him to scan the raw castings before beginning the machining process. Scan data tells them if there’s sufficient material to make the die or part.
“We find this practice becoming common when die parts have been weld-repaired,” says Watson. “The white-light scan will tell us if there’s enough weld metal there to machine the detail back to spec, or if there’s too much weld metal in an area. This situation would then prompt us to rough-machine that particular area prior to finish-machining.“For example, in a die crash recently experienced by a customer, a wear plate fell off of the die and, when the press stroked, the plate went clear-through the pad,” Watson shares. “They weld-repaired the pad and brought it to us to machine. We scanned it first, to ensure they had deposited enough weld metal. Sure enough, we found that they needed to add another 10 mm of weld in some areas. A lot of time would have been wasted had we not done the scan and started machining immediately.” MF
See also: Hexagon Metrology Inc.
Related Enterprise Zones: Tool & Die
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