Scanning Success

Laser light is an increasingly important tool in the press room for reasons that extend well beyond part inspection

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In 1960, Hughes Research Laboratories engineer Theodore Maiman invented the laser. He had help, and it’s almost certain that others would have reached the goalpost soon after had he not succeeded. Yet Maiman was, indeed, successful, and his “solution looking for a problem” has become one of the world’s most well-known, useful technologies.

Automated laser-based inspection cells like this one help automakers and other OEMs increase throughput and ensure part quality.

Switch hitter

There’s no room to discuss the many applications for lasers here, although we will point out a few of its increasing uses in the press room. Several of these come from Brandon Tillema, senior technical marketing manager at Keyence Corp. of America. He notes that when stamping metal blanks via a robot or other automated process, it is critical that only a single blank enters the press.

“If there is a double feed, it can cause damage to the press and die, an event that can lead to costly downtime and replacement costs,” he says. “Our Double Feed Blank Detection system uses a laser sensor to accurately differentiate between one blank or two, even if they are exceedingly thin.”

Portable measuring arms can be fitted with laser scanners as well as touch probes, providing a fast, flexible and user-friendly measurement solution.

Similarly, manufacturers can use lasers for thickness monitoring during stamping operations. One example comes from industrial instrumentation supplier Advanced Gauging Technologies of Ohio, which replaced its legacy measurement technology – a system that relied on radioactive sources – with Keyence LK-G Series 1D laser sensors. This eliminated the need for costly licensing and leak testing while delivering a thickness gauge that is “alloy insensitive and can measure virtually any material in sheet, strip or coil form.”

“Ensuring consistent thickness when stamping is extremely necessary for creating quality parts,” Tillema says. “So is controlling material width and meander. With progressive die stamping, for instance, it’s common to feed from a giant roll of metal, or coil. Confirming that the material is the right width and positioned correctly before entering the press is crucial. Our optical micrometers can be used to monitor the edge position to determine that both variables remain within specification.”

Confirming the press achieves the proper bottom position is equally necessary. Here, laser-equipped measurement devices monitor ram movement with high precision, alerting operators to potential issues, such as die wear, flash or discarded material being stuck, or a double blank feed.

Lasers are also used to measure the finished product once the stamping process is complete. “By utilizing height data, our 3-D profiler can inspect parts and pick up on warpage, cracks, deformations and other quality issues, all of which could be signs of problems with the press or tooling,” he says.

Structured take

Keyence isn’t the only supplier with a laser focus on the parts exiting the stamping press. Far from it. Capture 3D, a Zeiss company in Santa Ana, Calif., has numerous measurement solutions, including its T-Scan Hawk 2 handheld laser scanner and ATOS 5X laser-based 3-D and ATOS 5 blue light 3-D scanners, the latter of which employs structured light rather than a laser to complete its metrology mission.

By using lasers to precisely measure ram location during stamping operations, it’s possible to detect die wear, flash, double blank feeds and other potential problems.

So what’s the difference? “The products just mentioned are very well-suited for a variety of sheet metal and stamping applications,” says Griffin Gout, product sales manager. “However, while laser scanners do a good job when scanning surface topology [overall shape], they cannot use the Grey Value Feature technology available for the ATOS 5 family, which can also measure the location of holes and edges. This makes it a stronger, more efficient solution for these applications.”

Gout notes that users can apply surface defect detection and classification on stamped parts to ensure that no defects are created as part of the manufacturing process and perform flush and gap analysis with digital assembly tools to ensure sheet metal components fit together as they should.

“The main advantage of using this technology for stamping and sheet metal applications is the significant time and cost reduction compared to traditional sheet metal manufacturing,” he says. “For instance, a large body-in-white that can take hours to program with traditional measuring devices can be digitized completely in under an hour when using the ATOS blue light scanner configured with our ScanBox automated 3-D measurement cell, resulting in a full digital twin for analysis with an easy-to-read color map.”

He further suggests that the handheld Zeiss T-Scan Hawk 2 is often used to validate stamping dies, even when inside the press, comparing them against the CAD model to ensure the die is within specification. And for those concerned about using structured light to measure shiny surfaces, Gout says don’t worry. “This is our next-generation laser scanner that can scan highly reflective parts without the use of spray or powder.”

Let there be light

Reflectivity has long been a hot discussion topic in the world of laser and structured light scanners, although newer technologies like those mentioned are making it into a nothing burger.

The Keyence LK-G Series ultra-high-speed laser displacement sensor precisely triangulates distance and position of part features even on moving targets.

“We direct the laser beam toward the workpiece and actually need a certain amount of reflection to get the beam back for processing, so if it’s a completely light-absorbent surface, we can’t measure it. That said, these occasions are rare, seeing as we only need one-billionth of one percent of the transmitted energy reflected back to us, nor do we have problems with highly reflective or even mirror-like surfaces.”

That’s according to Paul Lightowler, APDIS global product manager for Nikon Metrology in the United Kingdom, and he’s talking about the system named in his job title, the APDIS Laser Radar. He’ll also tell you the system was originally developed for the aerospace industry more than 20 years ago, but it has since become a favorite among automakers. “It’s very effective at measuring body panels and other sheet metal components, up to full car body assemblies,” he says.

It’s also said to be quite accurate. Lightowler claims the device boasts single point accuracy of “around 10 microns per meter” and length accuracy roughly twice that. This “maximum permissible error,” or MPE, gives the APDIS capabilities comparable to that of another automotive favorite, the horizontal arm coordinate measuring machine (CMM).

“Very accurate CMMs measure down to the single digit micron range, a value we can’t yet achieve, but for many of these applications, under 100 microns is perfectly good,” he says. “That’s an area where we really shine.”

They shine so brightly that Lightowler and his team are augmenting and, in some cases, replacing CMMs on the production line.

“Moving from a touch probe to a laser scanning solution means that you can generally measure much more quickly, and we can help them accomplish this by integrating our LC15d or comparable laser scanner onto their existing CMM,” he says. “But if the customer is looking for even greater productivity, we frequently position the APDIS as a replacement for large horizontal arms. Not only can we reach the required accuracy range, we can also measure up to 10 times faster than a traditional, touch probe-equipped CMM.”

The ATOS blue light 3-D scanner configured with an automated ScanBox 3-D measurement cell creates a solution capable of digitizing a complete body-in-white in less than one hour.

Granted, most customers still have their CMMs and still use touch probes to reach areas that scanners can’t. “CMMs are a known technology, and if you need to measure the footwell on a car body, for instance, or a hole with a high aspect ratio, touch probes were often the only solution,” he says. “The Laser Radar, however, can measure these and even previously inaccessible areas due to its long range without needing to go near the part. By using these new technologies, you achieve maximum measuring flexibility as well as speed.”

Gaining interest

Chuck Chronicle, sales engineer and productivity specialist for Hexagon’s Manufacturing Intelligence division, describes a system similar to Nikon’s APDIS, the Leica Absolute Tracker AT960. Automaker Volvo has one at its Car Body Components facility in Olofström, Sweden, he says, where workers use it to scan test parts and the dies that make them and, in one notable instance, to perform the initial alignment for one of these massive tools on a large stamping press.

Chronicle agrees with Lightowler’s comment that trackers are edging into territory once occupied solely by CMMs and that laser scanning heads have become a common attachment on these machines. He also seconds what was said about reflectivity and the fact that it’s not the problem it once was.

The Zeiss T-Scan Hawk 2 is a next-generation laser scanner that can scan even shiny parts without the use of spray, making it ideal to scan smaller sheet metal dies for comparison against the CAD model to ensure the die is within spec.

“We’ve developed what’s called ‘SHINE technology,’ which stands for Systematic High Intelligence Noise Elimination,” Chronicle says. “It reduces the signal noise caused by reflective surfaces. In addition, we adapt the exposure settings based on the material as we detect it. This helps to create a feedback loop that improves the quality of the data fed back to the software.”

Chronicle is also quick to point out that laser scanning heads like the company’s T-Scan 5 have become quite common on portable measuring arms and are even finding their way onto robots. One example comes from another European automaker – Škoda Auto in the Czech Republic, part of the Volkswagen Group – that recently installed the T-Scan 5 onto Fanuc robot arms for the automated inspection of stamped body components.

And global forklift manufacturer Hyster-Yale of Northern Ireland routinely uses Hexagon’s Absolute Arm equipped with one of the company’s laser scanning heads to cut measurement times from eight hours with manual methods to “as little as 40 min., including programming.”

“We’re seeing a great deal of interest in laser measurement solutions, not only from automakers and large OEMs like Hyster, but also from smaller manufacturers,” Chronicle says. “We’re getting down into the 10-micron accuracy range, good enough that some shops – sheet metal fabricators among them – can use these systems to check a large percentage of their work. Laser scanners have also become much easier to use and program than they once were, so I expect that widespread adoption isn’t far away.”

Hexagon

Keyence Corp. of America

Nikon Metrology

Zeiss Group

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