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Choosing the best measurement device involves balancing the needs for accuracy, speed, flexibility, and workflow efficiency with the lightest possible data models.
Data are at the core of smart manufacturing; they’re pivotal to innovation and agility. At the same time, the vast amounts of new data captured daily in manufacturing present substantial challenges—no more so than within quality control, where this significant data load can lead to data analysis and management issues along with cumbersome and time-consuming workflows.
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As manufacturers seek to more rapidly improve both their operational efficiency and the quality of new products, metrology systems play a key role, starting with how to digitize parts in a more efficient, smarter way for quality control purposes.
How are we improving data gathering, inspection workflows, and agility to raise the bar of measurement productivity?
Here we explore some of the latest technology solutions in portable metrology—focusing on 3D scanning—that are helping manufacturers solve typical measurement productivity challenges by capturing crucial data more efficiently. We’ll look at:
• 3D laser scanning with laser trackers and portable measuring arms
• Structured light scanning
• Handheld 3D scanning
High-productivity large-scale inspection using an AS1-XL scanner and laser tracker (not shown)
Capturing what matters
Choosing the best measurement device in any situation is driven by specific application requirements, balancing the needs for accuracy, speed, flexibility, and workflow efficiency. Key considerations include the complexity and size of parts to be scanned, and the level of detail required.
Complex parts, or sections of a part, with a range of features, curvatures, or varying textures such as holes, slots, and struts benefit from scanning with a higher data-point density (i.e., higher resolution) to accurately capture finer-grained details.
But for most larger parts, and those with fewer details and more open and uniform surfaces, you don’t need this full resolution. You need enough accuracy—appropriate accuracy—to capture the data that matter. For many such applications, you primarily need the scan data to create a complete 3D model of the entire part. In cases like these, scanning everything with the finest resolution is unnecessary.
There can be too much data
Challenges when scanning at unnecessarily high resolutions • Longer, often infeasibly long measurement process times. When measuring larger, less complex surfaces, it’s like painting a wall with a tiny paintbrush. |
For large components and parts that are less feature-dense, scanning at the highest resolutions presents a massive productivity challenge, with full digitization and CAD modeling becoming an unnecessarily time-consuming and cumbersome process.
Especially when modeling larger parts, taking a very high resolution, high accuracy scan of the entire part results in a very data-heavy model that will be hard to work with and need extreme processing power. This is an increasing challenge as large-scale inspection applications become common across several manufacturing sectors. Measurement hardware is so good now that often too much data can be thrown at inspection engineers.
So anything that can reduce measurement times and lessen the computing burden to make post-processing and analysis faster and easier is beneficial. The solution starts with not being saddled with redundant, nonproductive data.
So how do we best provide a 3D model that is accurate and high resolution in all the places it needs to be but is lower resolution in the places where this isn’t needed?
Individual sensors tuned to the application
A well-established approach is to develop different measurement devices intended for high accuracy/fine detail capture on one hand and larger scale/high productivity applications on the other. Having specific sensors tuned to particular measurement tasks helps users alleviate the problem of collecting too much data, making measurement easier.
In Hexagon’s case, for laser trackers and portable measuring arms, this has meant developing two versions of its latest generation 3D laser scanners. One, the Absolute Scanner AS1, is ideal for scanning fine details and high-accuracy applications; the other, the AS1-XL, is dedicated to inspecting large, less complex surfaces for which fast measurement speeds and higher productivity are the priority. Key here is the ability to switch devices within seconds at the press of a button.
Large-scale high-productivity inspection using an ASI-XL scanner on a portable measuring arm
To make the full digitization of large surfaces faster and easier, the key innovation was to refine the technology to increase the area being scanned with every pass of the scanner. This boosted productivity, improved usability, and enabled faster measurement process times.
With the AS1-XL, accuracy is retained to within 150 microns when used with a laser tracker. That’s a key trade-off compared with the much finer accuracy you get with the AS1, but it’s ideal for digitizing larger, less complex surfaces and pieces that would typically otherwise demand impractical measurement process times.
Combining devices in an integrated metrology workflow
Where we’re seeing inspection engineers achieve even bigger productivity gains is when they combine both types of laser scanner within a single integrated measurement routine.
A user can scan feature-rich parts and edges with a scanner designed for high-resolution, fine-detail measurement and high accuracy, like the AS1, and simply switch on the fly to the XL device for high-productivity scanning of larger surfaces and deep cavities. This provides a 3D model that is accurate and high resolution in all the places it needs to be but is lower resolution where this isn’t needed. You get high-speed surface inspection at peak efficiency within the same measurement session.
Scanners with cross-platform compatibility like these allow sharing between different positioning devices—such as a portable measuring arm or laser tracker—and using whichever best fits the application at hand. For example, you can scan an automotive exterior with a tracker system, then switch to the portable arm for the vehicle interior, an area that would be difficult with the tracker due to line-of-sight limitations.
Flexible single-device solutions
Direct scanning: This is another valuable and quickly developing laser tracker technology for fast, large-scale measurement at metrology-grade accuracy over long distances, with capabilities that prevent data overload.
Technologies like Hexagon’s Leica Absolute Tracker ATS600, which combines time-of-flight and phase-shift measurement, allow users to freely define the target measurement area and point density. The operator is in complete control of the balance between process speed and the level of detail that will feed into the metrology software. For the ATS600, this means a quick check at 10 seconds per square meter to a scan at 135 seconds per square meter.
Selective scanning and fully configurable measurement point density equals high productivity with accuracy where it’s needed.
Direct large-scale scanning of a wind turbine blade using the Absolute Tracker ATS600
Structured light scanners (SLS): These are a tool of choice for many small to medium-size applications requiring high resolution and accuracy.
Recent innovations have introduced new functionalities that eliminate several limiting aspects of traditional SLS technology, delivering greater productivity and workflow flexibility along with lighter data models.
As Hexagon developed its new SLS technology, we wanted a solution that could meet the demands of the many applications where it’s not efficient to scan everything at high resolutions and not acceptable to scan everything at lower resolutions. And we wanted this in a single device.
Conventional structured light scanners have a fixed optical configuration that requires a user to decide on measurement coverage or resolution when setting up a scanning project, and then exchange optics or base units for different use cases. This entails a time-consuming setup, recalibration, and warm-up process that’s an industry-wide challenge to greater productivity.
Now, with the latest developments in scanner technology, a user doesn’t have to think about system configuration; there’s only one hardware setup with no interchangeable optics.
During measurement with Hexagon’s SmartScan VR800 structured light scanner, a user can control both the inspection resolution and volume of the measurement in software with no need for any mechanical adjustment. In a single, continuous workflow, data-heavy, high-resolution scans can be focused on the feature-rich areas of a part that matter most, while other areas can be covered more efficiently by larger or lower-resolution scans. These different-resolution scans can then be seamlessly combined into one comprehensive model.
Several measurement volume options are available. The largest has a diagonal of 800 mm, the smallest 160 mm, and changing between them delivers an X,Y resolution range of between 238 and 49 microns.
How is this done? The scanner uses four 20 MP cameras in a dual stereo setup for the range of measurement volumes. A motorized zoom lens on the digital projection unit enables the user to adjust data resolution and measurement volume entirely through software settings.
The other innovation that speeds up the scanning workflow and reduces data use is a new functionality where the two outer cameras take an alignment image at the same time as the user scans with the two inner cameras. This tightly knits together the separate scan pieces without needing overlaps of data-intensive, high-resolution scans that require heavy-duty processing power to achieve an aligned mesh. Fewer tiles are needed to get around the part, and less data are used overall to put the complete mesh together.
This all adds up to simpler and more flexible 3D part inspection workflows with faster processing of scans by cutting down on excess data while keeping the essential detail where it’s needed.
Inspection resolution and measurement volume can be controlled with the SmartScan VR800 structured light scanner.
Handheld 3D scanners: Scanners that require no referencing hardware (e.g., a laser scanner or portable measuring arm) are another single-device solution with flexible and data-efficient measurement capabilities.
Multiple scanning modes, like those on Hexagon’s two new handheld 3D scanners, enable the user to tailor scanner performance to the application at hand to achieve greater efficiency and larger coverage or higher resolution on intricate features. Users can change the scan mode as they measure with on-device controls to fine-tune performance to the features and surface characteristics of individual sections of the application. Data collected under these different modes are automatically combined into a single, efficient point cloud/mesh.
Flexible and data-efficient handheld measurement is possible using the MARVELSCAN.
Making metrology hardware smarter
We started this article by observing that data are pivotal to manufacturing innovation and agility, and that the search for better efficiency is never-ending.
Boosting inspection productivity is about turning the real world into actionable 3D data faster. As we’ve seen, this isn’t only about speed. It’s also about balancing accuracy, flexibility, and workflow efficiency—with the lightest possible data models—and solving this for specific measurement applications.
We’ve outlined an effective tool kit of versatile metrology technologies that are helping users capture and analyze crucial data more easily, efficiently, and smartly. From individual sensors specified for the highest accuracy or greater productivity to single-device solutions allowing varying resolutions and measurement coverage to capture only what you need, these devices are delivering workflow flexibility to improve the productivity of quality inspection.
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