Scanning systems define parts, improve quality
A discussion with Rick White, Capture 3D
A discussion with Rick White, Capture 3D
VSD: Can you provide some background information on Capture 3D? How are you using machine-vision components and systems?
White: Capture 3D was established in December 1997 based on the premise that incorporating “as built” part definitions at various stages of the product-development cycle would compress product design cycles, improve product quality, and optimize manufacturing processes.
Capture 3D is the exclusive North America provider of the ATOS 3D Optical Scanner and TRITOP Digital Photogrammetry systems designed and manufactured by GOM (Braunschweig, Germany; www.gom.com). With offices in California, Texas, Connecticut, and Michigan, Capture 3D provides quality process improvement solutions in the USA and Canada.
VSD: How would you categorize the market for both contact and noncontact measurement systems?
White: As with any tool, each system has its specific advantages. For example, parts with geometric shapes such as flats, cylinders, and spheres can be easily and quickly measured with contact measurement systems by touching only a few points. Another advantage of contact measurement systems is they have been used in the metrology industry for many years, and companies are comfortable with their results and can easily find operators.
For many applications for parts with organic shape or compound curves, noncontact measurement systems tend to provide a better fit. Because of the speed with which they acquire data and the amount of data they acquire, those complex shapes can typically be better defined and therefore measured, capturing even small flaws that might have been missed by a contact measurement system.
We are seeing the industry move away from the older contact measurement systems to newer technologies and processes introduced by the noncontact measurement systems because of speed and more comprehensive part definition.
VSD: What are the primary applications for which these systems are used?
White: When we first introduced the ATOS system to the US market almost 10 years ago, the primary application was product definition. This means creating a CAD model for those parts and tools that do not exist in CAD. For example, in the automotive industry, cars are typically designed as clay models to achieve the best shape. Clay models are scanned in and tools are created from that scan data to begin manufacturing car parts.
Today about 70% of our systems are being applied to quality-assurance applications. This includes first article inspection, tooling inspection, 100% part inspection in the turbine industry, and part sampling of stamped parts in the automotive industry.
VSD: What should a system engineer look for when evaluating these different technologies?
White: Not any one system is best for every application. Because of the complexity of the technologies, we find that it is quite complicated to compare systems even for experienced engineers and decision makers. As in any complex decision there are many factors that should be considered. The one we see getting missed the most is benchmarking. It is easy for a company to claim functionality, performance, and accuracy; the question is how do those factors play out on your parts and in your environment.
We recommend very thorough benchmarking on the evaluating companies’ parts at their location and do not let the potential supplier leave without leaving the data with you. It’s amazing how a company can leave and then two weeks later the data show up looking great, you might ask how that happened. Be critical evaluating the data, compare measurements to known values, put everyone through the same test. With measurement systems, the quality of the data is often the most important factor. The better the data, the more you can rely on it and the less time is spent with it in downstream applications. It’s worth it to spend more up front to save on the costs associated with poor quality data.
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VSD: In noncontact systems, the two main technologies use structured laser or white light. Can you describe the differences between these two approaches?
White: “Structured laser” is usually used for a laser line projection but it can also be a point projection. Typically a CCD camera is used to capture the projected light line (or light point) on the object. Because of the difference in projection and viewing direction in the structured laser sensor, a triangulation calculation defines the 3-D position of the laser line (point) on the object. With the known x-y-z and angular position of the sensor, the absolute 3-D position of the projected light on the object is defined.
With white-light patterns, multiple patterns are projected and observed by one or two cameras. From the captured images, a complete cloud of data can be calculated instead a line or a single data point. Then the different “patches” can be merged and therefore a complete part can be digitized without any “tracking” request for the scanner.
VSD: What are the differences in speed, measurement accuracy, and repeatability?
White: Because there are quite a few laser scanning systems as well as white light scanning systems, I’m not able to give a precise answer. It not only depends on the base technology used but how that technology is implemented by the developing company and the application it is being used in.
In reference to speed, laser scanners generally collect data one point at a time or one line of points at a time. The white-light scanners that I am familiar with collect whole field, which corresponds to an image collecting a complete volume of data in one measurement. For example, the ATOS III-S uses cameras with a 2000 × 2000 CCD array; therefore, in a couple of seconds it has the potential of capturing 4 million measured points. For some applications requiring detailed information on complex parts, this may be a quicker way to complete the measurement task. For other tasks that might require relatively few measured points on a part moving down an assembly line, the laser system would probably prove quicker.
The perception in the industry is that lasers are more accurate. This came to my attention a few years back when a company designing turbine blades cancelled a demonstration with one of our sales engineers. The director of quality, who had tremendous experience with CMMs, had the perception that a laser on a CMM must be more accurate than a white-light scanning system. Somehow the sales engineer was able to convince the director of quality to benchmark the different products. They found that the ATOS III had significantly cleaner, more accurate data and was faster for this application. Today that company has five ATOS systems installed. For some applications, laser systems may prove more accurate and repeatable.
VSD: What third-party software support is available to render point-cloud information? What does this software allow the user to evaluate?
White: There are actually many software applications that can be used to treat the collected data; a few that we see most often are Geomagic (Research Triangle Park, NC, USA; www.geomagic.com), Polyworks (Québec, QC, Canada; www.innovmetric.com), Tebis (Munich, Germany; www.tebis.com), and Rapid Form (Seoul, South Korea; www.rapidform.com). Typical downstream processing applications include turning the collected data into CAD, using the data for part/tool qualification, and generating tool path from the raw data for machining purposes.
VSD: How large is this market? What do you see as having the biggest impact on making this niche market grow over the next five years?
White: GOM has more than 1500 systems installed worldwide, which is quite a large number in relation to our traditional competitors. It is very small when compared to traditional vision-system solutions. Because it has been relatively time-consuming to collect complete 3-D data on complex parts, the market has been a niche market to help improve product development.
Speed and automation, which are somewhat tied together, are changing that and creating opportunities in production. Traditionally, applications requiring complete 3-D inspection have been best suited for first article applications rather than production environments. Over the past few years we have worked closely with GOM, defining and developing systems with faster acquisition and processing times and automating complete turnkey applications for production environments.
Today we can provide completely automated motion-control systems for smaller parts and robotic solutions for larger parts. Production is where we will have the biggest impact and, therefore, experience the most growth. We have customers using our automated solutions in the aerospace, automotive, power-generation, and consumer-goods industries.
Rick White is the director of business development at Capture 3D (Costa Mesa, CA, USA; www.capture3d.com) and has been with the company since its founding in 1997. Since that time he has been involved in defining and implementing more than 200 inspection solutions for the aerospace, automotive, power-generation, and consumer-goods industries. Editor in chief Conard Holton spoke with him about noncontact measuring systems.