Lights, Camera, Assemble!
While machine vision technology is not new, the latest generation of systems feature tools such as digital cameras, LED lighting, and the Camera Link and FireWire standards to help simplify and enhance assembly applications. Components are smaller, faster and more robust. Image-processing software is better than ever.
The bottom line: Vision is a viable option for many more assemblers than in the past.
True, state-of-the-art machine vision systems are not cheap. But they offer numerous benefits to assemblers interested in cutting retooling costs and labor costs, and improving flexibility and quality.
Today's manufacturers are also under increasing pressure to trace and validate the products on their assembly lines. Automotive, aerospace, medical device and electronics manufacturers, for example, are using identification codes to error-proof their processes and create an accurate history of each part from the beginning of its life to the end.
In addition, lean manufacturing initiatives demand that an inspection system be in place to detect defects and rejects before too much waste or scrap is generated. Vision systems often fill the need for reliable inline inspection.
Finally, increases in production volumes, faster production speeds and workforce attrition due to cost-cutting measures often make the use of manual inspection hard to justify. In some cases, the human eye is simply no longer able to detect flaws because products have become so small.
"Machine vision systems save companies money over time," says Kyle Voosen, data acquisition and vision product engineer at National Instruments Corp. (Austin, TX). "With manufacturing becoming cheaper overseas, and customers expecting defect-free products, a company is gambling with its own future if it ignores the long-term benefits of machine vision. If machine vision keeps a defective product out of the hands of a customer, then it has saved more than just money; it's also preserved the reputation of the company and the confidence of a customer."
New and Improved
The biggest difference in vision systems over earlier technology is more speed for less money. With faster processors, vision systems can both acquire more information from cameras at faster frame rates and take advantage of more complex algorithms to verify assembly, while maintaining high speeds.
Another difference is that machine vision has become much less difficult to deploy, with most vision systems now featuring user-friendly tools to simplify assembly applications.
"Machine vision systems are easier to use than 10 years ago," says Ed Roney, manager of vision products at FANUC Robotics America Inc. (Rochester Hills, MI). "The vision, setup and application tools are significantly better. Application-specific vision systems, like systems for robotic guidance, where the task of the vision system is constrained into the application and task at hand, offer the best opportunity for simple implementation. In most cases, the vision system can be applied ‘out of the box,' requiring no custom programming-just setup."
Not that setting up a vision system is always a piece of cake. Machine vision remains one of the most complicated technologies you can find in an assembly plant, and manufacturers have to deal with a number of different factors, such as lighting, optics, high-speed image processing and software.
Fortunately, there is a broad range of machine vision technologies available today-ranging from high-end, PC-based systems down to very low-level embedded sensors-that can vastly simplify the process, depending on the application.
One of the most critical components of any machine vision system is its cameras. Many machine vision applications today use digital cameras. Although they cost more, digital cameras are not bound by the resolution and speed specifications of their analog cousins, thanks to their higher resolutions, greater pixel depths and more variable frame rates.
Another option is "intelligent," or "smart," cameras, systems that include both the imager and image processor in a single package. Past intelligent cameras did not have the horsepower of full-fledged vision systems. But, with improving power, speed and image processing software, they are now offering features such as automatic recipe control, subroutines and multitasking.
Intelligent cameras offer great benefits by simplifying implementation. Among other things, manufacturing engineers can avoid the problems that can result from wedding together different types of hardware and software.
Bear in mind, though, smart cameras have limitations. They do relatively well in simple applications, such as barcode reading and low-resolution measurement applications. But, for more demanding applications, digital cameras offer greater flexibility, higher resolutions and the user's preference in terms of machine vision processing.