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Vision Engineering Ltd.

Metrology

Rapid Measurement of Plastic Automotive Components

Hawk noncontact measurement system combines optical image display with automatic video edge detection

Published: Thursday, March 24, 2011 - 09:52

(Vision Engineering: Surrey, UK) -- Vision Engineering Ltd. has developed Hawk, a noncontact measurement system that is the first to offer both a true optical image display combined with fully-automatic video edge detection. Both of these technologies have been available individually but never before as a combined package.

Hawk can be run manually, motorized, or in fully automatic mode. For rapid product changeover, manual operation allows for quick setup in any measurement task. For high-volume throughput, automation allows repeated, objective inspection much faster than manual measurement. In between these extremes, there are a host of application areas that benefit from partial automation (e.g., where components cannot be automatically checked or where product variety makes multiple measurement routines impractical). Hawk allows both techniques to be used in one system, and this opens up many opportunities where, previously, either technology alone would have been insufficient. One significant application area for the new technology is molded automotive component inspection.

Low-contrast colors hamper efficiency

Automotive components have critical quality requirements in terms of function, tolerance, and aesthetic appearance. Increasingly, plastic components are being used in automotive manufacture where previously steel or aluminum would have been necessary. This isn’t simply limited to interior trim but includes mechanical components as well. While reducing overall weight and improving the cosmetic finish available, this trend does demand that the manufacturing criteria for plastic components be equal to that previously associated with machined metal.

Automotive moldings tend to be manufactured in dark, low-contrast colors—most frequently black, near-black, or various shades of grey. As a result, these components coordinate well with the huge variety of color schemes available in today’s cars. While this is good for the car designer, it makes accurate viewing and gauging much more problematic. To measure a black low-contrast object on a black low-contrast background presents significant challenges to most noncontact measurement systems. This is where the  benefits of the Hawk system come into play.

As an example, a Peugeot climate-control fascia panel is molded in  dark grey. This panel must fit exactly into the climate control assembly or the unit may rattle, and the driver would see a bad fit. The panel is subcontract-manufactured in high volume and requires several key measurements to be accurately verified.

Having an operator use an optical system may not be cost effective because many of the measurement tasks are highly repetitive. An automated video-based system would face difficulties because the contrast between black-on-black edges is too low. The solution is the combined approach as used by Hawk. The basic, clearly defined edges can be automatically measured using video edge-detection (VED) technology. This allows for most of the checks to be fully automated, relieving an operator from time-consuming, repetitive tasks. Once these are completed, the optical display head can be used, allowing the operator to use subjective experience and manually define a feature to measure the difficult, low-contrast features. The result is a system that offers the best of both worlds.

Hawk's Dynascope technology presents a clear optical image to the operator through the expanded exit-pupil display head. This image has not been digitized and will not suffer from loss of color rendition or contrast problems. Video-based systems always suffer when viewing low-contrast, black-on-black, white-on-white, or transparent features as typified by many automotive moldings. The human brain is by far the most powerful image-processing system available, and for difficult optical subjects the best results will come from a pure optical image being presented to a human operator. By using a fully-automated system, the majority of measurements can be controlled by the PC software, and only complex parts will need to be presented to the operator, who can input edge locations.

Avoiding overspecification

Overspecification has become a problem in the production environment. Usability is equally important as capability on today’s shop floor because a powerful and comprehensive system will only earn its keep if it can be used day-to-day by production staff. It is this thinking that has driven the development of the Hawk family to be “designed by engineers, for engineers.” It is intended to be used on or close to the shop floor by the multiskilled, nonspecialist engineers who run the manufacturing process. Because components can be taken directly from the molding or machining station to the Hawk, feedback is rapid and available where the information is needed. If the component is distorted or out of tolerance, remedial action can be taken immediately.

Hawk can be set up to run manually or fully automatic. With the Peugeot climate-control panel molding, this means that initial preproduction runs can be closely monitored and measured using a completely manual inspection setup. The flexibility of manual operation means that changes can be quickly accommodated without the need for skilled programming knowledge. Once volume production has begun, many of these checks or measurements can be fully automated, resulting in higher throughput, reduced inspection-cycle time, and improved repeatability.

As automotive moldings become more complex and quality-critical, consumers are more demanding and have higher expectations. This drives the need for noncontact measurement systems that are accurate, user-friendly, and capable of measuring optically difficult components in volume.

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About The Author

Vision Engineering Ltd.’s picture

Vision Engineering Ltd.

Vision Engineering is a global leading-edge manufacturer of patented ergonomic stereo microscopes, digital microscopes, and noncontact measuring systems.Twenty-five years ago, Vision Engineering introduced the world’s first “eyepiece-less” stereo microscope, the Mantis. It was an ergonomic revolution that went on to win numerous design and innovation awards. Company headquarters are based in Send, Woking, UK, with manufacturing facilities in the UK and U.S. Regional offices are located throughout North America, Europe, and Asia.