Vision systems dash through inspection procedure

Citation

(2003), "Vision systems dash through inspection procedure", Sensor Review, Vol. 23 No. 3. https://doi.org/10.1108/sr.2003.08723caf.004

Vision systems dash through inspection procedure

Vision systems dash through inspection procedure

Keywords: Machine vision, Automotive, Inspection

The unblinking vigilance of six Omron industrial vision systems ensure that dashboard instrument panels meet the near-perfect quality standards of the 21st century automotive industry. It is a truism of the automotive industry that the instrument panel is the most important part of the car, because it is what the driver/ customer looks at constantly.

Doel Engineering of Witham in Essex has built a state-of-the-art inspection machine for Intier Automotive of Lenham, Kent. The inspection and control systems are based exclusively on Omron equipment, as are the machine safety systems (Plate 3). Doel had not worked with Omron before, but was encouraged to do so by Inteir's local branch of control equipment distributors, Underwoods Electrical, who knew that Omron had all the necessary technologies in its portfolio and that their comprehensive expert technical support would allow the project to proceed without a hitch.

Plate 3 The unblinking vigilance of six Omron industrial vision systems ensure that dashboard instrument panels meet the near-perfect quality standards of the 21st century automotive industry

The machine is based on a robust welded steel frame, onto which the instrument panel to be inspected is manually mounted and pneumatically clamped. A bar code identifies the individual fascia and lists its particular specification on the operator interface.

In operation, a number of static vision systems and sensors detect the presence and location of various parts of the assembly, including clips, springs, screws, etc. In several cases, the sensors detect the part through the body of the instrument panel, and the sensors were selected to ensure differentiation between these two media. A boom, driven by an Omron EU series servo, then traverses along the length of the instrument panel carrying out more checks. Any problem highlighted on the operator interface uses graphics rather than text for ease and speed of understanding. At the end of the operation, the system performs a double check on itself by detecting a couple of fixed targets at the end of the boom travel. The cycle time to complete this entire operation is less than 2min, well within the envelope set by the rest of the production procedure.

Various types of sensors including proximity and photo sensors are used. They all feedback to an Omron PLC, which acts as the central controller, as do the control units of the six vision systems. In total approaching 100 separate checks are made on each instrument panel.

The PLC at the heart of the Doel system is a CS1, which Omron developed specifically to provide a backbone for flexible automation requirements. It offers superior control performance, seamless networking options and extensive information management capabilities. Based around a high speed RISC processor, the CS1 fieldbus options and plug-in memory cards give it the ability to support many peripheral devices.

Doel had the original idea of lighting the inspection area with yellow light, as this heightens the visual contrast between many of the coloured parts, making them easier to assess with photoswitches and vision cameras. It also manages to detect the black felts against their black background by angling the light relative to one of the static cameras for optimum reflection.

In fact, Doel was originally founded to serve the OEM needs of the graphics and photographic industries, and about 10 years back it began to diversify into other sectors. These origins mean it has considerable expertise to bring to bear on projects involving cameras, vision systems and lighting. It also finds great affinity with Omron's light beam based curtains and other safety systems required for this machine.

Doel decided on an all-Omron solution when it was assessing the vision system requirements. The costs associated with vision systems can easily spiral upwards, and Doel was impressed by Omron's appreciation of this when it suggested that costs could be contained by using twin-headed low cost F-150 systems so that the number of control units is reduced by half and by having them communicate over a DeviceNet fieldbus to reduce wiring complexity.

The F-150's optional dual camera module allows two images, or two aspects of a single image to be checked in one pass, whilst intelligent light sources make it easy to light targets for reliable checking. Subsequent to networking capability, its DeviceNet interface gives the F-150 multi drop flexibility and allows it to store up to 23 images so that production trends can be monitored. These images can then be uploaded to a PC, along with any measurement data, for archiving to help with traceability.

Easy to set-up and easy to use the F-150 offers inspection for surface defects; image filtering for optimum inspection and measurement; grey edge measurement to detect the position of edges with a high degree of accuracy; a precision grey search for applications requiring highly accurate positioning; and a variety of data output calculations, including minimum and maximum values, calculating distances between points, and obtaining angles between lines.

In optimising the vision system for this application, the specialist from Omron and Doel selected cameras with 512 × 484 pixel resolution on a 50 &times 48 mm target area, achieving an accuracy of 0.25 mm was used. This was required for the clips and brackets, which are assessed for position and location as well as presence, although for the felt rubbing strips presence is more important than position.

The Doel inspection system is able to run 24 h a day, making it capable of inspecting nearly 1,000 instrument panels a day.

For further information, please contact: Robert Brooks, Omron Electronics Ltd, 1 Apsley Way, Staples Corner, London, NW2 7HF, UK. Tel: 020 8450 4646.