Vision system boosts automotive display quality

VDO approached Weber Systemtechnik to produce two complete process-integrated quality inspection solutions for its radios and navigation systems production lines.

Advanced production systems and exceptionally high quality requirements for car radios and navigation systems at VDO in Wetzlar, Germany, call for sophisticated inspection systems and flexibility in image processing.

In the face of global competition, the automotive supply industry is demanding a high degree of automation combined with very high quality.

It is no longer a question of statistical quality inspection, rather it is a case of satisfying the requirement for DPMs (defects per million) of fewer than 100.

Top quality products coupled with the ability to respond quickly to product changes is a critical factor in this highly competitive market.

The quality requirements have become extremely stringent because the end customer expects a perfect product.

For example, VDO in Wetzlar, Germany, supplies dashboard equipment to a number of international car manufacturers, and if one of the night-time illuminated symbols on a car radio or navigation system is considerably less bright than the others, or if the display has regions of different brightness, this creates acceptance problems.

The car radios and navigation systems therefore must be inspected extremely accurately for multiple features.

To cope with these increasingly strigent requirements VDO, approached Weber Systemtechnik, a system integrator that supplies turnkey measuring and inspection systems to produce two complete process-integrated quality inspection solutions for its radios and navigation systems production lines.

Apart from the quality issues Systemtechnik also had to consider that in different countries there are different specifications for car radios.

For instance, at any time a new model might be introduced with a symbol in a different size, shape or position.

At other times, a display from a new vendor may be introduced at short notice.

The machine vision system must be able to cope easily with such changes without interrupting production.

The machine vision system must therefore not only be capable of performing complex tasks, but it must also be extremely flexible.

This applies to the hardware, the software and the easy-to-use man-machine interface.

To ensure all these targets were achieved Weber selected DisplayInspect, a high-end machine vision solution from Cognex.

With its special vision tools, DisplayInspect covers the entire range of quality inspections for all different types of displays.

Like the well-known PatMax vision software from Cognex, DisplayInspect also features an easy-to-use user interface which ensures easy configuration.

This allows the user at any time to tune the system for optimised performance.

As well as the high precision algorithms in the various tools, DisplayInspect also helps the user and system integrator select the most appropriate camera for each application.

The inspection solutions installed incorporates several parts to not only check mechanical functionality; testing the keys by means of robots, but also to check the housing front panel by accurately inspecting for omitted components, scratches, surface differences, correct symbols, night-time illumination and correctly operating displays.

In addition they are able to deal with high quantities in short cycle times and small batch quantities with elaborate inspection requirements.

The maximum throughput in three-shift operation is 3300 car radios a day, ie a radio is completely inspected every 22s.

The first installed system uses two simultaneous acquisition cameras.

With the second system, eight cameras are used to cover the field of view at very high resolution.

The inspection tasks for the radio front panel includes inspection of buttons, symbols, illumination, display and housing.

The cameras are mounted on a traversing mechanism that provides optimum flexibility when inspecting small and large radios on the same system.

The intelligent, comprehensive features in the machine vision software help to guarantee a reliable robust implementation of the complex inspection tasks.

There was no problem in configuring the inspection operations to provide results equivalent to those of human inspectors.

The system offers a significant advantage over human inspectors because the results are reproducible and always identical.

This is what has led to a high level of acceptance of machine vision systems by a wide range of end users.

These were the decisive factors in selecting Cognex's DisplayInspect product.

Burkhard Weber said: "The DisplayInspect system was found to provide by far the best solution compared to any other machine vision systems.

This choice proved to be an advantage in the entire supply chain: from the preliminary work in the feasibility study, the development of the project phase, through to the testing of the complete solution.

It also allowed for the continual adaptation of the inspection tasks to the changing requirements of the customer, VDO Wetzlar.

All this was very helpful when setting up the production line, because meeting the delivery dates and the rapid production start-up timetable were critical issues.

Production ran up more or less immediately from 0 to 100%.

The customer would not have accepted any delay, which could have resulted in claims for compensation".

Weber completed the installation in only six months between order and installation.

The positive experience gained with the two machine vision systems is reflected in today's production expansion projects.

Weber Systemtechnik has already received the order for a third test, measuring and inspection system from VDO.

A further system is expected to be underway shortly.

DisplayInspect has already been chosen as the machine vision system.

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