Examinees put in the right light

drylin®®-linear axis in high-speed inspection systems

Visual inspection of small components in very high quantities: Gefra GmbH in Friedewald/Westerwald has set itself the task of automating this task - and is successful with it worldwide. Gefra uses complete linear drive units from the drylin® programme from igus® for the electrical adjustment of the lighting units.

How do you inspect 900 screws or 700 injection moulded parts per minute for damage? anyone asking themselves this question will find the right answer at Gefra GmbH, a company founded in 1995 that specialises in developing automated systems for the fast and precise optical inspection and measurement of components.

The reason for founding the company was the realisation that there was a need in this area. Dipl.-Thomas Rothweiler, founder and managing partner of the company, advised production companies on rationalisation and automation. In doing so, he realised that at the end of highly automated processes, goods are often still checked with the human eye and sorted manually.

Mechanics and computing speed set technical limits
With the continuous further development of the systems, the mechanics, i.e. feeding at such a high speed, have always reached their limits in the past. In some cases, however, the computing speed of the available control systems also reached its limit, which is also obvious when you consider that in some cases eight or ten cameras inspect the test specimen and the control system has to decide whether it is "good" or "not OK" within milliseconds.

Electrical adjustment of the lighting
Even though each machine is customised to the customer's requirements, Thomas Rothweiler emphasises that this is not a case of custom machine construction: "Our machines are based on a modular principle and we use many identical parts."

A current further development concerns the lighting, which is used to put the test specimens in the right light for the cameras. The distance between the lights and the test specimen varies depending on the product, and the user adjusts the lights manually using a dial with a scale. Thomas Rothweiler's aim was to integrate this process into the control system and thus make it reproducible. This was not only intended to save manual process steps and eliminate the possibility of incorrect settings. Even more important was the ability to integrate the position of the lights into the documentation.

Lubricant-free operation
Lubricant-free operation of the spindle and carriage was a crucial criterion in the selection process: As the lighting units are located directly above, next to and below the objects to be inspected in the system's working area, the drives must not emit any foreign substances that could impair the inspection process.

The compact nature of the drive units was equally important. Thomas Rothweiler: "As we will be offering electric adjustment as an option in future, it must be possible to integrate it into the existing design. It is also important to us that we obtain the entire unit with motor, carriage and mounting ready for installation from a single source."