When size matters

23 August 2017

An innovative compact control solution was specified for use on an equally innovative photochromic lense coating technology. Control Engineering Europe finds out more.

Today’s organic photochromic lenses, which darken automatically in response to short-wave light, involve a very complex manufacturing  process are very complex and therefore expensive. The photochromic process sees molecules of silver halides embedded into the lens material which transform into neutral silver atoms that absorb a significant percentage of visible light, resulting in the lens darkening. 

A new solution has been developed by Shyre Ltd, which allows for the production of photochromic lenses at one-tenth of the traditional cost.

The new coating technology makes it possible for large eyeglass retailers or labs to produce customised photochromic lenses made of all kinds of materials eliminating the need to stock large amounts of costly pre-made photochromic lenses.

Lee Gough and Dan Hancu, developers of this technology and directors at Shyre, explain the concept: “Developing a chemical process for coating the lenses was the first major challenge. The second involved designing the machine.”

The process starts with the lenses being placed on a conveyor that transports them into the machine where they undergo a five-stage chemical cleaning process before being dried. They then move into the dipping station, which applies the coating. Finally, the optician cuts the coated lenses to the correct size for a particular frame. In addition to the cost-saving benefits of the process the coatings can also applied in all colours and even with gradients, while the classic process is only able to produce lenses that turn either grey or brown.

A compact controller
The coating process required Gough and Hancu to find a compact controller and they turned to Beckhoff for a solution. Gough takes up the story: “What impressed us initially about Beckhoff’s offering was its One Cable Technology (OCT) for servo motors. We had been looking for a compact solution as the drives needed to be integrated into the machine. By implementing Beckhof AM8100 servo motors with OCT we were able to save a lot of space, because the control cabinet only needs to be 20 cm deep. Since laboratory facilities are generally expensive and space is at a premium, this was vital.” OCT combines power and feedback signals in one standard motor cable which can help reduce project material and commissioning costs.

The central controller of the resulting machine developed by Shyre includes a Beckhoff CX5120 embedded PC with an Intel Atom processor running TwinCAT 3 automation software functions. A CP2912 multi-touch panel is used for operator interaction and ‘recipe’ control. With IP65 protection at the front and IP20 at the rear, the panel is well suited for use in this application. 

Gough has been impressed by the control system’s flexibility, which allowed it to upgrade from TwinCAT 2 to TwinCAT 3 during the design phase. “The connectivity of the PC-based platform is another benefit, because it allows us to integrate it directly into our VPN system,” he said.

“Using a secure and dedicated Internet interface, we can support all of our customers remotely from our head office. The coating machine includes components such as solid-state switches and sensors, LED lighting, brushless motors and lubrication-free bearings to keep maintenance and downtime to an absolute minimum. Having access to the data stored on the system, our process experts are able to quickly identify the root of any issues or recommend improvements remotely.”

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