Compact pneumatics underpin lens making machine

Advanced automation components have helped system integrator Barr and Paatz produce what is believed to be the first fully-automated contact lens manufacturing machine.

Advanced automation components from Festo have helped system integrator Barr and Paatz produce what is believed to be the first fully-automated contact lens manufacturing machine.

Developed for Clearlab, the international supplier of daily disposable lenses, the new type of machinery integrates a complete lens manufacturing process - from injection moulding to foil packaging - into a footprint just eight metres square.

Moreover, by using highly flexible robotic handling arms to transfer products between the process stages, the machine can produce over 24 million lenses a year.

With seven major stations required to meet Clearlab's process requirements - injection moulding of a cast, plastic dosing, two stages of curing, hydration, packaging and autoclaving - the physical size of the automation was critical.

"Our focus in designing this machine was on implementing the best and smallest technical solution," says Stirling Paatz of Barr and Paatz.

"We were looking for the optimum pneumatic components available to provide us with benefits in areas including real estate, performance and energy efficiency." Over 400 Festo pneumatic actuators are used throughout the machine, organised into cells for each process stage.

Each pneumatics cell - consisting of one or two valve terminals - operates semi-autonomously, as an I/O extension to the control system inside a Bosch Rexroth articulated robot.

Nine robots perform the pick-and-place loading/unloading between the station and the conveyor.

Profibus is used as the communications mechanism within the machine, for both the real-time I/O commands that control the cell's operation, and the handshaking between robot arms that coordinate downstream and upstream handovers.

Barr and Paatz chose to base the pneumatics design exclusively on Festo components because of the added value this approach brings.

With such a large number of pneumatic components, a major element of this value lies in the common physical and interface standards that come with parts from a single supplier - simplifying the construction of complete handling axes, the integration of accessories and general system building.

A further advantage was the ability to choose optimised component designs.

Among the examples found on the machine are numerous Festo compact-design cylinders, which are around 40% shorter than industry-standard parts.

Other advanced components include VADM modules, which combine a vacuum pick-up function with a blow-off ejection mechanism.

These parts save precious space in the front-end lens handling area, as well as reducing air consumption through close-coupling and electronic control.

Elsewhere, a pre-integrated X-Z axis handling unit known as HSP provides a ready-to-use solution for high speed pick-and-place operations between stations.

The sheer size of the pneumatics system made the choice of valve terminal critical.

Here, Barr and Paatz selected the modular MPA valve, which provides a high flow capability in a width of just 10mm.

These valves are mounted on Festo's high density CPX valve terminal backplane.

The MPA portion accommodates up to 32 single- or dual-port valves - fitted with a Profibus interface for system integration.

Over a dozen of these backplanes are distributed around the machine.

In addition to controlling the pneumatics, the CPX backplanes also provide digital I/O expansion for the robot controllers.

The result is a highly space-efficient and distributed solution for the electrical sensors and actuators required in the machine.

"Festo components have clever surface features and a common interface system that provide a very tidy way to build a large automation system", adds Paatz.

"This has saved a considerable amount of space, which in turn allows our client to increase manufacturing capacity within a very small footprint." In addition to supplying the right pneumatic component functions, Festo assisted Barr and Paatz with a number of services to simplify this large-scale project.

CAD models of the components speeded machine design.

Barr and Paatz was also able to use these models to call off complete pneumatic sub assemblies using a single part number, which greatly simplified purchasing and system building.

This included the populated valve islands, which typically had a large number of digital I/Os, and a full complement of 32 valves - zoned into groups for vacuum, compressed air or nitrogen services.

Festo's assembly and logistics services are now expected to be of considerable benefit to Barr and Paatz in the future, as more of these machines and cells are manufactured to help Clearlab ramp production to meet growing demand for its unique lenses.

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