Adjustable spectacle manufacturer Eyejusters, based in Oxford, has used automation expertise from FANUC to apply techniques in injection moulding and robotics. Eyejusters also partnered with automation provider, Hi-Tech, for its expertise in 3D simulation.
Eyejusters product’s use a ‘SlideLens Technology’, a lens with a special profile containing both positive and negative power areas. When two of these lenses are placed together, the positive and negative power areas cancel each other out. When one lens is then moved across the other, the amount by which they interact varies, changing the focus.
Eyejusters and FANUC planned a way to bridge unique challenges in spectacles injection moulding by that could only be overcome through ongoing product and process development by focusing on a design as thin as possible, so that the two lenses, plus the protective rear cover, remained aesthetically neat and compact.
Because the unique Eyejusters lens design has special varying thickness profiles, it is almost impossible to mould the lens with conventional injection moulding techniques. This is because the injection melt front tends to move around the thicker sections before completing the fill at the thin sections, which, in this case, are located in the centre of the lens. Using conventional techniques, it is highly likely that problems with quality, such as hairline marks and air traps, would be present.
FANUC and Eyejusters ran a series of moulding development tests, to perfect the tool design so that it could work in combination with the unique CNC Roboshot special functions, gradually calculating the workable boundaries to achieve the thinnest possible and highest quality lens product.
The outcome of this process development exercise was a final production solution comprising a special patented mould design, combined with Roboshot’s precision ‘Pre-Injection-compression’ function. The material was injected into the tool under reduced clamp force. At a precise injection point, full clamp force was then applied to compress the moulding as injection completed. The precision nature of the Roboshot CNC control meant selected positions to control the process were repeatable within 0.001mm.
With the lens moulding techniques and processes fully defined, the next stage was to consider the integration of the injection moulding process within a production cell. This would also need to contain the additional technologies and processes required to assemble and finish the lens modules. It was at this point that the long-standing partnership between FANUC and Hi-Tech Automation helped the finished product. Hi-Tech Automation has years of experience within the plastics sector and, as a certified FANUC Strategic Partner, the company had an intimate knowledge of FANUC’s robot range, making Hi-Tech a valuable addition to the overall project team. This effectively seamless partnership between the different FANUC business areas - Roboshot and Robotics, together with Hi-Tech - proved to be highly beneficial to Eyejusters, as all of the expertise required for the project resided within this close-knit team.
As the “product” was the only fully-defined element of this project, Hi-Tech’s initial task was to develop a working specification for each of the production processes and steps. This would require day-to-day liaison with Eyejusters personnel to review each step and make decisions on processes, specifications and parameters.
The first step was to determine how best to remove the individual mouldings from the tool. In this instance, the team decided it would be beneficial to have the individual moulded parts attached to a runner and sprue for orientation purposes.
This would allow the parts to be removed, transported and handled safely through subsequent processes, without the need to touch the critical optical surfaces. The robot gripper systems were therefore designed, manufactured and integrated into the robots.
Now that the first task in the automation process had been resolved successfully, the team could turn its attention to the subsequent processes which needed to be considered, evaluated and fully defined, including: lens coating, component de-gating, ultrasonic welding and final packing into thermoformed trays.
Hi-Tech turned to FANUC’s unique Roboguide simulation software to design, model and create the layout virtually. Using Roboguide, the various elements of the system could be tested and developed before any equipment was ordered or manufactured. Further benefits included the ability to evaluate and determine accurate cycle times and to generate the robot programmes offline.
Cleanliness was a key consideration for the optical product, and the techniques used for de-gating and welding would have to eliminate the potential for the contamination of the lens components by particulate matter. Hi-Tech selected laser de-gating and ultrasonic welding processes to perform these delicate operations because they were clean and precise.
With the automation cell built and operational, a Class 5 Clean Room needed to be built around the cell before production level components could be produced. Hi-Tech specified a solution that met all cleanliness standards and incorporated full air handling through entry and exit air locks, thus allowing the cell to begin production.
After the completion of the Eyejusters venture, each partner was recognised for its individual contribution at the Plastic Industry Awards. FANUC received the award for Supplier Partnership – Prime Machinery and Hi-Tech received the Automation for Supplier Partnership – Ancillary Machinery award. Eyejusters also received the award for Best Business Initiative of the Year.
Adjustable lenses from Eyejusters