Robot automates prescription lens production, cutting labour costs

Citation

(2005), "Robot automates prescription lens production, cutting labour costs", Industrial Robot, Vol. 32 No. 6. https://doi.org/10.1108/ir.2005.04932faf.002

Robot automates prescription lens production, cutting labour costs

Robot automates prescription lens production, cutting labour costs

Keywords: Robotics, Automation

Making spectacle lenses to prescription was traditionally a labour-intensive, manual job. Then in the 1980s, one of the world's top three production machine manufacturers, the privately owned British company, Norville Group, introduced computer- controlled generators for grinding glass lenses automatically. The company scored a world first in 2003 with its Centaur twin-spindle machine for single-point, three-axis, CNC turning of two plastic lenses simultaneously. Now the company has taken the automation process a step further with the development of a robotic system for loading and unloading its machines.

Motoman, based in Banbury, was chosen to supply the 6-axis, articulated- arm robot, which is secured on a gantry and inverted to allow it to sit above a central conveyor and service two Centaur machines sitting either side. One turns a pair of lenses to the patient's prescription while the other produces a matching pair of plastic lapping tools turned to the same prescription, which are used in the subsequent surfacing process to finish and polish the lenses.

The prototype, robotically-loaded system started producing spectacle lenses in volume earlier last year at one of Norville's two major laboratories in Gloucester (Plate 2). The company not only builds production plant but is also one of the UK's largest prescription lens suppliers, corporately fulfilling 22,000 orders a week. It specialises in difficult prescriptions and sophisticated coatings, supplying opticians either directly or through one of its four smaller regional outlets around the UK.

Plate 2 A view of the robotically-loaded curve generating facility for prescription lens and lap tolls at Norville's Paul Street, Gloucester laboratory. Only the concave surface of the lens is turned, as blanks are semi-finished on the convex side by the supplier

In addition to using the equipment in- house, the company intends to supply other laboratories around the world with the new, automated plant; it is already a major exporter of an extensive range of machinery, practitioners products and consumables. Orders for robotically- loaded systems are expected imminently from other UK laboratories as well as from Japan, while the US market is being actively researched.

Said Tom Jones, general manager at Norville's Paul Street facility in Gloucester, where the new system was developed and is now in operation, “A conventional laboratory producing over 3,000 pairs of prescription lenses per week would need six operators to run it, whereas the ability to turn two lenses and two laps simultaneously and robotically load and unload them means that we only need two staff to run the equipment.”

To process a patient's order, two semi-finished plastic lens blanks (these days only a minority of lenses are made from glass) and two nylon lap blanks are loaded onto a platen which travels by conveyor to a preliminary station where the lenses are chamfered. A continuous stream of such platens travel around a U-shaped conveyor, arriving at the main production station where they are buffered to await machining. As a platen is released into the working area, it moves forward to a stop and the appropriate program for turning the prescriptions for each eye are fed into two CNC systems, one controlling the Centaur machine processing the lenses and the other to its sister machine on the other side of the conveyor making the bespoke lapping tools (Plate 3).

Plate 3 Close-up of the working area, showing the robot positioned above a platen about to load left and right hand lenses into the Centaur CNC generator on the right, and the respective red and yellow surfacing laps into the machine opposite

A Motoman SV3 robot first loads the lenses into the two spindles of one machine and then the laps into the second. All four components undergo three-axis machining simultaneously in a cycle that varies from 50 seconds to four minutes, depending on the complexity of the prescription. The lenses, at this stage still opaque, and the laps are loaded back onto the platen by the robot and the order continues by conveyor to an off-load station from where an operator takes it to the finishing and polishing line. These final lens surfacing operations are currently carried out by hand, although the processes are the next targets for automation, according to Mr Jones.