Project funded by the European Community under the 'Competitive and Sustainable Growth' Programme (1998 - 2002)

Project number: GRD1-2001-40538
Contract number: G1RD-CT-2002-00708
Start date: 2002-06-01
End date: 2006-06-30

Traditionally, most optical surfaces are produced by grinding followed by lapping (also called grinding in the optics field) and polishing. More recently some lenses were produced by moulding (typically plastic spectacle lenses and lenses for low-cost cameras) but this also required the moulds to be made in the traditional way

Nano Grind aims at producing cheap, smooth and curved optical surfaces (in glass, ceramics or hard metal) using an innovative grinding machine tool with electrolytic in-line dressing (ELID). Nano Grind will give a significant machining cost reduction with equal specs on dimensional accuracy and surface quality. This will be realized by a faster overall production process for direct manufacturing and by offering longer standing moulds for replication. This will result in an important cost reduction for the end-user. Nano Grind will enable production of curved surfaces with average roughness value comparable to polishing. Nano Grind will also enable production of curved surfaces with a very high dimensional accuracy. Combined with the previous objective this will allow high-precision optics with high shape accuracy.

The basic result of this project will be that products with surfaces of optical quality can be produced without (or with a much shorter) time-consuming polishing phase. In some cases it is not the time reduction effect that dominates the improvement but the fact that the shape-distorting effect of polishing can be abandoned.

The envisaged machine and technology will have the multiple applications.

• A first one is the manufacturing of advanced optical components like required for semi-conductor manufacturing. In this field, extreme accuracies, even beyond those of Nano Grind are requested. The project will allow a more efficient manufacturing by eliminating a great part of the polishing effort.
• Next to benefit from Nano Grind is the manufacturing of complex lenses (progressives) needed by elderly people. They will become affordable for a larger group of consumers when prizes decrease. And for the same prize, the quality can be improved.

• Also, the new grinding technology will improve the quality of medical equipment based on advanced optics (asphericals and free formed) or will decrease the price of existing optical components so that advanced facilities will become available for a less wealthy users group.
• Another application field are instruments for remote monitoring of environmental characteristics (by satellite or plane) that often make use of sophisticated optics. The availability of the new grinding technology will have a positive influence on the application of more advanced optics in new monitoring programmes.

• Finally the results of this project will improve the quality of reflectors of automobile spots. This will have a positive influence on the safety conditions of road users under poor light conditions.
  
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Current highly accurate ELID processing is only applicable to flat surfaces. Other high precision manufacturing processes are limited to symmetric surfaces or cannot guarantee high shape accuracy. With regard to the state-of-the-art, the main innovation of Nano Grind therefore will be the combination very stiff and accurate positioning elements with an improved ELID process in order to allow producing highly accurate and smooth curved optical surfaces in an efficient way. The process will be applied to various materials covering metals, ceramics and glass.

This requires the development of the following innovative concepts:

• · A stiff five-axis positioning system. The envisaged stiffness is about 5 times higher than the current industrial practice.
• · A reference measurement system capable of tracing tool and work piece position with nanometer precision
• · An industrially reliable ELID grinding technology for curved surfaces. Nano Grind will further refine and develop a novel and exclusive concept of dressing electrode that results in a much more stable process

It should also be mentioned that these innovations will lead to a production process for precision optics that is substantially more eco-efficient than the current industrial practice.

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The project team is structured to include the multi-disciplinary competencies necessary for the simultaneous development of a general technology and the push towards the envisaged applications. The partnership consists of 8 partners covering 7 European countries.Katholieke Universiteit Leuven and Cranfield University play the central role of two higher education institutes specialised in precision engineering, bringing in the state-of-the-art competence. Both partners already developed ELID grinding technology in other projects. They have lab set-ups for preliminary experiments available. TNO Industrial Technology, a research organisation specialised in manufacturing processes, and Tekniker , a research organisation specialised in precision engineering also contribute to respectively the development of de ELID process for free form surfaces and to the design and testing of the high precision machine tool.The main exploiting parties are Loh Optikmaschinen, a commercial manufacturer of precision machine tools, Berliner Glas, a commercial manufacturer of precision optics, Centro Ricerche FIAT, being the research centre of a commercial manufacturer of automotive products, and Gravitas 2000 an SME offering design and manufacturing services for high-precision components.

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An important field of application is the manufacturing of high precision optical systems for semiconductor lithography, especially for the next generation projection systems. Nano Grind will allow a reduction of production costs and will make fast prototyping possible. The improved ELID process will result in better surface quality and lower subsurface damage.

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ELID: electrolytic in-process dressing of the grinding wheel

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