Issue No 6: May 2003
Research growth continues
Quick reaction to SARS
Translation strategies lead to Chinese version of Buddhism
Database of 35 million characters helps scholars and writers
Confucius’ poetry collection delivers insights into symbolism
3D model smoothes problems in creating ultra-precision surfaces
Nano views of electrolyte behaviour
Sun block ‘skin’ applied to textiles
Greater efficiency for clean building formula
Spin-offs from world’s smallest nanotube
New generation of electrical ceramics

A first-of-its-kind computer-aided simulation model, devised by researchers at The Hong Kong Polytechnic University (PolyU), is helping industry in the ultra-precision machining of materials.
The model predicts how to machine material to an accuracy of less than 10 nanometers, producing a super mirror-like surface.
Said Principal Investigator, Prof W B Lee: “This is especially important today in producing optical microstructures such as DVD and camera lenses, lenses for photonics and optical fibre for telecommunications.”

Top: (from left) blank, rough machined and ultra-precision machined material; Prof Lee inspects an ultra-precision diamond cutting lathe.

The smoothness of lenses in a camera or telescope, for example, increases accuracy, effectiveness and quality.
Usually, lenses are produced by a tedious manual process of machining, grinding and polishing, said Prof Lee.
In ultra-precision machining, using a single-point diamond cutting tool, a surface roughness of less than 10 nanometers can be achieved.
An ultra-precision machined mould, for example, can produce lenses in an optimum state so that manual finishing is not required.
To predict the results of ultra-precision machining, Prof Lee’s model needs to be fed static and dynamic data involved in machining.
The data includes the physics and crystal structure of the work material itself, the geometry of the cutting tool, the cutting speed, the rate at which the cutter is “fed” into the work material, and relative vibration between the cutting tool and work material.
“By applying the model, we know how to optimise the cutting conditions without actually cutting,” said Prof Lee. “It increases efficiency and helps the better design of machine tools. We also use the model to help train engineers.”
Prof Lee’s fundamental research into nano-machining is transferred to industry via the PolyU’s Ultra-precision Machining Centre, one of the most advanced facilities of its kind in the region. Since being established in 1996, it has helped more than 100 companies with industrial applications.
Currently, Prof Lee’s simulation model is able to predict flat, spherical and aspherical surfaces, but he is now extending this to freeform shapes.
He is also incorporating into the basic model the effects of friction between the cutting tool and the work material, and how nano-machining can affect the crystal structure of material in what is termed “residual stress.”
“When you are machining, there is always stress,” said Prof Lee. “This can cause surfaces to distort. It’s an important problem at the nano level so we are trying to work out how to reduce residual stress to a minimum.”

Principal Investigator
Prof W B Lee :