computer-aided simulation model, devised by researchers at The Hong Kong
Polytechnic University (PolyU), is helping industry in the ultra-precision
machining of materials.
predicts how to machine material to an accuracy of less than 10 nanometers,
producing a super mirror-like surface.
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.
(from left) blank, rough machined and ultra-precision machined material;
Prof Lee inspects an ultra-precision diamond cutting lathe.
smoothness of lenses in a camera or telescope, for example, increases
accuracy, effectiveness and quality.
are produced by a tedious manual process of machining, grinding and polishing,
said Prof Lee.
machining, using a single-point diamond cutting tool, a surface roughness
of less than 10 nanometers can be achieved.
machined mould, for example, can produce lenses in an optimum state so
that manual finishing is not required.
the results of ultra-precision machining, Prof Lees 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.
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
fundamental research into nano-machining is transferred to industry via
the PolyUs 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.
Prof Lees 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.
you are machining, there is always stress, said Prof Lee. This
can cause surfaces to distort. Its an important problem at the nano
level so we are trying to work out how to reduce residual stress to a
Prof W B Lee : firstname.lastname@example.org