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Research
An Investigation of Anticlastic Forming in Sheet Metal
Anticlastic forming in sheet metal is a fairly recent development in
the area of gold- and silversmithing, having been developed by the
silversmith Heikki Seppä and the goldsmith Michael Good since the Seventies. This late
development is surprising considering that anticlastic forming is the
complementary action to raising, the fundamental technique of plastic
sheet metal forming: While raising stretches the central part of a
piece of sheet metal and compresses the edges, resulting in cup shapes,
anticlastic forming compresses the central part and stretches the
edges, resulting in forms most often described as saddle-shaped. The
process has to my knowledge only been applied towards aesthetic ends
and not been exploited commercially for functional applications,
besides a minor role in the forming of spout or handle for a teapot or
jug.
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synclastic raising
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synclastic sinking
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anticlastic forming
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The main aim of this
research has been to arrive at a proper understanding and documentation
of the transformation of shape taking place in the deformation of flat
templates into three-dimensional forms. A lot can be done with the
basic anticlastic 'channel' (below left, generally formed to a stronger
degree). Michael Good has developed a great variety of forms based on
this process. One interesting transformation is the helicoid, which can
be created by 'shifting the orientation of curvature'. In the channel
the principal curvatures follow the longitudinal 'axis' of the strip
and the perpendicular curved cross-section. In the helicoid the
curvatures are oriented at 45 degrees to the long, straight axis and
its straight cross-section.
The Irish silversmith/metalsmith Brian Clarke
Michael Good have also undertaken some research on the creation of
ancient Celtic anticlastic torques, which show a high level of
technical expertise. So in this respect anticlastic forming techniques
have been around for a long time.
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forming a 'channel'
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shifting the orientation
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channel and helicoid
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The forms I wanted to
create varied in their ratio, orientation and degree of curvature in
different sections of the forms and occasionally included synclastic
(domed) sections This required a careful planning of both the forming
process and the templates. A basic case is the Möbius band which
can be simplified as a rectangular strip going through a 180 degree
twist while closing back in on itself to form a circle. This not only
involves a change of orientation but also of the location of the centre
of the saddle in different sections of the form.
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twofold möbius strip
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threefold möbius strip
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minimal möbius
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The geometrical implications of these
transformations pointed towards the mathematical investigation of
minimal (area) surfaces, which is a branch of topology. Such surfaces
can be observed by dipping a non-planar wire frame into a soap
solution, which naturally seeks to minimise tension and thus, its
surface area. The connection to minimal surfaces is also apparent in
the work of several American sculptors, Brent Collins, Robert Longhurst and Charles O. Perry, Bathsheba
Grossman, and some sculptors/mathematicians make use
of the principle in more explicit ways (Stewart
Dickson, Carlo
Sequin and Helaman Ferguson).
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copyright©Benjamin Storch2007
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