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DigiCULT
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8
roughly the size of a grain of pollen) with
no optimising or averaging of the data.
Delcam used a complex cutting strategy
that involved cutting four times with pro-
gressively finer cutting heads on carefully
selected areas.The material used was a
dense polyurethane board a standard top
quality material for industrial routing.The
choice of routing material is critical
because it must be dense enough to retain
detail and very stable so that there is no
risk of distortion through expansion and
contraction. A total of four sections were
cut in this way. Some initial tests were
carried out to cut directly into limestone,
with very promising results. However, the
loose grain of the limestone resulted in
loss of detail and it was considered too
impractical to produce the entire sculptu-
re this way within the project timeframe.
small quantities of resin and conservation
mortar as a binder, to find the best grain
size to reproduce the look and feel of the
original surface. Different earth pigments
gathered at the site were also tried both as
part of the recipe and as surface treatments.
It took over 100 tests to find the best com-
bination of materials.
PRODUCTION OF THE REPLICA
A
fter extensive tests it was found
that a combination of techniques
would be needed to produce the
replica.There are a number of different
processes used in industry to produce
three-dimensional prototypes from digital
data.These processes are referred to as
rapid prototyping
. A model can either be
built up in layers using stereolithography,
lasersintering and 3D printing or it can be
cut from a solid block using industrial mil-
ling machines, a process referred to as mil-
ling, engraving, tooling or routing.Tests
showed that routing was the best approach
for reproducing the fine detail that was
essential when trying to capture the cha-
racter of the surface. However, routing is
less suited to producing a model in the
round, a task suited to the Z Corp 3D
printer.Therefore, it was decided to con-
struct a model out of sections of Z Corp
and routed data, creating a mould of this
model and then casting the entire replica
from this mould in a mixture of pulverised
stone and resin medium.
3D Printing
The rapid prototyping was carried out by
4D Concepts
(http://www.4dconcepts.com/) at their
workshops in Gross-Gerau, near Frankfurt,
using the data gathered by the
ModelMaker scanner. From data to model
it took three days to create the print using
the Z810 3D Printer (made by Z
Corporation (http://www.zcorp.com/)).
The Z Corp 3D printer uses a finely grai-
ned plaster-like material. A thin layer of
the dry material is spread onto the build
area and then water, which acts as a bin-
der, is printed onto the area to be bonded.
As soon as this has cured a new layer of
powder is spread on top. As the process
continues the model builds up layer by
layer.When the printing process is finis-
hed the build platform is removed and the
loose powder cleaned away to reveal the
3D print.The model is then infiltrated
with resin to make it durable.
Routed Sections
The routed sections were cut using the
data from the Seti Scanner.This work was
carried out by Delcam UK
(http://www.delcam.co.uk/) at their too-
ling workshop in Birmingham, using a
three-axis router.The routing was perfor-
med at 100 microns (0.1 millimetres;
Each stage of the routing is done with increasingly fine cutting tools.The
final pass is with a conical tool with a tip of 100 microns.
The first finished tests of the ear pieces from the Seti data in limestone with
pigment. Particular attention was paid to the complex layering of the colour.
ASSEMBLING AND CASTING
THE MODEL
M
oulds were made of the 3D
print and all of the routed sec-
tions.These pieces were then
all cast in plaster and the plaster pieces
were assembled into a complete model. A
final mould was then made from the pla-
ster model and the replica cast from this
mould. All of the moulding, casting and
finishing stages of the production were
carried out at Factum Arte's workshops in
Madrid.The replica was cast in a specially
Factum
Ar
te
,
2004,
www
.f
actum-ar
te
.com
Factum
Ar
te
,
2004,
www
.f
actum-ar
te
.com
Factum
Ar
te
,
2004,
www
.f
actum-ar
te
.com