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Snap
function
For the snap to be able work, the material must
not be too brittle. The SLS Nylon materials are known to work well, as
well as the FDM ABS plastic.
The most common SLA materials are normally not
so good, but all material vendors have developed special materials for
the purpose. Some examples are Vanticos (formerly Cibatool) material
SL-7510 and Somos materials of type 81xx or RPCure 200 xx. If your SLA
service bureau doesn’t supply these qualities, then you can contact the
material vendors to be able to find out who can produce your details.
Links to these can be found here.
Among the LOM and inkjet materials, there are no
suitable materials to recommend.
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Precision
Precision depends on the
chosen method, workmanship and how much time that is used to polish and adjust
measurement deviations. The two later parameters could have as big
influence on the final results as the first.
Analogous as with cutting treatment, there is a
clearly connection between precision and cost. The fact that a part is
produced with an FFF based techniques doesn’t mean that tolerance demands
are irrelevant. Measurement errors depend of an absolute and a relative
component.
Inkjet and SLA are the FFF methods that give the
best precision. To be able to achieve high precision in a process chain
with one or more castings, were an FFF part is the first step; it is
suitable to use one of these methods. Sanders Modelmaker (inkjet) gives
somewhat higher precision then SLA.
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Colour
Still today the most simple
way to get coloured FFF details is often to paint the parts after
manufacturing to get the requested colour and surface, but it’s becoming more common with techniques and
material for direct building of coloured FFF parts on the market. One
obstacle is software related, the STL data format doesn’t contain
representation of colours in its ground shape, but development is going
on in these area.
RPC
offer coloured photopolymers for SLA, which is sufficiently transparent
for example direct manufacturing of car rear taillights. Zcorp and DTM Somos offer
coloured infiltrates for 3DP- respective SLS materials.
Almost all FFF materials could be painted.
Thermo plastics (SLS, FDM and Inkjet) demand some knowledge about
chemistry so the solvent in the paint doesn’t affect the material.
An alterative method to achieve coloured details
in plastic is to use silicon moulding.
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Surface structure
None of the FFF methods give
a proven good result together with surface etching. It is
therefore still hard to get a surface with a specified surface structure.
If only a small amount of details should be produced, the company
Gravutex (GBR) offers a technique where a foil with decorative surface is
applied on a polished or smooth prototype part. Surface etching on SLS and DMLS metal sintered details could be
worth trying with unknown result. Tools in epoxy bonded metal powder also
have qualifications for surface etching.
Silicone moulding reproduces the master models
surface structure extremely well. The foil technique from above or a
manually produced structure surface on an FFF part could therefore be
reproduced with silicon moulding.
EDM machining and bleed blasting are two methods
which gives an unspecified, but tidy surface structure. One prerequisite
for EDM machining is metallic parts (electric conductive).
If details should be lying very close to each
other, for example different parts of an instrument panel, so is also the
brilliance of the surface important. This is however a difficult and complex
area, well outside the ambition of the FFF Selector.
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