Hi all,
A few weeks ago I recall speculating that complex metal gnomons might
be made in future by 3D printing followed by 'sintering' ( a bit like baking a
cake)
It was quickly pointed out that the process of sintering 3D printed objects is
already established. For 'know-how' enthusiasts, who have not encountered it,
a brief description of this remarkable process may be of interest as seen
recently on 'How it's Made'.
Similar to 'ink jet' printing the process begins in a metal 'build-box' using a
computer generated sequence of operations.
1. A thin layer of very fine stainless steel powder is spread across the box
base.
2. An adhesive 'binder' is 'printed' onto the powder layer in the shape of the
base of the component.
3. A second thin layer of stainless steel powder is spread across the whole
area where it sticks to the printed shape.
4. The next thin 'slice' of the component is printed in binder and coated in
metal powder.
5. The process is repeated over several hours until the component is built up
in layers of metal powder 'glued' together. and submerged in metal powder.
6. The build-box is then placed in an oven to dry the binder.
7. On removal from the oven the surrounding metal powder is removed by vacuum
leaving a complete but brittle component.
8. The component is placed in a metal box standing on a 'feed' structure (not
fully understood).
9. Surrounded and supported by aluminium oxide grains and adjacent to a supply
of bronze powder the assembly is placed in a furnace.
10. At high temperature the binder evaporates leaving a stainless steel
'sponge' which absorbs the molten bronze via the 'feed' to make a solid
steel/bronze item. As the stainless steel doesn't actually 'melt' I suppose
this isn't true sintering but ingenious just the same.
Tony Moss
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