Additive Manufacturing in Gold

Posted on July 29, 2013 by Richard Hoptroff

Birmingham, 29th July 2013

I've been pursuing additive manufacturing ('3D printing') for 18 months now and this folly has probably delayed our product launch by a year.  But it was worth it - the results are stunning.

Most people think of additive manufacturing as a technique for rapid prototyping in plastics.  There are several different techniques, but all are based on the idea of building up an object layer by layer.  Photo 1 shows how we first prototyped watch cases in plastic. 

What makes additive manufacturing so interesting is you can make structures that simply can't be made any other way.  Hollow shapes, interlocking parts, pieces within pieces.  And the number of materials in which you can manufacture is constantly growing - ceramics, wax, rubber.  (You wouldn't believe how excited girls get when you tell them you can 3D print shoes!)

But the most exciting is manufacturing in metal.  There are two ways of doing it.  The first is to print a wax model and then cast it in metal using a lost-wax process.  See photo 2, where we made a watch case in silver.  The results are quite pleasing, and we may well use it for making metal watch backs, but there are limitations because the wax is so fragile.  Direct Metal Laser Sintering (DMLS), on the other hand, works by fusing together metal dust using a laser.
Our initial DMLS results were disappointing (photo 3).  The slight pitting might be acceptable for military, aerospace and medical applications, but not jewellery.  With perseverance, a few clever techniques and more rejects than I like to think about, we're finally ready for production, and I believe we are the first watchmaker to be ready to do so.
See photo 4, an 18 carat gold watch case fresh out of a sintering facility up in Birmingham.  Photo 5 shows it after it has been extracted and polished, and photo 6 in a finished watch.  You simply can't make a structure like this any other way.  (We decided on an N3 reddish gold colour because it is the closest to to the colour of pure gold.)
Compare it to a traditional technique such as milling (photo 7).  Milling generates a simple part with cold, Germanic precision.  The sintered version feels like it's been grown and nurtured - which in truth it has - each with an individual life of its own.

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