Design & Technology Working in Perfect Harmony
One of the interesting aspects of jewellery design and manufacture in the 21st century is how old and new technology work together. Tried and trusted traditional jewellers skills are enhanced by the addition of new equipment and software, and that suddenly opens up a new world of possibility. To accomplish this successfully, designer and technician must collaborate very closely so that the original idea can be translated into the 3-dimensional product that the designer visualised. Here is a story that illustrates that point.
Marianne Forrest, silversmith and designer of watches and clocks, saw the possibilities. She had become fascinated by the concept of mass customisation – making unique pieces for every customer – and the emergence of rapid prototyping (RP) machines now made that possible. Working in conjunction with Simon Armitt, the Digital Prototyping Technician at Metropolitan Works (2006 – 2010), they began to work on the first designs, prototyped from resin and built on an RP system called the ‘Perfactory mini multi lens’, made by Envisiontec. Simon explains ” This machine uses visible light to cure light-sensitive resin and was used to make ‘Shatter’, Marianne’s first RP’d bracelet, the resin model being used as the casting pattern. All RP machines slice the object into horizontal layers and the Envisiontec system builds its models upside-down, adding layers from a resin bath. Although the build process is very slow, the model produced appears as if by magic from the liquid resin! The detail is quite extraordinary and its even able to replicate finger prints!`”
Marianne’s next project was a piece so complex that it would have been very time consuming or near impossible to produce by hand. This was the ‘Paleolith’ watch.
She heard about a brand new piece of equipment recently installed at Metropolitan Works, called the EOSINT M270 – a laser sintering machine that resembled an oversized microwave oven, and was built in Germany. It used a process called additive manufacturing – in other words it added material to build an object, rather than the more conventional subtractive machining process. With the equipment, software and a good technician, Marianne realised that at last her designs could be brought to fruition.
Simons takes up the story: “Marianne approached Metropolitan Works to chat about the feasibility of attempting a build from her new design. She supplied me with a 3D model, built in Rhino, and I was able to then run it through ‘file fixing’ software which checks to ensure that the 3D model was ‘watertight’.
“Protoyping software only recognises two surfaces – interior and exterior. All prototypes are hollow and surfaces are made from triangles, as far as the software is concerned. If a surface has mathematical holes, or the surface triangles are reversed (i.e. the inside surface of the triangle is on the outside of the model) which can occur from errors produced during the modelling stage – it then confuses the construction software and the model won’t build. Once the file was fixed, we set up a build on the M270 to manufacture in 17-4PH stainless steel.
“The watch design was split into the case, bezel and the bracelet, which was then split into four parts. The build took, as I remember, about 16 hours but came out pretty much as we’d hoped. So we did a second build to improve component positioning on the base plate so there was less support structure to cut off each part. The finished parts were cut off the build platform with a horizontal band saw. I was then able to clean as much unfused metal powder out of them as I could and give the parts to Marianne for hand fitting and assembly.
“The challenges with using this machine and handling finished parts were the health and safety implications. Every time there was a risk of exposure to the metal powders (which were extraordinarily fine), I had to wear a full-face respirator, paper all in one suit, gloves, anti static boots and ensure that I was electrically earthed to the M270. The powders were a huge respiratory hazard, and because they were so fine they were also presented an explosion hazard. Even the vacuum cleaner used for cleaning the build chamber of the M270 had to be spark resistant with the same level of exhaust filtration that my respirator had. It was hot and heavy work moving build platforms that are 30cm square of mild steel and up to 50mm thick and handling large quantities of metal powder. Usually I would load at least 8Kg of powder to run a build and most of this would have to be removed from the machine after the build for re-use.”
Simon and Marianne have worked on many projects together – although perhaps this is one of the more dramatic pieces. For further information, look at Marianne’s web site: http://www.marianneforrest.com
Simon is a highly skilled and experienced metalworker with a background in both aviation and jewellery design. He is now a professional photographer specialising in jewellery and silverware images, and his work can be seen on his web site: http://www.simonbarmitt.com
How the EOSINT M270 works.
The software on the M270 slices the CAD model into horizontal layers, each .4mm high, and this is pre-loaded into the control computer that runs the machine.
The M270 works by fusing ultra fine beads of metal powder together with a high powered laser. The design is built in a chamber which is sealed when in use, and has a low oxygen environment to stop the metals oxidising under heat, and help create a more solidified build. Metal powder is automatically spread over a steel build platform, at a thickness of .4mm height. The laser will then trace the respective layer plan form, over the steel powder, thus bonding it together and welding it to the steel build platform. The build platform is then lowered .4mm and fresh powder spread over it ready to receive the laser again. This process is repeated for every single layer until the machine reaches the maximum height of the component and the build finishes. Its worth noting that the stainless steel builds we produced were really ‘sintered’. This had a significant effect on the surface finish of parts built by the machine, with the 17-4PH stainless steel showing slight variations in surface finish when polished.