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Casting low-weight micro-structured materials – a new materials concept for jewelry components.

Filipe Samuel Silva MEMS-UMinho, Minho University, Guimaraes, Portugal

The rise of the price of gold originated a demand of low weight products by keeping its volume. Hollow casting is coming again as a good practice for low weight components. However the mechanical resistance of the alloys used in the jewelry field is a severe limitation for the thickness of the components.
It has been recently launched the concept of micro-structured components or materials. Micro-structured components are components where an external skin gives the shape of the final product and the internal part is a metallic structure where small metallic arms are combined with hollow areas. This approach allows the obtainment of low weight components with high mechanical resistance.
Casting of these components/materials is still a challenge in different ways: components design, casting/filling of thin walls/structures or disinvestment of obtained components.
This paper will provide information about this new materials design approach. It will present the main challenges and provide information about how to deal with the difficulties.

Property Measurement: What use is it to Jewellers?


In jewellery manufacture, it is recognised that alloys and other materials should meet the needs of the manufacturing processes and that the resulting jewellery should give good service performance when worn by the customer. To ensure these needs are met, it is necessary to know certain properties such as density, tensile strength, hardness, colour, tarnish resistance and precious metal content. It is a balance to ensure that the jewelry meets the needs of being ‘fit-for-purpose’ whilst keeping costs to a minimum, for example by reducing the weight of metal in the piece.
Sometimes we measure the properties ourselves but often we rely on data from external sources such as alloy suppliers and the scientific literature. How much reliance can we place on the values we obtain in property testing? This paper considers the measurement of the properties of jewellery alloys and of actual finished jewellery. It reviews the important properties, how they are measured and what they tell us in terms of their relevance to jewellery manufacture and service performance. Mechanical, physical and chemical properties are considered. The importance of making measurements in accord with international standards and the need for industry-agreed standards for testing of actual finished items of jewellery is emphasised.

White gold alloys and new European directive EN1811:2011 on nickel release: limitations and possibilities.

Massimo Poliero JTF President and CEO Legor Group S.p.A
Andrea Basso Plants and Processes Manager Legor Group S.p.A.

A new revision of European directive on nickel release will come into force the by the april 2013. The new norm will dramatically drop down the maximum allowed nickel release limit, leading to significant implications for the jewelry industry. This paper aims to provide an overview about how the scenarios will change after the april 2013 in comparison to the existing situation. The paper will also discuss what possibilities for materials and technologies with and without nickel will be able to provide satisfactory solutions to the jewelry market, together with a possible change in the way the white gold production is currently approached by the jewelry industry.

Materials and innovative solutions for the gold sector

Valeria Adriani Matech – Parco Scientifico Galileo - Padova - IT

In the current highly competitive market, the strategy of portfolio diversification and the consequent acquisition of new markets must be supported by the added value that the use of new materials able to improve the performance and emotional aspect of the product can achieve. Solutions and materials normally belonging to sectors that seem far removed from the gold industry, such as mechanics, automobile and furniture, can prove extremely interesting and provide ideas for highly aesthetic solutions and technologies.  

Precious metal microstructures in 3D

Paolo Battaini 8853 SpA, Pero (MI) - Italia - IT

That the microstructure of a material is important is a well-known fact. The cause, and possible solution, of a problem that arises while working a precious alloy can be identified by studying the microstructure of the material. An optical stereo microscope is extremely useful in providing a three-dimensional (3D) view of a sample, but enlargement is limited. Furthermore, the most common techniques of micro-structural observation, such as optical metallography and scanning electron microscopy, usually only give a two-dimensional picture. Some techniques that provide a 3D view of the microstructure of a surface are now available but have yet to be widely adopted, especially in the gold sector. The aim of this paper is to show 3D images of the microstructure of some precious materials, like ruptured surfaces, different surface finishings or surface defects, and to highlight any additional information that 3D imaging can offer. Anaglyph images obtained using an scanning electron microscope will be used and the audience will be provided with special two-colour glasses.

Do you know where your gold comes from? RJC Chain of Custody: providing support for supply chain due diligence.

Fiona Solomon PhD, Director - Standards Development, Responsible Jewellery Council (RJC)

The Responsible Jewellery Council (RJC) has developed Chain-of-Custody (CoC) Certification to support businesses which wish to provide their customers and stakeholders with independent assurance about conflict-free, responsible sourcing.  A ‘Chain-of-Custody’ is a documented sequence of custody of material as it is transferred along the supply chain. Chain-of-custody systems can provide an important point of differentiation and confidence in the business practices involved in production.  Certification of those systems provides recognisable assurance to customers, consumers and stakeholders against a known standard. This can add value to jewellery products and help protect and enhance jewellery brands.
This session will introduce some of the key drivers for supply chain due diligence, such as the US Dodd Frank Act and the OECD Due Diligence Guidance, and provide an overview of RJC Chain-of-Custody Certification:  key requirements, implementation and potential benefits and its relationship with other industry initiatives.

Sintering: the applicability of the various powder metallurgy techniques in gold manufacturing

Ilaria Forno Politecnico di Torino – Alessandria Campus - Alessandria, Italia

Powder Metallurgy is a technology that has been widely used for some time in several industrial sectors and has recently aroused considerable interest in gold manufacturing, especially when used in combination with rapid prototyping techniques such as laser sintering. The ever increasing availability of metal based and non-metal based alloys with advanced features, supplied in powder form, opens the doors to the use of alternative sintering techniques, borrowed from smelting sectors. This paper, therefore, aims at analysing the various sintering techniques, also in relation to the different materials used, ighlighting the advantages and limits.

The latest developments in Selective Laser Melting technology in the production of gold jewellery

Alessio Carlotto Progold S.p.A. - Trissino VI - IT

It has finally been ascertained that Selective Laser Melting technology can be used for  producing jewellery from powder alloys and the required standard of quality has been achieved.   
To master the technology, we programmed the production of a series of samples on which a systematic study was then conducted. 
To produce these samples, an 18kt yellow gold powder alloy was used at three different granulometric intervals which, together with laser power, scanning speed and the thickness of the powder layer, was one of the variables in our research. 
The aim was to obtain significant data in terms of wrinkling in the raw state, defectuosity and the physical-mechanical characteristics.
The analysis was carried out following a DOE (Design Of Experiments) approach, not only in order to highlight the effect of each individual variable, but also to show how they interacted.
Lastly, we compared the results with those obtained from samples produced using the lost wax technique.