Jewelry Technology Forum Web Site (Back to Legor Group)

Abstracts

The JTF preview

Contents

The JTF was developed with the aim of creating a culture in terms of technological innovation, design and marketing in a sector which is traditionally far removed from the rationale of business management.
After the forum, anyone who wishes to make use of the information can consult the conference proceedings edited and distributed by LEGOR GROUP SpA.

A change in jewellery retail


Beatriz Biagi Design & Research, Milano - IT

Global connectivity through the Internet is experiencing exponential growth. Sales practices for the more evolved luxury products, based on principles of exclusiveness, speed and personalization, focus on customer service with a buying trail that can be accomplished in both a physical or virtual store through various on-line platforms. The potential buyer is drawn into the brand’s life and increasingly involved in the productive process of the goods being purchased.

With the help of the Boxstylab agency, Biagi analyses both the physical and on-line retail scene as well as integrated multi-channel communication, reflecting on how technological innovations can radically transform the customers’ possibilities and expectations, and how customer-focussed sales strategies have become indispensable competition leverage for companies operating in the jewellery sector.

Do the new low-cost 3D printers have a place in the jewelry manufacturing environment?”


Frank Cooper Birmingham City University, UK

With the recent ending of a number of patents, along with the burgeoning home 3D printing movement (e.g., Fab@Home, RepRap), a huge and often confusing number of new, low-cost ‘home-user’ or ‘consumer-level’ printers have arrived onto the 3D printing scene. A possibly useful spin off from this for the jewelry industry has been the emergence of a number of, principally but not exclusively, low-cost Digital Light Processing (DLP) systems. Many of these have been developed specifically for, or are capable of, printing in castable resins (photopolymers), which are ideal for use in the jewelry lost-wax investment casting process.

Improving the Properties of Precious Metals by Heat Treatment”


Chris Corti COReGOLD TECHNOLOGY, READING, U.K.

Heat treatment of precious metal jewellery alloys is often referred to in the literature but many practitioners do not have a clear understanding of what this term means and its importance to the jewellery industry. It is a term often used by metallurgists to describe a range of thermal processes designed to manipulate properties of engineering and decorative alloys to meet requirements. Many will be familiar with heating and quenching of steel to harden it, whilst age-hardening of steels and aluminium alloys is an example of a two-stage treatment that is widely used to confer additional strength.

Many treatments involve heating of the alloys to specific temperatures for specified periods of time and then cooling at a defined rate that may be rapid or slow. In jewellery, annealing of precious metal alloys is often undertaken to soften cold-worked material to enable further working without cracking or fracture. But other types of annealing are also carried out, for example to stress relieve alloy items to prevent stress corrosion cracking or to ageharden them. In investment casting, the burning out of casting moulds (‘flasks’) requires a defined temperature and time cycle to enable good castings to be achieved. This is also an example of a heat treatment.

Whilst annealing and age-hardening of jewellery metals has been featured in previous JTF presentations, the ‘whys’ and ‘wherefores’ of such treatments have not, perhaps, been fully explained. There are several types of annealing treatments in use, each with different objectives. This presentation focuses on heat treatments used in the jewellery industry and attempts to explain the underlying principles involved. Examples of heat treatments of base metal alloys are also included to demonstrate that such treatments are universal.

Study of the microstructure, residual stresses, mechanical and corrosion properties of different gold alloys used in industrial processes


Manuele Dabalà Università degli Studi di Padova

Gold alloys, used in the production of gold chains, affect the optical and mechanical properties of various gold products. In fact, the corrosion resistance and the workability of the chains depends on these properties. It is important that gold alloys with high corrosion resistance do not degrade during the production process. The microstructure of the alloys strongly influences the mechanical properties, which have a key role in both the machinability and quality of the plates. In the present work, different compositions of gold alloys and different annealing steps in the deformation processes were analyzed and optimized. In particular, the choice of the suited grain refiner is very important to avoid particular unwanted behaviors of the gold alloys. The changing of the production parameters and the compositions of the alloys leads to the formation of different levels of residual stresses within the material, which can generate a variation in the behavior of gold sheets. The microstructures were analyzed by OM and SEM observation, whereas the variation of mechanical properties by micro-hardness test. The residual stresses were evaluated using XRD analysis and the corrosion resistance by potentiodynamic polarization tests. The results showed that a high homogeneity of the microstructure and a suitable recrystallization process, with an increase of the quality of semi-finished products, were obtained.

Strengthening pure gold significantly by no more than 1 wt.% Zr, Ce and Si


Juzi Li Gemmological Institute, China University of Geosciences (Wuhan)

Gold is an ancient metal, it can be widely used in the electronics, dentistry and jewelry industry. It is also well known that pure gold has good ductility and very lower vickers hardness. These mechanical properties of pure gold definitely lead to easy deformation, scratch, abrasion and so on when pure gold is put into application. Therefore, it is necessary to strengthen pure gold by micro-alloying to avoid Its obvious deficiencies and maintain its excellent properties such as yellow color, good thermal conductivity, chemical stability.

Our group chose Zr, Ce and Si as the micro-alloying elements, which are no more than 1.0 wt.%, to strengthen pure gold. The investigations showed that Zr, Ce and Si can strengthen pure gold significantly at as-cast from 30HV to 69HV and wrought state to 121HV . In this presentation, we share the investigation to show how Zr, Ce and Si modify pure gold in structure, thermal characteristic, mechanical properties and what the distributions of different phases and elements are. We also present how the new gold materials can be used in jewelry industry.

Additive Manufacturing of 18-Karat Yellow-Gold alloys


Ulrich Klotz Fem Research Institute for Precious Metals & Metals Chemistry Department of Physical Metallurgy

The present paper describes the results of a collaborative research project on the selective laser melting of 18-karat gold alloys. Three main objectives were pursued during the project: (1) to analyze the effect of the process parameters, (2) to investigate the role of powder treatments and alloy composition and (3) to identify design rules for additively manufactured jewelry items. The laser power, the layer thickness, the scan rate and the overlap of the scans were optimized in order to reduce the porosity of the parts built in 18K yellow-gold alloy. The production of defect-free parts in gold, silver or copper alloys is challenging due to their high thermal conductivity and their high reflectivity for the infrared laser light. Therefore, the alloy powder was slightly oxidized to form a partial oxide layer of several tens of nm thickness. A significant reduction of porosity was achieved with the oxidized powders compared to the untreated powder. Another way to reduce the reflectivity and the thermal conductivity of the powder is the alloying with certain elements. A series of alloys that contained additions of Fe, Ti or Ge showed reduced reflectivity and thermal conductivity.

High-Tech ceramics on jewellery: processing and applications”


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

High-tech ceramics (HTC) are becoming common in jewelry pieces. It comes from their exceptional properties that are noble in terms of mechanical properties, corrosion, aesthetical, among others. Although these materials are considered to be difficult to deal with, mainly processing, sintering, machining, polishing, etc, there are some steps that may allow it to be used by a common jeweller in it’s bench. This paper will present the steps that are common in the processing of high-tech ceramics manily, ZrO2 based ceramics. Sinthesys, mixing, coloring, pré-sintering, machining using computer numerical control (CNC) millers and/or manual machining (files, drills, etc.), final sintering and polishing. The importance of some parameters that are relevant on processing of these materials will be presented. It will present the main challenges and provide information about how to deal with the difficulties to process such materials. Examples of final components will be shown. A few considerations on design of jewelry components that contain high tech ceramics along with gold will also be presented.

3D direct metal printing: a trip through new opportunities and innovative alloys


Damiano Zito CEO Progold S.p.A. - Trissino VI - IT

Direct metal printing changes the rules when creating innovative jewels. Selective laser melting (SLM™) enables researchers to become creative and use new materials. This research tests different, new products, exploring new SLM horizons using incredible materials for gold-working applications.

Additional manufacturing through selective laser melting creates the opportunity to combine materials with thoroughly different properties, in ways that would be impossible otherwise. What incredible new possibilities can we expect while learning from the surprising properties obtained?