Diamante A&T Contents
Issue 107

Year XXVIII - March 2022

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Front Cover: FRATELLI MILANO SRL
Frazione Vai, 1/B - 10084 Forno Canavese (TO), Italy

Presses oleo-dynamic volumetric for powder compacting for: hard metal, diamond tools, abrasive wheels, ceramic. Fratelli Milano operates on the market since 1985, first only as technical designer and then as manufacturer. The company purpose is to give customers a "complete prompt delivery" for all standard and special machines.

www.fratellimilano.com




In the Spotlight

10) Stone+tec, looking optimistically to the future

14) Marmomac the landmark trade fair for the international natural stone sector

24) Announcing the launch of The Italian Glass Weeks: Italy's most important event dedicated to glass in all its forms and processes




Raw Materials

42) Renaissance of flake graphite in Finland - Part II: requirements for metal alloys

by S. Leinonen
Geological Survey of Finland, Kuopio Office, Finland

Abstract: Graphite is widely utilized in composite materials, e.g. refractories, metals and polymers, also to an increasing extent as an anode active substance in Li-ion batteries. Foundry industries hold the third largest market of flake graphite after refractories and batteries. There have been developing projects in several countries to find new graphite resources, also in Finland. According to the deposit investigations and laboratory studies there is great potential for high grade crystalline graphite. Preliminary tests result that new crystalline graphite can be processed by froth flotation and screened to required grain sizes applicable in manufacturing of metal matrix composites (45-90 ?m). To obtain fine particle sizes (<15 ?m), additional grinding is needed, and a jet milling appears to be the most efficient technique for doing it. A dry mineral separation method has found to be effective to collect large flakes, mostly used in refractories and materials utilizing expandable graphite. Part of the grain size distribution of floated concentrates fulfills the purity of commercial grades, instead adequate C-values (over 96 wt-%) for advanced applications, like reinforcing fillers and anode active graphite, have been reached by alkali roasting and acid leaching. The origin of, so called primary sources of crystalline graphite are natural or synthetic. The most interesting challenge is to define the graphite bearing industrial waste streams and how to recover it to a second or even more rounds benefitting production of advanced metals and other high-tech materials



Grinding

59) Determining the flowrate, pressure and nozzle aperture for a grinding process with consideration of abrasive type, coolant type and wheel structure

by J.A. Webster, A. Planakis, C. Winkel
Worldwide Superabrasives, USA

Abstract: Grinding is a thermally dominated process where many of the operational parameters such as feeds, speeds, wheel structure, dressing and abrasive type must consider the heat generated and how to remove it from the workpiece. Optimization of coolant application is a powerful tool to suppress thermal damage and allow greater control of the process setup parameters to create the required surface topography, integrity, productivity and size. It is well known that matching the jet speed with the grinding wheel speed is an effective way to remove the boundary layer of air, and to wet the grinding process. Mathematical models based on energy equations, such as Bernoulli's, have previously been used to predict jet velocity, however, these are generally flawed as they don't consider the kinetic energy of the coolant entering the nozzle. They are also flawed because no consideration is made of the viscosity of the coolant, which is a dramatic effect. This paper presents a much more precise analysis of the flow from a nozzle and also considers nozzle efficiency. The paper also presents the flowrate requirements based on grinding power, abrasive type (superabrasives versus conventional abrasive) and the influence of wheel structure. The models are verified by accurate flow tests performed by the author. Finally, a case study is presented that clearly shows the economic and technological advantages of coherentjet nozzles over a more conventional approach.