Dry Machining and Minimum Quantity Lubrication

The increasing attention to the environmental and health impacts of industry activities by governmental regulation and by the growing awareness in society is forcing manufacturers to reduce the use of lubricants. In the machining of aeronautical materials, classified as difficult-to-machine materials, the consumption of cooling lubricant during the machining operations is very important. The associated costs of coolant acquisition, use, disposal and washing the machined components are significant, up to four times the cost of consumable tooling used in the cutting operations. To reduce the costs of production and to make the processes environmentally safe, the goal of the aeronautical manufacturers is to move toward dry cutting by eliminating or minimising cutting fluids. This goal can be achieved by a clear understanding of the cutting fluid function in machining operations, in particular in high speed cutting, and by the development and the use of new materials for tools and coatings. High speed cutting is another important aspect of advanced manufacturing technology introduced to achieve high productivity and to save machining cost. The combination of high speed cutting and dry cutting for difficult-to-cut aerospace materials is the growing challenge to deal with the economic, environmental and health aspects of machining. In this paper, attention is focussed on Inconel 718 and recent work and advances concerning machining of this material are presented. In addition, some solutions to reduce the use of coolants are explored, and different coating techniques to enable a move towards dry machining are examined.

A review of developments towards dry and high speed machining of Inconel 718 alloy

Environmental friendly cutting fluids and cooling techniques in machining: a review

The past century has witnessed significant advancements in turning process, cutting tools, machine controls and coolant/lubricant chemistry. These developments have particularly enhanced the machining of difficult-to-cut materials, which are used for aerospace, steam turbine, bearing industry, nuclear and automotive applications. In turning operation, friction and heat generation at the cutting zone are the frequent problems, which affect the tool life and surface finish apart from other machining results. This mechanism of heat generation plays quite a negative role during the turning of modern materials due to their peculiar characteristics such as poor thermal conductivity, high strength at elevated temperature, resistance to wear and chemical degradation. A good understanding of the methods of lubrication/cooling at the cutting zone, reduction of heat generation will lead to efficient and economic machining of these modern materials. This paper presents an overview of major advances in techniques as minimum quantity lubrication (MQL)/near dry machining (NDM), high pressure coolant (HPC), cryogenic cooling, compressed air cooling and use of solid lubricants/coolants. These techniques have resulted in reduction in friction and heat at the cutting zone, hence improved productivity of the process. A brief survey of modeling/FEA techniques is also performed.

Cooling techniques for improved productivity in turning

Effects of minimum quantity lubrication on turning AISI 9310 alloy steel using vegetable oil­based cutting fluid

Environmental concerns call for the reduced use of cutting fluids in metal cutting practice. New cutting techniques are to be investigated to achieve this objective. Hard turning with Minimal Fluid application (HTMF) is one such technique, which can alleviate the pollution problems associated with cutting fluids. In the present work a specially formulated cutting fluid was applied as a high velocity, thin pulsed jet at the immediate cutting zones at an extremely low rate of 2 ml/min using a fluid application system developed for this purpose during turning of hardened steel. The performance of HTMF is studied in comparison with that of conventional hard turning in wet and dry form.

A.S. Varadarajan

Papers

Investigations on hard turning with minimal cutting fluid application (HTMF) and its comparison with dry and wet turning

Influence of cutting fluid composition and delivery variables on performance in hard turning using minimal fluid in pulsed jet form