When less is more A


lthough flood coolants have been traditionally used in many machining operations, the concept of minimum-


quantity lubrication (MQL) has been gaining ground over the last few years. Initially used for machining applications


in the automotive sector and within aluminium foundries, interest in MQL is today more widespread than it used to be, with manufacturers in the aerospace supply chain, for example, actively looking at MQL to boost productivity levels. It should be stated that dry machining is not dead and is still used, indeed preferred in certain steel and stainless steel machining applications when using indexable tooling, but MQL is where much of the action is today. MQL, also known as near-dry machining, uses a minute amount of high efficiency


MQL supports drilling


lubricant applied precisely to the cutting tool/workpiece interface. The process has proven effective for machining all non- ferrous metals and most grades of steel, and its future application is being investigated by a number of cutting tool specialists, working in close cooperation with customers.


RESERVATIONS REMAIN MQL is different from traditional cooling and lubricating methods and, as a consequence, has been slow to gain acceptance. Machine tool builders and precision component manufacturers are accustomed to the way things have always been done and, as a result, the initial acceptance of MQL was in those sectors where flood coolant simply wasn’t feasible. Although this is changing, there are still


MQL (Minimum Quantity Lubrication) provides many benefits to manufacturers, explains David Pearson, Seco Tools’ business development manager (aerospace)


some industry reservations. However, through extensive and continuous trialling and development, notably in the aerospace sector where the drive to increase productivity levels is a constant pressure, MQL is gaining wider acceptance. The incorporation of MQL systems that allow faster cutting speeds to be employed, combined with significant coolant cost reductions and environmental considerations, means that MQL’s future is assured. Seco Tools, for instance, is currently


working on two separate MQL (milling-led) projects to investigate the opportunities and benefits of the process. The first of these is UK-based and


involves customers, a University, a coolant manufacturer and Seco – and is a TSB- supported project [TSB=Technology Strategy Board]. The second project is being led by our


headquarters in Sweden and concerns a system that has been fitted to a CNC vertical machining centre. The system mixes the oil and air outside of the machine spindle, and is fed through a pipe to the cutting tool and then to each insert via coolant nozzles. Various diameter apertures of nozzles will be tested.” There are many benefits associated with


MQL (see box, right), but the cost of using flood coolant is put at 15% to 18% of total part manufacturing costs; MQL can typically reduce the cost to around 5%. The most common lubricants for the


process are bio-degradable vegetable oil derivatives, which, because of their polarity, exhibit good friction-reducing properties. Unlike mineral-based and synthetic fluids, vegetable-based fluids bond more effectively with the surface of metals, providing superior lubrication. When correctly applied, these fluids


reduce the friction and corresponding heat created when cut metal slides over the


14 May 2013 www.machinery.co.uk


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