Potential of Modern Lubricoolant Strategies on Cutting Performance

Abstract

Besides developments in the area of dry machining and minimum quantity lubrication, the use of coolant lubricants is still essential when machining high alloyed steels or heat resistant materials like titanium and nickel based alloys. Experts agree that this fact will not change in the next decade. For this reason it is necessary to use coolant lubricants as effectively as possible to maximise their positive effect on productivity and process stability. High-performance cooling strategies like high-pressure cooling and cooling with cold gases (cryogenic cooling) have received increased attention in the last years. Through the targeted supply of coolant lubricants to the cutting site it is possible to decrease tool wear, increase cutting speeds, guarantee defined chip breakage and chip transport and – in terms of cryogenic cooling – waive part cleaning. This paper shows current research results in the above mentioned field. Since the performance of a high-pressure coolant lubricant supply in turning difficult to cut materials has been shown in many previous papers, this paper focuses on the quantification of the potential in turning different steels, namely quenched and tempered but also stainless steel in comparison to the conventional flood cooling. Since energy efficiency is very crucial, pressure and flow rate have to be adjusted carefully and in accordance with the cutting parameters to guarantee best results with less energy. Moreover the effects of cryogenic cooling will be evaluated in comparison to high-pressure cooling and conventional flood cooling. In latter field, cutting tests were carried out under variation of the flow rate in order to find the minimum required value for a certain machining task with the overall aim to prevent waste of the media used. Especially in cryogenic cooling technologies, many fundamental research regarding the working mechanisms but also further developments in cutting tool and machine tool technology are still necessary to make this technology ready for industrial use.

High performance cutting of advanced aerospace alloys and composite materials

“…The application of a high-pressure lubricoolant supply may displace the vapour barrier and enable the lubricoolant to get closer to the cutting edge, thus resulting in enhanced cooling of the tool [65,113]. Moreover, the mechanical jet force acting on the chip's bottom side acts as a liquid chip former, decreasing the upward bending radius of the chip.…”

“…In this regard it has to be prevented that the flowing chip fragments captured by the high-pressure jet do not collide with the newly generated workpiece surface which may be damaged in this way. This undesirable effect can be influenced by the geometrical jet alignment and the jet force point of impact [44,113].…”

“…Even though numerous research studies have been conducted in the past, the scientific relations of the high-pressure lubricoolant supply has not been completely analyzed yet and further research is necessary [113,114]. The understanding of the basic mechanisms is fundamental to improve the systematic use of the highpressure lubricoolant supply and its optimal adjustments to maximize profitability and energy efficiency [114].…”

Sustainability Assessment of Advanced Machining Technologies

“…This combination can also be denoted as LCO 2 + MQL, as the two principles are combined. State-of-the-art LCO 2 assisted machining shows promising results in terms of prolonged tool life [10] to [17], improved surface integrity [11], [13], [14], [17] and [20], lower cutting forces [13], [14], and [16] and reduced cutting temperatures compared to MQL and/ or dry machining [10], [11], [16] and [18]. However, the LCO 2 is freely released into the atmosphere, contrary to conventional MWFs, which are stored back into the reservoir.…”

“…In continuous cutting, such as turning or drilling, long chips can be problematic especially when machining difficult-to-cut materials. In conventional High Pressure Jet Assisted Machining (HPJAM), one or more focused and high-energetic coolant jets are delivered into the chip-forming zone, thus increasing the productivity [20] to [22], tool life [15], [20] to [23] and chip breakability [24] and [25]. Two main high pressure MWFs supply variants are shown in Fig.…”