The effects of liquid-CO2 cooling, MQL and cutting parameters on drilling performance

An investigation is made into the effects of liquid carbon dioxide (LCO2) cooling, minimum-quantity lubrication (MQL) and cutting speed in drilling. Experimental measurements of torque, thrust force and temperature are made over a wide range of process and operating conditions. The resulting empirical models are used to quantify the individual contributions of the controlled parameters on drilling performance, and to facilitate temperature-based process optimization. Of particular interest is the need to carefully adjust the LCO2 flow rate for any combination of MQL flow rate and cutting speed. The optimization is validated both in simulation and actual drilling tests

The influence of single-channel liquid CO2 and MQL delivery on surface integrity in machining of Inconel 718

Sustainable machining of difficult-to-cut materials requires effective cooling and lubrication techniques. To substitute conventional flood cooling and lubrication, different techniques such as cryogenic cooling and/or minimum quantity lubrication (MQL) can be used. Liquid carbon dioxide (LCO2) can be pre-mixed with different lubricants before its delivery to the cutting zone. This article investigates the influence of this recently developed cooling and lubrication method on surface integrity characteristics in milling of Inconel 718. Surface roughness, surface topography and microstructure were evaluated for flood lubrication, dry cutting and LCO2 machining using a single-channel LCO2 and MQL strategy. Moreover, two different lubricants were evaluated for MQL: (i) conventional MQL oil and (ii) solid lubricant molybdenum di-sulphide (MoS2). In addition to being environmentally friendly, MoS2 lubricated LCO2 showed comparable surface characteristics to flood lubrication. Also, the use of lubricated LCO2 resulted in higher part surface cleanliness compared to flood lubrication

Tribology of solid-lubricated liquid carbon dioxide assisted machining

An investigation is made into the lubrication capabilities of solid-lubricated liquid carbon dioxide (LCO2) in comparison to flood lubrication, straight LCO2 and oil-lubricated LCO2 (MQL). The coefficient of friction is determined via tribological experiments, similar to machining, using an open tribometer which features an uncoated carbide insert sliding against a workpiece. Tribological experiments reveal superior performance of solid-lubricated LCO2. The milling experiments as well indicate that solid-lubricated LCO2 significantly reduces wear. The machined-surface topography is examined using high-magnification SEM, which shows no presence of adhered solid particles on the workpiece surface, providing a completely dry machining process

Lubrication and cooling device and a method for lubricating and cooling a workpiece

The disclosure relates to a lubrication and cooling device (1), comprising; a cooling fluid device (3), which comprises a first channel (5), which is connected to a first inlet port (7), and a lubricant fluid device (9), which comprises a second channel (11), which is connected to a second inlet port (13). The lubrication and cooling device (1) further comprises a heat exchanger (15), which comprises a cooling circuit (17) and a lubricant delivery circuit (19). The heat exchanger (15) is arranged to cool the lubricant fluid (24) by means of the cooling fluid (22), wherein the cooling fluid is a cryogenic fluid. The disclosure further relates to a method for lubricating and cooling a workpiece or a process by using a lubrication and cooling device (1), wherein the method comprises the steps of: a) cooling the lubricant fluid (24) by means of the cooling fluid (22) using the heat exchanger (15), and b) providing the cooled lubricant fluid (24) to the workpiece or process being lubricated and cooled

A novel cryogenic machining concept based on a lubricated liquid carbon dioxide

A novel single-channel supply of pre-mixed (a) liquid carbon dioxide (LCO2) and (b) oil – delivered via minimum quantity lubrication (MQL) – represents a significant advancement in cryogenic-machining technology. In this proof-of-concept study, an attempt is made to advance the understanding of the oil solubility in LCO2 and to analyze the oil-droplets and their impact on machining performance. The results indicate that the physical and chemical properties of oil distinctively affect its solubility in LCO2. The achieved solubility further influences the achievable oil-droplet size and distribution and tool life

Cryogenic machining and cooling capabilities when applying liquefied nitrogen to the machining zone

This paper presents the influence of nitrogen fluid phase on surface heat transfer coefficient in cryogenic machining. A novel optical nitrogen phase sensor is presented for characterizing the cryogenic fluid phase. Surface heat transfer coefficient was established experimentally, with the support of a new heat transfer model for cryogenic machining. Finite element models are developed with experimental data for Inconel 718, simulating the process behavior with varying nitrogen phases. Desired fluid phase at the delivery is found to be the key for achieving truly sustainable cryogenic machining

A lubrication and cooling device and a method for lubricating and cooling a work piece

The invention relates to a lubrication and cooling device(1), comprising;a cooling fluid device(3), which comprises a first channel (5), which is connected to a first inlet port (7), and a lubricant fluid device (9), which comprises a second channel (11), which is connected to a second inlet port (13). The lubrication and cooling device (1) further comprises a heat exchanger (15), which comprises a cooling circuit (17) and a lubricant delivery circuit (19). The heat exchanger (15) is arranged to cool the lubricant fluid (24) by means of the cooling fluid (22), wherein the cooling fluid is a cryogenic fluid. The invention further relates to a method for lubricating and cooling a workpiece or a process by using a lubrication and cooling device (1), wherein the method comprises the steps of: a) cooling the lubricant fluid (24 by means of the cooling fluid (22) using the heat exchanger (15), and b) providing the cooled lubricant fluid (24) to the workpiece or process being lubricated and cooled