Investigation of the influence of CO2 cryogenic coolant application on tool wear

The use of cryogenic coolants has emerged as an environmentally conscious alternative to emulsion coolant options. Cryogenic media can be delivered with a variety of methods to the cutting edge and they can be used in combination with other traditional coolant options such as Minimum Quantity Lubrication (MQL) and compressed air cooling in order to aid dissipation of heat generated in the cutting zone and maximize the lubrication of the cutting edge and thus prolong tool life. This study focuses on the investigation of tool life when milling aerospace grade titanium (Ti-6Al-4 V) under different coolant delivery options. Tool wear progression was recorded for the following coolant options: cryogenic CO 2 , emulsion flood cooling, dry machining, cryogenic CO 2 combined with air or MQL as well as MQL alone

Characterization of Machinability and Environmental Impact of Cryogenic Turning of Ti-6Al-4V

Abstract Titanium alloys are widely used in aerospace applications due to their physical and mechanical properties. However, their poor machinability remains the main challenge to improve the productivity and the surface quality. Cryogenic machining recently gained interest as a clean and economical cooling technique. It becomes a promising candidate for applications that involve aggressive metal removal, especially for hard-to-cut material. This research provides insight into the cryogenic machining performance compared to flood machining in terms of its effect on tool life, surface quality, cutting forces and environmental impact. For such analysis, turning tests of Ti-6Al-4V using cryogenic and flood technologies were conducted at different cutting conditions. Life cycle analysis was conducted using the Eco-indicator method to compare the environmental impact of each technology. The cryogenic technology significantly improved the process environmental performance in addition to enhancing the tool life and surface quality compared to flood, hence improved the process productivity

Sustainable machining of Ti-6Al-4V using cryogenic cooling: an optimized approach

Abstract Cryogenic machining is an effective, sustainable cooling approach in machining hard-to-cut materials. In this work, two multi-objective optimization techniques, namely; non-dominated sorting genetic algorithm, and grey relational analysis, were used to optimize the cutting performance during turning Ti-6Al-4V alloys under flood and cryogenic cooling. The machining performance was optimized in terms of surface roughness, material removal rate, tool performance and cutting forces. The optimal solutions, including cutting conditions and cooling technique, were determined for different machining strategies (i.e. roughing, finishing, and productivity). It was found that cryogenic cooling offers better cutting performance with a higher optimization index than flood approach

Effect of machining environment on surface topography of 6082 T6 aluminium

Environmental and health issues associated with the use of conventional cutting fluids in machining operations is an ever growing concern among industries, workers, environment activists and governments. The aim of this paper is to explore the effects of alternative environmentally friendly approaches on the machinability of 6082 T6 aluminium alloy as compared to traditional flood machining. The experimental studies indicated that the best surface roughness (Ra) can be produced by dry machining followed by flood. However, microscopic analysis of the surfaces revealed that the surfaces produced in dry and flood conditions suffer from micro defects such as ductile deformation, smearing and chip redeposition, which have been eliminated through using cryogenic cooling techniques.</p

Investigation of the effects of cryogenic machining on surface integrity in CNC end milling of Ti-6Al-4V titanium alloy

This paper presents the first comprehensive investigations on the effects of cryogenic cooling using liquid nitrogen on surface integrity of Ti-6Al-4V titanium alloy workpiece in end milling operations. Titanium is classified as a notoriously difficult-to-machine material, where its machining is characterised by poor surface integrity and short tool life. Increasing productivity, whilst meeting surface integrity requirements for aerospace and medical titanium-based components has always been a challenge in machining operations. Cryogenic machining using super cold liquid nitrogen at -197°C is a method to facilitate heat dissipation from the cutting zone and reduce the chemical affinity of workpiece and cutting tool materials and therefore improving machinability. Since milling is one of the major machining operations for aerospace components, this study is concentrated on cryogenic milling. The effects of cryogenic cooling on surface integrity are compared to conventional dry and flood cooling in end milling Ti-6Al-4V titanium alloy. A series of machining experiments were conducted at various combinations of cutting parameters. Surface roughness and microscopic surface integrity were investigated and subsurface microhardness was measured for each sample. The analysis indicated that cryogenic cooling has resulted in up to 39% and 31% lower surface roughness when compared to dry and flood cooling methods respectively. Furthermore, microscopic surface defects were significantly reduced as a result of cryogenic. The investigations indicated that cryogenic cooling considerably improves surface integrity in end milling of Ti-6Al-4V.<br/

Effect of cryogenic machining for titanium alloy based on indirect, internal and external spray system

Due to the excellent properties of Ti-6Al-4V titanium alloy such as lightweight, high wear and corrosion resistance and able to maintain high strength at high elevated temperature, this material has been used mostly in aerospace and biomedical industries. However, titanium alloy being considered as a hard-to-cut material with poor machinability due to its low thermal conductivity which leads to the excessive tool wear during machining and requires high machining cost. To overcome these problems, cryogenic machining has been taken place as a promising method for machinability improvement in terms of tool wear reduction, lower energy consumption and low machining cost. Even though this method has been implemented for titanium alloy machining, it is difficult to handle the excessive extremely low-temperature coolant (up to -150) that exposed directly to the workpiece. As a result, the workpiece hardness will be increased, hence will increase the required cutting force for the machining process. In concern with the problem, this paper presents a novel cryogenic cooling mechanism (indirect cryogenic cooling) that will be used as one of the cooling and lubrication strategy. The performance of the indirect cryogenic cooling will be compared with flood cooling, Minimum Quantity Lubrication (MQL) and conventional cryogenic cooling method by using the external and internal spray system. Liquid nitrogen (LN2) being selected as the cooling medium in this work since its temperature can reach lower -196, odorless and more environmentally friendly. A specially designed tooling kit that able to supply the liquid nitrogen to the cutting tool internally is used in this method. The developed indirect cryogenic supply method able to improve the machinability of Ti-6Al-4V. The cutting force is reduced by 54% and the tool life is improved by 90% compared to the conventional flood coolant strategy

Cryogenic High Speed Machining of Cobalt Chromium Alloy

AbstractCobalt chromium (CoCr) alloys are extensively used in medical industries for a variety of applications. Due to their unique material properties, machining CoCr alloys are associated with short tool life, poor surface quality and low productivity. This paper presents one of the first studies on using various cooling methods in CNC milling of these alloys. A series of machining experiments were conducted at 200m/min cutting speed. Cryogenic cooling, minimum quantity lubricant (MQL) and flood cooling with water-based emulsion were investigated. The analysis clearly demonstrated that a 71% reduction in surface roughness Ra and a 96% reduction in flank wear can be achieved using cryogenic cooling when compared to conventional machining best practice

Effects of lubricooling conditions on machining forces and surface roughness in radial grooving

Radial grooving is a machining process usually applied to generate grooves for thread relief, O-ring positioning, or even cutting-off operations. Due to the high machining forces and difficult chip removal, radial grooving is considered a critical process,and cutting fluids are usually applied for cooling, lubricating, and assistance on the chip removal. Compressed air (AIR) and minimum quantity lubrication (MQL) are lubri-cooling methods studied as environmentally-friendly alternatives to conventional flood (WET) applications of cutting fluids. Although already applied for years in several machining processes, the research associated with using alternative lubri-cooling techniques in radial grooving is incipient. This work presents a comparative analysis of these methods (WET, MQL, and AIR) and their radial grooving effects. In each case, a factorial design of experiments was used to evaluate the influence of lubri-cooling conditions, cutting speed, and feed rate over feed force, cutting force, and surface roughness. Results indicate that both AIR and MQL may be suitable substitutes for traditional WET lubrication when active force components and surface finish are considered. Besides, smaller cutting forces were obtained with AIR machining for radial grooving, followed by MQL and WET machining