Investigation of chatter detection with sensor-integrated tool holders based on strain measurement

Machining chatter is one of the most critical issues that restrict the productivity in milling of thin wall workpieces. Sensor-integrated tool/tool holders, which provide data collection during cutting, can be employed for online chatter detection. Recently, there has been an increasing number of strain-measurement-based smart tool holders, which can measure bending moments and/or torque. Although accelerometer-integrated tool holders have been tested, sensor-integrated tool holders based on strain measurement have not been evaluated for the chatter detection in milling. This paper investigates the potential of chatter avoidance using a commercial sensor-integrated tool holder based on strain measurement

Investigation of chatter detection with sensor-integrated tool holders based on strain measurement

Machining chatter is one of the most critical issues that restrict the productivity in milling of thin wall workpieces. Sensor-integrated tool/tool holders, which provide data collection during cutting, can be employed for online chatter detection. Recently, there has been an increasing number of strain-measurement-based smart tool holders, which can measure bending moments and/or torque. Although accelerometer-integrated tool holders have been tested, sensor-integrated tool holders based on strain measurement have not been evaluated for the chatter detection in milling. This paper investigates the potential of chatter avoidance using a commercial sensor-integrated tool holder based on strain measurement

A new hybrid Minimum Quantity Lubrication system for machining difficult-to-cut materials

A newly designed and manufactured hybrid MQL system is reported. Vegetable oil and tungsten disulphide suspension are mixed in an additively-manufactured nozzle and delivered through pressurised air as a coolant/lubricant spray. Cooling capability of the system is improved. Lubrication and the impact on machinability is assessed in high speed milling Ti6Al4V. Tool life and cutting forces with the new system are compared to those with air and with flood cooling and with commercial MQL. Over the reported practical range of cutting speeds, tool life is more than 2 times longer than with the commercial system and from 4 to 11 times longer than with air cooling

Electrohydrodynamic Atomization for Minimum Quantity Lubrication (EHDA-MQL) in End Milling Ti6Al4V Titanium Alloy

Titanium alloy Ti6Al4V is a difficult-to-machine material which is extensively used in the aerospace and medical industries. Machining titanium is associated with a short tool life and low productivity. In this paper, a new cooling-lubrication system based on electrohydrodynamic atomization was designed, manufactured and tested and the relevant theory was developed. The major novelty of the system lies within the use of electrohydrodynamic atomization (EHDA) and a three-electrode setup for generating lubricant droplets. The system was tested and compared with that of flood, minimum quantity lubrication (MQL) and compressed air machining. The proposed system can extend the tool life by 6 and 22 times when compared with MQL and flood cooling, respectively. This is equivalent to more than 170 min tool life at 120 m/min cutting speed allowing for significant productivity gains in machining Ti6Al4V

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/

Evaluation of Cryogenic CNC Milling of Ti-6Al-4V Titanium Alloy

Machining titanium alloys is always considered difficult due to special material properties of these alloys and their strange behaviour during machining operations. Cryogenic cooling by using liquid gases has attracted considerable research since the early 20th century and is acknowledged as an effective technique for controlling the cutting temperature and improving machinability. Despite announcement of the industrial use of cryogenic milling systems, there are limited scientific studies on the effects of cryogenic cooling in CNC milling of titanium alloys. This paper presents one of the very first scientific attempts to study the effects of cryogenic cooling in CNC milling of the Ti-6Al-4V titanium alloy in comparison with dry machining. A series of machining trials have been conducted at the University of Bath and it has been proven that cryogenic machining has the potential to significantly improve the machinability of titanium alloys in CNC milling with considerable reductions in surface roughness and improved tool life. Investigations revealed that the introduction of liquid nitrogen as a coolant resulted in 2.5 times improvement in surface roughness of the machined parts as compared to dry machining while a maximum increase of 1.9% in power consumption was recorded

Hybrid cryogenic MQL for improving tool life in machining of Ti-6Al-4V titanium alloy

It is estimated that there is a need for 37,000 new passenger aircrafts until 2037. About 15% of the modern aircrafts are made of titanium alloys due to their high strength to weight ratio. In typical aerospace manufacturing, there is a buy-to-fly ratio of 6:1 for titanium parts which identifies significant machining requirements. Machining titanium alloys is generally associated with short tool life, poor surface integrity, low productivity and high manufacturing costs. These issues have made Ti-6Al-4V a difficult to machine material. In this study, a new hybrid cryogenic MQL cooling/lubrication technique is proposed for end milling Ti-6Al-4V using coated solid carbide tools. The effect of the proposed system on machinability of Ti-6Al-4V was studied at various cutting speeds and compared with flood, minimum quantity lubrication (MQL) and cryogenic cooling. Tool life, tool wear and surface roughness were thoroughly investigated as key machinability metrices and a new model for tool life based on tool wear is proposed. The analysis indicates a significant shift in CNC milling performance, as the new hybrid cryogenic MQL technique shows an increased tool life of 30 times is achieved together with a 50% improvement in productivity compared to state-of-the-art flood coolant machining. <br/