S. Sun

Experimental investigation of cutting forces and tool wear during laser-assisted milling of Ti-6Al-4V alloy

The improvement of machinability during laser-assisted milling of Ti-6Al-4V alloy was investigated. The effects of laser processing and milling parameters on cutting forces and tool wear have been examined. It is found that local heating and softening of the workpiece by the laser beam in front of the cutting tool significantly reduced the cutting forces, especially the force in the feed direction during up-cut milling. Laser power, tool–beam distance, depth of cut and cutting speed are the parameters influencing the change of feed force during laser-assisted milling. Analysis of the workpiece temperature rise due to laser beam heating shows that the feed force is strongly dependent on the workpiece temperature in front of the cutting zone; significant reduction of feed force occurred when the temperature in front of thecutting zone was in the range 200–450°C. Edge chipping is found to be the tool failure mode for both conventional milling and laser-assisted milling. A significant improvement in tool life during laser-assisted milling was obtained when the workpiece temperature in front of the cutting zone was at an optimum value. Compressed air was used to remove the chip from the cutting tool, which made the milling process more effective. The optimum workpiece temperature in front of the cutting zone with compressed air delivered through the spindle is about 350°C, higher than that with compressed air delivered through a stationary nozzle (about 230°C). The maximum tool life in the former case is much longer than that in the latter case.

Machinability of a near beta titanium alloy

In this paper, the machinability of a near beta Ti25Nb3Mo3Zr2Sn titanium alloy with different heat treatment histories has been investigated in terms of cutting force, chip temperature and chip formation. A solution treatment was performed followed by ageing at different temperatures for the near beta alloy. It has been shown that the same alloy behaves differently during machining at various cutting speeds after different heat treatments. The observations have been explained in terms of friction effects and the hardness of the materials. It has been concluded that the ductility of a workpiece plays a significant role in determining its machinability. High friction at the tool–chip interface in a ductile workpiece resulted in a higher degree of chip segmentation and a larger undeformed surface length in each chip.

Mechanical properties of Ti6Al4V and AlSi12Mg lattice structures manufactured by selective laser melting (SLM)

Emerging additive manufacturing (AM) techniques such as selective laser melting (SLM) present an exceptional opportunity for the manufacture of lattice structures which exhibit attractive mechanical properties beyond the capabilities of solid materials. However, to apply SLM-manufactured lattices as structural elements, it is necessary to quantify their manufacturability as well as key mechanical properties, such as compressive strength and stiffness, under varying material, geometric and loading conditions. This work reports on the experimental investigation of the SLM manufacturability and mechanical properties of titanium (Ti6Al4V) and aluminium (AlSi12Mg) alloy lattice structures; the materials were selected because of their inherently high specific strength (pursuant to lattice structure design opportunities) and compatibility with SLM. A range of lattice structures are manufactured and experimentally assessed for compressive strength and stiffness, with varying materials, cell topology, cell size, number of unit cells and associated boundary conditions. The mechanical properties as well as deformation and failure characteristics are analyzed and compared with theoretically predicted behaviour.

Investigation of the Cutting Forces and Tool Wear in Laser Assisted Milling of Ti6Al4V Alloy

The current investigation evaluates laser assisted machining, which uses an external laser beam to heat and soften the material to be machined locally in front of the cutting tool and offers an alternative approach to improving the machinability of titanium alloys. By reducing the cutting resistance, the cutting tool sees less pressure and life is enhanced. This paper reports on the cutting forces and tool life during laser assisted milling of Ti6Al4V alloy. Cutting forces, especially the force in the feed direction, reduce dramatically with laser beam assistance. The reduction of feed force depends on the laser power, depth of cut and cutting speed. This paper also discusses the major tool failure mode observed during both conventional and laser assisted milling operations.

Experimental study on quality of PCD tools machined by different electric discharge grinding processes

Abstract Polycrystalline diamond (PCD) is a promising tool material which is utilized to cut difficult-to-machine materials used in aerospace industry. Because of its ultra-hardness, electrical discharge grinding (EDG), a variation of electrical discharge machining, is often adopted to manufacture PCD tools to reduce manufacturing time. This paper investigates the quality of PCD inserts manufactured by two different EDG eroding methods: “2-step machining” and “3-step machining”. Surface roughness and residual stress were investigated after EDG process. An orthogonal cutting experiment was conducted to test the performance of each PCD insert. PCD tools machined with the two methods do not have significant difference in surface roughness. The residual stress status changed from compressive to tensile after EDG process. Also, after being eroded by 3-step EDG process, there was an over 30% declination of residual stress compared with 2-step machining. The results of the orthogonal cutting test showed that the wear amount and the thrust force of PCD inserts machined by 3-step EDG were smaller for the CTB010 insert and the CTX002 insert. In contrast, the CTM302 machined by 3-step EDG did not show obvious improvement in tool wear resistance during the cutting tests.