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

Abstract

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.

Laser Assisted Milling of Ti-6Al-4V ELI with the Analysis of Surface Integrity and its Economics

“…The 20 % reduction in cutting force measured during LAML of Ti-6Al-4V ELI is not as large as the 60 % reduction observed during milling of Inconel 718 [26] or the 40 % reduction during milling of a Ti-6Al-4V alloy [27]. This is mainly a result of differences in laser power and configurations during machining.…”

“…Because the material properties of the final workpiece surface were of critical importance for the Ti-6Al-4V ELI alloy and the material is heat treatable by nature, laser power was limited during LAML experiments. This consideration was not included in the work presented by Brecher et al [26] and Sun et al [27]; therefore, with a higher laser power, a larger reduction in cutting force could be achieved.…”

“…Since milling is an interrupted process with continual rotation of the cutter, there are some potential challenges in implementing laser assisted milling. Some recent studies have shown successful results of laser-assisted milling in micro scale [19][20][21] and macro scale [22][23][24][25][26][27]. Shelton et al [19,20] carried out laser assisted micro-milling on difficult-to-machine materials of AISI 316, AISI 422, Ti-6Al-4V and Inconel 718 using side milling and slotting configurations.…”

“…Brecher et al [26] integrated a laser into a milling machine spindle and performed LAML experiments on an Inconel 718 workpiece and showed that the overall tool life could be improved through coordination of laser heating during tool rotation and workpiece interaction. Sun et al [27] presented the experimental work on LAML of a Ti-6Al-4V alloy using up-milling and showed a reduction of cutting force and reduced tool wear over conventional machining. The thermal modeling was carried out using a simple analytical solution to determine the temperature of the workpiece at a point on the top surface and a point at the depth of cut during the laser heating process.…”

Laser-assisted milling of Ti-6Al-4V with the consideration of surface integrity

“…Sun et al [24] presented experimental work on LAML of a Ti-64 alloy using up-milling. Basic temperature prediction was performed to determine the temperature of the workpiece at a point on the top surface, and the depth of cut, during the laser heating process.…”