Advisor : Tzu-Yao Tai Advisee : Lung-yu Chang Department of Mechanical Engineering & Institute of Nanotechnology, Southern Taiwan University of Science and Technology, Tainan, TAIWAN Date ﹕ 2015/06/08 A Hybrid Machining Process Combining Micro-EDM and Laser Beam Machining of Nickel-Titanium Based Shape Memory Alloy Materials and Manufacturing Processes A. Al-Ahmari ab, M. Sarvar Rasheed a, Muneer Khan Mohammed a & T. Saleh a a FARCAMT, Advanced Manufacturing Institute, King Saud University, Riyadh, Saudi Arabia b Industrial Engineering Department, College of Engineering, King Saud University, Riyadh, Saudi Arabia

2 Outline  Abstract  Experimental  Result and discussion  Conclusions

Micro-EDM is a slow process as compared to laser machining, on the contrary laser machining lacks good surface quality. To overcome the drawbacks of both these processes, this paper suggests a hybrid machining process which combines laser and micro-EDM processes for drilling micro-holes in advanced engineering materials such as Nickel- Titanium (Ni-Ti) based shape memory alloy. To achieve the objective of the suggested hybrid process, pilot holes are drilled with laser machine and rimmed out by micro-EDM drilling. The suggested process requires investigation of various combinations of micro-EDM drilling process conditions to obtain optimum machining parameters for the hybrid process. It has been found that the proposed hybrid machining process resulted in 50-65% reduction in machining time without affecting the quality of micro-holes as compared to the standard micro-EDM process. 3 Abstract

4 Experimental Figure 1 Schematic diagram of Micro-EDMFigure 2 Electrical Power Supply R C Circuit

5 Experimental Process ConditionsValues Electrode material and diameter Brass Diameter = 200 µm Workpiece materialNi-Ti alloy (SMA) PolarityElectrode = -ve Workpiece = +ve Pulse generator TypeRC Dielectric fluidKerosene Discharge voltage80 V 100 V Capacitor155 pF 475 pF Table 1: Micro-EDM Experimental Conditions

6 Experimental Figure 3 Micro-EDM Experimental Set-up based on Masuzawa, 2000 Figure 4 Components of the laser unit Wavelength1064 nm Pulse duration10 µs Frequency30 KHz Laser spot diameter30 µm Table 2: Laser parameters

7 Results and Discussion Figure 5 Variation of Overcut with Discharge energy

8 Results and Discussion Figure 6 Variations of Taperness with Discharge energy

9 Results and Discussion Figure 7 Variation of Material removal rate with Discharge Energy

10 Results and Discussion Figure 8 SEM images showing hole diameter at entrance (left) and exit (right) for different energy levels (a) 7.525μJ (b) 4.816μJ (c) 2.375μJ (d) 1.52μJ µm µm µm µm µm µm µm µm µm µm µm µm µm µm µm µm

10 Results and Discussion Figure 9 Comparison of micro-holes diameter at entrance and exit produced by (a) LBM and (b) LEDM

11 Results and Discussion Figure 11 Comparison of Taper angle in μ-EDM and LEDM (Hybrid Process) Figure 10 Comparison of Overcut in μ-EDM and LEDM (Hybrid Process)

12 Results and Discussion Figure 12 Illustration of Hybrid machining Figure 13 Comparison of Material Removal Rates in μ-EDM and LEDM (Hybrid Process)

13 Results and Discussion Machining Typeµ-EDMLaser MachiningHybrid Machining MRR (mm 3 /min) Table 3: MRR comparison in µ-EDM, Laser, Hybrid Machining

14 Results and Discussion Figure 14 SEM images of micro-holes produced on (a) standard μ-EDM, (b) Laser machining

15 Results and Discussion Figure 14 SEM images of micro-holes produced on (c) Hybrid Machining

15 Conclusions 1.The laser machining of micro-holes the material removal rate was very high but the quality of micro-holes produced was not good. On the other hand the micro-holes produced by micro-EDM were of high quality with good surface morphology but however the material removal rate was very low. Therefore, in order to overcome this problem and to take the advantage from the both the machining processes (high MRR during laser machining and good surface morphology with micro-EDM). 2.The hybrid machining process has resulted in the 50-65% reduction of machining time and about 40% to 65% increase in material removal rate (MRR) without effecting the quality of micro-hole.

Thank you for your attention 18