Laporan Akhir Projek Penyelidikan Jangka Pendek ... - ePrints@USM

In! J Adv ManuI' Technol570 515560 505E 550 E 4956 615 15 490ollOll'(i) 540 '0)::r:::530 475::r:5200 200 400 600 800 10004650 200 400 600 800 1000Cut off (J..Lm)Cut off (J..Lm)ab450 530510500485480470440 520E 430 E 510.'-' ::l..6~.c Oll15 Oll'0) 420 '0)::r:::r:500410 490Fig. 11400 480a 200 400 600 800 1000 0 200 400 600 800 1000Cut off (J..Lm)Cut off (J..Lm)CRoughness profiles of workpiece. a New tool. b After 50 min. c After 75 min. dAfter 175 mindand 0.4 mm/rev also revealed similar trends. The reason forthis can be explained by plotting the workpiece surfaceprofiles.As Fig. 11 a-d shows, the surface profile is repeatingmore or less periodically as expected and horizontal lengthof each cycle is nearly equal to the machining feed perrevolution (0.2 mm). The fluctuation in the periodic profilein some ofthe cases is due to disturbances in the machiningprocess because the maximum fluctuation is less than 5 J..Lm.The 'period' of each profile does not change when themachining time is increased, rather only the amplitudechanges. When the cutting tool is new (sharp) the roughnessis maximum and when the tool is used for some time theroughness decreases. This is due to increasing nose wear thatcauses a smearing effect on the workpiece. This phenomenoncontinues until a machining time of approximately 75 minfor feed rates of 0.25 mm/rev and 0.3 mm/rev. After 100'>1210-*- Feed rate", 0.2 mm/rev-+- Feed rate", 0.25 mmlrev-II- Feed rate", 0.3 mmlrev--+- Feed rate", 0.4 mm/revOL---'-_-.Jl-_-L.-_---'--_----'--_--'-_-.J__L----.-J20 40 60 80 100 120 140 160Machining time (min)Fig. 12 Effect of feed rate and machining time on R aid Springer