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Improving the surface quality of additive manufactured parts like poly lactic acid (+) is an important study that is currently being carried out by researchers. To reach the high-quality, different conventional and nonconventional methods are applied. In this study, the capability of ultrasonic vibration in drilling of an additive manufactured poly lactic acid (+)was examined. The process was implemented in two methods: conventional and vibratory drilling. Then, thrust force and chip type were analyzed, and the effect of them on surface roughness, delamination, circularity, and cylindricality have been investigated. As a result, it was indicated that lower thrust force and broken chips, which were generated in ultrasonic drilling, caused the surface quality parameters to be improved compared to the conventional method. [ABSTRACT FROM AUTHOR]

Conventional drilling (CD) which is known by two rotary and linear motions is considerably used in material removal processes; however, this method cannot satisfy the new demands of modern industry anymore, encountering with some serious technological constraints such as fast tool wear, high thrust force, and so on. A new and promising method which has been used recently as an alternative technique to cope or at least diminish common difficulties in CD is imposing ultrasonic vibrations to the cutting process, where vibrations usually with high frequency and low amplitude are superimposed in the movements of cutting tool. This study is a new exercise which considers the effects of one and two directional ultrasonic vibrations in drilling of AISI 1045 compared to CD. In one directional technique known as longitudinal ultrasonic assisted drilling (L UAD), ultrasonic vibrations are added to the feed motion and in two directional vibrations; ultrasonic vibrations are simultaneously applied to both feed and rotary motions known as longitudinal-torsional ultrasonic assisted drilling (L-T UAD). The study which is performed both experimentally and numerically does its best to evaluate and compare the obtained results in CD, L UAD, and L-T UAD. In experimental part, a system including two vibratory tools and a rotary mechanism is designed, fabricated, and then assembled with other equipment on a milling machine to accomplish drilling tests. In numerical part, a FE model is also developed with the aim of further understanding of experimental results, by which drilling operations either conventional or vibratory in different forms can be conducted and studied. As a brief conclusion, it was found that ultrasonic vibrations can be used as an effective tool for enhancement of drilling process and longitudinal-torsional vibrations reveal better results than longitudinal vibrations. [ABSTRACT FROM AUTHOR]

Conventional drilling (CD) which is known by two constant rotary and linear motions causes some problems in drilling of materials such as high thrust force, poor surface quality, and rapid tool wear. To get rid of these problems or at least minimize them, a promising technology has been employed in the recent years, where vibrations usually with low amplitude and high frequency are applied to the direction of feed motion results in a time-dependent velocity between drill tip and workpiece. This paper focuses on the design of a vibratory tool following by experimental and numerical approaches to study the influence of longitudinal ultrasonic vibrations on drilling of aluminum alloy 7075. Experimental part is a comprehensive exercise to design, fabricate, and test a system equipped with different instruments to work in desired conditions. Experimental results are supported by a finite element method to better comprehend what is happening in cutting process when ultrasonic vibrations are added. The achieved results prove that using ultrasonic-assisted drilling (UAD), the machining ability of drilled aluminum workpiece can enhance significantly. Improvement of up to 40% for drill circularity and a reduction of up to 37% in thrust force were achieved. [ABSTRACT FROM AUTHOR]

In this study, a combined drilling method consists of ultrasonic-assisted drilling (UAD) under the presence of minimum quantity lubrication (MQL), is evaluated. Effect of this method on machinability factors is investigated by implementation of a dynamometer and a vision-measuring microscope. Then the results are compared with the values obtained in conventional drilling, and separately UAD and MQL-drilling. As a result, it was revealed that the output parameters were significantly improved when combined MQL- UAD method was exerted. In particular, built-up edge and drill skidding have almost been eliminated. Moreover, it was shown that increase of tool rake angle and producing broken chips caused thrust force and surface roughness to be reduced in UAD and UAD-MQL. In the combined strategy, burr-less hole has been achieved due to the formation of solid burr at the exit surface of drilled hole. [ABSTRACT FROM AUTHOR]

In this study, 3D finite element simulation of ultrasonically-assisted drilling is carried out to analyze the effect of ultrasonic vibrations on common difficulties existed in conventional drilling. Influence of harmonic movement of drill bit on the formation of built-up edge is experimentally evaluated and also discussed by investigation of heat generation on the tool faces in simulation. At the end, it was revealed that intermittent movement of drill bit in vibration method causes the total time of heat transfer between workpiece and drill bit to be reduced resulting lower built-up edge formation compared to conventional drilling. Moreover, linear motion of cutting tool in the feed direction results in the increase of chip strain and consequently damage value which causes to generation of broken chips. [ABSTRACT FROM AUTHOR]

Application of glass fiber reinforced polymers (GFRP) has been appreciably increased in recent decades because of their admirable properties. Thus, various investigations are focused in machinability of GFRPs. Delamination is one of the major damages in drilling of GFRPs. Rotary ultrasonic drilling (RUD) is a state-of-the-art drilling operation that has been noticeably considered in composites machining industry. In this paper, delamination of GFRPs in RUD process is examined. To reach the goal, appropriate ultrasonic system was established and using a HSS tool, the experiments were carried out. Then, the influence of multi-walled carbon nanotube (MWCNT) addition, thermal fatigue and drilling parameters on delamination were investigated. Additionally, statistical analysis was performed. The results showed that the delamination quality can be well optimized by increase of the cutting velocity. It was also established that thermal fatigue condition results in delamination deterioration. In contrary, addition of nanoparticles enhances the delamination state. [ABSTRACT FROM AUTHOR]