Precision machining by Acoustic EmissionLiterature Review PaperCurt E. Everson and S. Hoessein Cheraghi 1 have studied the Acoustic emission for monitoring precision drilling process. To monitoring the drilling process is very helpful to minimize the total processing time also it gives the drilled hole with high tolerance. The purpose of this research paper is to identify the relationship between the different parameter like feed rate, spindle speed, drill bit lip height. Experiment is carried out on steel material to correlate the relation between different AE parameter and quality of hole. Digimatic indicator mounted on diatest probe is used to measure the diameter of hole to measure maximum, minimum and average value. M-42 cobalt drill bit is used for precision drilling in stainless steel. AC31 differential sensor is used for gathering data of AE. Six different tests was conducted to calculate the effect changing the variables on acoustic emission. The hole diameter can be correlates with the AE RMS.Y.B. Guo and S.C. Ammula 2 Have studied the AE signals for analyzing the hard-turning process. Monitoring of surface damages in hard turning by acoustic emission is very useful in order to improve the fatigue life of the component. The requirement of the monitoring is because of the damage of the surfaces in various forms like white layer. For capturing the AE signals piezoelectric AE sensor is attached. CNC Lathe is used with round CBN cutting tool. Work material is AISI-52100 used to identify the effect of various conditions. AE root mean square, AE frequency have significant relation with the white layer formation. Also AE frequency has strong relation with surface finish.J. Webster, W.P. Dong and R. Lindsay 3 have conducted the experiment on grinding process for analysis of Raw acoustic emission(AE) signals. AE signal analysis of grinding process by analyzing raw AE signal. For increasing accuracy and precision as well as reducing cost and processing time AE monitoring is useful. By knowing the response of sensor the results are compare with Raw AE signals. During the process grinding wheel and workpiece have different kind of contact that produce continuous as well as burst type AE signal. Analysis of this signals give the identification of work piece errors as well the errors in grinding wheel.J. J. Liu and D. A. Dornfeld 4have studied the AE signals to find the effects of cutting parameters on turning process. Analysis of diamond turning with help of acoustic emission. Kistler dynamometer is attached to measure force. Piezoelectric transducer is used for measures the signals which is mounted on the shank of the tool. Laser profilometer is used measures the eccentricity of the work material. AE is very useful for monitoring chip formation and diamond turning process. The energy releases during the turning in tertiary zone is similar to the load in the forming process which is theoretically calculated by upper bound method.S. Min, J. Lidde, N. Raue, D. Dornfeld 5 have studied the AE signals for finding the contact of tool with work-piece. For automated manufacturing technique precise tool length measurement is highly required to reduce the ideal time and error. Here the AE sensor is used to for tool contact detection. Continuous and incremental approaches are used for the precise tooling in which incremental approach accurate tool detection. Continuous approach damages the tool more due continuous movement of tool. For future DSP could be used for reducing the complexity.D.E Lee, I. Hawnag,, C.M.O Valent, J.M.G oliveira, D.A. Dornfeld 6 correlate the readings from the sensors with the process parameters. Increasing demand of precision manufacturing leads to the use of acoustic emission for monitoring the live process. AE is the elastic stress wave which are captured by the AE sensor and then by comparing the different cutting parameter relation has been developed like the cutting speed, chip thickness and RMS value of acoustic waves. By incorporating the monitoring process in manufacturing process also reduces the total production time.B. karpuschewski, M. Wehmeier, I. inasaki 7 have developed the relation between the signals of sensors and the grinding parameter for minimizing the effort required. In order to increase the reliability and to perform complex grinding on workpiece it is important to identify the relation between different cutting parameter and AE signals. So through experiments different relationship is established in this papers. AE and Power sensors are utilized for analysis of the precision grinding process. Future scope in the application of AE is to identify the relation of high frequency component of AE signals through which the accuracy as well as defects is minimized.D A Dornfeld 8 have develop the technique of the AE application for finishing the work piece. Work piece is made of from the Aluminum which is chamfered on milling machine, also AE signals are captured by AET sensors which are further amplified by Dunegan Endeveo amplifier. AE signal achieved during process is very noisy and further improvement could be possible by redesign the equipment in order to increase the precision of this technique to find out the contact between the work piece and deburring tool. This data would be useful to give the feedback to the machine controller in order to perform precision manufacturing operation. S. Hao, S Ramalingam, B.E. Klamecki 9 had analyze the RMS AE for the deep drawing process and compared that result to the known result. AE signal is obtained from deep drawing operation and then it is compared with experimentally calculated RMS value to establish the relations. So here the AE signal is used to identify the plastic deformation. Transducer are placed at the side of the punch to measure the AE signals which is fed to the processor and then controller take appropriate action. Because for different state of stress the AE signal behaves differently, so identification of initial plastic deformation is easy.The sensitivity of available AE transducer is less so the further development of the transducers are possible. References:-Curt E. Everson, S. Hoessein Cheraghi, Application of acoustic emission for precision drilling process monitoring, International Journal of Machine Tools & Manufacture 39 (1999) 371–387.Y.B. Guo, S.C Ammula, Real time acoustic emission monitoring for surface damage in hard machining, International journal of machine tools and manufacturing 45(2005) 1622-1627. J. Webster, W.P. Dong, R. Lindsay, Raw acoustic emission signal analysis of grinding process, CIRP Annals, volume 45, Issue 1, 1996, pages 335-340.J.J Liu, D.A Dornfeld, Modeling and analysis of acoustic emission in diamond turning, journal of manufacturing science and engineering, volume 118, issue 2(1996) S. Min, J. lidde, N.Rau, D. Dornfeld, Acoustic emission based tool contact detection for ultra-precision machining, CRIP Annals- Manufacturing technology 60(2011) 141-144.D.E. Lee, I. Hwang, C.M.O. Valente, J.F.G. Oliveira, DA Dornfeld, Precision manufacturing process monitoring with acoustic emission, International journal of machine tools and manufacture 46 (2006) 176-188.B. karpuschewski, M. Wehmeier, I. inasaki, Grinding monitoring system based on power and acoustic emission sensor, CIRP Annals, Volume 49, Issue 1,2000David A. Dornfeld, Acoustic emission feedback for precision deburring, CIRP Annals, Volume 41, Issue 1, 1992, Pages 93-96.S. Hao, S. Ramalingam, B.E. Klamecki, AE monitoring of sheet metal forming: characterization of the transducer, the work material and the process, Journal of material processing technology 101 (2000) 124-136.