Abstract
Micro drilled holes are utilized in many of today's fabrication processes.Precision production processes in industries are trending toward the use of smaller holeswith higher aspect ratios, and higher speed operation for micro deep hole drilling. However,undesirable characteristics related to micro drilling such as small signal-to-noise ratios,wandering drill motion, high aspect ratio, and excessive cutting forces can be observedwhen cutting depth increases. In this study, the authors attempt to minimize the thrustforces in the step-feed micro drilling process by application of the DOE (Design ofExperiment) method. Taking into account the drilling thrust, three cutting parameters,feedrate, step-feed, and cutting speed, are optimized based on the DOE method. Forexperimental studies, an orthogonal array L27(313) is generated and ANOVA (Analysis ofVariance) is carried out. Based on the results it is determined that the sequence of factorsaffecting drilling thrusts corresponds to feedrate, step-feed, and spindle rpm. Acombination of optimal drilling conditions is also identified. In particular, it is found in thisstudy that the feedrate is the most important factor for micro drilling thrust minimization.
Highlights
With increasing demand for precise micro components production, the importance of micro hole drilling processes is increasing in fields such as medical instruments, aerospace engineering, and computer industries.[1,2] It is required for micro deep hole drilling technologies to achieve higher accuracy and higher productivity, because deeper and smaller holes are required for specific applications in the aforementioned industries
Determining the number of factors and levels, a suitable orthogonal array can be selected by the total Degree of freedom (DOF) of the experiment, because the total DOF of factors and levels used in an orthogonal array is already determined [7]
On the bases of the S/N ratio graphs and ANOVA, it can be declared that A1, B3, and C3 correspond to the factors producing minimal drilling thrusts and there are no interactions between A*B and A*C
Summary
With increasing demand for precise micro components production, the importance of micro hole drilling processes is increasing in fields such as medical instruments, aerospace engineering, and computer industries.[1,2] It is required for micro deep hole drilling technologies to achieve higher accuracy and higher productivity, because deeper and smaller holes are required for specific applications in the aforementioned industries. Mechanical micro deep hole drilling process become increasingly difficult as the aspect ratio of drill increases This is caused by insufficient chip and heat discharging mechanisms, as well as problems related to ineffective lubrication arising from failure to adequately supply coolant. Experimental works are carried out based on DOE (Design of Experiments), and the obtained experimental data are analyzed using ANOVA (Analysis of variance).[6,7]
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