Optimizing the cutting conditions of hardened A2 tool steel based on optimum material removal rate technique using UHPT software

This thesis explores the optimum material removal end milling technique when applied to A2 tool steel hardened to 42 HRC using a half inch Hanita VariMill solid carbide cutting tool. The optimized cutting conditions of the intended operations are compared with respect to machining cycle times, tool life, and tool performance. The results are discussed in terms of tool life and the quantity of machined parts obtained out of one cutting tool. To understand the material-tool reactions under different cutting conditions, several experiments were performed on materials softer than A2 tool steel. For this purpose, 6061 aluminum was selected as the starting material followed by 1018 mild steel. Two flute high speed steel (HSS) end mills, !scar multi-master two and four flute carbide end mill inserts, and Hanita VariMill four flute solid carbide end mills were also used in this phase of the study. Also, a single-path side contouring operation was selected for these two rectangular block materials from which the toolpaths were generated by conventional CAM software (Esprit???). The last phase of the study was perfmmed on A2 tool steel with different Rockwell C hardness levels ranging from 33 to 42 HRC. To complete this phase, a new technique of tool path generation was employed to decrease the chance of tool failure and accelerate the cycle time of machining. Therefore, in place of using conventional CAM programs, VoluMill??? was considered as a toolpath engine to generate optimum material removal rate machining code and to produce ultra high performance toolpaths (UHPT), to XV not only extend tool life and reduce the stress on machine and cutting tools, but also to run the desired program as fast as possible. After finishing the experimental studies, the comparison results of the tool wear process between the used and new Hanita cutting tool were compared using a JEOL JSM- 6480L V scanning electron scientific microscope. The results indicate less than normal wear on the outside diameter of the cutter while the cutting tool tips were worn out naturally. It can be concluded that using the new CAM (VoluMill???) software to produce an Ultra High Performance Toolpath (UHPT) designed for optimum material removal rate causes this kind of tool wear process improvement. Overall after this study, a series of results were achieved based on selected cutting parameters, selected CAM program, and selected cutting tool. However, it can be concluded that different results may be obtained by changing the above parameters. The final conclusion is discussed based on a cutting speed of 350 ft/min and a feed speed of 90 in/min which resulted in a 0.0084 in/tooth (chip per tooth) and a 2.25 in3 /min material removal rate. But there is possibility to increase or decrease the cutting speed to achieve different results. However if the cutting speed increases, the chip load will be decreased, and this means the cutting tool needs more engagements to finish the same part and this will result in more tool wear. This statement is proven by the Taylor reference equation. On the other hand if the cutting speed decreases, the chip load will be increased, and in this case the chance of tool failure will be increased as well, because the 0.0084 in/tooth is on the borderline of the limit of the tool failure strength. So here, it is very important to make a right decision regarding which way is more profitable. In this study, the cutting speed (V c) of 350 ft/min and feed speed (V f) of 90 in/min are the optimized cutting parameters for a half inch axial depth of cut and 1 0 % stepover (RWOC=0.05) of a Hanita VariMill cutting tool on a hardened A2 tool steel with 42 HRC. It can be concluded that beyond the achieved optimized cutting conditions, the possibility of tool failure would be increased. But within or below this boundary, the cutting tool will experience a smooth and fluid machining environment that will also extend tool life, and reduce the stress on machine and cutting tools