Optimization of pressure and flow rate in HPC jet assisted turning of steel

Abstract

Although MRR increases with increase in velocities and feed rates but it raises tempcrarurc remarkably and such high cutting temperature adversely affects, directly or indirectly, chip fonnation, cutting forces, tool life, dimensional accuracy and surface integrity of the products. IWC (high pressure coolant) jet assisted turning is an effective method of machining, which allows overcoming the problems presented in the conventional turning of steels. The application of culting fluid with HPC leclmique causes a hydr<iulic wedge between the chip and the r$e face of the tool with very jXlsilive efiec( on machining which noticeably reduces the temperarure gradient and eliminates the sei~ure effect, offering adequate lubrication at the lool--<:hip interface with a significant reduction ill friction in addition to alteration of the chip flow conditions resulting in the lowering of component forces and consequently tool wear rate. But, to get the greatest benefit from the HPC (High Pressure Coolant) system it is very vital to use the optimum amount of pressure and flow, recognize the type of nozzle or orifice to place at the end of the tube that will properly direct the coolant stream, and &etting the correct angle and distance from the work piece required to properly hit the exact high temperature wne of the cutting area. lbis paper deals with experimental investigation on the role of HPC having various pressure and flow rate by cutting oil (HC straight run, VG 68) on cutting temperature, chip morphology, surface roughness in turning AISI.-4320 steel at industrial speed-feed combinations by uncoated SNMG insert. Then, optimization has been carried out with the help of Design of Experiment along with Multiple Attribute Decision Making method and multiple graphical plots. The analysis of results show that the optimal combinational effect of average chip-tool interface temperature, chip reduction co-efficient and surface roughness can be achieved by optimizing cutting speed, feed rate along \,ith the pressure and flow rate of HPC coolant jet. Other significant effects such as the interaction between the process parameters are also investigated. Finally, cutting forees (main cutting force and feed force) and dimensional deviation has heen measured under HPC (having optimum pressure and 'flow rate) and dry environment to compare with one another based on forces and dimensional deviation. In total, the encouraging results include significant reduction in temperature, force, dimensional inaccuracy and surface roughness by APe application mainly through reduction in the cutting wne temperature and favurablc cbange in the chip-tool and work-tool interaction.