The improvement of productivity, efficiency, and product quality requires the use of modern machining equipment, and modern process management. Successful management of the cutting processes requires a lot of knowledge about workpiece materials, cutting tool materials and geometry, tool machine, cooling and lubrication fluids including dosage techniques, and cutting conditions. However, the mentioned requirements are difficult to achieve in hard turning (Fig. 1). Hard turning is the cutting process for workpiece materials which are hardened above 45 HRc. This method has been introduced to replace traditional processes, which included turning, heat treatment and grinding [1]. Hard turning is almost performed using harder cutting tool materials such are the ceramics (Al 2 O 3) and cubic boron nitride tools (CBN), at lower cutting parameter values. The use of these tools and parameters causes expensive production, because of expensive tools and long machining time. The use of brittle tools requires continuous cut due to poor toughness of cutting tool edges. Use of cooling and lubrication fluid supplied under high pressure can bring some improvements in machining. This technique of fluid supplying dates from the fifties of the last century. In modern machining are used the high pressure tool systems that allow the fluid supply under pressures up to 15 MPa. The high pressure jet assisted machining (HPJAM) concept is to inject an extremely high pressure jet of cooling and lubrication fluid in the cutting zone, between chip and tool edge. In this techniques are used pressures from 40 to 200 MPa, so that jet is participating in the chips forming, similar to the non-conventional technologies [2-4]. HPJAM was established as a method that would substantially increase the removal rate and Abstract The machining of hard-to-machine bearing steel AISI 52100 (100Cr6), hardened to 62 HRc, is almost impossible using standard machining conditions and carbide cutting tools. The purpose of this research is machinability analysis and conclusions about the conditions that allow the machining of mentioned steel with carbide tools. In this paper, the turning process is carried out using coated carbide inserts and high pressure jet assisted machining, as a special technique of cooling and lubrication. In this technique, coolant circulation system with filters, environmentally acceptable, is used. A jet of cooling and lubrication fluid under extremely high pressure (50 MPa) is directed into the zone between the cutting tool edge and the workpiece. Experimental measurements were performed for different cutting parameters. Cutting forces, tool wear, surface roughness, chip shapes, and material removal rates were analyzed. The presented results show an increase in productivity, low intensity tool wear, and surface roughness in acceptable limits.

SummaryIn this paper, machinability of turned steel defined by monitoring of cutting forces, tool wear, surface quality and chip shape is presented. Experimental investigations were performed on untreated carbon steel C45E (hardness 45 HRc) and on surface induction hardened steel C45E (surface layer hardness 58 HRc). The analysis of machinability was performed under different cooling and lubrication conditions: conventional flooding, minimum quantity lubrication (MQL) and a hybrid machining method, i.e. high pressure jet assisted machining (HPJAM). The investigation was carried out for higher values of processing parameters. The results show the advantages of the advanced cooling and lubricating techniques, i.e. an increase in productivity and a reduction in production costs. The analysis of the results shows that the application of HPJAM gives superior machinability. Beside excellent chip breakability achieved in HPJAM, especially in hardened steel machining, significant improvement in tool life and reduction in cutting forces can be achieved.

The development of industry in the last ten years has caused the production of parts with relatively small dimensions. This has led to intensive development of efficient micro-technologies through research of processes, machines and tools. This paper presents the research of machinability, channels micro-milling in AISI D2 tool steel (X155CrVMo-5), hardened to 62 HRc. As the tool is used micro-milling cutter with diameter of 0.6 mm and relatively large working length of 5 mm. Analysis of surface roughness, burr on workpiece edges and reduction of cutter diameter due tool wear was performed.

High Pressure Jet Assisted Machining (HPJAM) in turning is a hybrid machining method in which a high pressure jet of cooling and lubrication fluid, under high pressure (50 MPa), leads to the zone between the cutting tool edge and workpiece. An experimental study was performed to investigate the capabilities of conventional and high pressure cooling (HPC) in the turning of hard-to-machine materials: hard-chromed and surface hardened steel Ck45 (58 HRc) and hardened bearing steel 100Cr6 (62 HRc). Machining experiments were performed using coated carbide tools and highly cutting speed. Experimental measurements were performed for different input process parameters. The cooling capabilities are compared by monitoring of tool wear, tool life, cooling efficiency, and surface roughness. Connection between the tool wear and surface roughness is established. Experimental research show that the hard turning with carbide cutting tools and HP supply CLF provides numerous advantages from the techno-economic aspect: greater productivity, reduce of temperature in the cutting zone, improved control chip formation, extended tool life, low intensity of tool wear, surface roughness in acceptable limits, significant reduce of production costs related to the CLF.

Components miniaturization in industry leads to intensive research and development of efficient micro-technologies through research of different production processes, machines and tools. This paper presents experimental research on machinability of inclined surfaces on hardened steel workpieces with long-neck micro-end-ball mills. Workpiece is hardened AISI D2 tool steel (X155CrVMo-5). Micro-parts of this material is usually produced by non-conventional technologies such as electro-discharge machining (EDM) and laser beam machining (LBM), that allows machining of 2D or simple 3D structures. The effects of geometrical and cutting parameters on output machinability parameters in ball micro-milling were evaluated. Analysis of tool deflection, surface roughness and tool wedge wear was performed, in order to obtain the recommended cutting parameters for more precise, accurate and quality of micro-parts.