Papers by Keyword: Hard Machining

Abstract: Based on the experiments there was investigated the tool life of various kinds of cutting materials by hard machining. Taylor equations can be used for the cutting conditions setting. The measured values of surface roughness, residual stresses and microhardness show possibility of hard machining usage in practice. In case of the white layer zone appearance this needs to be eliminated by superfinishing. The ceramic and CBN wiper inserts are the objects of further research.

Abstract: Inconel 718 is used for high-temperature applications in aerospace, nuclear, and automotive industries due to its resistance, at high temperatures, to corrosion, fatigue, creep, oxidation, and deformation. Unfortunately, these same qualities also impair its machinability and researchers have investigated on ways to machine it economically. Some unconventional machining practices such as: Plasma Enhanced and Laser Assisted Machining etc. have been applied. However these practices increase the machining cost. This research investigated the viability of high speed end milling of Inconel 718 using circular Silicon Nitride (ceramic) inserts under room temperature conditions. Tool wear (flank and notch wear), machining vibration amplitude and average surface roughness were evaluated for the feasibility analysis. A vertical CNC mill was used to machine Inconel 718 samples using different combinations of three primary machining parameters: cutting speed, feed, and depth of cut. Vibration data acquisition device and Datalog DasyLab 5.6 software were used to analyze machining vibration. Scanning Electron Microscope (SEM) and surface profilometer were utilized to measure tool (flank and notch) wear and surface roughness, respectively. It was observed that the machining vibrations, in high speed machining, was reasonable (0.045 V on the average). This resulted in acceptable tool wear (averages: flank wear = 0.25 mm, notch wear = 0.45 mm) and semi-finished surface roughness (0.30 µm) measured after every 30 mm length of cut. Thus, room temperature high speed machining of Inconel 718 using circular silicon nitride inserts is a practical option.

Abstract: High usage of hardened steel in the automotive, gear, bearing, tool and die making industries, makes it a highly suitable material for industrial production and research. This study was undertaken to investigate the performance of coated ceramic insert with different edge preparations in terms of cutting force and surface roughness. Plain turning experiments were carried out under dry cutting condition at two different cutting speeds and feed rates with a constant depth of cut. The workpiece material is ASSAB DF-3 hardened steel with a 55 ±1 HRC hardness. Results showed that insert edge preparation had a direct influence on the radial and feed forces but not on the tangential force. The use of T-land edge preparation results in the lowest radial and feed forces. In terms of surface finish, the use of honed with finishing wiper insert results in obtaining the lowest surface roughness values. Feed rate had a significant effect on surface roughness whereby by increasing feed rate, the surface roughness value also increased, whereas the effect of cutting speed was found to be insignificant. Increasing cutting speed resulted in lower feed and tangential forces however by increasing feed rate all cutting forces increased.

Abstract: Theoretical analysis and experiments on bearing race show that a suitable residual compressive stress on roll path of bearing race can prolong its contact fatigue life. However, residual tensile stress is often found on workpiece surface of bearing race. To actively control the residual stress state and improve fatigue life of bearing part, a new method of pre-stress hard cutting is applied. In this paper, the principle of pre-stress hard cutting for bearing race is introduced as well as the experiments on it. In the experiments, residual stress, hardness and roughness of machined surface are measured and analyzed. Moreover, micro-topography and texture characteristics of machined surface are investigated and experimental results are compared with that by grinding. It is found that we can get residual compressive stress and fine quality on machined surface of bearing race by pre-stress hard cutting and increase its productivity as well.