Effect of tool wear on tool life and surface finish when machining DF-3 hardened tool steel

Hard turning is a dominant machining operation perf ormed on hardened materials using single-point cutting tools. In recent years, hard t urning operation has become more and more capable with respect to various machinability crite ria. This work deals with machinability of hardened DF-3 tool steel with 55 ±1 HRC hardness at various cutting conditions in terms of tool life, tool wear mechanism and surface roughness. Co ntinuous dry turning tests were carried out using coated, mixed ceramic insert with honed edge geometry. Two different cutting speeds, 100 and 210 m/min, and feed rate values of 0.05, 0.125 and 0.2 mm/rev were used with a 0.2 mm constant depth of cut for all tests. Additionally s canning electron microscope (SEM) was employed to clarify the different types of wear. As far as t ool life was concerned, best result was achieved at lowest cutting condition whereas surface roughness values decreased when operating at higher cutting speed and lower feed rate. Additionally max imum volume of material removed is obtained at low cutting speed and high feed rate. Dominant w ear mechanism observed during the experiments were flank and crater wear which is mai nly caused by abrasive action of the hard workpiece material with the ceramic cutting tools

A nonlinear lumped parameter model of an externally pressurized rectangular grooved air pad bearing

Because of their low friction and wear, aerostatic pads are widely in many high precision applications, e.g., linear slides, coordinate measuring machines and medical equipment. However, especially grooved aerostatic pads can be unstable under certain operating conditions. This paper presents a lumped parameter model to study the static and the dynamic performance of a rectangular grooved aerostatic pad. The theoretical results are compared with the experimental ones

A Lumped Model for Grooved Aerostatic Pad

Air pads are often embedded into robotic devices for manufacturing and measuring applications. Investigating the performance of these pads is essential to obtain robot characterized by very accurate motions and positioning. Due to their simplicity, mathematical lumped parameter models can be adopted to evaluate quickly both the static and dynamic performance of such bearings. This paper describes a lumped parameter model to study the behavior of a grooved rectangular air pads. The static and dynamic results of the model are validated by using a purpose built test bench