Impellers are the most crucial components of pumps, as they directly determine the velocity profile of the fluid flowing through the pump and its efficiency. Given that the impellers have a complex geometry, they pose an important challenge to the manufacturer in order to construct them with the best possible dimensional accuracy and surface quality, and also achieve short machining times. In the present paper, the machining operations for the manufacture of a radial impeller were designed and implemented for the case of a single-entry semi-closed radial flow impeller. At first, the best milling strategies, optimum cutting conditions, and appropriate cutting tools were selected for each of the three machining phases, namely, roughing, semi-finishing, and finishing. Then, an experimental investigation was conducted, especially for the optimum process conditions during finishing of impeller blades, using Taguchi L16 orthogonal array. After the analysis of surface roughness was conducted for the 16 experiments, it was found that the most important parameters were spindle speed and feed. Furthermore, the optimum settings were determined as the maximum spindle speed and the lowest feed per tooth value and a regression model correlating process parameters with surface roughness was established with a high degree of accuracy.
High-speed machining is widely applied for the processing of lightweight materials and also structural and tool steels. These materials are intensively used in the aerospace and the automotive industries. The advantages of high-speed machining lie not only in the speed of machining (lower costs and higher productivity) but also in attaining higher surface quality (prescribed surface roughness without surface defects). Based on this concept, in the present paper the high speed-dry turning of AISI O, (manganese-chromium-tungsten / W.-Nr. 1.2510) tool-steel specimens is reported. The influence of the main machining parameters i.e., cutting speed, feed rate and depth of cut on the resulted center-line average surface roughness (Ra) is examined. Types of wear phenomena occurred during the course of the present experimental study as well as tool wear patterns were also monitored.
Abstract:The design and manufacturing of medical implants constitutes an active and highly important field of research, both from a medical and an engineering point of view. From an engineering aspect, the machining of implants is undoubtedly challenging due to the complex shape of the implants and the associated restrictive geometrical and dimensional requirements. Furthermore, it is crucial to ensure that the surface integrity of the implant is not severely affected, in order for the implant to be durable and wear resistant. In the present work, the methodology of designing and machining the femoral component of total knee replacement using a 3-axis Computer Numerical Control (CNC) machine is presented, and then, the results of the machining process, as well as the evaluation of implant surface quality are discussed in detail. At first, a preliminary design of the components of the knee implant is performed and the planning for the production of the femoral component is implemented in Computed Aided Manufacturing (CAM) software. Then, three femoral components are machined under different process conditions and the surface quality is evaluated in terms of surface roughness. Analysis of the results indicated the appropriate process conditions for each part of the implant surface and led to the determination of optimum machining strategy for the finishing stage.
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