A. Celaya

Plasma Assisted Milling of Heat-Resistant Superalloys

The term Thermal Enhanced Machining refers to a conventional cutting process in which an external energy source is used to enhance the chip-generation mechanism. The work presented here analyzes the basic aspects and the experimental results obtained when applying an assisting plasma jet to the milling process. This process, known as PAM (Plasma Assisted Milling) has been applied to the machining of three very low machinability materials: a Ni-base alloy (Inconel 718), a Co-base alloy (Haynes 25), (both belonging to the group of the heat-resistant alloys) and the Ti-base alloy Ti6Al4V. The study focuses on two major topics. First, the efficiency of the milling operation in terms of cutting speed, feed, axial and radial depths of cut and the plasma operating parameters has been addressed. Second, a study on the alterations of the metallurgical structure and the properties of materials after the PAM has also been performed. The process conditions for the above-mentioned Ni-base and Co-base alloys are detailed. The study under these conditions has shown an excellent performance of the whisker reinforced ceramic tools. In fact, cutting speeds as high as 970 m/min and large radial and axial depths of cuts are possible, driving to a cost-effective machining process. The absence of changes in the metallurgical structure of the alloys after applying the PAM process is also addressed. Therefore, it can be stated that this is a feasible approach to the optimization of the machining process of heat-resistant alloys. Finally, the results obtained in the PAM of Ti6Al4V are detailed. In this experimentation, a certain level of degradation was observed in the microstructure of the alloy when undergoing the PAM process, therefore the use of this technique is not recommended for this material.

Five-Axis Machining and Burnishing of Complex Parts for the Improvement of Surface Roughness

In this article, the ball burnishing is applied on sculptured surfaces, aiming at enhance surface roughness. Different strategies are possible for burnishing, the continuous burnishing (CB) which uses a five-axis interpolation of the machine tool, and the patch burnishing (PB) using a more simple 3 + 2 axis interpolation. Using both techniques complex parts are burnished and a big improvement in surface roughness achieved, but some differences between both approaches appear. Two parts have been previously machined in a five-axis milling center and finished using the ball burnishing approaches. The first one is a steel AISI 1045 with a hemisphere shape, whose geometry is simple. The second one is a steel DIN 1.2379 part (64 HRC), with more complex features. Surface quality was evaluated for both burnishing approaches, obtaining significant improvements on surface roughness and hardness. The main general conclusion is that ball burnishing reduces roughness without penalizing the manufacturing time or surface integrity and, therefore, is suitable for complex surfaces.

Ultrasonic Assisted Turning of mild steels

In this work, the advantages and drawbacks of Ultrasonic Assisted Turning (UAT) have been investigated focusing on the effect of tool vibration on surface quality. Several experiments have been performed on mild steels changing the cutting speed, feed and depth of cut, to study how the influence of the ultrasonic vibration on the surface roughness varies depending on the cutting conditions. The results obtained show that the ultrasonic vibration can improve the surface quality. The authors also propose a new booster design based on the theory of longitudinal vibration of a bar with varying cross-sectional area for a higher amplification of the ultrasonic vibration.

Machine Tool Performance and Precision

This chapter introduces main machine tool design, construction and testing aspects to achieve high precision on machined parts. Not only the machine tool but also the machining process itself is a source of errors on parts. Therefore, a holistic view involving machine and machining is required. The design of high precision machines involves some basic principles and methodologies which are presented in depth further on. A key factor is the identification of error sources, studying their physical causes and relevance to the final uncertainty. Thus, assembly error, thermal growth, component deformations and control inaccuracy are described. Errors in components and subassemblies are propagated along the kinematic chain of the machine, producing larger positional errors at the tool tip position and tool axis orientation. The use of homogeneous matrices is introduced as a very useful tool for estimating error propagation. Tool deflection and machine deformation caused by cutting forces is another important error source. Unfortunately deflection is impossible to avoid although some models are now provided with machining toolpath selector implying minimal cutting forces along error sensitive directions. After construction and just before the machine tool is delivered to the customer, the verification of precision and performance must be always performed. A description of the existing standards and procedures for this are described at the end of this chapter.

Ball burnishing application for finishing sculptured surfaces in multi-axis machines

In this paper the ball burnishing as a finishing process of sculptured surfaces is studied. This technique is a quick, easy and cheap process for a significant surface quality improvement of high-end parts. Aiming at the burnishing of sculptured surfaces, the influence of each burnishing parameter on flat surfaces was previously studied. Taking into account these results, burnishing of sculptured surfaces was performed by two different strategies: continuous burnishing (CB) using 5-axis interpolation and patch burnishing (PB) using 3 + 2-axis interpolation. The results obtained show the importance of choosing optimal burnishing parameters for a roughness and hardness improvement. Thus, CB achieves a great improvement in roughness, but the process feed is limited by the maximum speed of machine tool rotary axes. Otherwise, PB allows applying the machine maximum feed, reducing the time to finish the workpiece, but at the expense of a slight increase in roughness on the border line between patches.

Effect of coatings and tool geometry on the dry milling of wrought aluminium alloys

The work presented here is focused on the elimination of coolants in the high speed milling of wrought aluminium alloys. This is a very interesting issue from the point of view of the high costs of the coolant life cycle and for environment preservation. The main factor to be considered is the estimation of temperature at the tool/chip interface, since it acts directly on the tool degradation mechanism: the previous diffusion and the later adhesion of aluminium on the rake and clearance faces, the well-known BUL (built up layer) effect. Two techniques are discussed to keep the temperature below the diffusion threshold, the tool geometry optimisation making use of the simulation of the removal process using the finite element method and the measurement of the tool edge temperature with an infrared device. Five different types of hard metal tools have been tested under the same conditions.

The Effects of Ultrasonic Vibration Parameters on Machining Performance in Turning of Mild Steels

The present work presents the results obtained when an ultrasonic vibration is applied to tool on the turning of mild steels. Currently high‐end materials, usually present low machinability so it is necessary to employ new machining technologies. Ultrasonic assisted turning (UAT) is presented as an effective process for machining these difficult‐to‐cut materials. In order to achieve a better understanding of the process, a complete study of the influence of the vibration parameters is presented when machining mild steels. Several parameter of UAT were monitored, including surface roughness, tool wear, chip formation by a high‐speed imaging camera, and tool temperature by means of an infrared camera: surface roughness and tool temperature decrease and an tool life increase as compared to conventional turning (CT).

Implementation of Simulation Software for Better Understanding of Manufacturing Processes

The adaptation of universities to the European Higher Education Area (EHEA) plays an essential role in society, creating new knowledge, transferring it to students by means of new and more active methodologies aimed at learning that will enable students to put everything they learn into practice. However, such methodologies are not equally applicable in all subjects. Subjects such as Manufacturing Technology, taught at different levels in both undergraduate and graduate levels, are descriptive to a great extent. This descriptive nature must be supported by new technologies if these subjects claim to be more attractive to students. In this paper some examples of successful case studies are presented. They represent the new way of understanding the teaching replacing the old concept of traditional classroom lecture by more interactive ones and, therefore, more attractive to students.

Aeronautics Advanced Manufacturing Center, the Bet to Surpass the Valley of Death between University and Company

The present times are changing and need new formulas that satisfy the need for effective transfer between universities and companies. In the Basque Country, attending to this demand the Aeronautics Advanced Manufacturing Center (CFAA) has been founded. This center belongs to the University of the Basque Country (UPV/EHU) and has several companies related to this strategic sector as partners. The CFAA, equipped with the latest machinery and technology, born to be a catalyst for research activity in the field of advanced manufacturing for aeronautical sector, focusing its activity on the called Pillar 2 of the MRL scale (Manufacturing Readiness Level) as the proximity to the final application. Belonging to the UPV/EHU, this center allows stays of doctoral students, students for performing their master and bachelor’s degree projects. This implies a high quality training, and closer to reality, in manufacturing technologies.

About the Importance of Simulation Tools in the Learning Process of Metal Forming and Moulding

The European Higher Education Area has entailed some upheaval since it has involved deep changes in university education. Among the subjects taught in technical education such as Manufacturing Technologies, which involve strong experimental contents, the use of specific tools is helpful for better understanding of such subjects. This article highlights the need for the use of simulation tools in the field of manufacturing processes. The student may achieve optimal understanding and learning from them. They can understand, in a more visual way, complex phenomena that govern different processes and the influence of key variables. Applications related to sheet metal forming, forging and casting processes are presented. The main objective is to enable students to better understand the phenomena that govern the processes of moulding and forming, with the invaluable help of simulation software. The final aim is to ensure that the student reaches an optimum knowledge of moulding and forming processes using simulation software.