G. Urbicain

DRILLING OF INTERMETALLIC ALLOYS GAMMA TIAL

Due to their high strength/weight ratio and resistance to corrosion and wear, superalloys such as gamma TiAl or Inconel 718 appear as the best choice for the high mechanical/thermal demands in the vicinity of the combustion chamber of aircraft engines. There are assembled parts such as cases, disks or blisks; in the manufacturing of these components the last drilling operation could jeopardize the full work integrity adding new costs to the just very expensive parts. Therefore drilling is a high‐added value step in the complete sequence. The present work is framed within the study of hole making in advanced materials used for lightweight applications in aerospace sector. Within this context, the paper presents the results from milling tests on three types of gamma TiAl alloys (extruded MoCuSi, ingot MoCuSi and TNB) to define an optimal set of cutting parameters, which will contribute to open the increase in use of these special alloys. Drilling tools made of integral hard metal were used, applying differe...

Critical thickness and dynamic stiffness for chatter avoidance in thin floors milling

A common problem in the aeronautical industry is the chatter vibration due to the lack of dynamic stiffness in the milling of thin walls and thin floors. The present work proposes a method for chatter avoidance in the milling of flexible thin floors with a bull nose end mill. It allows the calculation of the thickness previous to finish milling or the minimum dynamic stiffness that the floor must have to avoid the chatter vibration appearance. To obtain these values, the stability model algorithm has been inverted to estimate the thickness or the dynamic stiffness required in a floor to allow a stable milling. This methodology has been validated satisfactorily in several experimental tests.

Stability Lobes in Turning of Low Rigidity Components

An accurate prediction of the dynamic stability of a cutting system involves the implementation of tool geometry and cutting conditions on any model used for such purpose. This study presents a dynamic cutting force model based on the collocation method by Chebyshev polynomials taking advantage from its ability to consider tool geometry and cutting parameters. In the paper, a simple 1DOF model is used to forecast chatter vibrations due to the workpiece and tool, which are distinguished in separate sections. The proposed model is verified positively against experimental dynamic tests.

New Strategies For Hole Making In Ti‐6Al‐4V

The working conditions for the aircraft engines components demand a good response of their mechanical properties at high temperatures and aggressive environments. Those challenging conditions force the use of new materials like titanium (and nickel) based alloys, qualified as difficult‐to‐cut materials due to their low machinability. Among them, the Ti‐6Al‐4V is very widespread because of its high strength/weight ratio. On the other hand, a very demand task for aeronautical components is the hole making operation, being in most cases, the last performed operation. For this reason, drilling operation is strongly related to the quality and productivity since any machining error could damage the component in the final steps. Thus, drilling operation determines the minimum machining time which is reflected upon the cost per unit. This study focuses the attention on a relative new technique that could replace the conventional drilling resulting in a more added‐value operation: ball helical milling (BHM). This ...

New Trends in Higher Education for a Thinner Approach to Technological Needs of Manufacturing Companies

The High Performance Manufacturing Group is established and grows from the 80s until now within the Department of Mechanical Engineering of the University of the Basque Country (UPV/EHU). The groups work focuses on teaching and research on manufacturing processes, primarily: metal removal processes, EDM, laser-processing techniques and grinding. To develop the investigations, the group has a workshop equipped with the latest technology machines manufactured by nearby companies of the machine tool sector. Furthermore, the workshop makes use of instrumentation systems for forces, temperatures or other parameters acquisition, in order to obtain the maximum amount of information from each test.With the objective of reducing the gap between industry and academic-scientific fields, it has been recently established the Machine Tool Unit. This initiative aims to provide advanced training in the field of Machine Tools and Manufacturing Technology. For this purpose, the unit gives strong theoretical formation along with practical training in companies and/or technological canters. Classes are taught both by own staff of the university as by external agents from research centers who develop R & D + i activities.

Collocation method for chatter avoidance of general turning operations

An accurate prediction of the dynamic stability of a cutting system involves the implementation of tool geometry and cutting conditions on any model used for such purpose. This study presents a dynamic cutting force model based on the collocation method by Chebyshev polynomials taking advantage from its ability to consider tool geometry and cutting parameters. In the paper, a simple 1DOF model is used to forecast chatter vibrations due to the workpiece and tool, which are distinguished in separate sections. The proposed model is verified positively against experimental dynamic tests.

The influence of cutting speed in austenitic stainless steel machining: Study of specific force coefficients

Although the turning process has been widely studied and is well-known, some limitations exist in the processing of certain materials due to an absence of their characterization. Such is the case of austenitic stainless steels, which in spite of being materials of great economic and technological value, their behavior in machining is still not well understood in some aspects. In industry there is not enough reliable and up-to-date technological data about austenitic stainless steels, especially when considering the state of the art in technology development where cutting speeds are higher and higher. In this paper a mechanistic model for cutting force prediction is developed; expressions for the specific coefficients of cutting are determined that characterize the behavior of austenitic stainless steels turning at high cutting speeds using coating tungsten carbide tools.

Mechanistic Model for High Speed Turning of Austempered Ductile Irons

This work proposes a mechanistic model to predict the cutting forces during machining of low machinability materials such as austempered ductile irons (ADI). For these cases, commonly used models are not accurate due to high rates of wear and a new coefficient is necessary to correctly estimate the cutting forces against time. As well, ceramic inserts are applied for the first time in dry turning of ADI.

A Mechanistic Model for High Speed Turning of Austenitic Stainless Steels

Behavior of austenitic stainless steels is not well known and these materials are still considered as difficult to machining materials. Moreover, the continuous increment of cutting speeds and other cutting parameters derived from last technological advances in tool material makes it more difficult to understand the behavior of these materials in high performance machining. A mechanistic model is presented in this paper for cutting force prediction of austenitic stainless steels turned at very high cutting speeds (up to 750 m/min). The developed model allows the estimation of cutting forces in turning when the cutting action occurs on the side cutting edge and nose radius edge for general turning tools. A tool-part geometrical model is proposed and the cutting force coefficients have been calculated by means of characterization tests.

Drilling Titanium Aluminides with Twist Drills

Due to their high strength/weight ratio and resistance to corrosion and wear, superalloys such as gamma TiAl or Inconel 718 appear as the best choice at the sight of the demands in the vicinity of the combustion chamber. Such kind of parts suffer one last drilling operation at the end of the manufacturing process. The present work is framed within the study of twist drilling in advanced materials used for lightweight applications in aerospace sector. Within this context, the paper presents the results obtained from different tests in gamma TiAl alloys. Tool life tests were performed on three types of γ-TiAl (extruded MoCuSi, ingot MoCuSi and TNB) to define an optimal set of cutting parameters.