Enrique García-Martínez

The surface integrity of γ-TiAl alloys is critical for the performance and reliability of aerospace components due to their limited ductility and inherent brittleness. Although wire electrical discharge machining (W-EDM), milling and heat treatments are commonly employed during the manufacture of γ-TiAl parts, their combined influence on surface integrity remains insufficiently understood. This study investigates the effects of finishing operations and post-machining heat treatments on a Ti-48Al-2Cr-2Nb alloy produced by vacuum arc remelting (VAR). Specimens were sectioned by W-EDM and subsequently finished by dry milling. Surface integrity was evaluated through metallographic observations, microhardness measurements, and residual stress analysis, while annealing treatments between 700 and 1100 °C for 2 h were applied to assess the recovery of machining-induced alterations. W-EDM generated a cracked surface layer, revealing a significant limitation of this process for γ-TiAl components. Milling removed the damaged layer and produced a defect-free surface, however, it induced a plastically deformed subsurface region about 50 μm thick, accompanied by increased hardness and residual stresses. Annealing at 700 °C provided only partial recovery, whereas treatments at 900 °C and above promoted complete recrystallization of the affected layer, restoring hardness to values close to those of the bulk material. The results demonstrate that milling followed by annealing at 900 °C for 2 h effectively restores surface integrity without altering the bulk microstructure.

This study reports the development and validation of a psychometric instrument designed to assess students’ perceptions of a practical learning activity in the Master’s program in Industrial Engineering. The activity, part of “Manufacturing Systems and Materials Forming” course integrates laboratory experimentation and Finite Element Method (FEM) simulation. It was structured around four latent dimensions: perceived usefulness, time and resources invested, understanding of academic concepts, and evaluation of pedagogical methodology. Items were generated through a top-down approach based on teaching experience, including both positively and negatively worded statements. After reliability testing, eight items were removed. Exploratory Factor Analysis revealed a two-factor structure, refined using Unweighted Least Squares. The final 17-item questionnaire showed high internal consistency and construct validity, with no bias between language or academic background groups. A second survey confirmed response stability and indicated higher time investment, offering a reliable tool for improving instructional design and workload management. Key words: Manufacturing Engineering, Engineering Education, Psychometry

Este texto tiene como objetivo servir de referencia docente para el aprendizaje de los fundamentos de programación mediante control numérico para tornos y fresadoras CNC. Para ello, el libro presenta de manera gradual la definición de las distintas órdenes de programación para el control Fagor 8055, apoyándose en numerosos ejemplos y proponiendo ejercicios, de nivel creciente, para la puesta en práctica de las distintas funciones. El nivel de los contenidos desarrollados permite que un usuario con conocimientos básicos de mecanizado y manejo de máquina-herramienta pueda aprender de manera autónoma a desarrollar programas completos de control numérico para el mecanizado de piezas complejas. El libro se estructura en tres partes. La primera parte presenta los conceptos generales sobre la programación en control numérico. La segunda parte se centra en código para fresadora CNC, definiendo las órdenes de movimiento y compensación de herramientas, sentencias para repeticiones y subrutinas, y ciclos fijos de mecanizado. La tercera parte engloba la programación para torno CNC, enfocada en el uso de ciclos fijos de cilindrado, refrentado, ranurado o taladrado, entre otros. Aunque el texto está dirigido a un público interesado por aprender a programar máquinas-herramienta de control numérico, puede ser especialmente útil para estudiantes y docentes de Grado y ciclos de formación profesional en asignaturas relacionadas con la Ingeniería de los Procesos de Fabricación.

The Monte Carlo method (MCM), applied to uncertainty calculation in metrology, is well-suited for nonlinear functions. It also provides more accurate solutions in certain complex linear models. Although MCM is extensively covered in the ISO Guide to the Expression of Uncertainty in Measurement (GUM) and in metrological guides from reference institutions in various countries, industrial engineering curricula typically only introduce concepts related to uncertainty propagation using the traditional analytical method. MCM requires programming to generate random numbers within the expected range for each variable involved in the metrological system, combining computing tools with metrology. This methodological proposal is based on a basic system for constructing an angle using a sine bar and gauge blocks. The problem progressively incorporates the temperature variable under different behavioural hypotheses and the influence of other factors, such as the roundness tolerance of the sine bar supports. The results obtained using MCM are compared with those from the classical GUM method, and the analysis demonstrates the robustness of MCM from a scientific perspective. Based on this methodology, further challenges could be explored, such as introducing the flatness tolerance of the surface plate used. Keywords: Montecarlo, dimensional metrology, angle construction, influence magnitudes

Titanium aluminides are being explored as potential materials for the aeronautical sector. However, their application is limited by the high costs of processing and their difficulties in machining. This research evaluates the effectiveness of the minimum quantity lubrication technique (MQL) on the turning process of Ti48Al2Cr2Nb aluminide in terms of tool wear, tool life, cutting forces, surface integrity, and temperature. It was found that MQL conditions can improve the process efficiency, reducing the thermally induced wear mechanisms and enlarging the tool life compared to dry machining. Furthermore, it allows the cutting speed to be incremented, leading to lower processing times. However, MQL seems to not be effective in the reduction of the strain-hardening effect near the machined surface and, although the number of microcracks is reduced, defect-free surfaces cannot be obtained. Moreover, similar microstructural alterations as for dry cutting were detected. The best cutting conditions in terms of surface quality were assessed using the central composite face (CCF) design and surface response methodology. Optimization of the surface roughness under industrially viable cutting conditions was achieved with an average surface roughness value, Ra, of 0.29 µm (feed rate of 0.05 mm/rev, a cutting speed of 54.6 m/min and a depth of cut of 0.125 mm).

Carbon fiber reinforced polymers (CFRPs) are interesting materials due to their excellent properties, such as their high strength-to-weight ratio, low thermal expansion, and high fatigue resistance. However, to meet the requirements for their assembly, the drilling processes involved should be optimized. Defects such as delamination, dimensional errors and poor internal surface finish can lead to the premature failure of parts when bolt-joined or rivet-connected. In addition, the characteristic anisotropy and heterogeneity of these materials, and the issues related to the temperature reached during drilling, make it difficult to obtain optimal cutting parameters or to achieve high material removal rates. This research focuses on the optimization of the CFRPs drilling process by means of experimental analysis—varying the feed and spindle speed—for two different types of commercial drills—a twist tool and a dagger tool. An automatic image processing methodology was developed for the evaluation of the dimensional accuracy and delamination of the holes. The optimization was carried out using a multi-objective regression technique based on the dimensional deviations, delamination and surface finish. The areas with favorable machining conditions have been delimited for both tools and the results indicate that the twist tool allows one to achieve more productive cutting conditions than the dagger tool, when the combination of low feeds and high spindle speeds are the conditions to be avoided.