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Recently, a new methodology for 5-axis flank computer numerically controlled (CNC) machining, called double-flank machining, has been introduced (see “5-axis double-flank CNC machining of spiral bevel gears via custom-shaped milling tools—Part I: Modeling and simulation”). Certain geometries, such as curved teeth of spiral bevel gear, admit this approach where the machining tool has tangential contact with the material block on two sides, yielding a more efficient variant of flank machining. To achieve high machining accuracy, the path-planning algorithm, however, does not look only for the path of the tool, but also for the shape of the tool itself. The proposed approach is validated by series of physical experiments using an abrasive custom-shaped tool specifically designed for a particular type of a spiral bevel gear. The potential of this new methodology is shown in the semifinishing stage of gear manufacturing, where it outperforms traditional ball end milling by an order of magnitude in terms of machining time, while keeping, or even improving, the machining error.

Inconel 718 is a widely used alloy in the aeronautic sector due to its excellent mechanical and corrosion wear resistance under high temperature conditions. However, its good mechanical properties can be a double edge sword in terms of manufacturing, especially in those processes based in mechanical principles, such as machining or forming. Considering that most aeronautic components are exposed to cyclic load and temperature, fatigue resistance becomes critical, and therefore, the finishing processes. The surface integrity of a component plays an important role on its fatigue behaviour, as the most common crack initiation area is usually the surface. The present work compares three different mechanical finishing processes that confer better surface properties to the component: polishing, burnishing, and hammer-peening. Each one achieves different degrees of roughness, and residual stress on the surface. The study is not only focused on the resultant mechanical properties, but also in productivity and process robustness. It is concluded that each technology excels in a different property.

Recently, a new methodology for 5-axis flank computer numerically controlled (CNC) machining, called double-flank machining, has been introduced (see “5-axis double-flank CNC machining of spiral bevel gears via custom-shaped milling tools—Part I: Modeling and simulation”). Certain geometries, such as curved teeth of spiral bevel gear, admit this approach where the machining tool has tangential contact with the material block on two sides, yielding a more efficient variant of flank machining. To achieve high machining accuracy, the path-planning algorithm, however, does not look only for the path of the tool, but also for the shape of the tool itself. The proposed approach is validated by series of physical experiments using an abrasive custom-shaped tool specifically designed for a particular type of a spiral bevel gear. The potential of this new methodology is shown in the semifinishing stage of gear manufacturing, where it outperforms traditional ball end milling by an order of magnitude in terms of machining time, while keeping, or even improving, the machining error.

Prosthesis production for hips, knees, and other human body elements, including dental implants and spine screws, requires eliminating any risk of material damage or contamination. Five-axis milling is the most suitable technique to manufacture tailor-made prostheses for different personalized sizes with affordable costs. Human life expectancy is growing, so the demand of a higher prosthesis lifecycle and manufacturing optimization is a current necessity. In this work, a robust five-axis milling process using cryogenic CO2 as coolant fluid is presented and applied to a Ti6Al4V knee implant. Ti6Al4V (grade 5 and grade 23) alloys are very difficult to cut without lubri-cooling using oil emulsion coolant; however, this emulsion implies risks from introducing little oil drops entrapped in surface roughness valleys, hampering the cleaning process before patient’s surgery. CO2 reduces this risk uncertainty, making machining operations more feasible and suitable regarding environmental sustainability. In terms of feasibility, the surface finishing, roughness, and residual stresses was analysed, obtaining a standard of IT4-IT5, N4 and compressive stresses, respectively. Virtual simulation of machining is also a key in five-axis to make a more robust industrial process.

In the energy and aeronautics industry, some components need to be very light but with high strength. For instance, turbine blades and structural components under rotational centrifugal forces, or internal supports, ask for low weight, and in general, all pieces in energy turbine devices will benefit from weight reductions. In space applications, a high ratio strength/weight is even more important. Light components imply new optimal design concepts, but to be able to be manufactured is the real key enable technology. Additive manufacturing can be an alternative, applying radical new approaches regarding part design and components’ internal structure. Here, a new approach is proposed using the replica of a small structure (cell) in two or three orders of magnitude. Laser Powder Bed Fusion (L-PBF) is one of the most well-known additive manufacturing methods of functional parts (and prototypes as well), for instance, starting from metal powders of heat-resistant alloys. The working conditions for such components demand high mechanical properties at high temperatures, Ni-Co superalloys are a choice. The work here presented proposes the use of “replicative” structures in different sizes and orders of magnitude, to manufacture parts with the minimum weight but achieving the required mechanical properties. Printing process parameters and mechanical performance are analyzed, along with several examples. Thanks are owed to H2020-FETOPEN-2018-2019-2020-01 ADAM2 PROJECT Analysis, Design, And Manufacturing using Microstructures and Authors are grateful to Basque government group IT IT1337-19 and the Ministry of Mineco REF DPI2016-74845-R, PID2019-109340RB-I00, KK-2020/00102, KK-2020/00042 and PID2019-104488RB-I00.

Standing sectors in the industry such as railroad or plastic injection moulds presents many challenges for manufacturing complex components in terms of finishing requirements and mechanical properties. Because of that, hydrostatic ball burnishing is considered an optimal solution since it reduces surface roughness and generates hardened surfaces and compressive residual stresses, increasing the performance and lifespan of this parts in terms of resistance and mechanical fatigue. Additionally, this technology could be integrated directly into the machining centres, what reduces times and dimensional errors arising from mooring changes. Therefore, lead times and production costs can be drastically reduced in comparison with other finishing techniques. The aim of this project is to analyse the use of the ball burnishing process to improve the final quality of medium carbon steel surfaces, minimizing surface roughness and improving hardness. In order to achieve significant results, different working pressures are analysed in terms of surface roughness and hardness in AISI 1045 and AISI P20 steels. The results showed a reduction in roughness parameters of more than 89% for both materials using a pressure of 10 MPa. Moreover, at a pressure of 30 MPa, the surface hardness has been increased by 15% and 34% respectively.