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The incipient implementation of the Industry 4.0 paradigm has led to an increase in the machines sensoring level, in the processes optimization and, thus, in the product manufacturing with a higher added value. In this article a new aspect is described where, through the machine monitoring, the utilization of innovative elements as fixture is enabled for high quality machining processes. These innovative elements are characterized by the great flexibility offered by them as holding component and by their low costs. However, these elements lack the enough geometrical accuracy for applications where a high shape and surface quality product are needed. First of all, in order to have a clear vision of the singularities of each fixture type present on the state of the art, a nomenclature and a classification has been proposed based on their geometry characteristics. Hence, based on this classification, an analysis of the different fixturing solutions provided by the market has been made, enhancing the advantages of this solution against the existing ones. With the aim of demonstrating its suitability for certain machining applications, the behavior of these sort of flexible materials has been characterized. Besides, the sensors implementation has been analyzed in order to capacitate this solution for processes where tough tolerances on parts are demanded. Therefore, this survey demonstrates that, through the massive information gathering, not only an optimization of the existing technologies is obtained, but it is possible to develop innovative solutions that provide improved capacities to the already existing ones in the Industry. Keywords: Flexible fixtures, fixtures classification, elastomers characterization, laser technology, accurate machining, Industry 4.0.

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In finishing processes, the quality of aluminum parts is mostly influenced by static and dynamic phenomena. Different solutions have been studied toward a stable milling process attainment. However, the improvements obtained with the tuning of process parameters are limited by the system stiffness and external dampers devices interfere with the machining process. To deal with this challenge, this work analyzes the suitability of elastomer layers as passive damping elements directly located under the part to be machined. Thus, exploiting the sealing properties of nitrile butadiene rubber (NBR), a suitable flexible vacuum fixture is developed, enabling a proper implementation in the manufacturing process. Two different compounds are characterized under axial compression and under finishing operations. The compression tests present the effect of the feed rate and the strain accumulative effect in the fixture compressive behavior. Despite the higher strain variability of the softer rubber, different milling process parameters, such as the tool feed rate, can lead to a similar compressive behavior of the fixture regardless the elastomer hardness. On the other hand, the characterization of these flexible fixtures is completed over AA2024 floor milling of rigid parts and compared with the use of a rigid part clamping. These results show that, as the cutting speed and the feed rate increases, due to the strain evolution of the rubber, the part quality obtained tend to equalize between the flexible and the rigid clamping of the workpiece. Due to the versatility of the NBR for clamping different part geometries without new fixture redesigns, this leads to a competitive advantage of these flexible solutions against the classic rigid vacuum fixtures. Finally, a model to predict the grooving forces with a bull-nose end mill regardless of the stiffness of the part support is proposed and validated for the working range.

In the present scenario, citizens’ concern about environment preservation creates a necessity to mature more ecological and energy-efficient manufacturing processes and materials. The usage of glass fiber reinforced polymer (GFRP) is one of the emerging materials to replace the traditional metallic alloys in the automotive and aircraft industries. However, it has been comprehended to arise a sustainable substitute to conventional emulsion-based coolants in machining processes for dropping the destructive effects on the ecosystem without degrading the machining performance. So, in this study, the comparison of the two sustainable cutting fluid approaches, i.e., dry and LCO2, has been presented based on machining performance indicators like temperature, modulus of cutting force, tool wear, surface roughness, power consumption, and life cycle assessment (LCA) analysis for end milling of GFRP. The cutting condition of LCO2 has been found to be superior in terms of machining performance by providing 80% of lower cutting zone temperature, tool wear, 5% lower modulus of cutting force, and reduced surface roughness with 9% lower power consumption that has been observed in the case of LCO2 in comparison with dry machining. However, to compress the CO2 for converting in liquid form, a higher amount of energy and natural resources is consumed resulting in a higher impact on the environment in comparison with dry machining. Considering the 18 impact categories of ReCiPe midpoint (H) 2016, 95% higher values of impacts have been observed in the case of LCO2 in comparison with dry machining.