Within the Faculty of Machine Building from the Technical University of Cluj-Napoca, Romania unconventional technologies researches were performed for 20 years. The team focused on national research projects referring to micro machining and special applications. EDM process (Electric Discharge Machining) has a great importance to the industry. Even if it never be able to compete with the metal cutting manufacturing process in terms of material removal rate, today it is the main manufacturing process of complex die and mould, due to the major advantages presented in this paper. Today, also the precision of the process competes with the milling process in terms of quality of the surface, which can arrive at values that, in some cases, are better than the values for grinded surfaces. The article presents the importance of the process in the industry of stamps, which can not be processed with other methods, due to special materials and forms that are wished to be obtained. The article presents comparatively the values of the roughness obtained by EDM process on different types of materials and by different process parameters. Concerning the optimisation of the EDM technological parameters, the research has been done on different types of EDM machines. The final scope is to elaborate a technological data base with the purpose of optimising the EDM process on different machines.

Abstract. The paper presents an experimental study on processing composite materials using abrasive water jet cutting (AWJC) process, analysing one of the main process parameter, standoff distance (SOD). Carbon Fibre Reinforced Plastics (CFRP) are used in a wide range of industrial applications, like aerospace and automotive. Cutting CFRP using AWJC involves several challenges like high dimensional accuracy and good surface quality. To produce precise parts by using this process must be understand the influence of the process parameters on quality characteristics. On this study was investigated the standoff distance influence on kerf characteristics. The characteristics of the cut surface (kerf geometry, surface roughness and topography) were analyzed.

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The improvement of the microgeometry became a subject of a great interest in cutting tools optimization. This paper approaches the process of cutting edge preparation of solid carbide reamers. It has been analyzed the evolution of cutting edge wear resistance in the material GGG 40 using the scanning electron microscope (SEM). The work also compared the rounded cutting edge reamers realized using wet abrasive jet machining with standard unprepared cutting edge. To obtain different microgeometries were experienced a number of machining strategies, which resulted in four combinations of roundness and forms for the cutting edge. In order to validate the results, the author studied the wear resistance during the reaming tests, the influence of prepared surface of the cutting edge on metallic coating layer adhesion. The final purpose was to determinate the optimal strategy of cutting edge preparation considering the evolution of wear during the reaming process.

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In this paper, an attempt has been made to model the surface roughness through response surface method (RSM) and ANOVA when drilling CFRP composites. Drilling is the most common machining process applied to CFRP. However, the users of this kind of composites are facing difficulties to machining it, due to its properties. Because of the bad effects that lubricants have on the fiber-reinforced composites, the machining of these materials is performed without coolant. On the other hand dry machining offers the risk of a thermal damage induced by high process temperatures. The current experimental analysis is focused towards determining process temperatures with different tools and drilling parameters.

Titanium dioxide (TiO2) is a promising lubricant additive for enhanced engine efficiency. In this study, pure base engine oil 10 W-30 was improved with titanium dioxide (TiO2) nanoparticles at different concentrations and experimentally evaluated with the scope of tribological behavior improvement. The tribological tests were performed at ambient temperature as well as at 75°C using a four ball tribometer for 30 minutes. Due to their small particle size (approx. 21 nm), the TiO2 nanoparticles were properly dispersed in oil based on optical microscopy evaluation. The tribological results indicate that the friction coefficient of engine oil with 0.075 wt.% TiO2 reached 0.05 at 75°C, which was much lower that of pure oil (1.20), and at room temperature (23°C), it decreased from 1.8 for pure oil to 0.4 for oil with 0.075 wt.% TiO2 due to the formation of a stable tribofilm formed by the MoS2, MoO3, FeS, and FeSO4 composite within the wear track. The lowest wear volume was measured on samples tested at 75°C for the oil with 0.075 wt.% TiO2. The TiO2 additive lubricant effect on the tribofilm properties led to a decrease in friction and wear at an operating temperature of 75°C. The main objective of the paper is to present the recent progress and, consequently, to develop a comprehensive understanding of the tribological behavior of engine oil mixed with TiO2 nanoparticles.

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