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This paper describes the results of a comprehensive evaluation programme for cutting fluid efficiency, when machining the aerospace ‘superalloy’, Inconel 718. The machining methods used were milling, drilling, tapping and VIPER grinding. Results from three cutting fluids were evaluated: a water-based semi-synthetic, a water-based synthetic and a high-oil emulsion fluid. Cutting forces, torque and spindle power were acquired during machining, while geometrical accuracy, surface texture and surface integrity of the workpiece were analysed afterwards. The experimental results demonstrate the difficulty of identifying the ‘best’ cutting fluid, especially when several different machining methods are to be employed on the same machine tool. It is unlikely that a single fluid will show the best performance on all machining trials and output measures. Therefore, prioritization of the output measures and specification of the relative importance of each machining operation becomes essential, in order to evaluate and rank the cutting fluid efficiencies. A flexible multicriteria model for the evaluation of cutting fluid efficiency, relative to the performance of a benchmark fluid, is proposed and described. The advantage of the model consists in its flexibility and capability to compare the efficiency of cutting fluids across different machining methods and output criteria. An application of the evaluation model is provided, using results from the tested cutting fluids.

Finite element analysis studies have been of interest in the field of orthodontics and this is due to the ability to study the stress in the bone, periodontal ligament (PDL), teeth and the displacement in the bone by using this method. Our study aimed to present a method that determines the effect of applying orthodontic forces in bodily direction on a healthy and reduced periodontium and to demonstrate the utility of finite element analysis. Using the cone-beam computed tomography (CBCT) of a patient with a healthy and reduced periodontium, we modeled the geometric construction of the contour of the elements necessary for the study. Afterwards, we applied a force of 1 N and a force of 0.8 N in order to achieve bodily movement and to analyze the stress in the bone, in the periodontal ligament and the absolute displacement. The analysis of the applied forces showed that a minimal ligament thickness is correlated with the highest value of the maximum stress in the PDL and a decreased displacement. This confirms the results obtained in previous clinical practice, confirming the validity of the simulation. During orthodontic tooth movement, the morphology of the teeth and of the periodontium should be taken into account. The effect of orthodontic forces on a particular anatomy could be studied using FEA, a method that provides real data. This is necessary for proper treatment planning and its particularization depends on the patient’s particular situation.

Plasma nitriding has significant advantages: very low running costs (reduced consumption of energy and gases); optimized structure and layers; and nitriding of stainless steels. Plasma nitriding is totally safe and has no poisonous gas emissions and no negative environmental impact. However, conventional plasma nitriding has a number of well-known difficulties, including the direct application of plasma on the parts to be treated, the risk of arcing, hollow cathodes, white layers, non-homogenous batch temperature and the impossibility to mix parts of different geometries in the chamber made this technology to be almost forgotten. In the last years, due to the ecofriendly character of the technology, several atempts were made in order to establish an improvement in this technique in terms of batch damages. Active screen plasma nitriding technology is a new industrial solution that enjoys all the advantages of traditional plasma nitriding but does not have its inconveniences. A comparative study regarding quality surface and formed layer properties between conventional plasma nitriding and active screen plasma nitriding was conducted, in order to highlight the advantages that comes with this relatively new technique.

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