In this article, the use of acoustic emission signal analysis for in-process assessment of the surface quality in abrasive waterjet machining is presented. The authors carried out an analysis of the influence of the cutting head traverse speed (considered in this case as the performance measurement) on the flatness, waviness and roughness of surfaces made of aluminium alloy 5251 after cutting process, as well as the influence of changing the quality factor on values of selected descriptors of the emitted high-frequency acoustic emission signal processed in the frequency domain. This was a new approach, different from the norm, in which an acoustic emission signal is usually studied for low frequencies. The obtained results confirmed the clear influence of machining conditions on the geometric structure of the obtained cuts and the registered values of the emitted stress waves. This influence can be accurately determined by the use of the high-frequency acoustic emission signal analysis being proposed. Additionally, statistical dependence models developed between the given process quality indicator and the registered selected acoustic emission signal parameters in the frequency domain allowed for the prediction of the surface texture of the obtained cuts on the basis of the acoustic emission signal emitted during the machining process.

The condition of the cutting tool is one of the most important factors as it directly affects the technological and economic efficiencies of the woodworking process. The large variety of raw materials of wood combined with possible impurities and inclusion of solids puts high demands on planing machines. One of the methods to modify their operational properties is to apply antiwear coating on their working surfaces using vacuum deposition methods, such as physical vapor deposition (PVD). The use of such coatings reduces the adhesion of planing products to the surface of industrial planer knives, reduces the friction between the cutting tool and the workpiece, and limits the penetration of heat into the tool, thereby contributing to extending its effective working life. This study examines the impact of PVD-based CrCN/CrN coating on the operational durability and intensity of wear of planer knives operating in production conditions compared to unmodified knives (typically used in the wood processing industry for pine wood planing). For the unmodified and CrCN/CrN-coated planing blades (before and after processing), detailed analyses were carried out. These analyses included determining the rounding radius and profile along the blade (worn edge displacement), calculating surface texture parameters of the rake face of planer knives, and carrying out visual microscopic analysis of its condition. The results of the experiments indicated an increase in durability of up to 142% for the CrCN/CrN-coated tools. It was also found that the use of PVD-based modified industrial planer knives turned out to be more beneficial in each analyzed area of analysis.

Control of thermal conditions in the grinding zone is possible through effective delivery of substances with cooling, lubricating and antiadhesive properties during the machining process. In addition to the benefits of coolants, however, a number of economic and ecological problems arise, which include the costs of purchase, use and maintenance as well as the environmental impact of its disposal. These negative aspects of the use of cooling and lubricating liquids have contributed to the modern trend of minimizing their output in machining processes, including grinding. This article presents comprehensive characteristics of knowledge in the field of liquids, gases and solids with cooling, lubricating and antiadhesive properties. The author’s original classification of cooling and lubricating agents by their physical state was proposed and a complete list of known modern environmentally friendly methods of cooling and lubrication of the grinding zone was presented. In order to highlight their beneficial features, the background of conventional methods of delivery coolants, lubricants and antiadhesives to the grinding zone used for years were also characterised. A comprehensive list of all known methods of cooling and lubrication of the grinding zone classified according to the physical state of the delivered medium with a clear separation of hybrid methods consisting in simultaneous delivery of many cooling and lubricating agents was described in the summary. The article concludes with the characteristics of directions of further development in the field of cooling and lubrication of the grinding zone.

The paper presents the results obtained for abrasive electro-discharge grinding (AEDG) of Ti6Al4V titanium alloy with the use of super hard grinding wheels of cubic boron nitride with a metal bond. The experimental investigations were focused on process monitoring for sharp and worn grinding wheels. For the evaluation of the grinding process, the grinding force amplitude and a few descriptors of the high-frequency stress waves were investigated in both time and frequency domains. The results show that during the AEDG, specific elastic waves are generated. Since these waves have characteristic amplitudes, frequencies, and other different descriptors dependent on the current grinding wheel cutting ability and discharge parameters, they can be applied to estimate a statistically significant regression function. For each measurement signal, a few statistical features are calculated and used as input for data selection and classification procedures. Registration and classification of forces and acoustic emission signals can be used to analyse the abrasive electro-discharge grinding process and allow for the determination of the machining results and the lifespan of super hard grinding wheels.

Raw pine wood processing and especially its mechanical processing constitute a significant share among technological operations leading to obtaining a finished product. Stable implementation of machining operations, ensuring long-term repeatable processing results depends on many factors, such as quality and invariability of raw material, technical condition of technological equipment, adopted parameters of work, qualifications and experience of operators, as well as preparation and properties of the machining tools used. It seems that the greatest potential in the search for opportunities to increase the efficiency of machining operations has the modification of machining tools used in it. This paper presents the results of research work aimed at determining how the life of cutting tools used in planing operations of wet pine wood is affected by the application of chromium aluminum nitride (AlCrN) coating to planar industrial planing knives in the process of physical vapour deposition. For this purpose operational tests were carried out under production conditions in a medium-sized wood processing company. The study compares the effective working time, rounding radius, the profile along the knife (size of worn edge displacement, wear area of the cutting edge), selected texture parameters of the planar industrial planing knife rake face and visual analyses of cutting edge condition of AlCrN-coated planar knives and unmodified ones. The obtained experimental results showed the possibility of increasing the life of AlCrN-coated knives up to 154% compared to the results obtained with uncoated ones. The proposed modification of the operational features of the knives does not involve any changes in the technological process of planing, does not require any interference with the machining station nor its parameters, therefore enabling rapid and easy implementation into industrial practice.