This paper presents the results of experimental research concerning the possibility of supporting the cooling function during internal cylindrical grinding using the minimum quantity lubrication (MQL) method by additional delivery of a compressed cooled air (CCL) stream. The article presents a description of a hybrid method of cooling and lubrication of the grinding zone integrating centrifugal (through a grinding wheel) lubrication with the minimum quantity of lubricant and cooling with a compressed cooled air stream generated by a cold air gun (CAG). The methodology and results of experimental studies are also presented in detail, with the aim of determining the influence of the application of the hybrid method of cooling and lubrication of the machining zone on the course and results of the internal cylindrical grinding process of 100Cr6 steel in comparison with other methods of cooling and lubrication, as well as compared with dry grinding. The research results obtained using the described hybrid method of cooling and lubrication of the grinding zone are related to the results obtained under the conditions of centrifugal MQL method, cooling with a stream of CCA, cooling and lubrication with a stream of oil-in-water emulsion delivered using the flood method, and dry grinding. The efficiency of the grinding process is evaluated (based on the average grinding power Pav, grinding wheel volumetric wear Vs, material removal Vw, and grinding ratio G), along with the thermal conditions of the process (based on the analysis of thermograms recorded by infrared thermal imaging method), the textures of machined surfaces (based on microtopography measured by contact profilometry), the state of residual stress in the surface layers of workpieces (determined by X-ray diffraction method), and the state of the grinding wheels’ active surfaces after grinding (based on microtopography measured by laser triangulation and images recorded with a digital measuring microscope). The obtained results of the analyses show that the application of the hybrid method allows for the longest wheel life among the five compared grinding methods, which is about 2.7 times the life of grinding wheels working under the flood cooling and centrifugal MQL methods, and as much as 8 times the life of grinding wheels working under the conditions of CCA only and dry grinding.

This paper describes simulation studies regarding the application of the centrifugal minimum quantity lubrication (MQL) method simultaneously with the delivery of a compressed cooled air (CCA) stream in the internal cylindrical grinding process. The idea of a new hybrid cooling and lubrication method connecting centrifugal (through a grinding wheel) lubrication by MQL with a CCA stream is described. The methodology of computational fluid dynamics (CFD) simulation studies, as well as the results of numerical simulations, are presented in detail. The aim of the simulations was to determine the most favourable geometrical and kinematic parameters of the system in the context of air-oil aerosol and CCA flow, as well as heat exchange. In the simulation, the variables were the grinding arbor geometrical parameters, the angle of CCA supply line outlets, and the grinding wheel and workpiece peripheral speed. As a result of the simulation studies, the most favourable geometrical parameters were designated, determining the orientation of the ends of the two CCA supply line outlets before and after the grinding zone, the number of openings in the drilled-out grinding arbor, and the influence of the grinding speed on the parameters of the coolant flow and temperature of objects in the grinding zone. In addition, the results of simulation tests made it possible to visualise the velocity vectors of the two-phase coolant flow in a complex system of air-oil aerosol delivery centrifugally through an open structure of a very fast rotating porous layer (grinding wheel), with an additional supply of CCA using an external cold air gun (CAG).

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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.

W artykule scharakteryzowano rolę i rodzaje płynów chło-dząco-smarujących (PCS) stosowanych w procesach szlifowania. Opisano konwencjonalne metody doprowadzania PCS do strefy szlifowania, takie jak metoda zalewowa, strumieniowo-ciśnieniowe doprowadzenie PCS, dysze trzewikowe oraz sposoby odśrodkowego podawania chło-dziwa. Na tle tej charakterystyki przedstawiono metody umożliwiające zminimalizowanie wydatku PCS oraz chło-dzenie strefy obróbki z użyciem dysz podających schłodzo-ne sprężone powietrze. W podsumowaniu wskazano trendy rozwojowe wynikające z przedstawionej analizy.SŁOWA KLUCZOWE: płyn chłodząco-smarujący, chło-dzenie strefy szlifowania, smarowanie strefy szlifowaniaThe article describes the role and types of grinding fluid (GF) used in the grinding processes. Described the conventional method of supplying GF into the grinding zone, such as flood method, pressure nozzles, shoe nozzles, and methods of centrifugal coolant provision. On the basis of these characteristics were presented methods to minimize the expenditure of GF as well as cooling the machining zone using cold air guns. In summary the trends of development arising from presented analysis were indicated. KEYWORDS: grinding fluid, cooling of the grinding zone, lubrication of the grinding zoneProces szlifowania wiąże się ze znaczącym wzrostem temperatury w strefie obróbki. Rozkład ciepła, który powstaje w obszarach odkształcanych ma charakter nierównomier-ny, co wpływa na zwiększenie naprężeń cieplnych zarówno w ściernicy jak i w przedmiocie obrabianym (PO). Większa część energii wykorzystanej do procesu szlifowania przekształcona zostaje w ciepło w miejscu styku narzędzia z przedmiotem obrabianym [1]. Ponieważ przestrzeń między-ziarnowa jest stosunkowo mała a utrzymanie zdolności skrawnej na wysokim poziomie wymaga, aby była ona wolna i sprawnie wspomagała transport produktów szlifowania ze strefy obróbki, w większości procesów szlifowania stosuje się płyn chłodząco-smarujący (PCS). Głównymi jednak powodami stosowania PCS są: smarowanie strefy kontaktu ściernicy z materiałem obrabianym, mające na celu zmniejszenie tarcia ostrzy o niezidentyfikowanej geometrii i często ujemnym kącie natarcia, oraz chłodzenie tej strefy [2]. Do podstawowych zadań płynów chłodząco-smarujących w procesie szlifowania należy zaliczyć [3]: -tworzenie stabilnej warstewki smaru, która zmniejsza tarcie między ziarnem ściernym i PO oraz między spoiwem i PO, -chłodzenie powierzchni PO i czynnej powierzchni ścier-nicy (CPS), poprzez przejmowanie i odprowadzanie ciepła, -zwilżanie i czyszczenie ściernicy, -wypłukiwanie wiórów ze strefy szlifowania, -zabezpieczenie antykorozyjne obrabiarki i materiału obrabianego, -przeciwdziałanie rozwojowi bakterii, spienianiu się itp.Niezwykle istotny dla poprawnego przebiegu procesu szlifowania jest dobór odpowiedniego PCS ze względu na znaczne zróżnicowanie w ich właściwościach biologicznych, fizycznych i chemicznych [3][4][5].Płyny chłodząco-smarujące stosowane w procesach szlifowania * Mgr inż. Seweryn Kieraś (seweryn.kieras@gmail.co...