Szymon Wojciechowski

Structural and Microhardness Changes After Turning of the AISI 1045 Steel for Minimum Quantity Cooling Lubrication

This work presents the cooling effect under minimum quantity cooling lubrication and dry cutting on structural changes and microhardness of the ferritic-pearlitic AISI 1045 steel after turning. Due to the fact that the AISI 1045 steel has a two-phase structure, microhardness tests using the Vickers method were conducted with a load of 0.05 HV separately for ferrite and pearlite grains. The tests showed that cooling of the cutting zone under minimum quantity cooling lubrication (MQCL) condition decreased the depth of the hardened layer compared to dry cutting by approximately 40% for both pearlite and ferrite. Scanning electron microscopy analysis revealed that applying MQCL limits the formation of plastic deformations, among others, by reducing the surface crumple zone by approximately 50% compared to dry cutting. As a result of cooling being applied to the cutting zone using the MQCL method, the average diameter of ferrite grains has been decreased in the entire surface area compared to dry cutting. When using dry cutting, clear structural changes of the surface layer were also observed. This may be the result of sulfide inclusions which have formed, causing microcracks on the edge of the hardened layer and surface deformation visible as notches.

Surface roughness analysis of hardened steel after high-speed milling.

The work refers to analysis of various factors affecting surface roughness after end milling of hardened steel in high-speed milling (HSM) conditions. Investigations of milling parameters (cutting speed v(c) , axial depth of cut a(p) ) and the process dynamics that influence machined surface roughness were presented, and a surface roughness model, including cutter displacements, was elaborated. The work also involved analysis of surface profile charts from the point of view of vibrations and cutting force components. The research showed that theoretic surface roughness resulting from the kinematic-geometric projection of cutting edge in the workpiece is significantly different from the reality. The dominant factor in the research was not feed per tooth f(z) (according to the theoretical model) but dynamical phenomena and feed per revolution f.

The Influence of the Application of EP Additive in the Minimum Quantity Cooling Lubrication Method on the Tool Wear and Surface Roughness in the Process of Turning 316L Steel

The paper presents the influence of the application of the EP additive based on pure phosphor in minimum quantity cooling lubrication. During investigation, three methods of cooling the cutting zone have been applied in the process of turning 316L steel: dry machining, MQCL, MQCL + EP. The wear of the tool depending on the cooling method has been monitored, as well as its influence on the machined surface roughness. Scanning analysis has shown formation of a tribofilm as result of the application of the EP additive on the surface of a plate with (Ti, Al) N coating deposited by the PVD method. Experimental evidence suggests that the application of the MQCL + EP method results in reduction of the VBB parameter as compared to dry machining and cooling with emulsion mist up to the moment of the tool coating damage. It has been found that, as result of the application of the EP additive in the MQCL method, after damage of the (Ti, Al) N coating rapid increase of the tool wear takes place and, consequently, increase of the machined surface, which is due to the reaction with the base material (sintered carbide). This is caused by the chemical action of pure phosphor without the carbon matrix on the exposed area of the tool made of sintered carbide; the latter appears as result of adhesive wear of the coating

The Influence of EP/AW Addition in the MQL Method on the Parameters of Surface Geometrical Structure in the Process of Turning 316L Steel

The methods of cooling with minimum lubrication, MQL, and with minimum cooling and lubrication, MQCL, are often applied in machining nowadays due to their ecological and environmental advantages. The MQL and MQCL methods are a good alternative to dry cutting, especially during machining of hard-to machine steels, where high temperature occurs in the cutting zone and process engineers want high quality of the machined surface. The paper compares four methods of cooling when turning austenitic steel, 316L: dry cutting, MQCL method, MQL method and MQL + EP/AW method. During the experiment, 2D height parameters were monitored, as well as Abbott Firestone curve with the spatial parameters and profiles of selected surfaces have been presented. Due to the large number of variables in the tests, the planning method of Parameter Space Investigation has been used. When applying the MQL cooling method with the addition of EP/AW, the smallest values of Ra and Rz parameters have been obtained in the whole range of the variable parameters of machining. The Abbott Firestone curve, together with the spatial parameters, has proved that a surface manufactured after the process of turning in the MQL + EP/AW conditions shows better exploitation properties.

Hybrid numerical-analytical model for force prediction in end milling

Numerical technique finite element method (FEM) was used by researchers dealing with machining at the turn of the 1970s and 1980s. Due to the high complexity of the problem, the cutting analysis was limited to the orthogonal model. This treatment was to bring the problem to a plane strain, to facilitate the modeling of geometry and to limit the number of degrees of freedom. Despite such far-reaching simplifications, modeling of the machining process in FEM software presents many problems, which even today is dominated by two-dimensional models in scientific publications [3, 6, 8]. Orthogonal models, although seemingly simple, provide researchers with a unique insight into the cutting zone, but are still often insufficient to solve problems in the industry. The paper presents a hybrid numerical-analytical model for prediction of forces during end milling of 42CrMo4 steel (40HM) [4, 5]. In the model, the FEM simulation was used to determine the correct specific cutting force for a given tool geometry in orthogonal cutting. These data, in turn, using an analytical model based on the Altintas mechanical model [1], will be converted into forces acting in the machine tool system for the variable uncut chip thickness during milling. This approach to the problem can be applied at the design stage of monolithic milling cutters prior to prototyping.

Comparison of various tool wear prediction methods during end milling of metal matrix composite

Abstract In this paper, the problem of tool wear prediction during milling of hard-to-cut metal matrix composite Duralcan™ was presented. The conducted research involved the measurements of acceleration of vibrations during milling with constant cutting conditions, and evaluation of the flank wear. Subsequently, the analysis of vibrations in time and frequency domain, as well as the correlation of the obtained measures with the tool wear values were conducted. The validation of tool wear diagnosis in relation to selected diagnostic measures was carried out with the use of one variable and two variables regression models, as well as with the application of artificial neural networks (ANN). The comparative analysis of the obtained results enable.

Optimization of cutting parameters for the longitudinal turning of combustion engines’ pistons

Głównym celem optymalizacji procesów skrawania jest poprawa efektów ekonomicznych oraz technologicznych obróbki. Z przeglądu literatury wynika, że problematyka ta dotyczy głównie skracania czasu i obniżania kosztów produkcji, wydłużania trwałości ostrza, podnoszenia jakości obrobionej powierzchni, a także minimalizacji drgań układu obrabiarka–uchwyt–przedmiot–narzędzie [1÷5]. Jedną z metod mających na celu poprawę efektów ekonomicznych skrawania jest optymalizacja ze względu na trwałość ostrza [6]. Podejście to umożliwia wyznaczenie ekonomicznej prędkości skrawania vce, odpowiadającej wygenerowaniu minimalnych kosztów jednostkowych Kj zabiegu, oraz wydajnościowej prędkości skrawania vcw, zapewniającej maksymalizację wydajności obróbki W. Aby zrealizować to zadanie, niezbędne jest przeprowadzenie badań trwałościowych ostrzy skrawających i wyznaczenie wykładnika potęgowego s występującego we wzorze Taylora:

Machining Characteristics of Direct Laser Deposited Tungsten Carbide

Machinability can be defined as the relative susceptibility of the work material to the decohesion phenomenon and chip formation, during cutting and grinding. This feature depends on work and tool’s material physic-chemical properties and condition, method of machining, as well as cutting conditions [1]. Therefore, there is no unique and unambiguous meaning to the term machinability. This feature, can be described by many various indicators. Each one of them carries out a wide variety of operations, each with a different criteria of machinability. A material may have good machinability by one criterion, but poor machinability by another [2].