No abstract

Commonly used as a finishing operation, lapping has been applied for achieving ultra-high finishes and close tolerances between mating pieces. It can be carried out by applying loose abrasive grains between work and lap surfaces, and causing relative motion between them resulting in the finish of a multi-directional lay.The activity of grains (sliding and rolling) in the working gap causes not only the removal of the material but also a rise in the temperature of the lap plate. The authors of this work analyse the influence of the temperature of the elements of the lapping machine executory system on the results of the lapping process stimulated applying ABRALAP 380 lapping machine the executory system of which consisted of three working conditioning rings. The temperature of the elements of the executory system was measured employing Thermo Gear G100 infrared camera. The workpieces were ceramic (Al2O3) valve sealing parts. After grinding, they were being lapped during 15 and 20 minutes. Machining was started following 10, 140, and 270 minutes of the working time of the machine (tp). The abrasive mixture was boron carbide powder with grain number F400/17, mixed with kerosene and machine oil with grain concentration equal to m = 0.25. Two sets of lapping parameters were executed:lapping pressure p = 0.051 MPa, and lapping speed v = 27 m/min;lapping pressure p = 0.03 MPa, and lapping speed v = 38 m/min.The rate of material removal in g and mm and roughness parameters Raand Rkof the surface were analysed.The conducted studies showed that the temperature of the elements of the machine executory system affected only parameter Rawhich is higher for the surfaces that were processed starting from the 270thminute of the working time of the machine. Only a slight increase in the values of parameter Rawas observed. It can be caused by a change in conditions for the process of material removal due to different properties of grain carrier under a higher temperature. Its viscosity decreases with an increase in temperature, which implies direct interactions between the plate and workpiece surface. Normally those two surfaces interact indirectly via abrasive grains. The rest of the tested lapping results were independent of the temperature of the elements of the lapping machine executory system. The values obtained under different temperatures were almost the same.

Lapping process is commonly used for ultra-precision machining of various materials. An essential role during lapping plays flatness of the wheel-working surface because workpiece surface takes mirror image of it. Due to its applications requiring extreme size accuracy, straightness and concentricity, it is very important that working surface remains flat in the course of machining. Getting out of flatness can be caused by uneven wear or heating. To prevent nonuniform wear of lapping plate surface, conditioning rings should be suited appropriate. Lapping machines producers and researchers make recommendations about proper rings position during machining. To provide constant temperature of the wheel, cooling systems are applied in modern machines, but not in all of them. Therefore, wheel temperature problem is significant one, and it should be known. This paper presents results of authors work on choosing proper measurement method of lapping plate temperature. During lapping process wheel is rotating. Maximum velocity value for ABRALAP 380 lapping machine is 65 rev/min. Mainly for this reason, contactless infrared method was selected. Because getting an accurate temperature of an object using this method is difficult, during experiments temperature rise not exact value were analysed. There were also presented results of experiments which goal was to find lap plate emissivity.

Temperature on the chip-tool interface is important parameters in the analysis and control of turning process. Due to the high shear and friction, energies dissipated during a machining operation the temperature in the primary and secondary shear zones are usually very high; hence, affect the shear deformation and tool wear. In a single point cutting, heat is generated at three different zones i.e. primary shear zone, chip tool interface and the tool-workpiece interface. The primary shear zone temperature affects the mechanical properties of the work piece-chip material and temperatures at tool-chip and tool-work piece interfaces influence tool wear at tool face and flank respectively. Total tool wear rate and crater wear on the rake face are strongly influenced by the temperature at chip-tool interface. Therefore, it is desirable to determine the temperatures of the tool and chip interface to analyse or control the process. To measure the temperature at the tool-chip interface many experimental methods have been developed over the past century. Since at the interface there is a moving contact between the tool and chip in this work, authors propose infrared method for temperature measuring. To assure possibly high accurate of noncontact temperature measurement there is a need to keep in mind several factors, including determining appropriate value of emissivity. In this work, authors present results of experimental determining emissivity value of tool-chip interface. As initial value, emissivity of polished steel was taken.

Nowadays lot of scientific work inspired by industry companies was done with the aim to avoid the use of cutting fluids in machining operations. The reasons were ecological and human health problems caused by the cutting fluid. The most logical solution, which can be taken to eliminate all of the problems associated with the use of cooling lubricant, is dry machining. In most cases, however, a machining operation without lubricant finds acceptance only when it is possible to guarantee that the part quality and machining times achieved in wet machining are equalled or surpassed. Surface finish has become an important indicator of quality and precision in manufacturing processes and it is considered as one of the most important parameter in industry. Today the quality of surface finish is a significant requirement for many workpieces. Thus, the choice of optimized cutting parameters is very important for controlling the required surface quality. In the present study, the influence of different machining parameters on surface roughness has been analysed. Experiments were conducted for turning, as it is the most frequently used machining process in machine industry. All these parameters have been studied in terms of depth of cut (ap), feed rate (f) and cutting speed (vc). As workpiece, material steel S235 has been selected. This work presents results of research done during turning realised on conventional lathe CDS 6250 BX-1000 with severe parameters. These demonstrate the necessity of further, more detailed research on turning process results.