Vibration suppression methods at high performance drilling

Abstract This article discusses the possibility of suppressing vibrations when drilling holes with spiral drills. This article presents two methods of suppressing vibrations: modal analysis and modulation of cutting speed (changes in spindle speed - Spindle Speed Variation - SSV). There is a description of the considered methods with an indication of their advantages and disadvantages. The article also points out to experimental data that characterize the possibility of suppressing vibrations when drilling holes and a comparative analysis of various methods of suppressing vibrations when machining holes in samples of their structural steel. There is an assessment of the possibility of joint application of modal analysis methods and modulation of cutting speed during high-performance drilling.</jats:p

Analysis of advanced transpedicular screw machining technologies

Abstract: The purpose is to improve the machining efficiency of titanium alloy transpedicular screws on highperformance machine-tools based on the selection of advanced technological approaches, and to analyze the current manufacturing technology of implants on CNC machines of the semi-automatic longitudinal turning lathe type. The efficiency is assessed using the following criteria: process performance determined by the machine time and the quality of implant processing (surface roughness, geometric accuracy, mechanical properties). It is found that semi -automatic longitudinal lathes equipped with a collet feed system and drive heads for thread whirling allow processing the implants of the transpedicular screw type in a single set-up with maximum efficiency. It is shown that the machining technology of transpedicular screws is largely determined by the features of their design. The type and shape of the thread have the greatest influence on the used cutting tool and cutting modes. The analysis of screw breakages revealed that the main failure reasons are design defects and poor machining quality of the threaded part. It is determined that the use of the thread whirling method makes it possible to obtain the thread in one cutting pass and, therefore, significantly increase the machining performance compared to the traditional technology without any loss of quality. Additional advantages of this method are the reduction in the number of tools used and follow-on finishing deburring operations. Based on the conducted analysis the manufacture of transpedicular titanium alloy screws is recommended to perform using advanced cutting tools, primarily thread whirling cutters ensuring 4 times increase in machining performance without any loss of the processed item quality and 2 times reduced surface roughness. In this case the temperature in the cutting zone decreases, which has a positive effect on processed product service life. The condition for the effective use of the cutters is equipping of the machine-tools involved in the technological process with special drive heads.</jats:p

Investigating the impact of chucks on the stability of a milling process

The impact of a tool chuck on the dynamic stability of a milling process with an end mill was investigated using a workpiece made of aluminium wrought alloy V95pchT2. To assess the dynamic stability, we analysed a Fourier transformed signal recorded during milling using a Shure PGA81 -XLR tool directional microphone. The milling was performed on an HSC75 linear high-production machining centre with an H10F solid carbide end mill. Cutting conditions were calculated based on a stability diagram derived from an operational modal analysis of a manufacturing system. The surface roughness was measured with a Taylor Hobson Form Talysurf i200 contact profilometer. Performance defined by the rate of material removal and the roughness of a treated surface was used to evaluate the cutting process. A correlation was found between the type of tool chuck fixating the end mill, the rate of material removal and the roughness of the machined surface. It was found that, for milling using a power chuck, the areas of stable cutting correspond to the max imum cutting depth equal to 5.6 mm at a cutting width of 16 mm and a cutting feed of 0.1 mm/rev. However, for the other studied chucks, this indicator was 20 to 30% lower. End milling conducted using a power chuck with a solid carbide cutter with a diameter of 16 mm and three cutting teeth resulted in dynamically stable cutting with the highest material removal rate (575.6 cm3/min) and minimum surface roughnes s (0.56 μm). Based on the conducted analysis, for the operation of end milling on a machine with computerised numerical control (CNC), a power tool chuck is recommended that improves milling performance by over 25% relative to the considered tool setups. Furthermore, this preserves the quality of a treated surface and increases the tool cutting life owing to dynamically stable cutting.</jats:p

Study of the effect of cutting modes on output parameters under high-speed steel turn-milling

Introduction. The article elucidates increasing the efficiency of turn-milling of powdered metal high-speed steel products. Turn-milling can be used as an alternative to the traditional turning method. The article describes advantages of the turn-milling method. A review of studies devoted to improving the surface quality of parts when turning by milling is given. The work aims at determining the effect of cutting modes on the surface roughness by the orthogonal turning method through milling powdered high-speed steel with a monolithic cutter.Materials and Methods. Statistical analysis methods based on the creation of a mathematical model for predicting microgeometric deviations of the treated surface were used. An experimental research method was applied to verify the adequacy of the mathematical model. The experiment was planned according to the non-composite design proposed by Box and Behnken. The experiment was carried out on a turning machining center with a driving tool. Powdered highspeed steel BÖHLER S390 MICROCLEAN was used as sample material for the experiment. A monolithic carbide milling cutter served as a cutting tool. During the experiment, the cutting speed, milling width, and feed per tooth varied. The roughness of the treated surface was measured by a contact profilometer.Results. A mathematical model of the formation of surface roughness depending on the processing modes was developed. During the experiments, the effect of cutting speed, tool feed, and radial cutting depth on the roughness of the treated surface was determined. It was established that the dependence of roughness on feed had a linear character over the entire investigated range of cutting modes. In turn, the dependence of roughness on the cutting speed and cutting width had a parabolic character. The results obtained allowed us to achieve the roughness of the treated surface Ra = 1.85 without reducing the processing performance. Discussion andConclusions. The developed mathematical model reflects the impact of cutting modes on the surface roughness when turning high-speed steel with a monolithic cutter. The results of the conducted research can be used to determine the optimal cutting modes that provide a given surface quality in the manufacture of real parts under the production conditions. It is recommended to continue the research with the control of additional output parameters, such as temperature and vibration. Reducing the effect of regenerative self-oscillations on the roughness of the treated surface can be reached through assigning the cutting modes based on the results of a modal analysis of the process system

Study of the effect of cutting modes on output parameters under high-speed steel turn-milling

Introduction. The article elucidates increasing the efficiency of turn-milling of powdered metal high-speed steel products. Turn-milling can be used as an alternative to the traditional turning method. The article describes advantages of the turn-milling method. A review of studies devoted to improving the surface quality of parts when turning by milling is given. The work aims at determining the effect of cutting modes on the surface roughness by the orthogonal turning method through milling powdered high-speed steel with a monolithic cutter.Materials and Methods. Statistical analysis methods based on the creation of a mathematical model for predicting microgeometric deviations of the treated surface were used. An experimental research method was applied to verify the adequacy of the mathematical model. The experiment was planned according to the non-composite design proposed by Box and Behnken. The experiment was carried out on a turning machining center with a driving tool. Powdered highspeed steel BÖHLER S390 MICROCLEAN was used as sample material for the experiment. A monolithic carbide milling cutter served as a cutting tool. During the experiment, the cutting speed, milling width, and feed per tooth varied. The roughness of the treated surface was measured by a contact profilometer.Results. A mathematical model of the formation of surface roughness depending on the processing modes was developed. During the experiments, the effect of cutting speed, tool feed, and radial cutting depth on the roughness of the treated surface was determined. It was established that the dependence of roughness on feed had a linear character over the entire investigated range of cutting modes. In turn, the dependence of roughness on the cutting speed and cutting width had a parabolic character. The results obtained allowed us to achieve the roughness of the treated surface Ra = 1.85 without reducing the processing performance. Discussion andConclusions. The developed mathematical model reflects the impact of cutting modes on the surface roughness when turning high-speed steel with a monolithic cutter. The results of the conducted research can be used to determine the optimal cutting modes that provide a given surface quality in the manufacture of real parts under the production conditions. It is recommended to continue the research with the control of additional output parameters, such as temperature and vibration. Reducing the effect of regenerative self-oscillations on the roughness of the treated surface can be reached through assigning the cutting modes based on the results of a modal analysis of the process system.</jats:p