Papers by Keyword: Milling

Abstract: Machine tool vibrations cause uncomfortable noise, may damage the edges of cutting tools or certain parts of machine tools, but most importantly, they always have negative effect on the quality of the machined surface of workpieces. These vibrations are especially intricate in case of milling processes where complex tool geometries are used, like helical, serrated, non-uniform pitch angles, and so on. During the milling process, the arising vibrations include free, forced, self-excited, and even parametrically forced vibrations together with their different combinations. Regarding surface quality, the most harmful is the self-excited one called chatter, which is related to the regenerative effect of the cutting process. Its relation to machined surface quality is demonstrated in an industrial case study. The modelling and the corresponding cutting stability are presented in case of a helical tool applied for milling with large axial immersions. The extremely rich spectrum of the measured vibration signals are analyzed by means of model-based predictions, and the results are compared with the spectral properties of the corresponding machined surfaces. The conclusions open the way for new kinds of chatter identification.

Abstract: Thin-walled elements are widely used in aerospace engines, such as blisk,casing, blade etc. There are significant vibrations while machining because of thesmall thickness and the poor rigidity of thin-walled workpieces which will lead to lowsurface machining quality, low machining efficiency and even worse the huge damageto the workpieces and the tools. Nevertheless, the vibration during milling does nothappen frequently, as it is closely related to the position of the workpiece structureand the machining parameters. The stiffness of the workpiece varies due to thechanging of cutting position. Therefore, vibration only appears in some positionswhen milling thin-walled workpieces. This paper mainly focus on monitoring themachining process in order to analyze the vibration and the position where it occurs.Moreover, with confirming the vibrated position and analyzing the reason of vibration,the paper provides a valid reference to the machining vibration controlling, the qualityand effectiveness of workpiece surface.

Abstract: In the present work, an attempt has been made to analyze the factors influencing tool wear while milling Al/Al₂O₃/Gr particulate composites. Materials used for the present investigation are Al 6061-aluminium alloy reinforced with alumina (Al₂O₃) of size 45 microns and graphite (Gr) of an average size 60 microns, which are produced by stir casting route. Central composite design (CCD) was employed in developing the tool wear model in relation to machining parameters such as feed rate, cutting speed, depth of cut and weight fraction of Alumina. From the Analysis of variance (ANOVA), it is found that feed is the dominant parameter for tool wear whereas weight fraction of alumina shows minimal effect on tool wear compared to other parameters. From the Scanning Electron Microscope (SEM), the Al₂O₃ and Gr particles get adhered to the tool surface owing to the high pressure generated at the tool-workpiece interface.

Abstract: Surface quality is very important for the finished components. One of the most important parameters that define surface quality in milling is surface roughness . Depending on the cutting conditions chosen, different milling strategies can be applied. One of the ways to reduce the production costs is to optimize the number of inserts that are involved in machining. The aim of present paper is to investigate the behavior of surface roughness under the influence of the number of inserts used in an operation.

Abstract: In the last years there has been an increased demand to lower the impact of industrial activities on environment quality. Cutting fluids, among other products, are an important pollutant but they have often been associated with the need for a higher productivity of machining processes. Cutting fluids are a mean of reducing temperature in the cutting area, friction and tool wear but they also represent 7% to 17% of the production costs. Other problems raised by cutting fluids are: microorganism infestation, which can cause pulmonary and dermatological diseases and poor lubrication or corrosion caused by some of the chemicals. Dry cutting is regarded as the cleanest cooling method, but it has a reduced heat dissipation efficiency and practically there is no lubrication. Other relatively new green solutions concern the use of minimum quantity lubrication (MQL) and cryogenic machining.

Abstract: The ball nose end milling process, which use a ball nose cutter, is very complex and, generates a pronounced area variation of the cross section in the uncut chip. In this sense, the current paper looks into and assesses some aspects regarding the geometric simulation of the chip generating mechanism in 5 axes ball nose end milling. The influence of tool inclination, however, was not considered in the machining strategy, starting with the tool path program in CAM software, which allows the management of various ways of tool path generation, but cannot decide which one is the best. The present study advances, with minimal approximation, a geometrical method to establish the volume of the uncut chip and area variation of the cross section, obtained in 3D-CAD by four surfaces intersection [1]. Both rotations in 5 axes are considered for the tool and degree range is 0 to 30 for rotary axis A and 0 to-30 for rotary axis B (A+B-in fourth geometrical quadrant).

Abstract: In the context of the increasingly frequent use of curved surfaces in the design of products surrounding us, ball end mills are at present the only usable tools in the cutting of complex surfaces, either concave or convex. This aspect, once correlated with the need to reduce the surface roughness, which means an increase in the cost of processing, directs our research to those on the milling with ball end mill. In this way we can identify the optimum cutting data in terms of costs to ensure the prescribed surface roughness. The paper is based on a set of experiments on the correlation of roughness with the parameters of the cutting process, for the C45 material treated with heat at 54HRC. The paper presents a part of a complex industrial research in this area and is complementary to the published works [1, 2]

Abstract: Reverse engineering process has been demonstrated to be reliable solution in solving problems regarding missing information and/or details referred to the functional areas of parts. Based on the specific activities of the chain of processes that defines the reverse engineering concept it can be collected essential information in order to reconstitute important zones of broken parts. The present paper describes an approach that was used to recover a plastic gear part. The case study provided a moulded injected plastic part that was broken during the normal function. The entire process supposed scanning the toothed area that remained and rebuild the contour that was used in CAM software as input data and especially the machining strategy used to perform both sides of the part. The machining process was employed on a CNC graving machine tool.

Abstract: In this paper is presented an experiment whose aim is to determine the cutting forces that appear when machining Ti6Al4V titanium alloy, in order to optimize its working rate and productivity. This experiment uses carbide coated milling tools for milling titanium alloy. It has studied the influence that milling parameters have upon the three dimensional cutting forces. The equipment which was used included stationary dynamometer for measuring cutting forces, with piezoelectric transducers. The cutting force model is developed in terms of cutting speed, feed rate, axial depth and length of milling (radial depth), with values established according to response surface methodology in intervals from the specialised literature. Titanium alloys are a continuous challenge. This paper is important because is getting relevant results for improving manufacturing efficiency.

Abstract: The aim of the present paper is to establish the optimal parameter values of the cutting regime of a milling process. The paper presents a study regarding the influence of the cutting parameters on the surface roughness of the material and also on the vibration generated by their combinations, during a processing by milling. The studies are made on samples made from S355 JR steel with a metal milling machine FUS 25, which is used also for the experiments. The samples dimensions are 210x150x16mm. For the experiments there was used a cylindrical - frontal milling tool, with 32mm diameter and 10 tooth. Basic parameters of milling processing of materials we have considered in this paper are: feed rate [mm/min]; cutting speed RPM [rot/min]; depth of cut [mm]. For each of this parameters three levels were envisaged. For a 100% accurate experiment results at least 27 experiments must be done. Using an L₉ orthogonal array, the number of experiments is reduced to nine and the accurate of the method is around 99.96%. The optimal process parameters values are obtained using Taguchi method considering three situations. In the first case the goal is to get only a fine roughness for the sample. The second studied case is focused on finding a low level for the vibration generated during the milling process. The aim of the last study is to find a fine roughness and also a low level of vibration for the process. The analysis of variance (ANOVA) is applied, in all cases, in order to estimate the error variance and to rank the process parameters according to their importance.