Abstract: In this work, the prediction and analysis of cutting forces in precision turning operations is presented. The model of cutting forces is based on the oblique cutting force model which was rebuilt by two coordinate conversions from the orthogonal cutting model. Then the cutting field in precision turning was divided into two fields which are characterized as curve change and linear change on cutter edge and they were modeled respectively. Cutting field of cutter nose was modeled by differential method and its cutting force distribution is predicted by the proposed method. The predicted results for the cutting forces are in agreement with the experimental results under a variety of operation variables, including changes in the depths of cut and in the feedrate.
Abstract: Drilling process of the ceramic composite component (ceramics/FRP/aluminum alloy), as an example of similar ceramics/FRP laminate composite components, was studied intensively. According to the diverse machining properties of the composing materials of ceramic composite components, the special thinwall diamond core bit was developed, with copper based matrix of complex alloy and hot pressing process. Through machining competitive experiments, the feeding mode with constant pressure was determined. After analyzing the diverse hole defects, the process equipment with compressive pre stress was introduced to improve the hole drilling quality, with good validity proved theoretically by the finite element analysis and on this condition, water can be used as the coolant. The process technology presented in this paper can be used for hole drilling in similar composite components made of the same composing materials.
Abstract: A set of horizontal ultrasonic vibration deep-hole honing device is designed and developed, for honing the workpieces which diameter are between 80 to 100 mm. The honing experiments in the titanium alloy are carried out with the device, and the results indicate that the ultrasonic vibration honing can improve working surface quality.
Abstract: Four micro-holes were fabricated on the tool-chip contact area of the cemented carbide (WC+14%TiC+6%Co) tool face. MoS2 solid lubricants were embedded into the micro-holes to form self-lubricated tool (SLT-1). Dry machining tests on hardened steel were carried out with the SLT-1 self-lubricated tool, the SLT-2 tool with four micro-holes on the rake face embedded without solid lubricants and the SLT-3 conventional tool. The variation of cutting forces with cutting speed were tested by the Kistler force tester. The result shows that the three cutting force components of SLT-1 self-lubricated tool decreased obviously. They went down by 25-35% in comparison with those of the SLT-3 tool. And the three force components of SLT-2 tool decreased about 10-14% compared with those of the SLT-3 tool. Through the analysis of cutting force distribution theory and test results, the mechanism of cutting forces decrease was considered to be forming a self-lubricating film on the rake face which decreases the shear stress and the reduction of contact length between the chip and the tool.
Abstract: Three cutting tools, YG8, YT15 and YW1, which are different in hardness and toughness, were adopted for deposited materials cutting. From the analysis of test results, it can be known that the toughness is the most importance factor for improving cutting capability when the hardness of deposited materials is low. And with the growth of hardness of workpieces, the hardness of cutting tools plays more and more important roles. When the hardness of deposited materials arrives to HRC56, the hardness of cutting tools becomes the main role for improving cutting capability. On the basis of the results of two orthogonal experiments and extremum deviation analysis, the best scheme for three deposited materials were achieved after obtaining the best level of the factor by computation.
Abstract: Friction coefficient is an important index to evaluate the cooling and lubrication effects. In this study, the orthogonal milling experiments with different cooling/lubrication methods (dry, cutting fluid, MQL) were performed and the milling forces were measured to calculate the apparent friction coefficients with the mechanistic model. The effects of cutting parameters and cooling/lubrication methods on the apparent friction coefficients were analyzed.
Abstract: Experimental investigations have been conducted on the chips and common types of discreteness in the form of serrated saw teeth (primary or secondary) have been identified. It has been observed that the chip formation process has a discrete nature, associated with the periodic shearing process of the chip during machining of stainless steel. Mechanism of formation of these teeth has been studied and the frequency of their formation has been determined. The different modes of the vibrating components of the vertical machining centre have been extracted by modal analysis and the vibration responses during cutting conditions have also been recorded using an online monitoring data acquisition system. It has been concluded from the findings that chatter is the outcome of resonance, which occurs in the system when the frequency of secondary or primary serrated teeth formation is approximately equal to or an integer multiple of the ‘prominent mode frequencies’ of the system components.
Abstract: This paper presents a prediction model of flank milling forces in ruled surface impeller machining process with cylindrical, helical, end mills. Flank milling is widely used in machining objects such as gas turbines, impellers, fan vanes and all workpieces defined by non-developable, ruled surfaces. In the present paper, a short review on the development of milling force prediction is given first, and then a simple introduction about ruled surfaces is presented. Having defined the milling surfaces, flank milling forces with cylindrical milling cutters are analyzed. A cutting force prediction model of tangential, radial and axial is evaluated. The methodology allows prediction of average cutting load on the tool and workpiece, which can be used for cutting tool selection and chatter vibration avoidance. At last, the proposed model is demonstrated experimentally in milling an impeller with ruled surfaces.
Abstract: The roller gear cam surface is manufactured with nonequivalent milling method in many cases, by which the machining error is unavoidable. In order to simplify the tool position, we can transform one problem approximating the designed surface with the tool envelope surface to another problem approaching the theoretical tool axis trajectory surface with the actual one. Furthermore, the theoretical tool axis trajectory surface, which is an offset surface of the designed cam surface, is reconstructed by the NURBS ruled surface. In order to find the best tool axis vector to minimize the machining error, a simple least square approximation method is established to figure out all the control points of the NURBS tool axis trajectory surface. A numerical calculation and simulation example is described to verify the effectiveness of the tool position method proposed in the paper.
Abstract: The involute cam is used for generating tooth form of an involute gear in gear grinder with involute cam-link stopper, and its profile error is one of the factors which decide the tooth form precision of gear. The conventional processing means of involute cams can't achieve a sufficient accuracy. In this paper, a double-disc mode grinding device is introduced. Based on analysis of grinding principle, the device's structure and working process are described, and the main sources of grinding profile errors are analyzed. It is confirmed that the introduced device has the ability of accomplishing a highly precise grinding of involute cams.