Papers by Keyword: High Speed Machining (HSM)

Abstract: Independent research studies have shown notable dissimilarity in the machining behaviour of aluminum alloys AA6061−T6 and AA7075−T651 commonly used in automotive and aeronautical applications. The present work attempts to investigate this dissimilarity based on experimental and numerical data with a focus on chip formation and generated residual stresses under similar high−speed machining (HSM) conditions. The numerical data were calculated by a finite element modeling (FEM) developed using Deform^TM 2D software. The results showed that both studied alloys exhibit different chip formation mechanisms and residual stress states at the machined surfaces. On one hand, the AA6061−T6 alloy generates continuous chips and tensile residual stresses whereas the AA7075−T651 alloy produces segmented chips and compressive residual stresses. FEM results showed that the AA6061−T6 alloy generates lower cutting temperature at the tool−chip interface along with higher equivalent total strains at the machined surface as compared to the AA7075−T651 alloy. Based on the experimental and numerical results, it was pointed out that the differences in terms of thermal conductivity and initial yield stress are the main reasons explaining the dissimilarity observed.

Abstract: The article deals with the experimental investigation of cutting conditions from the view of force load during machining high alloyed tool steel EŠ 419556 (standard by Škoda a.s. Pilsen, based on DIN 1.2326) at high speed milling. The aim of presented research is investigation of the most favourable contact and cutting conditions to minimize the power load of the cutting edge. Processing of measurement results within presented investigation was focused only on the components of cutting force F_C (tangent) and F_CN (normal) that adequately characterize the cutting process. The experiments were also carried out at cutting depth (a_p) changing during high speed milling. The obtained results are presented in the paper by means of graphs that clearly show the behaviour of cutting force components at given conditions.

Abstract: Hardened tool steels are widely used materials for forming dies, due to their increased strength and hardness. However, their machinability is very poor, due to the high hardness of the material, which leads to high cutting forces and premature failure of the cutting tools. This is also associated with machining induced tensile stresses within the work piece. No full factorial design has been performed when end milling tool steel, due to the high associated costs. Instead of physical experiments, numerical models are commonly used to save cost and time. However, most of the recent research focus was only on 2D FE-Models. 2D model can be used for simulation of some simplified process, however, the results are not sufficient for accurate prediction. Therefore, a 3D FE-model of a precision end milling process with a two-flute ball nose cutter were established in this paper, in order to build a multi cutting edge model. In the FE-Model, a subroutine was implemented to model work piece hardening during the cutting process. The subroutine realised an accurate prediction of the residual stress and cutting forces. In addition, a material removal criterion was developed and implemented. The influence of cutting parameters on cutting force for end milling H13 tool steel was studied, through full factorial numerical simulations, to evaluate the effectiveness of this FEA model. Subsequently, after validation of the FEM model through machining trials, empirical models were developed for predicting cutting forces and residual stress. The cutting parameters evaluated were cutting speed, feed rate and depth of cut. In summary, it was found that the simulation and the experiments had a good agreement on the value and trend of the residual stress. The FEM model can be effectively used to predict residual stress in the machined surface.

Abstract: High-speed cutting (HSC) or high-speed machining (HSM) is an issue that the scientists deals with in long-term. To demonstrate the explicitness, that a full HSC machining process is considered, it is necessary to monitor the series of factors. In particular, the process of chip formation, cutting forces, cutting temperature, vibration, tool life and surface finish quality in relation to the method of machining, machined material and its properties. The article deals with the detailed analysis and evaluation of the chip formation in order to determine the hard area, transition area and veritable HSC machining. The evaluation process is based on the proposed experimental model, which is confronted with the measurement results.

Abstract: In present scenario most of airframe components employ aluminum alloy materials having wall thickness of 1.2 to 3mm. With advancement of manufacturing techniques such as high speed machining, it is possible to machine components with wall/floor thickness up to 0.3 to 0.5 mm with high aspect ratio. The aim of making such parts is to reduce weight of payload. The machining of monolithic structure involves removing of material up to 95% from the raw material. The objective of the study is to achieve maximum material removal rate without compromise on geometry, dimensional accuracy while machining the part. This paper proposes a working methodology for high speed machining which includes efficient process planning, based on static and dynamic analysis. This paper provides insight knowledge of selection of cutting tool, fixture design, clamping method, cutting process parameters; machine tool and computer aided manufacturing (CAM) strategy, optimum stock for minimal bending and distortion. This technology has been demonstrated in hexagonal test specimen of 0.5 mm thin wall and also proven on the indigenous developed global positioning system (GPS) components.

Abstract: High-speed motorized spindle of NC machine tools is the core component for high speed machining. Production efficiency, machining accuracy, processing quality are greatly improved, and production cost is reduced by high speed machining. The paper describes the common failure modes of high-speed motorized spindle. By the fault tree analysis method, failure modes of motorized spindle are modeled, and the main fault reasons of motorized spindle for NC machine tools are gotten. Qualitative analysis is performed for the fault tree by the mean of the structure function. At the end of this paper, the minimal cut sets which are the main sets of failure modes are all obtained. It has laid a good foundation for further study of quantitative analysis of motorized spindle failure modes.

Abstract: The key technology of the cutter that cutting hardened steel was researched by high speed milling machining method. At first ,three cutting elements of high speed milling machining was narratived, and we can obtain the principle of selection of parameters of cutting velocity, feed per tooth, longitudinal cutting depth and cutting width of axial, etc. With HSM ,we discussed the performance and selection points of tool material of coated cemented carbide, ceramic, cubic boron nitride , synthetic diamond and so on, and obtained the effect of the main tool geometry for the cutting process in HSM. The second, it analysised type and reason of damage of high speed cutting tools, and introduced three detection methods of tools. Finally, it was summarized and concluded.

Abstract: High-speed cutting technology is widely used in aviation, mold, automotive industries and other fields for its high machining efficiency, smaller cutting force, less cutting heat and high machining precision. However, the production site in China, high-speed machine tools do not really play its role in some enterprises, without real sense of the high-speed machining. Aluminum alloy 2A70 as the research object, using single-factor test, study the effect law of high-speed milling parameters on milling force here. The results show that: the cutting force is varying for high-speed milling, showing a periodic variation, with the transient characteristic, the milling force is large amplitude fluctuations in X and Y direction, the amount of change is respectively 55.544N and 56.306N. Milling force influenced by the spindle speed, with the increase of spindle speed, X contribute to the greatest change in the direction of milling, Y direction second, Z direction is almost unchanged. Under the experimental conditions, the stability high-speed cutting area of 2A70 is the spindle speed in the area of 21000rpm~27000rpm. The results of high-speed milling of aluminum alloy have certain significance.

Abstract: Thin-walled parts are widely used in aerospace engineering. For their complexity under loading and the higher shape precision, it’s difficult for their manufacturing on high speed machine. In order to understand manufacture process, characteristic of aviation part in high speed machining is investigated. Error sources on parts are classified and the maximum error, dynamic errors are studied on its main influence factors, such as cutting force and vibration. Finally, useful method on cutting test part is proposed, which can observe and control dynamic accuracy of aviation part and ensure effective manufacture.

Abstract: Surface roughness is an important parameter to evaluate the quality of high-speed machining (HSM). This paper establishes a mechanical model based on the molecular-mechanical theory of friction to study factors that influence the surface roughness in HSM. The relationship between flow stress and the remnant height on the machined surface is obtained. The HSM process of AISI-1045 steel is simulated by using finite element method (FEM) based on DEFORM-2D and the flow stress is obtained. The surface roughness of workpiece machined by HSM is calculated based on the value of flow stress and the mechanical model. The result shows that the surface roughness of workpiece in HSM is acceptable, and the mechanical model supplies a method to study the surface roughness in HSM.