Papers by Keyword: Material Removal

Abstract: Due to the unfixed state of the workpiece and the dissimilarity between sections in through-feed centerless grinding, the positions and orientations of the workpiece keep changing in the grinding process, which are coupled with the workpiece roundness generation. In this paper the positions and orientations of the workpiece are described by the dynamic equations obtained from Lagrange equation. And the homogeneous coordinate transformation is applied to present the profiles of the workpiece, grinding wheel and control wheel in the reference frame. Finally the time varying profile of the workpiece is obtained for the investigation of the material removal process in 3D space. The material properties of the workpiece, the wheels and the workrest combined with the geometric relationship of their profiles are utilized to calculate the interaction between them, including the three forces along the axes and the three moments about the axes.

Abstract:

Nonconventional machining methods are based on the transfer of the energy to the work zone in ways distinct from those applied in the case of the so-called classical machining methods. A group of nonconventional machining methods achieve material removal from workpiece by using the motion of the electrical charged particles in a liquid. Practically, some machining techniques included in the larger groups of electrical discharge machining and in electrochemical machining are based on the motion of electrical charged particles in fluid. The problem addressed in this paper is to identify the zones where differences between the two groups of machining methods appear. A theoretical analysis was developed in order to identify the common aspects and respectively the differences between the electrical discharge machining and electrochemical machining, if the machining liquid is considered. Some experimental tests were developed to highlight aspects specific to the above mentioned machining techniques. The research facilitated obtaining a more complete image of some common and distinct characteristics of electrical discharge machining and electrochemical machining. The significance of the electroconductive or insulating properties of the work liquid was highlighted.

Abstract: The examination of the main machining methods applied in manufacturing processes from machine building and based on material removal from workpiece highlights essentially the existence of distinct processes able to generate material. An analysis of certain machining methods able to develop processes of material removal from workpieces was initiated by taking into consideration the principle machining schema and the capacity of generating machined surfaces. One concluded that within distinct machining processes, various phenomena are applied in order to obtain material removal from workpiece.

Abstract: Belt grinding is characterized by elastic contact grinding. Generally, the non-uniform material in complex machining area could be removed by repeated grinding or longer dwell-time grinding to obtain the required grinding capacity, which leads to low efficiency, difficult dimension accuracy control and poor surface quality. It should be considered thoroughly surface geometry, grinding force and system stiffness in surface belt grinding. Belt grinding parameters can be then dynamically adjusted. This paper focuses on controlling material removal efficiently and uniformly in marine propeller belt grinding. The material removal process is modelled considering elastic contact between grinding wheel and workpiece. Then, a grinding depth and grinding dwell time control strategy of surface belt grinding is proposed based on rigid-flexible coupled analysis. The variable feed grinding experiments were carried out on the developed five-axis CNC belt grinding machine integrated measuring and machining. The marine propeller with cast aluminum bronze (ZCuAl₈Mn₁₃Fe₃Ni₂) was employed to validate the proposed controllable material removal strategy. It is shown that the proposed strategy is feasible and efficient.

Abstract: The majority of aero-engine components are designed and manufactured with nickel-based superalloy GH4169 in mind. There is little information available in the literature related to belt grinding processes of aero-engine components. Up to now, limited research has been reported in the use of belt for grinding aero-engine components made of nickel-based superalloy GH4169. A case study of an abrasive belt grinding performance applied on nickel-based superalloy GH4169 in manufacturing processes is presented, aiming to investigate the possibility of using belt grinding as a operation for components made of nickel-based superalloy GH4169. For the ‘optimised’ grinding conditions, the belt service life is evaluated by changing grinding parameters (grinding speed, contact force and oscillation frequency), and the following output measures are obtained: material removal, belt wear and grinding ratio. As a result, the maximum grinding ratio of G is 8.8, it could be concluded that belt grinding might be considered as a viable process for grinding aero-engine components.

Abstract: YL10.2 and YF06 are ultrafine-grained cemented carbides, and grinding experiments were carried out with resin-bonded diamond grinding wheel. Based on measured grinding force, surface roughness and SEM topography, experimental results were analyzed; grinding forces and depth of grinding approach linear correlation; and the grinding force of YF06 is greater than that of YL10.2 in rough grinding, but the grinding force increases significantly if depth of cut is greater than a certain value in finish grinding. The trend of machined surface roughness looks like “V” type with the increasing of depth of cut; the material removal behavior of ultrafine-grained cemented carbides in grinding was observed; the ploughing and fragmentation exist simultaneously on the ground surface, and the dominated material removal behavior depends on the grinding parameters or chemical composition of workpiece.

Abstract: For the same hard machining materials, the tool life, the axial distance for cutting and the material removal amount were adopted for the orthogonal test. The results show that the high tool life usually corresponds to low cutting parameters, which means the poor processing efficiency. The results have poor potential applications. The axial distance for cutting and the material removal amount can represent the machined surfaces and the removal quantity of materials, respectively, which can perfectly reflect the relation between cutting parameters and application effect. In the optimization test, the processing efficiencies by two evaluation parameters are all better than by tool life. But it's important to note that the results by two parameters are different, the special works still need to be made according to the real situation.

Abstract: Laboratory X-ray diffraction is commonly used for surface residual stresses determination. Nevertheless, the in-depth residual stress gradient also needs to be known. Chemical or electro-polishing method is generally used for material removal. However, material removal may seek a new equilibrium and stress field may change in such a way that experimental residual stress values must be corrected. Different methods exist to account for the residual stress relaxation associated with the material removal operation and will be discussed in this paper.

Abstract: Chemical mechanical polishing (CMP) is often employed to obtain a super smooth work-surface of a silicon wafer. However, as a conventional CMP is a loose abrasive process, it is hard to achieve the high profile accuracy and lots of slurry must be supplied during CMP operations. As an alternate solution, a fixed abrasive CMP process can offer better geometrical accuracy and discharges less waste disposal. In this paper, in order to enhance the polishing efficiency and improve the work-surface quality, a novel ultrasonic assisted fixed abrasive CMP (UF-CMP) is proposed and the fundamental machining characteristics of the UF-CMP of a silicon wafer is investigated experimentally. The results show that with the ultrasonic assistance, the material removal rate (MRR) is increased, and the surface quality is improved.

Abstract: In this paper, material removal mechanism of monocrystalline silicon by chemical etching with different solutions were studied to find effective oxidant and stabilizer. Material removal mechanism by mechanical loads was analyzed based on the measured acoustic signals in the scratching processes and the observation on the scratched surfaces of silicon wafers. The chemical mechanical polishing (CMP) processes of monocrystalline silicon wafers were analyzed in detail according to the observation and measurement of the polished surfaces with XRD. The results show that H₂O₂ is effective oxidant and KOH stabilizer. In a certain range, the higher concentration of oxidant, the higher material removal rate; the higher the polishing liquid PH value, the higher material removal rate. The polishing pressure is an important factor to obtain ultra-smooth surface without damage. Experimental results obtained silicon polishing pressure shall not exceed 42.5kPa.