Advanced Materials Research Vols. 69-70

Abstract: Chatter phenomenon often occurs during end milling of metal-cutting and becomes a common limitation to achieve high productivity and part quality. This paper studies the relationship expression between the parameters of oblique cutting and milling coefficients by analyzing the geometrical relationship of oblique cutting, and derives the mathematic expressions in theory between the cutter parameters and chatter. For the purpose of chatter avoidance, this paper studies the effect of helix angle and normal rake angle on milling stability under the condition of the same milling parameters, and plots the three-dimensional stability lobes of the spindle speed, axial and radial depths. It can be found that the milling stability is increased with the increment of helix angle and normal rake angle. Through the three-dimensional lobe, it is possible to choose the appropriate cutter parameters to reduce and avoid the chatter.

Abstract: Damage of fine grained hard metals WC-10%Co was investigated using the laser thermal shock method. Cemented carbide insert was irradiated with a high power laser and scanning electron microscopy was used to characterize the damage in the surface. Stress was analysis with thermo-elastic theory after thermal shock cycles. Crack initiation of cemented carbide was primarily induced by high thermal shock cycles under high rotation speed and low feed rate. Tangential stress played a primary role in crack initiation and it was demonstrated that why the thermal cracks always perpendicular to the cutting edge.

Abstract: Cutting tools suffer severe abrasive friction and wear in high speed milling of graphite. Cutting forces were measured and analyzed using time-frequency analysis method to reveal the correlation between cutting force variations and tool wear evolution. The static and dynamic force components increased prominently with tool wear. The cutting force Fy was found the most sensitive to the tool wear evolution. The waveform of cutting force became periodic and irregular with the increase of tool wear. Good correlation was found between the first force harmonic and tool wear.

Abstract: In micromachining, the uncut chip thickness is comparable to the tool edge radius, and chip won’t be generated if the uncut chip thickness is less than a critical value, besides that, the minimum uncut chip thickness affect many factors such as the cutting force, the chip’s modality, the cutting surface quality, etc. In this paper, a geometric model is developed to predict the minimum uncut chip thickness values. The model accounts for the theory that the critical condition of producing chip is when the friction of the surface deformation asperities is zero. Two situations when the minimum value is larger or smaller than the tool edge radius respectively to predict the minimum value are discussed. The influences of tool edge radius and material’s property on the minimum uncut chip thickness are taken into account.

Abstract: Cutting force is a key factor influencing the machining deformation of weak rigidity workpieces. In order to reduce the machining deformation and improve the process precision and the surface quality, it is necessary to study the factors influencing the cutting force and build the regression model of cutting forces. Firstly, the cutting parameters influencing cutting force are analyzed for LF21. Secondly, how certain cutting parameter influence the cutting component forces (Fx, Fy, Fz) are studied by the correlation analysis and the approach to choosing the right cutting parameters for machining the weak rigidity workpieces are presented. Finally, the regression model of cutting forces based on the cutting parameters is investigated in this paper.

Abstract: Hardened steel P20 at 50 HRC is milled at high speed by TiN coated and TiAlN coated solid carbide straight end mills, and the cutting forces and tool wear are measured. The result shows that TiAlN coated tool is more suitable for cutting hardened steel at high speed. Then the hardened steel is milled under different cutting parameters. It is indicated that the effect of cutting speed on cutting forces is small, but the effect of cutting speed on machine vibration should be considered. Increase feed per tooth or radial depth of cut will increase the cutting forces.

Abstract: TiAlSiN coatings with different Al content were prepared by hollow cathode discharge ion plating (HCDIP) and medium frequency magnetron sputtering ion plating (MFMSIP) hybrid physical vapor deposition (PVD) coating system. The composition, microstructure, mechanical properties of these coatings were systematically investigated by means of EDX, XRD, SEM, nanoindentation, scratch and tribological tests. It was found that the coatings had (111) or (200) preferred orientation with addition of Al. Proper content of Al led to increase of microhardness and adhesion. The flank wear of carbide end mill coated with TiAlSiN had the least wear than those coated with TiAlN and TiSiN coatings under the high speed milling of hardened steel experiments.

Abstract: A method for predicting the stability of thin-walled workpiece milling process is described. The proposed approach takes into account the dynamic characteristics of workpiece changing with tool positions. A dedicated thin-walled workpiece representative of a typical industrial application is designed and modeled by finite element method (FEM). The workpiece frequency response function (FRF) depending on tool positions is obtained. A specific 3D stability chart (SC) for different spindle speeds and different tool positions is then elaborated by scanning the dynamic properties of workpiece along the machined direction throughout the machining process. The dynamic optimization of cutting parameters for increasing the chatter free material removal rate and surface finish is presented through considering the chatter vibration and forced vibration. The investigations are compared and verified by high speed milling experiments with flexible workpiece.

Abstract: Using the typical CAD/CAM software UG, an aero-engine integral impeller was studied in this paper, including 3-D modeling, tool-path planning and simulation. A regular impeller was machined with a 5-axis machine tool, which showed the process plan was feasible.

Abstract: In order to enhance the processing accuracy, the surface quality and the processing efficiency of camshaft grinding, a processing parameters selection in NC camshaft grinding based on uniform design, neural network and genetic algorithm was proposed by using CNC8312A NC camshaft grinder to test training samples. The nonlinear mapping relation between processing requirements (inputs) and processing parameters (outputs) was achieved. By comparing the theoretical values with the output values of the neural network, and analyzing the errors between actual measurement results and processing quality requirements, a satisfied result was obtained by applying the model to actual production.