Cai Xu Yue

Adiabatic shear mechanisms for the hard cutting process

The most important consequence of adiabatic shear phenomenon is formation of sawtooth chip. Lots of scholars focused on the formation mechanism of sawtooth, and the research often depended on experimental approach. For the present, the mechanism of sawtooth chip formation still remains some ambiguous aspects. This study develops a combined numerical and experimental approach to get deeper understanding of sawtooth chip formation mechanism for Polycrystalline Cubic Boron Nitride (PCBN) tools orthogonal cutting hard steel GCr15. By adopting the Johnson-Cook material constitutive equations, the FEM simulation model established in this research effectively overcomes serious element distortions and cell singularity in high strain domain caused by large material deformation, and the adiabatic shear phenomenon is simulated successfully. Both the formation mechanism and process of sawtooth are simulated. Also, the change features regarding the cutting force as well as its effects on temperature are studied. More specifically, the contact of sawtooth formation frequency with cutting force fluctuation frequency is established. The cutting force and effect of cutting temperature on mechanism of adiabatic shear are investigated. Furthermore, the effects of the cutting condition on sawtooth chip formation are researched. The researching results show that cutting feed has the most important effect on sawtooth chip formation compared with cutting depth and speed. This research contributes a better understanding of mechanism, feature of chip formation in hard turning process, and supplies theoretical basis for the optimization of hard cutting process parameters.

Off-line error compensation in corner milling process

Tool deflection induced by cutting force could result in dimensional inaccuracies or profile error in corner milling process. Error compensation has been proved to be an effective method to get accuracy component in milling process. This article presents a methodology to compensate profile errors by modifying tool path. The compensation effect strongly depends on accuracy of the cutting force model used. The mathematical expression of chip thickness is proposed based on the true track of cutting edge for corner milling process, which considers the effect of tool deflection. The deflection of tool is calculated by finite element method. Then, an off-line compensation algorithm for corner profile error is developed. Following the theoretical analysis, the effect of the error compensation algorithm is verified by experimental study. The outcome provides useful comprehension about selection of process conditions for corner milling process.

Hardening Effect on Machined Surface for Precise Hard Cutting Process with Consideration of Tool Wear

During hard cutting process there is severe thermodynamic coupling effect between cutting tool and workpiece, which causes quenching effect on finished surfaces under certain conditions. However, material phase transformation mechanism of heat treatment in cutting process is different from the one in traditional process, which leads to changes of the formation mechanism of damaged layer on machined workpiece surface. This paper researches on the generation mechanism of damaged layer on machined surface in the process of PCBN tool hard cutting hardened steel Cr12MoV. Rules of temperature change on machined surface and subsurface are got by means of finite element simulation. In phase transformation temperature experiments rapid transformation instrument is employed, and the effect of quenching under cutting conditions on generation of damaged layer is revealed. Based on that, the phase transformation points of temperature under cutting conditions are determined. By experiment, the effects of cutting speed and tool wear on white layer thickness in damaged layer are revealed. The temperature distribution law of third deformation zone is got by establishing the numerical prediction model, and thickness of white layer in damaged layer is predicted, taking the tool wear effect into consideration. The experimental results show that the model prediction is accurate, and the establishment of prediction model provides a reference for wise selection of parameters in precise hard cutting process. For the machining process with high demanding on surface integrity, the generation of damaged layer on machined surface can be controlled precisely by using the prediction model.

2D FEM Estimate of Tool Wear in Hard Cutting Operation: Extractive of Interrelated Parameters and Tool Wear Simulation Result

Tool wear plays an important part during cutting process, and wear loss has a close relationship with cutting condition, which affects machined surface mostly. In order to accomplish tool wear prediction in way of FEM, based on founding of cutting model under steady state, interrelated parameters needed for tool wear prediction, such as cutting temperature, contact pressure and raletive sliding velocity are extracted. By compiling Python subprogram and using Abaqus tool in hard cutting process PCBN tool wear is predicted, which provide foundation for optimizing cutting condition.

Experimental Investigation on Air Cooling of GCr15

Air cooling is a near dry machining method, which cools cutting area and evacuates chips using low temperature cold wind instead of cutting liquid. It can decrease tool wear, increase tool life, reduce machining cost and bring no chemical pollution. In this paper, air cooling test was carried on, in which vortex tube was used for cooling and high hardness bear steel GCr15 was machined by PCBN tool. Experiment results indicated that cold air from vortex tube has a significant effect on cutting force, cutting temperature and chip formation process. This paper’s conclusions will have a great reference value for the practical application of air cooling technology.

Kinematic Analysis of Detection of Steel Ball Surface Defect Based on ADAMS

In the detection process of the ball detector, surface can not unfold effectively, which brings about that the camera can not capture the image which we want, resulting in a high rate of defect and at a low efficiency in the test with the ball detector. In order to solve this problem, the optimized design on the mechanical control parts of the expansion organization was carried out, besides, kinematics analysis model the expansion organization and a motor control timing schedule were created by ADAMS, enabling expansion process consistent with the mathematical modeling. To a certain extent the optimization results improve overall performance of the system, which plays a guiding role in the improvement of the system.

An Investigation of Wear of Ball End Milling Cutter for High-Speed Milling of Hardened Cr12MoV Steel

The high-speed milling experiments on hardened Cr12MoV steel were carried out with ball end milling cutter of different edge parameters. The influences of helix angle and rake angle on tool life and surface roughness were focused on. Meanwhile, the impacts of edge parameters on cutting edge stiffness and flank wear were analyzed on the condition of high-speed milling. It carried out that smaller helix angle and negative rake angle selected during high speed milling can guarantee quality of surface manufactured as well as longer tool life.

Tool Path Planning of 5-Axis Finishing Milling Machining for Closed Blisk

To solve the difficult problem of NC machining of closed blisk, the paper combines with the structure characteristics of processing surface and the characteristics of Channel processing, and at the same time to study the technology of processing impeller channel tool path planning. By planning different processing methods of tool axis control for different processing parts, take outer arc processing as an example, tool path planning method is analyzed. By the method to generate the ruled envelope surfaces in view of blade offset surfaces, to put forward new methods of dividing plunging region. The method of surface offset was applied to determine the safety space of tool axis movement. To determine the range of tool axis angle by the relationship between the boundary curves and division the processing area by the tangent method. Finally, The results of tool path planning were verified by using five-axis processing, which proved the reasonability and feasibility of the scheme.

Research on Machined Surface Quality of High Speed Hard Machining for Harden Steel

For its good processing flexible, economic and environmental protection performance, hardened steel GCr15 is used widely in car and energy industry. Although surface quality in machining process is not controlled well, that restricts application of hardened steel GCr15 extensive to a certain degree. Therefore, this study revealed the effect of cutting parameters on surface roughness. Also influence of cutting conditions on surface morphology and organization generation mechanism of subsurface were stuied for high-speed cutting hardened steel GCr15. Appear reasons of plastic side flow on surface was researched. Also, effect of tool wear on surface quality was studied as well. The research results provided theoretical basis for rational choice for high speed hardened steel cutting process.

Layer Face Milling Cutter Parametric Modeling and Modal Analysis

Performance-based parametric design method for improving the face milling cutter design efficiency and ensuring the use of performance has an important significance. Three kinds of parameter design method are described in this paper, and parametric design of series of layer milling cutter is completed by modeling parametric design method with UG software. Also, modal analysis is made with FEM. Therefore the study results provide examples for optimization of tool structural and analysis of restrain vibration.