Multi-objective Optimization of Turning Tool Geometric Parameters Based on Kriging Model

Cutting performance parameters of turning tool in different geometric parameters are obtained using finite element model, and the Kriging models of cutting stress and temperature are constructed, taking the cutting performance parameters as training samples. The multi-objective optimization model of turning tool geometric parameters is established based on the constructed cutting performance Kriging models, in which the design variables are rake angle, relief angle and cutting-edge radius, the objective parameters are cutting stress and temperature. The multi-island genetic algorithm is used to obtain the optimum turning tool geometric parameters: rake angle γo is 10.59°, relief angle λs is 6.15°and cutting-edge radius γE is 0.73mm. The simulation results after optimization demonstrate that the corresponding cutting temperature reduces 263.1°C, cutting stress drops by 550.8MPa.

Effect of cutting edge geometry change due to tool wear on hole quality in drilling of carbon fiber reinforced plastics using advanced ceramic coated tools

This paper aims to study the evolution of cutting edge geometry due to tool wear and discuss its impact on the hole quality of a carbon fiber reinforced plastic (CFRP) laminate. A drilling experiment was conducted using three types of twist drills: uncoated, BAM (AlMgB14) coated, and (AlCrSi/Ti)N nanocomposite coated tungsten carbide tools. After generating 120 holes, the uncoated drill had the largest cutting edge radius (∼36 µm), while the BAM coated drill had the most extensive flank wear (∼287 µm) among the three drills. This relatively rapid tool wear results in a reduction of average hole size and a considerable variation on the hole profiles. The worn drills with the cutting edge radius greater than 19.3 µm form the fiber pull-outs in not only the 135° plies but also the adjacent 45° and 90° plies from the cutting direction, creating deep void networks. This type of networked fiber pull-out damage was observed with the holes machined by the uncoated and BAM coated drills. The (AlCrSi/Ti)N coated drill, which experienced the least amount of flank wear and the least increase of cutting edge radius, generated consistently sized holes up to 120 holes. However, the relatively sharp (AlCrSi/Ti)N coated tool results in the higher arithmetic roughness average (Ra) and the maximum roughness height (Rz) values than the other tools due to the localized fiber pull-outs and the absence of severe matrix smearing.

An Improved Cutting Force Model in Micro-milling Considering the Comprehensive Effect of Tool Runout, Size Effect and Tool Wear

Tool runout, cutting edge radius-size effect and tool wear have significant impacts on the cutting force of micro-milling. In order to predict the micro-milling force and the machining performance related to the cutting force, it is necessary to establish a cutting force model including tool runout, cutting edge radius and tool wear. In this study, an instantaneous uncut thickness (IUCT) model considering tool runout, a nonlinear shear/ploughing coefficient model including cutting-edge radius and a friction force coefficient model embedded with flank wear width, are constructed respectively. By integrating the IUCT, the nonlinear shear/ploughing coefficient and the friction force coefficient, a comprehensive micromilling force model including the tool runout, size effect and tool wear is derived. Experiment results show that the proposed comprehensive model is efficient to predict the micro milling force.

Change in Edge Radius of Cutting Tool from Surface Tension Between Solid Materials

In this study, the “surface tension defined from stress” was used to predict the change in the cutting edge radius in the tool’s initial-stage wear regime. An analysis of the “surface tension defined from the stress” between solids showed that the flow of the material and the adhesion phenomenon must occur simultaneously at the interface. From the experimental and simulation results, it was confirmed that the proposed model can be used to predict the stress distribution acting on the cutting tool and evaluate the “surface tension defined from the stress” at the tool and workpiece interface. It was also verified that the cutting-edge radius under a state of equilibrium changes based on the cutting condition. These results indicate that simply using a cutting tool with a smaller cutting-edge radius will lead to a rapid increase in the cutting-edge retreat at the beginning of the cutting. For the unmanned operation of the cutting processes, it is desirable to use a cutting tool with a cutting-edge radius under a state of equilibrium at the beginning of the cutting to improve the cutting efficiency and reduce the cutting cost.

FE analysis of the effects of process representations on the prediction of residual stresses and chip morphology in the down-milling of Ti6Al4V

In part II of these two-part papers, the effects of four FEM representations of the milling process on the prediction of chip morphology and residual stresses (RS) are investigated. Part II focuses on the milling of conventional uncut chip thickness h with finite cutting edge radius and flank wear, while part I of these two-part papers has reported on the results in the case of milling small uncut chip thickness in the micrometre range with finite cutting edge radius. Two geometric models of the flank-wear land composed of flat and curved wear land are proposed and assessed. The four process representations are: i) orthogonal cutting with flat wear land and with the mean uncut chip thickness h ¯; ii) orthogonal cutting with flat wear land and with variable h, which characterises the down-milling process and which is imposed on a flat surface of the final workpiece; iii) modelling the true kinematics of the down milling process with flat wear land and iv) modelling the true kinematics of the down milling process with curved wear land. They are designated as Cte-h, Var-h, True-h and True-h*. The effectiveness of these representations is assessed when milling Ti6Al4V with a flank-wear land of VB = 200µm.

Investigation on the size effect in micro end milling considering the cutting edge radius and the workpiece material

Previous research has found that the peripheral and end cutting edges of the cutter had different cutting mechanisms in the micro end cutting process considering the size effect. This investigation is a further study on this point considering the cutting edge radius of the cutter and the material of the workpiece based on the methods of finite element simulation and the micro end cutting experiment. This study adopts a combination of simulation and experiment research methods and the cutting edge radius and the workpiece material as two variables. Considering the cutting mechanisms of the peripheral cutting edge and the end cutting edge are different, the peripheral cutting edge and the end cutting edge are studied respectively. Meanwhile, the minimum undeformed chip thickness (MUCT) value is determined in three ways, chip morphology, cutting force, and surface roughness, so the final result obtained by comparing three kinds of results has a very important reference value. Not only are the chip morphology obtained by finite element simulation and the surface roughness obtained by the micro end cutting experiment used to identify the MUCT value, but also the cutting force. The simulation and experimental results show that the cutting force can be used to identify the MUCT value for the peripheral cutting edge, but it cannot be used for the end cutting edge. The MUCT value increases with the increase of the cutting edge radius, no matter which process it is. The material property has some effects on the MUCT value; even the cutting parameters and the cutting edge radius remain unchanged for the peripheral cutting edge. However, the material property has no effect on the MUCT value for the end cutting edge. In this study, the influence of important variables on MUCT is studied as much as possible to reflect a real application situation.

Tool Wear Evaluation Based on Design Space Exploration Coupled with Explicit Cutting Simulations and Cutting Forces Excitation Signature

Cutting operations are still one of the main methods used in the industry for surface generation in mass production. The dynamics of these processes are complex and having a good insight into the interdependencies of the nonlinear physical phenomena can be translated into better cutting performance. One of the main cutting tool geometrical parameter, usually associated with wear, is the cutting edge radius. Continuous direct evaluation of this parameter exhibits some important limitations offline, if this evaluation needs to be online the whole process becomes very complicated due to the measurement limitations that might appear. For online cases, the best approach is to determine the amplitude of this parameter indirectly using various side effects that can be correlated. One possible option is to monitor the vibrations generated by the resulting cutting forces. In the latest years, the usage of explicit finite element methods (FEM) to simulate the cutting processes has grown exponentially with the continuous increase of computation efficiency. With the help of Computer-Aided Engineering (CAE in short) solutions and using the latest advances in design space exploration (DSE) solutions, it is possible to create models able to parametrically explore a design space (DS), having precise targets, and also get the important correlations for all the important, quantifiable, cutting parameters. This paper presents an innovative method to create tool wear evaluation models focused mainly on the cutting edge radius indirect evaluation. The proposed method uses guided simulation loops able to generate a variety of dynamic signatures which are further post-processed to get a complex correlative model. The model can be applied in real cutting cases using the reciprocity property and can determine online the state of the cutting edge radius for further tool wear evaluation. The paper concludes with an analysis of the obtained model and the applicability of the data for the intended purpose.