Optimization of pocket machining strategy in HSM

Our two major concerns, which should be taken into consideration as soon as we start the selecting the machining parameters, are the minimization of the machining time and the maintaining of the high-speed machining machine in good state. The manufacturing strategy is one of the parameters which practically influences the time of the different geometrical forms manufacturing, as well as the machine itself. In this article, we propose an optimization methodology of the machining strategy for pockets of complex forms. For doing this, we have developed analytic models expressing the feed rate of the cutting tools trajectory. Then, we have elaborated an optimization method based on the analysis of the different critical parameters so as to distinguish the most suitable strategies to calculate the cutting time and define the machine dynamics. To validate our results, we have compared them to the experimental ones and also to those found in literature

Compensation of a ball end tool trajectory in complex surface milling

This work is consecrated to the minimising of machining errors based on a method for the compensation of the trajectory to be machined in hemispherical milling. This compensation is found to be necessary because of the tool deflection due to the cutting forces. In order to remedy to the machining errors, caused by this deflection, a compensation method has been proposed. The latter is inspired from the mirror method, since the compensated position is going to be determined as being the trajectory reflection, deviated onto the mirror. The advantage of this proposed method is that it takes into account the three deflections dx, dy and dz, respectively to the directions X, Y and Z. After that, two-parallel machinings, separated by a groove and achieved absolutely in the same conditions and with the same tool, are carried out, on the same complex part. The first machining is with compensation, but the second is without compensation. The coordinates of the two obtained surfaces are recorded by a 3D measuring machine. The comparison of the two-surfaces shows the presence of an important correction of the tool trajectory, and reveals a similarity between the part obtained by simulation and the one conceived in CAM

Influence of interpolation type in high-speed machining (HSM)

The recourse to the high-speed machining for the manufacture of warped shapes imposes an evolution towards a very high technicality of the CAM methods and of the machining operation execution. Due to its own characteristics, the high-speed machining (HSM) implies the use of new machining interpolations, in such a way that it assures the continuity of advances in the best way possible. Among these interpolations, we mention the polynomial interpolation. In this article, we propose a complete study of the interpolation type influence on the HSM machine dynamic behavior and also on the generated errors. For this, we have measured the feed rate of the cutting tool path for each type. Then, in terms of accuracy, we have measured the errors. In order to validate our approach, we have compared the simulated results to the experimental ones

Compensation of machining errors of Bspline and Cspline

The evolution of the interpolation methods towards a very high technicality requires a good choice of used type in the operation of high-speed milling (HSM). The “Bspline” and “Cspline” interpolations present good solutions to guarantee the tool’s continuous movement during machining. However, in a previous article, we have shown by a simulation tool that they generate significant dimensional errors that decrease the precision of the machined part. In this article, a method of compensating for these errors based on the insertion of the nodes, while respecting the predefined tolerance, has been developed. To do this, we have modeled and simulated machining errors before and after compensation for each type of interpolation. To validate our results,we have machined a test piece with the compensated and uncompensated Bspline and Cspline interpolations on theHuron KX10 machine and we have measured the corresponding machining errors. The results have shown that the method of compensation by the insertion of the nodes causes a significant reduction of the machining errors

Experimental analysis of the defects of drilling woven CFRP

International audienceIn this paper, experimental analysis has been done to study delamination phenomenon when drilling 4 shaft satin weave carbon fiber and epoxy matrix using twist drill. The composite is exposed to generate damage during processing due to delamination phenomenon. It was found that the increase of the feed rate was related to the apparition of superficial defects. Indeed, this increase gave birth to new types of drilling defects

A new feature-concept applied in cost estimation model for a weld assemblage : Additional Information

This paper presents a cost estimation model of weld assemblages. It is based on the product decomposition into parts and then into assemblages. The study is about a proposition of an original definition of welding and preparing features attributed to each assemblages. This proposed approach is based on knowledge modelling at the level of process and product perception. The decomposition of the product into features and the identification of cost features remain manual. The proposed model consists in combining two cost estimating model applied to the products and to the processes on one hand, we have used an analytic model for the formalizing of the welding time, of the electrode consumption and of gas consumption according to the different parameters of the preparing and the welding features. The decomposition into features allows to formalize the time estimating expertise related to the welding. On the other hand, we have used the parameter method for the cost structuring caused by the different feature cost preparing and by the feature cost welding

Simulation of machining errors of Bspline and Cspline.

The high-speed milling operation is widely used in industry for the production of aircraft parts, molds, and dies. The machining based on the polynomial programming (especially Bezier or basic spline (Bspline) and cubic spline (Cspline)) brings an interesting gain in cycle time. However, part quality can be degraded by using this type of programming. In this paper, we suggest a simulation methodology for errors caused by the interpolations: Bspline and Cspline in high-speed machining of warped shapes. To do this, we have developed analytical models expressing the basic paths of these interpolations. Then, we have designed a simulation tool based on these models. Experimental verifications have been done to validate our approac

Modélisation et simulation des efforts de coupe en fraisage 2.5 axes

L'opération de fraisage est une opération d'usinage fondamentale dans l'industrie pour la production des pièces mécaniques et des moules. La productivité et la précision géométrique de la pièce fabriquée diminuent par les vibrations dues à la discontinuité du contact outil pièce et à la variation de la passe radiale provoquée par le choix de la stratégie d'usinage. L'objectif de cette communication est de proposer un modèle d'efforts de coupe en fraisage 2.5 axes qui tient compte de la variation de la passe radiale. La simulation d'usinage est appliquée sur une poche complexe avec plusieurs stratégies d'usinage afin de déterminer les variations des efforts de coupe et leurs répartitions en fonction des conditions d'usinage

Numerical analysis of the Ti6Al4V behavior based on the definition of a new phenomenological model

The finite element modeling is significantly dependent on the accurate prediction of the material behavior. In order to increase the accuracy of numerical simulations, a new phenomenological model is proposed in this study. Its mathematical formulation allows suitable predictions of the Ti6Al4V sensitivity to strain rates and temperatures, while maintaining a low identification cost of its constitutive coefficients.A subroutineVUMATis developed, and its reliability is investigated in the case of themodeling of uniaxial tensile and impact tests. In addition, the 3D numerical analysis of the machining process is investigated based on the definition of the rheological Johnson-Cook model and the proposed one. Experimental orthogonal machining tests are also established for several cutting conditions. The significant sensitivity of the chip serration, the segments geometry, and the cutting forces to the feed rate is pointed out. Comparisons of the numerical results corresponding to different constitutive models are carried out. High-correlation levels with the experimental results are reached with the definition of the proposed phenomenological model, which is not the case of the Johnson-Cook empirical law.Moreover, intuitive insights about the effect of cutting conditions on the material flow towards the workpiece edges are provided with the 3D modeling. A pronounced increase of the width of side burrs with the feed rate rise was underlined. The results presented in this study point out the inability of 2D numerical simulations to accurately predict the phenomena induced during the machining process, even in the case of an orthogonal machinin

Numerical analysis of constitutive coefficients effects on FE simulation of the 2D orthogonal cutting process: application to the Ti6Al4V

In this paper, a deep study of constitutive parameters definition effect is done in order to guarantee sufficient reliability of the finite element machining modeling. The case of a particular biphasic titanium alloy Ti6Al4V known by its low machinability is investigated. The Johnson-Cook (JC) elasto-thermo-visco-plastic-damage model combined with the energy-based ductile fracture criteria is used. Segmentation frequency, chip curvature radius, shear band spacing, chip serration sensitivity and intensity, accumulated plastic strain in the formed chip segments, and cutting forces levels are determined where their dependency to every constitutive coefficient is examined and highlighted. It is demonstrated from the separate variation of every plastic and damage parameters that an interesting finite element modeling (FEM) relevance is reached with the adjustment of JC strain hardening coefficients term, thermal softening parameter, exponent fracture factor, and damage evolution energy. Moderate and high cutting speeds are applied to the cutting tool in the aim to test their impact on shear localization, chip segmentation, and numerical forces levels as well as to approve previous highlighted findings related to constitutive parameters definition. In general, this study focuses on a prominent decrease in identification process cost with the previous knowledge of the most affecting constitutive coefficients while keeping an interesting agreement between numerical and experimental results