High Speed Blanking: An Experimental Method to Measure Induced Cutting Forces

Lien vers la version éditeur: http://link.springer.com/article/10.1007/s11340-013-9738-1A new blanking process that involves punch speed up to 10 ms −1 has obvious advantages in increased productivity. However, the inherent dynamics of such a process makes it difficult to develop a practical high speed punch press. The fracture phenomenon governing the blanking process has to be well understood to correctly design the machine support and the tooling. To observe this phenomenon at various controlled blanking speeds a specific experimental device has been developed. The goal is to measure accurately the shear blanking forces imposed on the specimen during blanking. In this paper a new method allowing the blanking forces to be measured and taking into account the proposed test configuration is explained. This technique has been used to determine the blanking forces experienced when forming C40 steel and quantifies the effect of process parameters such as punch die clearance, punch speed, and sheet metal thickness on the blanking force evolution

Dynamic Study of Thin Wall Part Turning

The numerical simulation of machining process is a key factor in the control of parts machining process. Its development aims at improving the process reliability and reduces the time spent during the process planning stage. In this context, we use a specific time domain simulation allowing modeling the dynamics of a thin wall part turning operation. After having introduced the basics of the proposed approach we present a specific cutting test that has been designed to specifically measure and control the dynamics of the part and the cutting conditions of a finishing toolpath. The influences of the cutting speed and damping coefficient on the chatter occurrence are discussed. In order to better control the simulation uses, an analysis of the simulation parameters influences on the simulated results is proposed

Simulation temporelle du fraisage de parois minces

Quel que soit le secteur industriel concerné, la réduction de masse est un objectif récurrent dont la première conséquence est l'augmentation des parties à faibles épaisseurs sur les pièces à fabriquer. L'usinage de ces parois minces engendre fréquemment des problèmes vibratoires qui doivent être anticipés notamment à partir de simulations visant à prédire l'état des surfaces usinées. Cet article revient sur la simulation temporelle de l'usinage de parois minces et souligne que ce type de simulation est long et délicat à mettre en œuvre et à analyser. Une méthode permettant d'accélérer l'analyse et la prise de décision par l'orientation des calculs est proposée. Cette méthode est basée sur la recherche du régime stationnaire effectif. Initialisée à partir de ce régime, la simulation converge plus rapidement et conduit à l'état de la surface usinée. En confrontant les résultats obtenus par simulation à ceux obtenus expérimentalement, l'apport de cette méthode est prouvé

Dynamic Study of Thin Wall Part Turning

The numerical simulation of machining process is a key factor in the control of parts machining process. Its development aims at improving the process reliability and reduces the time spent during the process planning stage. In this context, we use a specific time domain simulation allowing modeling the dynamics of a thin wall part turning operation. After having introduced the basics of the proposed approach we present a specific cutting test that has been designed to specifically measure and control the dynamics of the part and the cutting conditions of a finishing toolpath. The influences of the cutting speed and damping coefficient on the chatter occurrence are discussed. In order to better control the simulation uses, an analysis of the simulation parameters influences on the simulated results is proposed

Prediction of the machining defects in flank milling

In peripheral milling with great axial engagements,the tool deflections generate some geometricaldefects on the machined surface. This article present aprediction method of these defects which is applicableon every ruled surface. The cutting forces are estimatewith the cutting pressure notion. The parameters of thetool/workpiece material couple are identified by a testpart. The prediction of the tool deflections requirescontrolling the tool immersion angle for each angularposition of the tool. The deflections can be significant.An original procedure which is based on an engagementcards avoids an iterative calculation of the radialengagement. The experimental checking of the methodof prediction is presented in a test

Deviation of a machined surface in flank milling

International audienceThe flatness defects observed in flank milling with cutters of long series are mainly due to the tool deflections during the machining process. This article present the results of an identification procedure of the coefficients of a force model for a given tool workpiece couple for the prediction of the defects of the tool during the cutting. The calibration method proposed meets a double aim: to define an experimental protocol that takes the industrial constraints of time and cost into account and to work out a protocol which minimizes uncertainties likely to alter the interpretation of the results (environmental, software or mechanical uncertainties). For that, the procedure envisages the machining of a simple plane starting from a raw part formed by a tilted plane, allowing for the variation of the tool engagement conditions. The tool deviation during the cutting process is indirectly identified by measuring the machined surface. The observed straightness defect conditions can be explained by the evolution of the cutting pressures applied to the cutting edges in catch during the cutter rotation. The precision was considerably improved by the taking into account of the cutter slope defect in the calculation of the load applied to the tool. After identification of the tool-workpiece couple, the prediction model was applied to some examples and allowed to determine the variations of form and position of the surface points with a margin of 5%

Contribution to the generation of tool paths in a cam system

The flank milling of complex forms is a very effective process from the point of view of productivity and surface quality. Many works deal with research on the optimal positioning of the tool which is considered as a rigid body in order to minimize tool path errors. The purpose of our work is to integrate the compensation of the tool distortions in this optimal positioning calculation. In flank milling with long tools, the distortion of the cutter generates a significant wave (that can reach 0,6mm) on the machined surface due to the effects of the helical angle and the radial force which varies during the cutter rotation. After detailing an analysis of the force evolution and the associated model calculation, we will present a test protocol, that can be implemented in industry, in order to characterize the model parameters as a function of the couple tool-workpiece material. Then we will present a test to assess our prediction model of the straightness defects of the machined surface according to all machining parameters. These results make it possible to make up for defects by applying a translation to the tool in 3-axis and by applying a translation combined with a rotation in 5-axis milling

Simulation temporelle du fraisage de parois minces

Colloque avec actes et comité de lecture. Internationale.International audienceQuel que soit le secteur industriel concerné, la réduction de masse est un objectif récurrent dont la première conséquence est l'augmentation des parties à faibles épaisseurs sur les pièces à fabriquer. L'usinage de ces parois minces engendre fréquemment des problèmes vibratoires qui doivent être anticipés notamment à partir de simulations visant à prédire l'état des surfaces usinées. Cet article revient sur la simulation temporelle de l'usinage de parois minces et souligne que ce type de simulation est long et délicat à mettre en œuvre et à analyser. Une méthode permettant d'accélérer l'analyse et la prise de décision par l'orientation des calculs est proposée. Cette méthode est basée sur la recherche du régime stationnaire effectif. Initialisée à partir de ce régime, la simulation converge plus rapidement et conduit à l'état de la surface usinée. En confrontant les résultats obtenus par simulation à ceux obtenus expérimentalement, l'apport de cette méthode est prouvé

Prise en compte des déformations d'un outil dans le calcul des trajectoires d'usinage en fraisage de profil

CACHAN-ENS (940162301) / SudocSudocFranceF

Proposition d'une démarche pour identifier les efforts de coupe en présence de talonnage

Le talonnage d'un outil lors de l'usinage fait amortir les vibrations générées et impacte la stabilité du processus d'usinage. Alors, il faut prendre en compte ce phénomène lors de la simulation d'usinage. Ce travail de thèse présente une méthode pour l'identification, la modélisation, et la simulation numérique de talonnage d'un outil lors de l'usinage. La modélisation du talonnage est basée sur l'approche classique du calcul du volume de l'interférence entre la face de dépouille et la surface usinée de la pièce. Un dispositif spécifique a été conçu qui peut créer les conditions nécessaires pour générer l'interférence entre la face de dépouille de l'outil et la surface générée de la pièce. Les modèles géométriques de la pièce et l'outil sont représentés par les z-buffers qui permettent de déduire numériquement le volume de l'interférence en fonction des positions relatives de z-buffers à chaque instant. Les coefficients des efforts de coupe liés au talonnage sont estimés à partir de la méthode de la minimisation d'une erreur des efforts de coupe mesurés et les efforts de coupe simulés.The process damping results from the interference between tool clearance face and the workpiece generated surface and affects the stability of a machining process. Therefore it is necessary to take this phenomenon into consideration during the simulation of machining process. This thesis work presents a practical method for identification, modelling, and numerical simulation of process damping during machining of a workpiece. A special fixture has been used which creates the vibrations conditions necessary to generate the interference between tool clearance face and the specifically designed workpiece. The modelling of process damping is based on the numerical calculation of the interference volume between tool clearance face and the workpiece generated surface. The tool and workpiece geometries are represented by z-buffers whose relative positions at each instant permit to evaluate numerically the interference volume. The process damping coefficients are then estimated by minimization of the error between measured cutting force and the simulated cutting forces.PARIS-Arts et Métiers (751132303) / SudocSudocFranceF