Method of determining the process applied for feature machining : experimental validation of a slot

In this paper, we will be evaluating the "manufacturability" levels for several machining processes of "slot" feature. Using the STEP standard, we will identify the slot feature characteristics. Then, using the ascendant generation of process method, we will define the associated milling process. The expertise is based on a methodology relative to the experience plans carried out during the formalization and systematic evaluation of the machining process associated with the feature

Virtual manufacturing: prediction of work piece geometric quality by considering machine and set-up

Lien vers la version éditeur: http://www.tandfonline.com/doi/full/10.1080/0951192X.2011.569952#.U4yZIHeqP3UIn the context of concurrent engineering, the design of the parts, the production planning and the manufacturing facility must be considered simultaneously. The design and development cycle can thus be reduced as manufacturing constraints are taken into account as early as possible. Thus, the design phase takes into account the manufacturing constraints as the customer requirements; more these constraints must not restrict the creativity of design. Also to facilitate the choice of the most suitable system for a specific process, Virtual Manufacturing is supplemented with developments of numerical computations (Altintas et al. 2005, Bianchi et al. 1996) in order to compare at low cost several solutions developed with several hypothesis without manufacturing of prototypes. In this context, the authors want to predict the work piece geometric more accurately by considering machine defects and work piece set-up, through the use of process simulation. A particular case study based on a 3 axis milling machine will be used here to illustrate the authors’ point of view. This study focuses on the following geometric defects: machine geometric errors, work piece positioning errors due to fixture system and part accuracy

Method of determining the process applied for feature machining : experimental validation of a slot

In this paper, we will be evaluating the "manufacturability" levels for several machining processes of "slot" feature. Using the STEP standard, we will identify the slot feature characteristics. Then, using the ascendant generation of process method, we will define the associated milling process. The expertise is based on a methodology relative to the experience plans carried out during the formalization and systematic evaluation of the machining process associated with the feature

Study of burr formation and phase transformation during micro-milling of NiTi alloys

Micro-milling can be defined as milling with end mills smaller than 1 mm of diameter. The top-down approach from milling to micro-milling is often used to define cutting conditions. Unfortunately geometries either for the active part or the overall shape are quite different from conventional tools, leading to inexistent problems at the macro-scale, such as a larger cutting edge radius to uncut chip thickness ratio leading to ploughing effect. Moreover, micro-milling can be used on particular material such as shape memory alloys in biomedical domain which are difficult to machine. This study focuses on burr formation during shoulder milling for two biocompatible NiTi alloys: a martensitic NiTi (shape memory effect) and an austenitic one (pseudo-elasticity effect). Design of experiment is used to highlight the influence of various parameters (cutting parameters and material phases) on the burr formation in micro-milling NiTi alloys. Burrs were observed and measured using confocal, optical and electronic microscopy and tend to be as large as shoulders dimensions. Material phase transformation was also examined. Analysis of variance emphasizes that the larger the feed per tooth and the smaller the width of cut are, the smaller the top burr is. Cutting strategy leads to different burr shape: up-milling burrs have a large curvature, whereas down-milling burrs are slightly bent. An affected layer of about 10 μm has been observed for the austenitic NiTi. The proposed experimental approach give the opportunity to study burr formation in micro-milling, the machinability of alloys or superelastic NiTi shape memory and a qualitative explanation of burr formation has been developed

Study of burr formation and phase transformation during micro-milling of NiTi alloys

Micro-milling can be defined as milling with end mills smaller than 1 mm of diameter. The top-down approach from milling to micro-milling is often used to define cutting conditions. Unfortunately geometries either for the active part or the overall shape are quite different from conventional tools, leading to inexistent problems at the macro-scale, such as a larger cutting edge radius to uncut chip thickness ratio leading to ploughing effect. Moreover, micro-milling can be used on particular material such as shape memory alloys in biomedical domain which are difficult to machine. This study focuses on burr formation during shoulder milling for two biocompatible NiTi alloys: a martensitic NiTi (shape memory effect) and an austenitic one (pseudo-elasticity effect). Design of experiment is used to highlight the influence of various parameters (cutting parameters and material phases) on the burr formation in micro-milling NiTi alloys. Burrs were observed and measured using confocal, optical and electronic microscopy and tend to be as large as shoulders dimensions. Material phase transformation was also examined. Analysis of variance emphasizes that the larger the feed per tooth and the smaller the width of cut are, the smaller the top burr is. Cutting strategy leads to different burr shape: up-milling burrs have a large curvature, whereas down-milling burrs are slightly bent. An affected layer of about 10 μm has been observed for the austenitic NiTi. The proposed experimental approach give the opportunity to study burr formation in micro-milling, the machinability of alloys or superelastic NiTi shape memory and a qualitative explanation of burr formation has been developed

Virtual manufacturing: prediction of work piece geometric quality by considering machine and set-up

Lien vers la version éditeur: http://www.tandfonline.com/doi/full/10.1080/0951192X.2011.569952#.U4yZIHeqP3UIn the context of concurrent engineering, the design of the parts, the production planning and the manufacturing facility must be considered simultaneously. The design and development cycle can thus be reduced as manufacturing constraints are taken into account as early as possible. Thus, the design phase takes into account the manufacturing constraints as the customer requirements; more these constraints must not restrict the creativity of design. Also to facilitate the choice of the most suitable system for a specific process, Virtual Manufacturing is supplemented with developments of numerical computations (Altintas et al. 2005, Bianchi et al. 1996) in order to compare at low cost several solutions developed with several hypothesis without manufacturing of prototypes. In this context, the authors want to predict the work piece geometric more accurately by considering machine defects and work piece set-up, through the use of process simulation. A particular case study based on a 3 axis milling machine will be used here to illustrate the authors’ point of view. This study focuses on the following geometric defects: machine geometric errors, work piece positioning errors due to fixture system and part accuracy

Micro-end milling of NiTi biomedical alloys, burr formation and phase transformation

This paper focuses on burr formation in micro-end milling of two Nickel-Titanium shape memory alloys (SMA), an austenitic and a martensitic NiTi. Phase transformation during machining was also examined. The experimental design approach was used to study the effect of cutting parameters on burr formation. The studied parameters were cutting speed, feed per tooth, depth and width of cut, 20 machining strategy and initial material phase of the NiTi alloy. Different types of burrs were formed during micro-end milling of NiTi alloys; it was observed that top burrs are the most important. The height of top burrs can reach values close to those of the depth of cut. Burrs were observed and characterized using a Scanning Electron Microscope (SEM), confocal and optical microscopes. The affected layer under the machined surface, and phase transformation 25 were investigated by using SEM. The results of the analysis of variance showed a significant formation of burrs, deeply influenced by the feed per tooth and width of cut. An increase in the feed per tooth and a decrease of width of cut tend to decrease the height and width of the top burr. In a thin layer under the machined surface, phase transformation was observed for the martensitic NiTi

Stress and heat flux distribution in rake face. Analytical and experimental approaches

International audienceMetallurgical solutions for an improvement in machinability currently use nonmetallic inclusions in order to create solid lubricants at the interfaces between tool and workmaterial. It is possible to identify and quantify these layers afterwards. However it is important to know the conditions for which these layers appear: tribological conditions, kinematical conditions (i.e. cutting speed, feed and depth of cut) and thermomechanical conditions (stress and temperature distribution in the interfaces). We focus on the tool / chip interface and more precisely on the thermomechanical conditions. This contribution is concerned with both the analytical modeling and measurement of the temperature distribution in the chip forming zone. We propose a correlation between theoretical and experimental values

Caractérisation des bavures lors du micro-fraisage d'alliages de Nickel-Titane

Le micro-fraisage est souvent défini comme une homothétie du fraisage conventionnel à des outils dont le diamètre n’excède pas 1 mm. Or, les géométries de l’outil que ce soit pour la partie active ou la forme globale sont très différentes des outils plus conventionnels, soulevant des problématiques propres à l’échelle d’étude. A ceci s’ajoute le fait que le micro-fraisage peut s’appliquer à des matériaux qualifiés d’exotiques comme les alliages à mémoire de forme ou superélastiques dans le domaine du biomédical. L’étude proposée porte sur la formation de bavures lors du fraisage d’épaulement pour deux alliages Nickel-Titane (NiTi) biocompatibles. L’approche par plan d’expériences a été utilisée pour cette étude, elle a permis de mettre en évidence l’influence de différents paramètres sur la formation de bavure lors du micro-fraisage d’alliages de NiTi. Ces paramètres concernent les conditions de coupe (la vitesse de coupe, l’avance par dent, l’engagement axial, l’engagement radial, la stratégie d’usinage) ainsi que l’état métallurgique de l’alliage NiTi (martensitique ou austénitique). Les bavures ont été observées et caractérisées géométriquement (hauteur, largeur et épaisseur) à partir d’images obtenues au MEB, aux microscopes confocal et optique. Les résultats issus de l’analyse de la variance montrent que la formation de bavures est largement influencée par l’avance à la dent et par l’engagement radial. Il est à noter que les dimensions des bavures sont de l’ordre de l’engagement de l’outil dans la matière et qu’il est souhaitable de les réduire. Une augmentation de l‘avance par dent et une diminution de l’engagement radial permettent de diminuer significativement la hauteur et la largeur des bavures. L’approche expérimentale proposée a permis d’examiner la formation de bavures en micro-fraisage et d’analyser les paramètres influents; elle a permis, de plus, d’étudier l’usinabilité des alliages de Nickel-Titane biocompatibles au comportement particulier, superélastique ou à mémoire de forme

Study of elementary micro-cutting in hardened tool steel

In order to model micro-milling cutting forces, a way is to apply a local model on discretized elements of the cutting edge and then summing on the whole edge to obtain the global cutting forces. This local model is usually obtained by numerical simulation or cutting experimentation. This paper focuses on orthogonal and oblique micro-cutting experiments of AISI 6F7 with tungsten carbide tools. Results show the influence of cutting edge sharpness on cutting forces and the existence of different mechanisms corresponding to different ranges of uncut chip thickness values. A phenomenological model has been identified to model correctly these zones. Then, by comparing experimental micro-milling forces with those deduced from these micro-cutting model and tests, a good agreement has been found. In order to complete this study, phenomenological and thermo mechanical models are being developed. The aim is to obtain an elementary cutting model that can be used for micro-milling simulation and optimization