Toolpaths Programming in an Intelligent Step-NC Manufacturing Context

The current language for CNC programming is G-code which dates from the beginning of the eighties with the norm ISO 6983. With the new technologies, G-code becomes obsolete. It presents drawbacks that create a rupture in the numerical chain at the manufacturing step. A new standard, STEP-NC, aims to overtake these lacks. A STEP-NC file includes all the information for manufacturing, as geometry description of the entities, workplan, machining strategies, tools, etc. For rough pocket milling, the ISO norms propose different kind of classical strategies as bidirectional, parallel or spiral contour, etc. This paper describes a new way of toolpath programming by the repetition of a pattern all along a guide curve. It presents several advantages as building fastness and easiness. The integration of pattern strategies in STEP-NC standard is an other step for the development of these strategies but also for the enrichment of STEP-NC possibilities. A complete STEP-NC numerical chain was built, integrating these pattern strategies. The implementation of this approach of building pattern strategies was made by the development of tools for the complete manufacturing cycle, from the CAD file to the machined part. Several application cases were experimented on machine tool to validate this approach and the efficiency of the developped tools

Manufacturing complexity evaluation at the design stage for both machining and layered manufacturing

International audienceIn this paper, a methodology to estimate manufacturing complexity for both machining and layered manufacturing is proposed in order to realize tools (dies or molds) by a combination of a subtractive and an additive process. Manufacturability indexes are calculated at the tool design stage, these indexes provide an accurate view of which areas of the tool will advantageously be machined or manufactured by an additive process. In this case, tools are not seen as single pieces but as 3-D puzzles with modules, manufactured aside by the best process and further assembled

TOOLPATHS PROGRAMMING IN AN INTELLIGENT STEP-NC MANUFACTURING CONTEXT

International audienceThe current language for CNC programming is G-code which dates from the beginning of the eighties with the norm ISO 6983. With the new technologies, G-code becomes obsolete. It presents drawbacks that create a rupture in the numerical chain at the manufacturing step. A new standard, STEP-NC, aims to overtake these lacks. A STEP-NC file includes all the information for manufacturing, as geometry description of the entities, workplan, machining strategies, tools, etc. For rough pocket milling, the ISO norms propose different kind of classical strategies as bidirectional, parallel or spiral contour, etc. This paper describes a new way of toolpath programming by the repetition of a pattern all along a guide curve. It presents several advantages as building fastness and easiness. The integration of pattern strategies in STEP-NC standard is an other step for the development of these strategies but also for the enrichment of STEP-NC possibilities. A complete STEP-NC numerical chain was built, integrating these pattern strategies. The implementation of this approach of building pattern strategies was made by the development of tools for the complete manufacturing cycle, from the CAD file to the machined part. Several application cases were experimented on machine tool to validate this approach and the efficiency of the developped tools

UNE PLATE-FORME STEP-NC POUR LA PROGRAMMATION AVANCEE ET INTELLIGENTE DES MACHINES OUTILS

National audienceLa programmation actuelle des machines outils à commandes numériques s'appuie sur le standard ISO 6983, ou code G, dont les principes datent du début des années 60. Ce standard désuet ne satisfait plus les attentes actuelles de la programmation de machines toujours plus évoluées et complexes. Le standard STEP-NC offre de nouvelles solutions et l'intégration de la fabrication au sein de la chaîne numérique complète. Ce papier expose les choix et la situation des travaux de l'IRCCyN dans ce domaine prometteur. Une plateforme interprétée STEP-NC a été développée pour pouvoir permettre des démonstrations de l'usinage STEP-NC sur machines outils actuelles. C'est aussi un outil de base pour les futurs travaux et implémentations liés au standard STEP-NC, en particulier en termes de simulation et d'optimisation de l'usinage, des parcours outils et des paramètres opératoires. Cette plateforme ouvre également la voie de travaux sur le concept de supervision multiprocess rendu possible par l'utilisation de la programmation de haut niveau orientée objet du standard STEP-NC

Technological form defects identification using discrete cosine transform method

12 pagesAbstract Manufacturers need precise tools to simulate, validate, or improve a process plan for given tolerances. Some simulation methods calculating position and orientation defect of manufactured surfaces have already been developed. A lack in these methods is the integration of form defect of surfaces. Indeed, many methods do not study manufactured surfaces, but nominal models associated to these surfaces. The method developed in this article proposes a tool describing precisely form error in order to take it into account. The work is based on a method of the literature, using discrete cosine transformation, completed by a method for identification of classical defects composing global form error and quantification of their contribution to this defect. The method is validated on simulation examples and then applied on a milled plane

A new versatile in-process monitoring system for milling

International audienceTool condition monitoring (TCM) systems can improve productivity and ensure workpiece quality, yet, there is a lack of reliable TCM solutions for small-batch or one-off manufacturing of industrial parts. TCM methods which include the characteristics of the cut seem to be particularly suitable for these demanding applications. In the first section of this paper, three process-based indicators have been retrieved from literature dealing with TCM. They are analysed using a cutting force model and experiments are carried out in industrial conditions. Specific transient cuttings encountered during the machining of the test part reveal the indicators to be unreliable. Consequently, in the second section, a versatile in-process monitoring method is suggested. Based on experiments carried out under a range of different cutting conditions, an adequate indicator is proposed: the relative radial eccentricity of the cutters is estimated at each instant and characterizes the tool state. It is then compared with the previous tool state in order to detect cutter breakage or chipping. Lastly, the new approach is shown to be reliable when implemented during the machining of the test part

Angular approach combined to mechanical model for tool breakage detection by eddy current sensors

International audienceThe paper presents a new complete approach for Tool Condition Monitoring (TCM) in milling. The aim is the early detection of small damages so that catastrophic tool failures are prevented. A versatile in-process monitoring system is introduced for reliability concerns. The tool condition is determined by estimates of the radial eccentricity of the teeth. An adequate criterion is proposed combining mechanical model of milling and angular approach. Then, a new solution is proposed for the estimate of cutting force using eddy current sensors implemented close to spindle nose. Signals are analysed in the angular domain, notably by synchronous averaging technique. Phase shifts induced by changes of machining direction are compensated. Results are compared with cutting forces measured with a dynamometer table. The proposed method is implemented in an industrial case of pocket machining operation. One of the cutting edges has been slightly damaged during the machining, as shown by a direct measurement of the tool. A control chart is established with the estimates of cutter eccentricity obtained during the machining from the eddy current sensors signals. Efficiency and reliability of the method is demonstrated by a successful detection of the damage

Environmental Impact Assessment Studies in Additive Manufacturing

International audienceThis chapter focuses on the environmental studies in additive manufacturing. For a cleaner production, environmental impacts that occur during the manufacturing phase should be assessed with accuracy. First, the literature on all the studies led to the characterization of the environmental impact of additive manufacturing processes. The studies on electric energy consumption of these processes are analyzed here, and then some studies taking into account raw material and all the flows through the process are detailed. Secondly, a new methodology in order to evaluate, with accuracy, the environmental impact of a part from its CAD model is presented. In this methodology, the work is not focused only on electrical consumption but also on fluids and material consumption which also contribute to the environmental impact. In addition, the inputs of this methodology correspond to the set part process, which allows taking into account different manufacturing strategies and their influences on the global environmental impact. The methodology developed is based on both analytic models (validated by experiments) and experimental models. And finally, an industrial example shows that for some manufacturing strategies, the environmental impact due to electrical consumption is not the predominant one. In this case study, material consumption has an important impact and has to be taken into consideration for a complete environmental impact assessment

Environmental performance modeling for additive manufacturing processes

International audienceSustainability means considering economic, social and environmental aspects. In the mechanical product design field, sustainability means thinking about eco-design and life cycle analysis, when the whole life cycle of the product (from raw material extraction to end of life) is concerned with environmental impacts. Nowadays, most of the manufacturing methods are driven only by money, and the environmental and social aspects are not taken into account. The goal of this paper is to propose an environmental assessment methodology of the manufacturing processes. In this methodology, all flows consumed and produced (material, fluids, electricity) are considered. A predictive model of flow consumption is defined from the CAD model of the product and the manufacturing program. The aim is to be able to minimize the environmental impacts of the manufacturing during the design stage. In this paper, the focus is put on additive manufacturing

Évaluation de la performance environnementale des procédés de fabrication

Le développement durable repose sur le couplage de trois piliers : économie / environnement / social. Pour la conception des produits manufacturés, la prise en compte de ces aspects se fait classiquement en utilisant le concept d’écoconception, basé sur l’étude du cycle de vie complet du produit (de l’extraction des matières premières à la fin de vie du produit). Cependant, les choix faits lors de la phase de fabrication sont encore majoritairement dirigés par un seul pilier : l’économie. Ainsi, les outils qui visent à optimiser la phase de fabrication sont dictés par une réduction des coûts, une diminution des délais de développement ou une amélioration de la qualité des produits, mais rarement par une maîtrise de l’impact environnemental. Il convient alors de s’interroger sur les moyens de prendre en compte les deux piliers environnement et social pour la phase de fabrication des produits mécaniques, ainsi que leurs couplages forts et nécessaires dans une démarche globale de développement durable. Cet article propose une méthodologie d’évaluation de la performance environnementale des procédés de fabrication. Il s’agit d’estimer quantitativement les consommations de matières, fluides et énergie lors de la fabrication de produits, afin de proposer un modèle prédictif des impacts environnementaux à partir de la définition numérique du produit, associée au programme de pilotage de la machine de production. L’objectif est de proposer des pistes de réduction des impacts environnementaux liés à la phase de fabrication dès la conception du produit ou lors de la génération du programme de fabrication. Dans cet article, la méthodologie est appliquée à la fabrication additive