The prevalence of digital manufacturing in creating increasingly complex products with small batch sizes, requires effective methods for production process planning. Toolpath generation is one of the challenges for manufacturing technologies that function based on the controlled movement of an end effector against a workpiece. The current approaches for determining suitable tool paths are highly dependent on machine structure, manufacturing technology and product geometry. This dependence can be very expensive in a volatile production environment where the products and the resources change quickly. In this research, a novel approach for the flexible generation of toolpaths using a mathematical formulation of the desired objective is proposed. The approach, based on optimisation techniques, is developed by discretising the product space into a number of grid points and determining the optimal sequence of the tool tip visiting these points. To demonstrate the effectiveness of the approach, the context of milling machining has been chosen and a genetic algorithm has been developed to solve the optimisation problem. The results show that with meta-heuristic methods, flexible tool paths can indeed be generated for industrially relevant parts using existing computational power. Future computing platforms, including quantum computers, could extend the applicability of the proposed approach to much more complex domains for instantaneous optimisation of the detailed manufacturing process plan.

Une prothèse de genou est généralement, composée de deux parties fixées respectivement sur le fémur et sur le tibia et d’une troisième, dite intercalaire. Durant le processus de fabrication de ces composants des déformations apparaissent au niveau des bruts de fonderie. Les fabricants de prothèses choisissent d’assurer l’épaisseur nominale de la prothèse en enlevant une épaisseur constante sur le brut de fonderie. Cette opération est généralement réalisée manuellement. L’objectif de ces travaux de thèse est de contribuer à l’automatisation de ces opérations en proposant une méthode d’adaptation des trajectoires d’usinage aux variations géométriques de la surface cible. L’objectif de ce travail de recherche est d’adapter une trajectoire d’usinage sur un modèle nominal pour enlever une épaisseur constante sur une surface brute de fonderie mesurée. La méthode proposée commence par une étape d’alignement de la surface mesurée sur la trajectoire nominale en utilisant un algorithme d’ICP. Par la suite, la trajectoire nominale est déformée pour venir enlever l'épaisseur désirée sur la surface brute mesurée. Cette dernière est définie, dans ces travaux, suivant un modèle STL. Naturellement, les discontinuités de ce type de modèle induit une impression des motifs du STL sur la trajectoire adaptée et, donc, sur la pièce usinée. Par la suite, afin de d’atténuer ce problème et d’améliorer la qualité de fabrication, il est proposé de procéder à un lissage de la trajectoire.Afin de valider les développements théoriques de ces travaux, des essais ont été réalisés sur une machine cinq axes pour l’ébauche de composants fémoraux d’une prothèse uni-compartimentale de genou. / Commonly, knee prostheses are composed of two parts fixed respectively on femur and tibia, and a third one called intercalary. During the manufacturing process, of these components distortions appear on roughcast workpiece geometry. Thus, prosthesis manufacturers choose to ensure the nominal thickness of the prosthesis by removing a constant thickness on the roughcast workpiece. This operation is generally carried out realized manually.The aim of this thesis is to contribute to the automation of these manual operations by providing a method to adapt the machining toolpaths at geometrical variations of the target surface. The aim of this research work is to adapt a machining toolpath computed on a nominal model to remove a constant thickness on a roughcast measured surface. The proposed method starts with an alignment step of the measured surface on the nominal toolpath using an ICP algorithm. Subsequently, the nominal toolpath is deformed to remove the desired thickness of the measured rough surface defined in presented case by a STL model. Naturally, discontinuities of this type of model induce the apparition of pattern for the STL on the adapted toolpath and thus on the machined workpiece. Subsequently, to limit this problem and to improve the quality of realized surface, it is proposed a toolpath smoothing method. To validate theoretical developments of this work, tests were carried out on a five-axis machine for roughing of femoral components of a unicompartmental knee prosthesis.

In this thesis, an actuation system is developed for a Two-Axis Gyroscopic (TAG) adapter. This adapter is a fixture with two auxiliary axes which is used for the Single Point Incremental Forming (SPIF) technique to enhance a three-axis mill to have five-axis capabilities. With five-axis mill capabilities, variable angles between line segments of the toolpath and the tool can be obtained. To achieve specialized angles between a line segment and the SPIF tool, the sheet is rotated. Inverse kinematic equations for the TAG adapter are derived to calculate the required rotations for the TAG adapter’s auxiliary axes for a line segment of a toolpath. If the next line segment requires a different orientation of the sheet, the sheet is rotated while the tool follows the rotation of the sheet to maintain its position at the connecting point of the line segments of the toolpath. Five equations of motions are derived to calculate the three translations of the mill and two rotations of the TAG adapter’s frames, during forming. A toolpath execution algorithm is implemented in MATLAB which uses the five equations of motion to execute a toolpath. The algorithm generates an array of data points that can be used by a Computer Numerically Controlled (CNC) machine to follow a desired path. A visual representation for the execution of the toolapth is implemented in MATLAB and is used to illustrate the successful completion of a toolpath. A computer controlled motor system is selected and tested in this thesis which will ultimately be integrated with a worm gear system and a CNC machine to develop a full CNC actuation system. / UOIT

Planning of optimal toolpath, cutter orientation, and feed rate for 5-axis Computer Numerical Control (CNC) machining of curved surfaces using a flat-end mill is a challenging task, although the approach has a great potential for much improved machining efficiency and surface quality of the finished part. This research combines and introduces several key enabling techniques for curved surface machining using 5-axis milling and a flat end cutter to achieve maximum machining efficiency and best surface quality, and to overcome some of the key drawbacks of 5-axis milling machine and flat end cutter use. First, this work proposes an optimal toolpath generation method by machining the curved surface patch-by-patch, considering surface normal variations using a fuzzy clustering technique. This method allows faster CNC machining with reduced slow angular motion of tool rotational axes and reduces sharp cutter orientation changes. The optimal number of surface patches or surface point clusters is determined by minimizing the two rotation motions and simplifying the toolpaths. Secondly, an optimal tool orientation generation method based on the combination of the surface normal method for convex curved surfaces and Euler-Meusnier Sphere (EMS) method for concave curved surfaces without surface gouge in machining has been introduced to achieve the maximum machining efficiency and surface quality. The surface normal based cutter orientation planning method is used to obtain the closest curvature match and longest cutting edge; and the EMS method is applied to obtain the closest curvature match and to avoid local gouging by matching the largest cutter Euler-Meusnier sphere with the smallest Euler-Meusnier sphere of the machined surface at each cutter contact (CC) point. For surfaces with saddle shapes, selection of one of these two tool orientation determination methods is based on the direction of the CNC toolpath relative to the change of surface curvature. A Non-uniform rational basis spline (NURBS) surface with concave, convex, and saddle features is used to demonstrate these newly introduced methods. Thirdly, the tool based and the Tri-dexel workpiece based methods of chip volume and cutting force predictions for flat-end mills in 5-axis CNC machining have been explored for feed rate optimization to achieve the maximum material removal rate. A new approach called local parallel slice method which extends the Alpha Shape method - only for chip geometry and removal volume prediction has been introduced to predict instant cutting forces for dynamic feed rate optimization. The Tri-dexel workpiece model is created to get undeformed chip geometry, chip volume, and cutting forces by determining the intersections of the tool envelope and continuously updating the workpiece during machining. The comparison of these two approaches is made and several machining experiments are conducted to verify the simulation results. At last, the chip ploughing effects that become a more serious problem in micro-machining due to chip thickness not always being larger than the tool edge radius are also considered. It is a challenging task to avoid ploughing effects in micro-milling. A new model of 3D chip geometry is thus developed to calculate chip thickness and ploughing volume in micro 5-axis flat-end milling by considering the minimum chip thickness effects. The research forms the foundation of optimal toolpath, cutter orientation, cutting forces/volume calculations, and ploughing effects in 5-axis CNC machining of curved surfaces using a flat-end mill for further research and direct manufacturing applications. / Graduate / 0548 / luoshan@uvic.ca

L’usinage 5 axes à grande vitesse est de plus en plus utilisé dans l’industrie pour réaliser des pièces de géométrie complexe à forte valeur ajoutée avec pour contrainte de respecter la qualité géométrique tout en maximisant la productivité. Dans ce contexte, la FAO et plus particulièrement la génération des trajectoires d’usinage jouent un rôle prépondérant. Ces travaux proposent de définir des trajectoires en fonction de la pièce à réaliser mais aussi de la structure poly articulée et de ses performances cinématiques. La grande diversité des structures en termes d’architecture et de cinématique impose une méthode de calcul générique facilitant la définition de trajectoires adaptées pour leur suivi. L’état de l’art des travaux réalisé dans les domaines de l’usinage et de la robotique pour répondre à cette problématique conduit à utiliser des polytopes de manipulabilité cinématique pour modéliser les contraintes cinématiques. L’analyse de ces polytopes et de la géométrie de la pièce à usiner permet de générer des trajectoires avec une vitesse outil/pièce maîtrisée et un temps de parcours réduit dans le cas de l’usinage 5 axes positionné et de l’usinage 5 axes continu. Ce formalisme met en avant les fortes dépendances entre les différents paramètres de la stratégie d’usinage (positionnement de la pièce, direction d’avance et orientation de l’outil) et permet de privilégier certaines combinaisons de ces paramètres pour maîtriser la vitesse d’exécution de la trajectoire. / 5 axes high speed milling is increasingly used for manufacturing high addedvalue parts with complex forms in order to respect surface quality while maximizing productivity. In this context, CAM and more specifically toolpath computations play a major part. This work proposes to define toolpath depending on the workpiece but also onkinematical capacities of the polyarticulated structure.The large variety of structure in terms of architecture and kinematic enforce a generic calculation method to simplify adaptative toolpath generation. A state of the art realized in machining and robotics proposes to investigate the use of kinematical manipulability polytopes to represent kinematical capacities. An analysis of the polytopes and of the workpiece allows to generate toolpaths with a controlled feedrate and a decreasing time in 5 axes positionned milling and in 5 axes continous milling. This formalism highlights strong interactions between milling strategy parameters (workpiece setup, feed direction, tool orientation) and allows to prioritize specific parameters mix to have a controlled execution feedrate.