Analysis and design of rapid prototyped mechanisms using hybrid flexural pivots

The ability of fabricating flexure based mechanism is of great importance in modern technology fields such as nanotechnology and precision engineering. For an instance, a great number of nanopositioning systems are made out of flexures. Examples of these systems are those used in scanning probe microscopy and many other types of metrology tools. Not having friction is a requirement to achieve nanometer scale motion and thus flexural systems are preferred as they lack of sliding surfaces. Moreover, flexure hinges are able to produce accurate and repeatable motion when properly designed. Conventionally, flexure-type systems are manufactured from high performance metals such as stainless and alloyed steel or aluminum alloys for high material performance and durability. Functional requirements such as high bandwidth, accuracy performance and geometric complexity require them to be manufactured as monolithic structures using conventional precision machining and electro discharge machining (EDM). However, such an approach is expensive and not practical for mass production. They can only be used for custom and high-value added applications. Conventional and emerging additive manufacturing technologies such as Direct Metal Laser Sintering (DMLS) offer an opportunity to fabricate cost effective flexure-based mechanisms with complicated spatial structures. However, the reported limitations of this approach are: dimensional accuracy, low quality surface finish, anisotropic properties, thermal instability, low holding force capabilities and severely reduced durability of the flexural elements as most rapid prototyping materials are unsuitable in fatigue loading conditions. This thesis work envisions an approach to manufacture hybrid mechanisms that uses i) economic methods like casting and molding (for high volume production) or 3-D printing (for custom, one-off systems) for manufacturing the mechanism structures/skeletons and ii) inserts of simple geometry with specialized materials (e.g. spring steel, etc.) to get the right material properties where need it. The objective of this research is to develop and exemplify a methodology that integrates a host material (rapid prototyping) with a flexure material and combines them to create a much more easy to produce mechanism. For this purpose, we focus on the design of the interfaces between the two materials and, particularly, the penetration depth of the insert into the host. Using Finite Element simplified model and tracking mechanical variables such as stress, pressure and elastic energy we arrived to the functions relating the optimum penetration depth (insertion iii distance where the elastic work done by the host material is minimum relative to that one done by the flexure) with the thickness of the flexure and the elastic properties of the two materials. For example, in the case of an aluminum host and steel inserts; the optimum penetration distance is six times the thickness of the insert whereas in the case of an ABS structure and steel inserts, the optimum penetration distance is ten times greater than the insert thickness. Further results include the study of extra compliance introduced to the system in design scenarios considering materials and manufacturing consideration for the fabrication, alignment and assembly of the mechanism. Finally, we demonstrate a piezoelectric-actuated four-bar mechanism, and an XYZ force sensor for suture training as general applications of these devices to the precision motion field and the medical industry. The methodology implemented in this work poses a simple and affordable way to fabricate, assemble and customize low-cost devices for precision motion application and it applies to both, systems fabricated by polymer and metal rapid prototyping technologies

21st century manufacturing machines: Design, fabrication and controls

Advances in nanotechnology, microfabrication and new manufacturing processes, the revolution of open electronics, and the emerging internet of things will influence the design, manufacture, and control of manufacturing machines in the future. For instance, miniaturization will change manufacturing processes; additive and rapid prototyping will change the production of machine components; and open electronics offer a platform for new control architectures for manufacturing systems that are open, modular, and easy to reconfigure. Combined with the latest trends in cyber-physical systems and the internet of things, open architecture controllers for CNC systems can become platforms, oriented for numerical control as a service (NCaaS) and manufacturing as a service, tailored to the creation of cyber-manufacturing networks of shared resources and web applications. With this potential in mind, this research presents new design-for-fabrication methodologies and control strategies to facilitate the creation of next generation machine tools. It provides a discussion and examples of the opportunities that the present moment offers. The first portion of this dissertation focuses on the design of complex 3D MEMS machines realized from conventional 2.5D microfabrication processes. It presents an analysis of an example XYZ-MEMS parallel kinematics stage as well as of designs of the individual components of the manipulator, integrated into a design approach for PK-XYZ-MEMS stages. It seems likely that this design-for-fabrication methodology will enable higher functionality in MEMS micromachines and result in new devices that interact, in three full dimensions, with their surroundings. Novel and innovative research exemplifies the opportunities new and economical manufacturing technologies offer for the design and fabrication of modern machine tools. The second portion of this dissertation describes the demonstration of a new flexural joint designed with both traditional and additive manufacturing processes. It extrapolates principles based on the design of this joint that alleviate the effects of low accuracy and poor surface finishing, anisotropy, reductions in material properties of components, and small holding forces. Based on these results, the next section presents case examples of the construction of mesoscale devices and machine components using multilayered composites and hybrid flexures for precision engineering, medical training, and machine tools for reduced life applications and tests design-for-fabrication strategies. The results suggest the strategies effectively address existing problems, providing a repertory of creative solutions applicable to the design of devices with hybrid flexures. The implications for medical industry, micro robotics, soft robotics, flexible electronics, and metrology systems are positive. Chapter number five examines to positive impact of open architectures of control for CNC systems, given the current availability of micro-processing power and open-source electronics. It presents a new modular architecture controller based on open-source electronics. This component-based approach offers the possibility of adding micro-processing units and an axis of motion without modification of the control programs. This kind of software and hardware modularity is important for the reconfiguration of new manufacturing units. The flexibility of this architecture makes it a convenient testbed for the implementation of new control algorithms on different electromechanical systems. This research provides general purpose, open architecture for the design of a CNC system based on open electronics and detailed information to experiment with these platforms. This dissertation’s final chapter describes how applying the latest trends to the classical concepts of modular and open architecture controllers for CNC systems results in a control platform, oriented for numerical control as a service (NCaaS) and manufacturing as a service (MaaS), tailored to the creation of cyber-manufacturing networks of shared resources and web applications. Based on this technology, this chapter introduces new manufacturing network for numerical control (NC) infrastructure, provisioned and managed over the internet. The proposed network architecture has a hardware, a virtualization, an operating system, and a network layer. With a new operating system necessary to service and virtualize manufacturing resources, and a micro service architecture of manufacturing nodes and assets, this network is a new paradigm in cloud manufacturing

Journal Article on Computational Geometry Application in Parametric Modeling

El modelado digital de representaciones humanas es un tópico con un interés creciente en las comunidades académica e industrial. La posibilidad de obtener una aproximación 3D económica de cualquier humano es útil en aplicaciones como la sastrería virtual, simulación de vestimentas, modelado de los movimientos humanos, creación de avatares, etc. Por lo tanto, existe un interés particular en encontrar métodos que obtengan dichos maniquís con la mínima información e interacción humana posible.Digital modeling of human representations or mannequins is a topic with an ever-increasing interest in research and industrial communities. The possibility to obtain a 3D model approximation of any human in a cost-effective manner presents benefits for applications such as virtual tailoring, garment fitting simulation, human motion modeling, avatar creation, etc. Therefore, special interest is placed on finding methods to obtain such mannequins with minimal information and human interaction