Digitally interpreting traditional folk crafts

The cultural heritage preservation requires that objects persist throughout time to continue to communicate an intended meaning. The necessity of computer-based preservation and interpretation of traditional folk crafts is validated by the decreasing number of masters, fading technologies, and crafts losing economic ground. We present a long-term applied research project on the development of a mathematical basis, software tools, and technology for application of desktop or personal fabrication using compact, cheap, and environmentally friendly fabrication devices, including '3D printers', in traditional crafts. We illustrate the properties of this new modeling and fabrication system using several case studies involving the digital capture of traditional objects and craft patterns, which we also reuse in modern designs. The test application areas for the development are traditional crafts from different cultural backgrounds, namely Japanese lacquer ware and Norwegian carvings. Our project includes modeling existing artifacts, Web presentations of the models, automation of the models fabrication, and the experimental manufacturing of new designs and forms

Design and analysis of a reconfigurable discrete pin tooling system for molding of three-dimensional free-form objects

This paper presents the design and analysis of a new reconfigurable tooling for the fabrication of three-dimensional (3D) free-form objects. The proposed reconfigurable tooling system comprises a set of matrices of a closely stacked discrete elements (i.e., pins) arranged to form a cavity in which a free-form object can be molded. By reconfiguring the pins, a single tool can be used in the place of multiple tools to produce different parts with the involvement of much lesser time and cost. The structural behavior of a reconfigurable mold tool under process conditions of thermoplastic molding is studied using a finite element method (FEM) based methodology. Various factors that would affect the tool behavior are identified and their effects are analyzed to optimally design a reconfigurable mold tool for a given set of process conditions. A prototype, open reconfigurable mold tool is developed to present the feasibility of the proposed tooling system. Several case studies and sample parts are also presented in this paper

Design for Additive Manufacturing of Conformal Cooling Channels Using Thermal-Fluid Topology Optimization and Application in Injection Molds

Additive manufacturing allows the fabrication parts and tools of high complexity. This capability challenges traditional guidelines in the design of conformal cooling systems in heat exchangers, injection molds, and other parts and tools. Innovative design methods, such as network-based approaches, lattice structures, and structural topology optimization have been used to generate complex and highly efficient cooling systems; however, methods that incorporate coupled thermal and fluid analysis remain scarce. This paper introduces a coupled thermal-fluid topology optimization algorithm for the design of conformal cooling channels. With this method, the channel position problem is replaced to a material distribution problem. The material distribution directly depends on the effect of flow resistance, heat conduction, as well as forced and natural convection. The problem is formulated based on a coupling of Navier-Stokes equations and convection-diffusion equation. The problem is solved by gradient-based optimization after analytical sensitivity derived using the adjoint method. The algorithm leads a two -dimensional conceptual design having optimal heat transfer and balanced flow. The conceptual design is converted to three-dimensional channels and mapped to a morphological surface conformal to the injected part. The method is applied to design an optimal conformal cooling for a real three dimensional injection mold. The feasibility of the final designs is verified through simulations. The final designs can be exported as both three-dimensional graphic and surface mesh CAD format, bringing the manufacture department the convenience to run the tool path for final fitting

Process planning for rapid manufacturing of plastic injection mold for short run production

This thesis presents a process planning methodology for a rapid injection mold tool manufacturing system that involves additive and subtractive techniques, whereby slabs are sequentially bonded and milled using layered tool paths. Mold tools are grown in a bottom up fashion, eliminating the need for multi-axis machining operations (beyond three axes) and allowing small features in deep cavities. In this research, a new layer bonding method using friction stir welding of aluminum plates is presented. In this manner, one can create seam-free laminated aluminum injection mold tooling using a unique combination of industrial adhesives and friction stir spot welding to initially secure the slab, then continuous friction stir welding of layer perimeters that are sequentially machined in a layer wise process. The original research is presented as a journal article. This research includes three areas of interest that will enable highly automated process planning. The first research area focuses on determining the process plan for applying adhesives on the laminated plates that will be sufficient to resist the forces acting on the plate due to subsequent friction stir spot welding. The use of fixtures and clamps for machining in rapid manufacturing create a potential problem for collision of the tool/spindle and the workpiece setup. Therefore, the process proposed in this thesis uses a combination of industrial adhesives and friction stir spot welding to secure the aluminum plates for machining. The second area focuses on determining the number, location and sequence of friction stir spot welds sufficient to secure the plate prior to continuous friction stir welding. The use of adhesive alone is assumed to be not sufficient to withstand the high forces involved in the friction stir welding process. Therefore, there is need to friction stir spot weld the plates to hold them against the previously formed stack. The location and the number depend on the geometry of that particular layer. The final research area focuses on creating a toolpath planning method for the friction stir welding and CNC machining of each laminated plate. The FSW toolpath is generated based on a predetermined offset distance from the boundary of the polygon representing each cross sectional slice of the mold, while the CNC machining uses a basic waterline toolpath strategy. The impact of this research is that it will provide a completely automated process planning approach for rapid tool manufacturing that is currently not possible using existing additive- or subtractive- only approaches

Simplified Production of Large Prototypes using Visible Slicing

Rapid Prototyping (RP) is a totally automatic generative manufacturing technique based on a “divide-and-conquer” strategy called ‘slicing’. Simple slicing used on 2.5-axis kinematics of the existing RP machines is responsible for the staircase error. Although thinner slices will have less error, the slice thickness has practical limits. Visible Slicing overcomes these limitations. A few visible slices exactly represent the object. Each visible slice can be realized using a 3- axis kinematics machine from two opposite directions. Visible slicing is implemented on Segmented Object Manufacturing (SOM) machine under development. SOM can produce soft large prototypes faster and cheaper with accuracy comparable to that of CNC machining.Mechanical Engineerin

Process planning for an Additive/Subtractive Rapid Pattern Manufacturing system

This dissertation presents a rapid manufacturing process for sand casting patterns using a hybrid additive/subtractive approach. This includes three major areas of research that will enable highly automated process planning; a critical need for a rapid methodology. The first research area yields a model for automatically determining the locations of layers, given the slab height, material types and part geometry. Layers are chosen such that it will avoid catastrophic failures and poor machining conditions in general. First, features that are possible thin material machining positions are defined, and methods for detecting these feature positions from an STL model are studied. Next, a layer thickness calculation model is presented according to positions of these features. The second area focuses on tools and parameters for the subtractive side of processing each layer. A tool size and machining parameter selection model is presented that can automatically select tool sizes and machining parameters, given layer thickness, part geometry, and material types. Machining strategies and related machining parameters are studied first. Then the method for Stepdown parameter calculation is presented. Finally, an algorithm based on both accessibility and machining efficiency is proposed for the selection of tool sizes for the rough cutting operation, finish cutting operation and optional semi-rough cutting operation. The final research area focuses on a cutting force analysis for thin material machining with additional layer thickness & tool size interaction. Popular cutting force models are reviewed, and a suitable model for cutting force calculation in this process is evaluated. Then, a cantilever beam model is used to analyze the thin material machining failure problem, and a minimum layer thickness model is presented. Third, a combined layer thickness & tool size model is constructed based on the machining tool deflection under cutting forces. This rapid pattern manufacturing process and related software has been implemented, and experimental data is presented to illustrate the efficacy of this system and its process planning methods

Manufacturability analysis for non-feature-based objects

This dissertation presents a general methodology for evaluating key manufacturability indicators using an approach that does not require feature recognition, or feature-based design input. The contributions involve methods for computing three manufacturability indicators that can be applied in a hierarchical manner. The analysis begins with the computation of visibility, which determines the potential manufacturability of a part using material removal processes such as CNC machining. This manufacturability indicator is purely based on accessibility, without considering the actual machine setup and tooling. Then, the analysis becomes more specific by analyzing the complexity in setup planning for the part; i.e. how the part geometry can be oriented to a cutting tool in an accessible manner. This indicator establishes if the part geometry is accessible about an axis of rotation, namely, whether it can be manufactured on a 4th-axis indexed machining system. The third indicator is geometric machinability, which is computed for each machining operation to indicate the actual manufacturability when employing a cutting tool with specific shape and size. The three manufacturability indicators presented in this dissertation are usable as steps in a process; however they can be executed alone or hierarchically in order to render manufacturability information. At the end of this dissertation, a Multi-Layered Visibility Map is proposed, which would serve as a re-design mechanism that can guide a part design toward increased manufacturability

Energy efficient engine high-pressure turbine single crystal vane and blade fabrication technology report

The objective of the High-Pressure Turbine Fabrication Program was to demonstrate the application and feasibility of Pratt & Whitney Aircraft-developed two-piece, single crystal casting and bonding technology on the turbine blade and vane configurations required for the high-pressure turbine in the Energy Efficient Engine. During the first phase of the program, casting feasibility was demonstrated. Several blade and vane halves were made for the bonding trials, plus solid blades and vanes were successfully cast for materials evaluation tests. Specimens exhibited the required microstructure and chemical composition. Bonding feasibility was demonstrated in the second phase of the effort. Bonding yields of 75 percent for the vane and 30 percent for the blade were achieved, and methods for improving these yield percentages were identified. A bond process was established for PWA 1480 single crystal material which incorporated a transient liquid phase interlayer. Bond properties were substantiated and sensitivities determined. Tooling die materials were identified, and an advanced differential thermal expansion tooling concept was incorporated into the bond process

Design and fabrication of conformal cooling channels in molds:Review and progress updates

Conformal cooling (CC) channels are a series of cooling channels that are equidistant from the mold cavity surfaces. CC systems show great promise to substitute conventional straight-drilled cooling systems as the former can provide more uniform and efficient cooling effects and thus improve the production quality and efficiency significantly. Although the design and manufacturing of CC systems are getting increasing attention, a comprehensive and systematic classification, comparison, and evaluation are still missing. The design, manufacturing, and applications of CC channels are reviewed and evaluated systematically and comprehensively in this review paper. To achieve a uniform and rapid cooling, some key design parameters of CC channels related to shape, size, and location of the channel have to be calculated and chosen carefully taking into account the cooling performance, mechanical strength, and coolant pressure drop. CC layouts are classified into eight types. The basic type, more complex types, and hybrid straight-drilled-CC molds are suitable for simply-shaped parts, complex-shaped parts, and locally complex parts, respectively. By using CC channels, the cycle time can be reduced up to 70%, and the shape deviations can be improved significantly. Epoxy casting and L-PBF show the best applicability to Al-epoxy molds and metal molds, respectively, because of the high forming flexibility and fidelity. Meanwhile, LPD has an exclusive advantage to fabricate multi-materials molds although it cannot print overhang regions directly. Hybrid L-PBF/CNC milling pointed out the future direction for the fabrication of high dimensional-accuracy CC molds, although there is still a long way to reduce the cost and raise efficiency. CC molds are expected to substitute straight-drilled cooling molds in the future, as it can significantly improve part quality, raise production rate and reduce production cost. In addition to this, the use of CC channels can be expanded to some advanced products that require high-performance self-cooling, such as gas turbine engines, photoinjectors and gears, improving working conditions and extending lifetime