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

Fab + Craft: Synthesis of Maker, Machine, Material

Within contemporary architecture a fundamental disjunction exists between design and building facilitated by the use of advanced computational methods, and the relationship between form, material, and maker. The making of buildings demands an expertise that is familiar with the physical and involves a level of skill that many designers cannot claim to fully possess or practice. This doctorate project presents a study of a design-through-making methodology that incorporates craft with the material exploration of sandwich panels, digital technology and fabrication in the process of ‘making’ architecture. A focus is placed on the development of a specific design intent through the manipulation of materials, using skills and techniques guided by the practiced hand. This interaction between technology, material, and the designer-maker referred to as “fab+craft” creates a narrative that allows for the physical translation of ideas into the built environment

Computer Aided Design of Side Actions for Injection Molding of Complex Parts

Often complex molded parts include undercuts, patches on the part boundaries that are not accessible along the main mold opening directions. Undercuts are molded by incorporating side actions in the molds. Side actions are mold pieces that are removed from the part using translation directions different than the main mold opening direction. However, side actions contribute to mold cost by resulting in an additional manufacturing and assembly cost as well as by increasing the molding cycle time. Therefore, generating shapes of side actions requires solving a complex geometric optimization problem. Different objective functions may be needed depending upon different molding scenarios (e.g., prototyping versus large production runs). Manually designing side actions is a challenging task and requires considerable expertise. Automated design of side actions will significantly reduce mold design lead times. This thesis describes algorithms for generating shapes of side actions to minimize a customizable molding cost function. Given a set of undercut facets on a polyhedral part and the main parting direction, the approach works in the following manner. First, candidate retraction space is computed for every undercut facet. This space represents the candidate set of translation vectors that can be used by the side action to completely disengage from the undercut facet. As the next step, a discrete set of feasible, non-dominated retractions is generated. Then the undercut facets are grouped into undercut regions by performing state space search over such retractions. This search step is performed by minimizing the customizable molding cost function. After identifying the undercut regions that can share a side action, the shapes of individual side actions are computed. The approach presented in this work leads to practically an optimal solution if every connected undercut region on the part requires three or fewer side actions. Results of computational experiments that have been conducted to assess the performance of the algorithms described in the thesis have also been presented. Computational results indicate that the algorithms have acceptable computational performance, are robust enough to handle complex part geometries, and are easy to implement. It is anticipated that the results shown here will provide the foundations for developing fully automated software for designing side actions in injection molding

Nonterrestrial utilization of materials: Automated space manufacturing facility

Four areas related to the nonterrestrial use of materials are included: (1) material resources needed for feedstock in an orbital manufacturing facility, (2) required initial components of a nonterrestrial manufacturing facility, (3) growth and productive capability of such a facility, and (4) automation and robotics requirements of the facility

RAPID-PROTOTYPING OF PDMS-BASED MICROFLUIDIC DEVICES

Microfluidics uses the manipulation of fluids in microchannels to accomplish innumerous goals, and is attractive to analytical chemistry because it can reduce the scale of larger analytical processes. The benefits of the use of microfluidic systems, in comparison with conventional processes, include efficient sample and reagent consumption, low power usage and portability. Most microfluidic applications require a development process based on iterative design and testing of multiple prototype microdevices. Typical microfabrication protocols, however, can require over a week of specialist time in high-maintenance cleanroom facilities, making the iterative process resource-intensive and prohibitive in many locations. Rapid prototyping techniques can alleviate these issues, enabling faster development of microfluidic structures at lower costs. Print-and-peel techniques (PAP), including wax printing and xurography, are low-cost fast-prototyping tools used to create master molds for polydimethylsiloxane (PDMS) miniaturized systems. In this work, three different methods were created to improve the rapid-prototyping of PDMS-based microfluidic devices. Using the wax printing method, PDMS microdevices can now be fabricated from design to testing in less than 1 hour, at the cost of $0.01 per mold, being one of the fastest and cheapest methods to date. If extensive fluidic manipulation is required, xurography becomes the method of choice. The xurography technique presented here is the most rapid tool to fabricate PDMS-based microdevices to date, presenting turnaround times as fast as 5 minutes. The first hybrid technique that can be used either as a PAP or a scaffolding method is also presented here, using the same materials and fabrication process. The green, low-cost, user-friendly elastomeric (GLUE) rapid prototyping method to fabricate PDMS-based devices uses white glue as the patterning material, and is capable of fabricating multi-height molds in a single step, improving even further the development of PDMS microfluidic devices. Device fabrication is only one of the steps in the iterative process of designing a fully-functional microfluidic tool. The design of the microdevice itself plays a crucial role in its performance, which directly impacts processes conducted in miniaturized devices. In this work, the influence of hydrodynamic resistance in sample dispersion on a microfluidic multiplexer was studied using paper-based analytical microfluidic devices (µPADs) as the testbed. When microfluidic devices are not rationally designed, and when the influence of fluidic resistance is not taken into account, sample dispersion can be biased. A bias can influence the output of colorimetric enzymatic assays supported on these microstructures, which are the most common applications of µPADs, demonstrating the need for rational design of microdevices. The third essential component of developing microfluidic devices is their effective testing, especially when incorporating active pumping elements on-chip. To overcome issues in the manual operation or coding for operation of microvalves, a program that can automatically generate sequences for fluidic manipulation in microfluidic processors was written in Python, with the only inputs required from the user being reservoir positions, mixing ratio and the desired input and output reservoirs. To further improve testing and avoid the use of fixed mounts, a modular system was created to aid the testing of devices with different designs, another advance in the area. This research enables better design and testing of microfluidic devices in shorter times and at lower costs, enabling improvements in the interfacing between different unit operations on-chip, a challenge in the microfluidics area. More than that, it also makes this area, traditionally confined into expensive cleanroom facilities, available to more research groups worldwide.Ph.D

Algorithms for generating multi-stage molding plans for articulated assemblies

Plastic products such as toys with articulated arms, legs, and heads are traditionally produced by first molding individual components separately, and then assembling them together. A recent alternative, referred to as in-mold assembly process, performs molding and assembly steps concurrently inside the mold itself. The most common technique of performing in-mold assembly is through multi-stage molding, in which the various components of an assembly are injected in a sequence of molding stages to produce the final assembly. Multi-stage molding produces better-quality articulated products at a lower cost. It however, gives rise to new mold design challenges that are absent from traditional molding. We need to develop a molding plan that determines the mold design parameters and sequence of molding stages. There are currently no software tools available to generate molding plans. It is difficult to perform the planning manually because it involves evaluating large number of combinations and solving complex geometric reasoning problems. This dissertation investigates the problem of generating multi-stage molding plans for articulated assemblies. The multi-stage molding process is studied and the underlying governing principles and constraints are identified. A hybrid planning framework that combines elements from generative and variant techniques is developed. A molding plan representation is developed to build a library of feasible molding plans for basic joints. These molding plans for individual joints are reused to generate plans for new assemblies. As part of this overall planning framework, we need to solve the following geometric subproblems -- finding assembly configuration that is both feasible and optimal, finding mold-piece regions, and constructing an optimal shutoff surface. Algorithms to solve these subproblems are developed and characterized. This dissertation makes the following contributions. The representation for molding plans provides a common platform for sharing feasible and efficient molding plans for joints. It investigates the multi-stage mold design problem from the planning perspective. The new hybrid planning framework and geometric reasoning algorithms will increase the level of automation and reduce chances of design mistakes. This will in turn reduce the cost and lead-time associated with the deployment of multi-stage molding process

National Educators' Workshop: Update 1989 Standard Experiments in Engineering Materials Science and Technology

Presented here is a collection of experiments presented and demonstrated at the National Educators' Workshop: Update 89, held October 17 to 19, 1989 at the National Aeronautics and Space Administration, Hampton, Virginia. The experiments related to the nature and properties of engineering materials and provided information to assist in teaching about materials in the education community

Interlocking structure design and assembly

Many objects in our life are not manufactured as whole rigid pieces. Instead, smaller components are made to be later assembled into larger structures. Chairs are assembled from wooden pieces, cabins are made of logs, and buildings are constructed from bricks. These components are commonly designed by many iterations of human thinking. In this report, we will look at a few problems related to interlocking components design and assembly. Given an atomic object, how can we design a package that holds the object firmly without a gap in-between? How many pieces should the package be partitioned into? How can we assemble/extract each piece? We will attack this problem by first looking at the lower bound on the number of pieces, then at the upper bound. Afterwards, we will propose a practical algorithm for designing these packages. We also explore a special kind of interlocking structure which has only one or a small number of movable pieces. For example, a burr puzzle. We will design a few blocks with joints whose combination can be assembled into almost any voxelized 3D model. Our blocks require very simple motions to be assembled, enabling robotic assembly. As proof of concept, we also develop a robot system to assemble the blocks. In some extreme conditions where construction components are small, controlling each component individually is impossible. We will discuss an option using global controls. These global controls can be from gravity or magnetic fields. We show that in some special cases where the small units form a rectangular matrix, rearrangement can be done in a small space following a technique similar to bubble sort algorithm

Lean Transformation for Composite-Material Bonding Processes

Composite materials can greatly reduce production and transportation costs and so that they are widely used in the aerospace industry. Traditional composite materials manufacturers are facing competitive challenges such as shorter delivery time, high quality, and quick response to customer demand. Lean methods have been effectively applied to various industries for improving production quality and efficiency. In this study, a framework of lean transformation are organized and presented in a systematic way. The proposed lean transformation techniques are implemented in an aerospace company to improve the composite-material bonding process. Implementation results suggest the overall productivity of the composite-material bonding process increase significantly due to the elimination of bottlenecks, reduction of cycle time, and decrease of WIP inventory. The proposed approach can be applied to other manufacturing enterprises for improving their productivity