CofiFab: Coarse-to-fine fabrication of large 3D objects

This paper presents CofiFab, a coarse-to-fine 3D fabrication solution, which combines 3D printing and 2D laser cutting for cost-effective fabrication of large objects at lower cost and higher speed. Our key approach is to first build coarse internal base structures within the given 3D object using laser-cutting, and then attach thin 3D-printed parts, as an external shell, onto the base to recover the fine surface details. CofiFab achieves this with three novel algorithmic components. First, we formulate an optimization model to compute fabricatable polyhedrons of maximized volume, as the geometry of the internal base. Second, we devise a new interlocking scheme to tightly connect laser-cut parts into a strong internal base, by iteratively building a network of nonorthogonal interlocking joints and locking parts around polyhedral corners. Lastly, we also optimize the partitioning of the external object shell into 3D-printable parts, while saving support material and avoiding overhangs. These components also consider aesthetics, stability and balancing in addition to cost saving. As a result, CofiFab can efficiently produce large objects by assembly. To evaluate its effectiveness, we fabricate objects of varying shapes and sizes, where CofiFab significantly improves compared to previous methods

Tunable Digital Material Properties of 3D Voxel Printers

Digital materials are composed of many discrete voxels placed in a massively parallel layer deposition process, as opposed to continuous (analog) deposition techniques. We explore the material properties attainable using a voxel-based freeform fabrication process and simulate how the properties can be tuned for a wide range of applications. By varying the precision, geometry, and material of the individual voxels, we obtain continuous control over the density, elastic modulus, CTE, ductility, and failure mode of the material. Also, we demonstrate the effects of several hierarchical voxel “microstructures”, resulting in interesting properties such as negative poisson’s ratio. This implies that digital materials can exhibit widely varying properties in a single desktop fabrication process.Mechanical Engineerin

Towards Zero-Waste Furniture Design

In traditional design, shapes are first conceived, and then fabricated. While this decoupling simplifies the design process, it can result in inefficient material usage, especially where off-cut pieces are hard to reuse. The designer, in absence of explicit feedback on material usage remains helpless to effectively adapt the design -- even though design variabilities exist. In this paper, we investigate {\em waste minimizing furniture design} wherein based on the current design, the user is presented with design variations that result in more effective usage of materials. Technically, we dynamically analyze material space layout to determine {\em which} parts to change and {\em how}, while maintaining original design intent specified in the form of design constraints. We evaluate the approach on simple and complex furniture design scenarios, and demonstrate effective material usage that is difficult, if not impossible, to achieve without computational support

A Digital Workflow for the Design and Manufacturing of 3D Printed Concrete Bridges in a Circular Economy:A Parametric Approach to Integrated Design and Fabrication

Low productivity, material depletion, waste, and emissions are widespread in the construction industry. On top of this, many bridges reaching the end of their service life need repair or replacement.This design project investigates how digitisation and integrated design and manufacturing processes can aid in addressing sustainability and productivity issues. This project develops a digital workflow for bridge design and manufacturing using 3D printed concrete in combination with circular economy design concepts of disassembly and material reduction.Design CriteriaFor the development of the project, design criteria were established. This process initially looked at two previously printed bridges in the Netherlands. From this, design criteria for both the design tool and the resulting bridge designs were established. These criteria include:• Use concrete 3D printing and work with relevant printing systems.• Use structural analysis to guide user decisions.• Use prestressed tendons and modularise for simple assembly and disassembly.• Implement principles of the circular economy.Design ToolThe project developed a parametric design tool for creating bridges using 3D-printed concrete. Five ‘blocks’ manage distinct design elements in the design tool.1. Alignment allows the user to match the bridge to an existing location or shape a new bridge through length, span and shape.2. Cross-sections along the curve allow the user to shape the bridge. Size and thickness control linked to a structural check enables efficient material distribution.3. 3D Form interpolates the cross-sections into a 3D shape. Here the user can see how the beam will look.4. Segments are created in the beam to engage with material, manufacturing and transport constraints.5. Code Generation block generates code suitable for standard printing systems.The user can make changes and modifications at any stage in the process. The manufacturing constraints are embedded into the design process, helping to ensure that what is designed can be produced.Design ConceptsTwo bridge concepts were created to demonstrate the tool’s flexibility in different scenarios. One design uses a freeform cross-section type to create a pedestrian bridge over a river. The other is a more straightforward highway bridge using a modular cross-section type and reuses existing supports.Public DisseminationOne of the ambitions is to share results and knowledge generated throughout the project. This knowledge dissemination is demonstrated by three public presentations reaching an industry, academic and general public audience.Conclusions and RecommendationsThe tool created helps demonstrate how integrated approaches to design and fabrication can help with the challenges presented in sustainability and productivity but simultaneously with the ambition that what we produce is attractive and appropriate to its location

Thermoplastics 3D Printing Using Fused Deposition Modeling on Fabrics

The creation of objects with integrated flexibility is desired and this can be achieved by additive manufacturing on fabric. We propose to use a textile fabric as a flexible joint and create to create an entire object with smaller parts called segments. Such a novel technique will bring integrated flexibility and folded assemblies using extrusion based additive manufacturing machines. The proposed process allows segments to be created flat one at a time on a continuous fabric, which will be suitable for flat to folded assemblies and eliminate size limitations of the 3D printer. Techniques considering object segmentation were used to unfold 3D models of objects into 2D patterns based on paper folding. The unfolding of models was specifically designed to allow manufacturability of the segmentations with no impedance from the 3D printer’s frame, where minimal segments were also desired. Three different textile fabrics based on cotton plain weave, plane weave acrylic, and polyester 200 denier ripstop fabrics were considered in investigations of the interfacial strength created with additively manufactured polylactic acid. Both treated and untreated fabrics were prepared simultaneously so that parts can be printed on top of them at a predefined spatial location. The interfacial strength of additive manufactured parts printed on the fabric were also tested as a function of print process parameters, fiber morphology, fabric properties, as well as surface modification of fabrics. The highest interfacial strength between additive manufactured materials and fabric was desired and tested for. Both adhesion peel testing and stress pull testing is used to determine the strength of the interface between the fabric and deposited additive manufactured parts. Results found that the interfacial strength reached a maximum of 5.18 and 0.435 MPa. For a conceptual square shelter design a series of triangular panels were created on fabric to be assembled into the shelter. It was conceptually determined that the resulting interfacial strength could keep a 40-kilogram large triangular, panel of this shelter, held upside done from removing from the fabric, given its own weight. From this result, it was determined that the interfacial strength is strong enough for use with the creation of large heavy objects that require flexibly in them for hinges. Rough and thick fabrics were found to promote interfacial strength the greatest with higher bed temperatures, this was because of mechanical interlocking being promoted. Pre-treatments of the fabrics were found to help with interfacial strength as well and have potential with higher environmental temperatures, but not as much as mechanical interlocking. Adhesion forces desired between fabric and 3D printed parts can be tailored per specific large object as needed, per segmentation, using this information. The proposed manufacturing method helps fabricate multifaceted large single objects with localized optimum process parameters and objects with integrated flexibility. The additive manufacturing on fabric method of object fabrication addresses the anisotropic nature of additive manufactured parts by allowing parts of the object be created separately from each other. This allows each part to be tailored for specific mechanical properties to achieve desired mechanical properties for the entire object. Mechanical strength, optimization of weight, interfacial strength, specific features or properties, and the ability to fold for storage or transportation of these objects could be tailored per application

Effects of Schisandrin B on Rod Photoreceptors in the pde6c Larval Retina

Current Rapid prototyping tools although reduce development time, they still have several restrictions such as print volume and print times. Through this thesis, two prototyping kits are proposed, a rod connector based, user controlled computational support system that re-purposes surface models and transforms them into structurally scaffolded constructs with movable joints; and a planar connector based system that implements movable joints to create functional prototypes. The rod based system enables users to interactively personalize scaffolded structures by re-purposing existing surface mesh models; analyze scaffolded constructs in-situ for better structurality, add movable joints to increase functionality, and attach personalized appearances to the scaffolding for increased customization.vThe planar connector system uses movable and electronic embedded connectors to functionalize planar surfaces to create multi-fidelity prototypes capable of interacting with the environment

Remote Collaborative 3D Printing - Process Investigation

The Remote Collaborative 3D Printing project is a collaboration between Strategic System Programs (SSP), the Naval Postgraduate School (NPS), NAVFAC Headquarters Asset Management - Facilities Integrated Product Support (IPS) Program, and the NAVFAC Engineering and Expeditionary Warfare Center (EXWC). The intent of the project was to investigate the end-to-end process of transferring, receiving, manipulating, and printing a digital 3D model into an additively manufactured component. Several digital models were exchanged, and the steps, barriers, workarounds, and results have been documented.Strategic System Programs, Naval Postgraduate SchoolNAVFAC Headquarters Asset Managemen

From 3D Models to 3D Prints: an Overview of the Processing Pipeline

Due to the wide diffusion of 3D printing technologies, geometric algorithms for Additive Manufacturing are being invented at an impressive speed. Each single step, in particular along the Process Planning pipeline, can now count on dozens of methods that prepare the 3D model for fabrication, while analysing and optimizing geometry and machine instructions for various objectives. This report provides a classification of this huge state of the art, and elicits the relation between each single algorithm and a list of desirable objectives during Process Planning. The objectives themselves are listed and discussed, along with possible needs for tradeoffs. Additive Manufacturing technologies are broadly categorized to explicitly relate classes of devices and supported features. Finally, this report offers an analysis of the state of the art while discussing open and challenging problems from both an academic and an industrial perspective.Comment: European Union (EU); Horizon 2020; H2020-FoF-2015; RIA - Research and Innovation action; Grant agreement N. 68044