M.A. Jafari, W. Han, F. Mohammadi, A. Safari, S.C. Danforth and N. Langrana
In this article we present the system that we have developed at Rutgers University for the solid freeform fabrication of multiple ceramic actuators and sensors. With solid free…
Abstract
In this article we present the system that we have developed at Rutgers University for the solid freeform fabrication of multiple ceramic actuators and sensors. With solid free form fabrication, a part is built layer by layer, with each layer composed of roads of material forming the boundary and the interior of the layer. With our system, up to four different types of materials can be deposited in a given layer with any geometry. This system is intended for fabrication of functional parts; therefore the accuracy and precision of the fabrication process are of extreme importance.
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N. Venkataraman, S. Rangarajan, M.J. Matthewson, B. Harper, A. Safari, S.C. Danforth, G. Wu, N. Langrana, S. Guceri and A. Yardimci
Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded…
Abstract
Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament feedstocks has been developed. It was found that feedstock materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Dan Qiu, Noshir A. Langrana, Stephen C. Danforth, Ahmad Safari and Mohsen Jafari
To fabricate high quality parts, and to make the development generic yet compatible with the in‐house hardware, a virtual simulation system has been developed, and an in‐house…
Abstract
To fabricate high quality parts, and to make the development generic yet compatible with the in‐house hardware, a virtual simulation system has been developed, and an in‐house intelligent multi‐material toolpath generation system has been under development. This new development includes the issues such as multiple fill‐toolpaths for the same material, interface mismatch between adjacent materials and the intelligent toolpath features for machine control. After the multi‐material toolpath file generated by the in‐house software, the existing virtual graphical simulation as well as well selected part fabrication experiments were used to validate it. Based on the authors’ ongoing research about multi‐material layered manufacturing, it was determined that the build characteristic was heavily dependent on the material being used. Therefore, it was important to develop the hardware/software that will accommodate this requirement.
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Mukesh K. Agarwala, Vikram R. Jamalabad, Noshir A. Langrana, Ahmad Safari, Philip J. Whalen and Stephen C. Danforth
Commercial solid freeform fabrication (SFF) systems, which have been developed for fabrication of wax and polymer parts for form and fit and secondary applications, such as moulds…
Abstract
Commercial solid freeform fabrication (SFF) systems, which have been developed for fabrication of wax and polymer parts for form and fit and secondary applications, such as moulds for casting, etc., require further improvements for use in direct processing of structural ceramic and metal parts. Defects, both surface as well as internal, are undesirable in SFF processed ceramic and metal parts for structural and functional applications. Process improvements are needed before any SFF technique can successfully be commercialized for structural ceramic and metal processing. Describes process improvements made in new SFF techniques, called fused deposition of ceramics (FDC) and metals (FDMet), for fabrication of structural and functional ceramic and metal parts. They are based on an existing SFF technique, fused deposition modelling (FDM) and use commercial FDM systems. The current state of SFF technology and commercial FDM systems results in parts with several surface and internal defects which, if not eliminated, severely limit the structural properties of ceramic and metal parts thus produced. Describes systematically, in detail, the nature of these defects and their origins. Discusses several novel strategies for elimination of most of these defects. Shows how some of these strategies have successfully been implemented to result in ceramic parts with structural properties comparable to those obtained in conventionally processed ceramics.
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This bibliography is offered as a practical guide to published papers, conference proceedings papers and theses/dissertations on the finite element (FE) and boundary element (BE…
Abstract
This bibliography is offered as a practical guide to published papers, conference proceedings papers and theses/dissertations on the finite element (FE) and boundary element (BE) applications in different fields of biomechanics between 1976 and 1991. The aim of this paper is to help the users of FE and BE techniques to get better value from a large collection of papers on the subjects. Categories in biomechanics included in this survey are: orthopaedic mechanics, dental mechanics, cardiovascular mechanics, soft tissue mechanics, biological flow, impact injury, and other fields of applications. More than 900 references are listed.
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Dan Qiu and Noshir A. Langrana
For extrusion based multi‐material layered manufacturing (LM) processes, a CAD system has been developed which generates high quality toolpath for part fabrication. This closed…
Abstract
For extrusion based multi‐material layered manufacturing (LM) processes, a CAD system has been developed which generates high quality toolpath for part fabrication. This closed loop CAD system includes solid model design and slicing, single‐material toolpath generation, multi‐material toolpath generation and virtual simulation modules. The solid model is sliced equally. Intelligent features and adaptive roadwidth optimum toolpath generation algorithm computes void sizes and their location and generates void free toolpath. The virtual simulation visualizes and validates the toolpath generated for the part. When the computed toolpath quality is acceptable, it is sent to the in house hardware Fused Deposition of Multiple Ceramics (FDMC) machine for fabrication.
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Apart from the geometries to be dealt with, rapid prototyping (RP) of heterogeneous objects requires additional material information to be processed. This generally involves a…
Abstract
Purpose
Apart from the geometries to be dealt with, rapid prototyping (RP) of heterogeneous objects requires additional material information to be processed. This generally involves a large amount of information to be processed simultaneously. The robustness and efficiency problems, which seem less critical in homogeneous solid fabrications, become an issue. The direct impetus of this paper is to present robust and efficient algorithms for RP of heterogeneous objects.
Design/methodology/approach
The robustness is benefited from using the proposed non‐manifold heterogeneous cellular model, which guarantees gap‐free material depositions around material interfaces. The efficiency enhancement is achieved by eliminating repetitive boundary intersections and using a heuristic material interrogation approach.
Findings
By using the proposed algorithms, the robustness and efficiency of RP of heterogeneous objects can be improved. It is found that an average 30 percent efficiency improvement is obtained using the proposed heuristic material interrogation approach.
Originality/value
Non‐manifold heterogeneous cell representation (HC‐Rep) is used in RP fields for the first time. Based on the HC‐Rep, the robustness and efficiency of RP of heterogeneous object is addressed in this paper.
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Wenbiao Han, Mohsen A. Jafari and Kian Seyed
Compared to conventional manufacturing processes, fused deposition (FD)‐based layered manufacturing processes have dramatically reduced the part design and manufacturing time…
Abstract
Compared to conventional manufacturing processes, fused deposition (FD)‐based layered manufacturing processes have dramatically reduced the part design and manufacturing time. However, it is necessary to further enhance their process productivity. To this end, improvement of FD process efficiency is studied in this paper. A build time analysis is conducted and the deposition parameters that can be used to speed up fabrication processes are identified. The tool path‐based deposition planning approach is extended for ensuring layer quality when the build process is expedited under adjusted deposition parameters. A test part was built to demonstrate the proposed approach.
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Özgür Keleş, Eric H. Anderson and Jimmy Huynh
Mechanical reliability (variations in mechanical properties) of fused deposition modeled (FDMed) short-fiber-reinforced composites are unknown, which limits wider and safer use of…
Abstract
Purpose
Mechanical reliability (variations in mechanical properties) of fused deposition modeled (FDMed) short-fiber-reinforced composites are unknown, which limits wider and safer use of these composites. Accordingly, this paper aims to investigate the mechanical reliability of FDMed model material short-carbon-fiber-reinforced acrylonitrile butadiene styrene (SCFR-ABS). A new vibration-assisted FDM (VA-FDM) process was used to reduce porosity.
Design/methodology/approach
Tensile tests were performed on FDMed SCFR-ABS produced with and without vibrations. Weibull analysis was performed to quantify the variation in fracture strength, tensile strength, strain at break and strain at tensile strength.
Findings
Introduction of vibrations to the extrusion head during FDM decreased the inter-bead porosity in SCFR-ABS and thus improved elastic modulus, toughness, fracture strength, tensile strength and strain at break. Weibull modulus of fracture strength increased from 25 to 57 with vibrations.
Practical implications
The reported Weibull analysis offers a practical design guideline to predict failure rates at specific service stresses.
Originality/value
A detailed Weibull analysis of the variations in the mechanical properties of FDMed SCFR-ABS was performed for the first time. A new vibration-assisted FDM process was reported to reduce inter-bead porosity in FDMed composites.
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Hochan Kim, Jae‐Won Choi and Ryan Wicker
To operate a multiple material stereolithography (MMSL) system, a material build schedule is required. The purpose of this paper is to describe a scheduling and process‐planning…
Abstract
Purpose
To operate a multiple material stereolithography (MMSL) system, a material build schedule is required. The purpose of this paper is to describe a scheduling and process‐planning software system developed for MMSL and designed to minimize the number of material changeovers by using low‐viscosity resins that do not require sweeping.
Design/methodology/approach
This paper employs the concept of using low‐viscosity resins that do not require sweeping to minimize the number of material changeovers required in MMSL fabrication. A scheduling and process‐planning software system specific to MMSL is introduced that implements four simple rules. Two rules are used to select the material to be built in the current layer, and two rules are used to determine at which layer a material changeover is required. The schedule for the material to be built depends on the material properties stored in a user‐defined materials library. The developed algorithm produces sliced loop data for each material using the predetermined layer thickness from an input CAD model, and the four rules are applied at each layer. The algorithm then determines the build order for each material, the material‐specific number of layers to be built, and whether or not sweeping is required. Output data from the program are the scheduling and process‐planning report and the partitioned computer‐aided design models to be built before changing a material according to the process planning. Two examples of the algorithm applied to multiple material parts are provided.
Findings
The MMSL scheduling and process‐planning software system is developed using Microsoft Visual C++7.0. For verification, a simple demonstration is conducted on a two material part where the process plan could be easily determined through intuition. A more complex multiple material part is also tested that consisted of four subparts. Several cases of resin assignment are tested showing that the ultimate scheduling and process planning vary significantly depending on the material combinations and specifications. These examples demonstrate that the strategy, method, and software developed in this paper can be successfully applied to prepare for MMSL fabrication.
Research limitations/implications
Although the software system is demonstrated on two multiple material parts, more extensive work will be performed in the future on fabricating multiple material parts using the MMSL machine. It is expected that additional rules will be developed as additional limitations of MMSL are identified. It is also anticipated that particular emphasis will be placed on building without sweeping as well as development of advanced non‐contact recoating processes.
Originality/value
As designs incorporating multiple materials increase in the future and additive manufacturing (AM) technologies advance in both building out of multiple materials and fabricating production parts, the scheduling and process‐planning concepts presented here can be applied to virtually any AM technology.