Showing papers in "Rapid Prototyping Journal in 2006"
TL;DR: In this paper, a simple theoretical model is developed to predict residual stress distributions in selective laser sintering (SLS) and selective laser melting (SLM), aiming at a better understanding of this phenomenon.
Abstract: Purpose – This paper presents an investigation into residual stresses in selective laser sintering (SLS) and selective laser melting (SLM), aiming at a better understanding of this phenomenon.Design/methodology/approach – First, the origin of residual stresses is explored and a simple theoretical model is developed to predict residual stress distributions. Next, experimental methods are used to measure the residual stress profiles in a set of test samples produced with different process parameters.Findings – Residual stresses are found to be very large in SLM parts. In general, the residual stress profile consists of two zones of large tensile stresses at the top and bottom of the part, and a large zone of intermediate compressive stress in between. The most important parameters determining the magnitude and shape of the residual stress profiles are the material properties, the sample and substrate height, the laser scanning strategy and the heating conditions.Research limitations/implications – All exper...
1,415 citations
TL;DR: A comprehensive review of 3D printing applications is presented in this paper, which includes design, manufacturing, the medical field and architecture, as well as further implications in design and engineering analysis, medicine, and architecture.
Abstract: Purpose – This paper surveys the current state and capabilities of three dimensional printing (3DP). A comprehensive review of 3D Printing applications is presented. The scope of the applications includes design, manufacturing, the medical field and architecture.Design/methodology/approach – A large variety of manufacturing applications such as rapid pattern making and rapid tooling using the 3DP process directly or as core technology, as well as further implications in design and engineering analysis, medicine, and architecture are presented and evaluated.Findings – Some research issues are also discussed. An attempt, based on the state of the art, to show weaknesses and opportunities, and to draw conclusions about the future of this important process rounds up this paper.Research limitations/implications – The scope of this research survey is limited to evaluation and comparison of processes that may be characterised as 3D printing technologies.Practical implications – The study is very useful as a basi...
401 citations
TL;DR: In this paper, the authors investigate the mechanical properties and porosity relationships in fused deposition modeling (FDM) fabricated porous structures, which can be interdependent and exhibit varying effects on scaffold properties, were identified and examined using the design of experiment (DOE) approach.
Abstract: Purpose – The purpose of this paper is to investigate the mechanical properties and porosity relationships in fused deposition modelling (FDM) fabricated porous structures.Design/methodology/approach – Porous structures of numerous build architectures aimed at tissue engineering (TE) application were fabricated using the FDM. The employment of FDM to fabricate these non‐random constructs offers many advantages over conventional scaffold fabrication techniques as patient specific scaffolds with well‐defined architectures and controllable pore sizes can be fabricated accurately and rapidly. There exist several FDM parameters that one needs to specify during the scaffold fabrication process. These parameters, which can be interdependent and exhibit varying effects on scaffold properties, were identified and examined using the design of experiment (DOE) approach. Essentially, the effects of five FDM process parameters, namely air gap, raster width, build orientation, build layer and build profile, on the poro...
242 citations
TL;DR: In this article, the authors illustrate a number of instances where RP and associated technology has been successfully used for medical applications, but the technology has numerous limitations that have been analysed in order to establish how the technology should develop in the future.
Abstract: Purpose – This paper aims to illustrate a number of instances where RP and associated technology has been successfully used for medical applications.Design/methodology/approach – A number of medical case studies are presented, illustrating different uses of RP technology. These studies have been analysed in terms of how the technology has been applied in order to solve related medical problems.Findings – It was found that RP has been helpful in a number of ways to solve medical problems. However, the technology has numerous limitations that have been analysed in order to establish how the technology should develop in the future.Practical implications – RP can help solve medical problems, but must evolve if it is to be used more widespread in this field.Originality/value – This paper has shown a number of new applications for RP, providing a holistic understanding how the technology can solve medical problems. It also identifies a number of ways in which the technology can improve in order to better solve ...
223 citations
TL;DR: In this article, the authors discuss the integration of the rapid prototyping environmental aspects with the primary focus on electrical energy consumption, and propose several rules to minimize this electrical power consumption during a job.
Abstract: Purpose ? To discuss integration of the rapid prototyping environmental aspects with the primary focus on electrical energy consumption. Design/methodology/approach ? Various manufacturing parameters have been tested on three rapid prototyping systems: Thermojet (3DS), FDM 3000 (Stratasys) and EOSINT M250 Xtended (EOS). The objective is to select sets of parameters for reduction of electrical energy consumption. For this, a part is manufactured in several orientations and positions in the chamber of these RP systems. For each test, the electrical power is noted. Finally, certain rules are proposed to minimize this electrical energy consumption during a job. Findings ? It is important to minimize the manufacturing time but there is no general rule for optimization of electrical energy consumption. Each RP system must be tested with energy consumption considerations under the spotlight. Research limitations/implications ? The work is only based on rapid prototyping processes. The objective is to take into consideration the complete life-cycle of a rapid prototyped part: manufacturing of raw material as far as reprocessing of waste. Practical implications ? Reduction of electrical energy consumption to complete a job. Originality/value ? Currently, environmental aspects are not well studied in rapid prototyping.
165 citations
TL;DR: In this article, a program was written to measure the features on a numerically controlled coordinate measurement machine and a statistical analysis was done in terms of statistical parameters and international tolerance (IT) grades.
Abstract: Purpose – The research was undertaken to characterise the three dimensional printing (3DP) process in term of the achievable dimensional and geometric accuracy.Design/methodology/approach – New benchmark models were developed that represent characteristics needing to be investigated. The parts were fabricated in different materials. A program was written to measure the features on a numerically controlled coordinate measurement machine. Finally, a statistical analysis was done. The results are reported in terms of statistical parameters and international tolerance (IT) grades.Findings – The paper provides general IT grades of the 3DP process for parts printed using different materials (powders).Research limitations/implications – The research is limited to specific materials and equipment.Practical implications – The data is very useful for designing products to be manufactured on 3DP machines applying either direct or indirect methods.Originality/value – 3DP is more and more used for rapid prototyping wi...
149 citations
TL;DR: In this paper, a part carrying regular surface patterns with different feature sizes and aspect ratios has been manufactured on a fused deposition modeling (FDM) system with different build orientations to detect the occurrence of quality defects on textured surfaces.
Abstract: Purpose – Test the detail resolution of fused deposition modeling (FDM) in the direct manufacture of rapid prototypes with textured surfaces.Design/methodology/approach – A benchmark part carrying regular surface patterns with different feature sizes and aspect ratios has been manufactured on a FDM system with different build orientations. Layered parts have been inspected to detect the occurrence of quality defects on textured surfaces.Findings – The experiments reveal the ability of currently available FDM systems to enhance prototype surfaces with form details on a millimeter scale. Results assist in identifying conditions which need to be satisfied in order to successfully reproduce generic texture geometries.Research limitations/implications – Although the testing method can be applied to any layered manufacturing technique, results are limited to a specific process, and may be influenced by technical improvements of commercial fabrication systems.Practical implications – A first contribution is give...
136 citations
TL;DR: In this article, the effect of layer thickness on the tensile, yield, impact strength and residual stress of a part was investigated using the hole drill method, and the analysis revealed that when the layer thickness is smaller, the part is higher.
Abstract: Purpose – Mechanical properties such as tensile, yield, impact strengths, and development of residual stresses play an important role intooling applications. The objective of this paper is to investigate the effect of layer thickness – one of the influential process parameters in stereolithography (SL) process, on mechanical properties of SL components.Design/methodology/approach – Test specimens are constructed as per the ASTM standards for different layer thicknesses in SL 5000 machine, using epoxy resin CIBA tool ® SL5530, a high temperature resistant SL material that is suitable for rapid tooling applications. Tensile, yield and impact tests are carried out with suitable equipments. Residual stress is analysed using hole drill method.Findings – The analysis reveals that when the layer thickness is smaller, the strength of the part is higher.Research limitations/implications – Conclusion of this research is drawn based on the analysis of the most widely used three layer thicknesses of 100, 125 and 150 ...
127 citations
TL;DR: A successful case study demonstrates that an RM approach can produce fully functional, precisely fitting RPDs, designed using computer‐aided design software according to well‐established dental technology design principles.
Abstract: Purpose – The aim of this study was to explore the application of rapid manufacturing (RM) to the production of patient specific, custom‐fitting removable partial denture (RPD) alloy frameworks. RPDs are metal frameworks designed to retain artificial replacement teeth in the oral cavity.Design/methodology/approach – The study was undertaken by applied case study. An RPD was designed using computer‐aided design software according to well‐established dental technology design principles, based on a digitally scanned cast produced from an impression of the patient's mouth. The RPD design was then exported as an STL file in preparation for direct manufacture using selective laser melting. Dimensionally accurate frameworks were manufactured in 316L stainless steel and chromium‐cobalt alloy. These were assessed for accuracy of fit and function on the patient cast and on the patient in clinic.Findings – This successful case study demonstrates that an RM approach can produce fully functional, precisely fitting RPD...
126 citations
TL;DR: In this article, the authors provide a comprehensive state-of-the-art review of environmental impact assessment of existing rapid prototyping and rapid tooling, and identify prospective research needs.
Abstract: Purpose – To provide a comprehensive state of the art review of environmental impact assessment (EIA) of existing rapid prototyping (RP) and rapid tooling (RT), and identify prospective research needs.Design/methodology/approach – The sparse literature on the EIA of RP and RT is balanced by that of the comparatively mature field of industrial ecology (IE). Hence, the review emphasizes portable IE measurement and evaluations methods. As RP and RT can also be viewed as design tools and mass customization manufacturing, other EIA may be needed.Findings – The scarcity of research to date combined with rapid technological advances leaves a large number of unresolved issues. In addition, the special character of RP and RT, as design and manufacturing enablers implies that future research is needed.Research limitations/implications – This review is drawn from a technology in rapid evolution. Hence, unresolved issues focus on technologies that already are on the market and the research needs are formulated in ter...
125 citations
TL;DR: In this paper, a new indirect scaffold fabrication method for soft tissue based on rapid prototyping (RP) technique and preliminary characterization for collagen scaffolds is presented, where the process described in this paper overcomes these problems while retaining the strength of RP techniques.
Abstract: Purpose – This paper presents a new indirect scaffold fabrication method for soft tissue based on rapid prototyping (RP) technique and preliminary characterization for collagen scaffolds.Design/methodology/approach – This paper introduces the processing steps for indirect scaffold fabrication based on the inkjet printing technology. The scaffold morphology was characterized by scanning electron microscopy. The designs of the scaffolds are presented and discussed.Findings – Theoretical studies on the inkjet printing process are presented. Previous research showed that the availability of biomaterial that can be processed on a commercial RP system is very limited. This is due mainly to the unfavorable machine processing parameters such as high working temperature and restrictions on the form of raw material input. The process described in this paper overcomes these problems while retaining the strength of RP techniques. Technical challenges of the process are presented as well.Research limitations/implicati...
TL;DR: In this article, the physical properties of stereolithography epoxy-based resins were tailored by dispersing controlled small amounts of multi-walled carbon nanotubes (MWCNTs) directly in SL resins prior to layered manufacturing.
Abstract: Purpose – The present research investigates tailoring the physical properties of stereolithography (SL) epoxy‐based resins by dispersing controlled small amounts of multi‐walled carbon nanotubes (MWCNTs) directly in SL resins prior to layered manufacturing.Design/methodology/approach – A modified 3D Systems 250/50 SL multi‐material machine was used where the machine was equipped with a solid‐state (355 nm) laser, unique ∼ 500 ml vat, overfill drain vat design that continuously flowed resin into the vat via a peristaltic pump, and 8.89 by 8.89 cm2 platform. The vat did not include a recoating system. Pumping the composite resin assisted in maintaining the MWCNTs dispersed over long periods of time (with MWCNT settling times on the order of one week). The research approach required developing a method for dispersing the MWCNTs in SL resin, determining new SL build parameters for the modified resin and SL machine, and building and testing tensile specimens.Findings – Mechanical mixing and ultrasonic dispersi...
TL;DR: In this paper, a simplified overlapping model between deposited tracks was established to investigate the relationships among the overlapping parameters, such as the ratio of width to height of the deposited track cross-section (λ), scan spacing and overlapping ratio.
Abstract: Purpose – To fabricate fully dense components with low costs, a rapid prototyping (RP) system based on micro‐plasma arc welding (MPAW) was developed. The appropriate process parameters were investigated to build the parts with good mechanical properties and surface smoothness.Design/methodology/approach – A simplified overlapping model between deposited tracks was established to investigate the relationships among the overlapping parameters, such as the ratio of width to height of the deposited track cross‐section (λ), scan spacing and overlapping ratio. Some ER308L stainless steel parts were built by different overlapping parameters, and the surface smoothness, tensile strength and elongation of the parts were tested.Findings – The overlapped surface smoothness, tensile strength and elongation of the parts built with larger λ were better than those built with smaller λ. The longitudinal tensile strength and elongation of the parts were better than the transverse data.Research limitations/implications – T...
TL;DR: Overall, excellent mandible symmetry and stability were achieved with the custom made implants, and the patient was able to eat and there was no saliva drooling after the reconstruction.
Abstract: Purpose – This paper describes computer‐aided design (CAD) and rapid prototyping (RP) systems for the fabrication of maxillofacial implantDesign/methodology/approach – Design methods for medical RP of custom‐fabricated are presented in this paper Helical computed tomography (CT) data were used to create a three‐dimensional model of the patient skull Based on these data, the individual shape of the implant was designed in CAD environment and fabricate by RP process One patient with a large mandible defect underwent reconstruction with individual prefabricated implant resulting from initial surgical failure with hand contoured reconstruction plateFindings – Results shows that the custom made implant fit well the defect Overall, excellent mandible symmetry and stability were achieved with the custom made implants The patient was able to eat There was no saliva drooling after the reconstruction The operating time was reducedResearch limitations/implications – The methods described above suffer from
TL;DR: In this article, the authors presented the first demonstration of complete, functional, ionomeric polymer-metal composite (IPMC) actuators produced entirely by free-form fabrication, which can operate continuously in air for more than 4'h and 3'000 bidirectional actuation cycles.
Abstract: – To seek to produce low‐voltage, soft mechanical actuators entirely via freeform fabrication as part of a larger effort to freeform fabricate complete electromechanical devices with lifelike and/or biocompatible geometry and function., – The authors selected ionomeric polymer‐metal composite (IPMC) actuators from the literature and the authors' own preliminary experiments as most promising for freeform fabrication. The authors performed material formulation and manual device fabrication experiments to arrive at materials which are amenable to robotic deposition and developed an SFF process which allows the production of complete IPMC actuators and their fabrication substrate integrated within other freeform fabricated devices. The authors freeform fabricated simple IPMC's, explored some materials/performance interactions, and preliminarily characterized these devices in comparison to devices produced by non‐SFF methods., – Freeform fabricated IPMC actuators operate continuously in air for more than 4 h and 3,000 bidirectional actuation cycles. The output stress scaled to input power is one to two orders of magnitude inferior to that of non‐SFF devices. Much of this difference may be associated with process‐sensitive microstructure of materials. Future work will investigate this performance gap., – Device performance is sufficient to continue exploration of SFF of complete electromechanical devices, but will need improvement for broader application. The feasibility of the approach for producing devices with complex, non‐planar geometry has not been demonstrated., – This work demonstrates the feasibility of freeform fabricating IPMC devices, and lays groundwork for further development of the materials and methods., – This work constitutes the first demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.
TL;DR: In this article, the capabilities and product quality of four state-of-the-art metal rapid prototyping and manufacturing (RPM) systems were compared to evaluate and compare four identical benchmarks fabricated from different metallic powders using four recently developed RPM systems for metals.
Abstract: Purpose – To compare the capabilities and product quality of four state‐of‐the‐art metal rapid prototyping and manufacturing (RPM) systems. This comparison could help industrial companies to know the advantages and disadvantages of each system and decide which system is the most appropriate for their application field.Design/methodology/approach – This work evaluates and compares the quality of four identical benchmarks fabricated from different metallic powders by using four recently developed RPM systems for metals. The evaluation considers benchmark geometry, dimensional precision, material type, product strength and hardness, surface quality, building speed, materials, operation and running cost.Findings – Results show that using RPM technology for the production of metallic products proved to be successful and promising technology to fabricate high strength products such as dies and molds parts which have complicated geometry and fine features. The best quality and strength was developed by the techn...
TL;DR: In this paper, a 3D freeform model of a femur bone was reconstructed based on computerized tomography images via reverse engineering and the 3D reconstruction accuracy was evaluated.
Abstract: Purpose – To present a custom design and fabrication method for a novel hemi‐knee joint substitute composed of titanium alloy and porous bioceramics based on rapid prototyping (RP) and rapid tooling (RT) techniques.Design/methodology/approach – The three‐dimensional (3D) freeform model of a femur bone was reconstructed based on computerized tomography images via reverse engineering and the 3D reconstruction accuracy was evaluated. The negative image of artificial bone was designed with interconnected microstructures (250‐300 μm). The epoxy resin mould of a hemi‐knee joint and the negative pattern of an artificial bone were fabricated on Stereolithography apparatus. Based on these moulds, a titanium‐alloy hemi‐knee joint and a porous‐bioceramic artificial bone were created by quick casting and powder sintering (known as RT) techniques, respectively. After assembling, a composite hemi‐knee joint substitute was obtained.Findings – The 3D reconstructed freeform model of the femur bone conformed to the origina...
TL;DR: In this article, the main objective is to analyse all stages of the CastForm™ polystyrene (CF) pattern fabrication process, identify the reasons leading to inferior quality, and outline techniques for its improvement and reduction of failures.
Abstract: Purpose – The main objective of this paper is to analyse all stages of the CastForm™ polystyrene (CF) pattern fabrication process, identify the reasons leading to inferior quality, and outline techniques for its improvement and reduction of failures.
Design/methodology/approach – This paper describes rapid manufacturing of patterns for shell or flask investment casting using the laser sintering (LS) technique with CF material. The process involves data preparation, LS fabrication of a “green” part, cleaning, and wax infiltration. All process stages are equally important for successful project completion in terms of pattern quality and delivery time. A failure at any stage requires a part or pattern to be produced again, which would incur additional time and cost.
Findings – The conducted experiments show how the CF material strength varies at different process stages and temperatures. Cleaning and wax infiltration are considered the main reasons for part distortion and breakage.
Originality/value – The paper proposes a new approach for wax infiltration. Deformation and breaking of unsupported features could be reduced or eliminated by introducing a supporting structure under these features.
TL;DR: In this paper, a slab grid is generated in each layer of the object and it consists of a number of pixels, and the interior properties of each pixel in the slab grid are checked so that slab models of the fractal are created.
Abstract: Purpose – Fractal geometry can be used to model natural objects which cannot be easily represented by the euclidean geometry. However, contemporary computer‐aided design (CAD) and computer‐aided manufacturing (CAM) systems cannot be used to model a fractal object efficiently. In a general layer manufacturing (LM) workflow, a model described by the euclidean geometry is required in order to generate the necessary toolpath information. So this workflow cannot be applied for a fractal object. In this paper, to realize the fabrication of a fractal represented object by the LM technology, a methodology is proposed.Design/methodology/approach – In the proposed methodology, a slab grid is generated in each layer of the object and it consists of a number of pixels. The interior property (corresponding to the fractal object) of each pixel in the slab grid is checked so that slab models of the fractal are created. The boundary of each slab is traced and refined so that the toolpath of the object can be generated fr...
TL;DR: In this paper, the authors used a stereolithographic apparatus (SLA) to fabricate a ceramic green part for aluminium casting, which was then used as a green mold for aluminum casting.
Abstract: Purpose – In this work, the production of ceramic moulds for aluminium casting using a stereolithographic apparatus (SLA) is presented.Design/methodology/approach – Suspensions of silica powders in a photoreactive resin were used in a standard SLA equipment in order to build green parts. SLA, SLA‐250 (3D System, Valencia, CA) was modified in order to fabricate a ceramic green parts.Findings – A characterization of mechanical properties of the material samples was performed. Finally, moulds for aluminium casting were obtained either using the stereolithographic part as a green mould, either by pyrolisis of the organic binder and subsequent sintering at high temperature.Research limitations/implications – Future investigations will be devoted to optimise the process and the mechanical performances of the sintered parts, improving the rheological properties of suspensions and reducing the building time.Originality/value – This is a novel work on the production of ceramic moulds for aluminium casting using a SLA.
TL;DR: In this article, a post-processing method is proposed to reduce the shrinkage and creep of porous metal skeletons by using a nanoparticle suspension that strengthens the bonds between particles to reduce shrinkage during steel infiltration.
Abstract: Purpose – Solid freeform fabrication processes such as three‐dimensional printing (3DP) and selective laser sintering (SLS) produce porous parts. Metal parts produced by these processes must be densified by sintering or infiltration to achieve maximum material performance. New steel infiltration methods can produce parts of standard alloy compositions with properties comparable to wrought materials. However, the infiltration process introduces dimensional errors due to both shrinkage and creep — particularly at the high temperatures required for steel infiltration. Aims to develop post‐processing method to reduce creep and shrinkage of porous metal skeletons.Design/methodology/approach – The proposed process treats porous metal parts with a nanoparticle suspension that strengthens the bonds between particles to reduce creep and sintering shrinkage during infiltration. The process is tested by comparing the deflection and shrinkage of treated and untreated cantilevers heated to infiltration temperatures. T...
TL;DR: In this article, the effects of discharge current, pulse-on-time, flushing pressure are optimized for minimum tool wear rate (TWR), maximum metal removal rate (MRR), and minimum surface roughness (Ra).
Abstract: Purpose – The purpose of this paper is to optimise the electro‐discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as EDM electrodes.Design/methodology/approach – In this paper the effects of discharge current, pulse‐on‐time, flushing pressure are optimized for minimum tool wear rate (TWR), maximum metal removal rate (MRR) and minimum surface roughness (Ra). Taguchi‐based L9 orthogonal array has been used for performing experiments on EDM machining of EN 24 steel using DMLS electrodes. The grey relational analysis combined with ANOVA techniques have been employed to determine the optimal level as well as their significance.Findings – Experimental results have shown that the performance characteristics of the EDM process (TWR, MRR and surface roughness) using DMLS electrode can be quantified and controlled effectively by grey relational approach presented in the study. Current is found to be the most affective parameter in EDM machining using ...
TL;DR: In this article, an experimental implementation of the rapid product and process development (RPPD) methodology is described for composite functional prototype design and rapid manufacturing (RM), where the simultaneous integration of VP/RP/RT/RE/RM technologies consolidates a powerful methodology to achieve the RPPD objectives.
Abstract: Purpose – To provide an innovative way for manufacturing in which the integration of rapid technologies is simultaneously used methodologically in real‐time for the rapid product and process development (RPPD).Design/methodology/approach – A range of related works are discussed and an experimental implementation of the RPPD methodology is described for composite functional prototype design and rapid manufacturing (RM). The simultaneous integration of VP/RP/RT/RE/RM technologies consolidates a powerful methodology to achieve the RPPD objectives.Findings – The RPPD developed methodology takes advantage of both virtual prototyping (VP) and physical prototypes made by rapid prototyping (RP) technology to evaluate performances and design ergonomic aspects. The increasing needs to reduce lead‐time and costs have direct converting RP in rapid tooling (RT) technology for RM. Furthermore, to verify the parts and tools geometry accuracy the simultaneous use of scanning techniques for metrology control aided by reve...
TL;DR: In this article, a mesoscale RF relay that integrates advanced high resolution stereolithography (SL) and micro wire electro discharge machining (μEDM) technologies is presented.
Abstract: Purpose – This paper presents a novel mesoscale RF (mRF) relay that integrates advanced high resolution stereolithography (SL) and micro wire electro discharge machining (μEDM) technologies. Methods and infrastructure for reliable batch assembly of electromechanical actuators and structural parts less than 5 mm3 in volume are described. Switches made using these techniques are expected to have greater power handling capability relative to current micro RF relay products.Design/methodology/approach – The conjecture is that the integration of SL and similar rapid additive manufacturing with other mesofabrication technologies can yield innovative miniature products with novel capabilities. A series of mRF prototypes consisting of a contact mechanism and actuator with return spring were fabricated assembled, inspected, and characterized for electromechanical performance. Characterization results led to specific conclusions regarding capabilities of the mRF product, and the integrated manufacturing technique.F...
TL;DR: In this paper, the compensation zone approach is used to compensate for the increase in the Z dimension that would occur due to print-through, and three process variables have been identified: thickness of compensation zone, thickness of every layer and exposure distribution across every image used to cure a layer.
Abstract: Purpose – Print‐through results in unwanted polymerization occurring beneath a part cured using Mask Projection Stereolithography (MPSLA) and thus creates errors in its vertical dimension. In this paper, the “Compensation Zone approach” is presented to avoid this error.Design/methodology/approach – Compensation zone approach entails modifying the geometry of the part to be cured. A volume (compensation zone) is subtracted from underneath the CAD model in order to compensate for the increase in the Z dimension that would occur due to print‐through. Three process variables have been identified: thickness of compensation zone, thickness of every layer and exposure distribution across every image used to cure a layer. Analytical relations have been formulated between these process variables in order to obtain dimensionally accurate parts. The compensation zone approach is simulated on a test part with a slanted down‐facing surface.Findings – The simulation results show that the compensation zone approach can ...
TL;DR: In this article, an in situ Al-alumina structured composite was constructed using the direct fused deposition process using a commercial fused deposition modeler, FDM 1650, to process controlled porosity green ceramic structures.
Abstract: Purpose – Al‐alumina interconnected phase composites were processed using the direct fused deposition process. These materials with tailored microstructures can find applications as structural materials with gradient properties.Design/methodology/approach – In this process, feedstock material with fused silica as a starting material was compounded at a high shear mixer and then extruded as a filament using a single screw extruder. Extruded filaments were used with a commercial fused deposition modeler, FDM 1650, to process controlled porosity green ceramic structures. Porous green ceramic preforms were subjected to binder removal and sintering cycles in furnace air. Controlled porosity sintered ceramic structures were infiltrated with Al 5052 metal by pressureless reactive metal infiltration to form an in situ Al‐alumina structured composite.Findings – The main advantage for this approach is to control distribution of both metal and ceramic phases in the composite. During metal infiltration good bonding w...
TL;DR: In this paper, a high-resolution stereolithography (SL) system was developed to satisfy the demands for rapid prototyped small-size objects with intricate microstructures, which consists of a single mode He-Cd laser, an improved optical scanning system, a novel recoating system and a control system.
Abstract: Purpose – To satisfy the demands for rapid prototyped small‐size objects with intricate microstructures, a high‐resolution stereolithography (SL) system is developed.Design/methodology/approach – This novel SL system consists of a single mode He‐Cd laser, an improved optical scanning system, a novel recoating system and a control system. The improved optical system consists of a beam expander, an acoustic‐optic modulator, a galvanometric scanner and an F‐θ lens; the recoating system consists of roller pump, resins vat with an integrated high‐resolution translation stage and part building platform and a scraper. Experimental studies were performed to investigate the influences of building parameters on the cured line width and depth.Findings – With the SL system, a laser light spot with a diameter of 12.89 μm on the focal plane and resin layers with a thickness of 20 μm have been obtained. The experimental results indicate that cured depth and width increase with the ratio of laser power to scanning speed,...
TL;DR: In this article, a new fabrication method for fuel cell current collectors is presented, where the selective laser sintering (SLS) technique is used to create green parts followed by a high temperature curing process and pressureless infiltration treatment to meet basic part design requirements.
Abstract: Purpose – This paper aims to present a new fabrication method for fuel cell current collectors. Demonstration of its usefulness and discussion of its impact on current collector design and performance are also given.Design/methodology/approach – The selective laser sintering (SLS) technique is used to create green parts followed by a high temperature curing process and pressureless infiltration treatment to meet basic part design requirements.Findings – A material system and process satisfying both manufacturing constraints and product property requirements can be used for fabrication of current collectors via SLS. Relative particle size and composition of the constituents play an important role in successful manufacture of the plates. Strategies to improve electrical conductivity are also discussed.Originality/value – A new manufacturing method has been developed for the construction of fuel cell current collectors that could generate opportunities for performance enhancement and fuel cell application by...
TL;DR: In this paper, the authors present a case study where an anaesthetist's idea was to develop a product that could hold an endo-tracheal (ET) tube in place in a more secure manner than is possible with current technologies.
Abstract: – The paper reflects on the development of a medical product using rapid prototyping technologies and customer interaction through a quality function deployment (QFD) approach to speed up the process, and to result in customer satisfaction. The purpose of the specific medical product was to develop a device for fixing an Endo‐tracheal (ET) tube in a patient during anaesthesia, as it is common for an ET tube to move and/or become dislodged due to various extraneous reasons. If the tube deviates from the correct position it can cause one or both lungs to collapse, which can be fatal. The paper reviews how the anaesthetist's idea, which was to develop a product that could hold an ET tube in place in a more secure manner than is possible with current technologies, was brought to fruition through customer interaction., – Using an action‐research approach, the design evolved through series of design concepts, which through customer interaction contributed to a total optimized design. Virtual and physical prototypes, together with silicone mouldings were used as part of the customer interaction., – As with any new product, some functional parts were needed to conduct tests, which in turn would help to prove the product, and hence, the design. Traditionally this meant the manufacturing of a hard tool and proving of the design through trial and error. Hard tooling allows for some small changes to be made, but if the changes are radical a new tool will have to be designed and manufactured., – Following a developmental approach through the application of various types/stages of prototyping (such as virtual prototypes), revolutionised this process by simplifying and accelerating the development iteration process – it also developed a new version/paradigm of QFD., – Opposed to traditional forms of QFD where customer inputs are gathered through questionnaires, this case study proved that functional models provide an efficient client‐feedback, through constant involvement in the development process, as well as evaluation of the systematic progress., – The case study shows that experts in other disciplines can become involved in the product development process through the availability of functional prototypes, and builds on previous work to introduce a concept of customer interaction with functional prototypes.
TL;DR: In this paper, the authors introduce the principle of mask exposure and scanning stereolithography (MESS) and develop a simulation code to analyze the MESS process, which can analyze the shrinkage effect in accordance with scanning path and mask exposure pattern.
Abstract: Purpose – This paper aims to introduce the principle of the mask exposure and scanning stereolithography (MESS) and to develop a simulation code to analyze the MESS process.Design/methodology/approach – Photopolymerization is a key reaction in stereolithography. It brings about molecular linkage and releases exothermic temperature. The shrinkage effect is the major cause of prototype deformation, and the shrinkage resulting from scanning and mask exposing is different. It is important to analyze the inaccuracy of each curing layer after the mask exposing in order to optimize the scanning parameters. A simulation code, based on dynamic finite element method, to analyze the shrinkage effect in accordance with scanning path and mask exposure pattern. A benchmark model has been proposed to validate the implementation of the developed code.Findings – The simulation results show that the developed code can analyze the deformation in laser scanning, masking exposing and the MESS process. In benchmark model study...