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Magnetic-field assisted finishing (MAF) is a surface finishing process that utilizes a flexible brush composed of iron and abrasive particles typically mixed in a liquid medium. This paper presents an innovative approach to enhance the MAF performance by adding nano-scale solid lubricant into the brush. In particular, exfoliated graphite nanoplatelets (xGnPs), multi-layered graphene platelets with micro-scale diameter and nano-scale thickness, have been introduced into the brush. The modified brush consisting of iron particles, abrasives (cubic boron nitride, cBN), and xGnPs in silicone oil was applied to finish the surface of mold steel. While varying magnetic flux density, cBN particle sizes, and xGnP content in the MAF brush, a series of MAF experiments was conducted to examine their impact on the achieved surface quality on a workpiece and the life of MAF brush. For a given content of xGnPs in the brush, the quality of surface finish was improved and the life of MAF brush was extended significantly with larger abrasives in the brush. Furthermore, the effect of xGnPs with respect to abrasive size was investigated with various factors such as relative number and surface area coverage of xGnPs per abrasive, the relative size of xGnP to abrasives, and depth indented by abrasives on the workpiece, which enabled us to identify the change in the underlying mechanisms in relation to the abrasive size. The new MAF brush is also expected to improve the efficiencies of the overall MAF process in terms of energy consumption and material utilization.

Haynes 214 high temperature heat exchanger assembly with enclosed heat flow channels and internal fin structures was successfully fabricated using our scalable and expeditious additive manufacturing (SEAM) process, a new metal additive manufacturing (AM) technology developed at Michigan State University (MSU). Three dimensional green objects can be fabricated by selectively photopolymerizing Haynes 214 metal suspension on a powder bed system in a layer-by-layer fashion. An innovative strategy to attain a complete binder removal and high density as well as dimensional accuracy were developed and employed to achieve final metal parts with relative density above 99.5% and no geometrical distortion.

Haynes 214, a nickel-based superalloy, and its oxide dispersion-strengthened (ODS) versions (addition of 0.3, and 1.5 wt. % yttria (Y2O3)) have been successfully fabricated using selective laser melting (SLM). For each feedstock formulation, optimal processing conditions were identified and high temperature tensile testing coupons were produced. Feedstock preparation and laser scanning strategy have been proven to be critical in the dispersion of nanoparticles in the metal matrix, as well as preventing the formation of extensive crack networks. The impact of Y2O3 addition on the high-temperature tensile properties of Haynes 214 was evaluated and discussed.

Open product architecture is a key enabler for product personalization, as it allows the integration of personalized modules in a product architecture to satisfy individual customer needs and preference. A critical challenge for integrating personalized modules into a product architecture is determining the optimal assembly architecture when considering market expectations and manufacturing constraints. In this paper, an optimization method is proposed for determining the personalized product design architecture that incorporates individual customer preferences. First, a decision hierarchy is presented to describe the integrated design decisions of the product architecture, including product variety determination, module variant selection, and personalized module configuration. Next, a profit model is formulated as an overall performance metric that incorporates customer preferences and manufacturing cost. The systematic patterns and randomness of diverse customer preferences are modeled by combining conjoint analysis and market segmentation with a multivariate normal mixture model. Individual customer product utilities in the target market and their product purchase intent probability are estimated through Monte-Carlo simulation, which is incorporated into the profit calculation. Manufacturing limitations on processes and materials are included as they influence manufacturer’s planning on candidate module variants and production strategies of personalized modules. These models are used to determine a product family architecture that maximizes profit by optimally determining its offering of product variants, module combinations, and personalized module configuration through a genetic algorithm. The proposed method is demonstrated by a personalized bicycle architecture design example.

This paper introduces a new additive manufacturing (AM) process which significantly improves the productivity of the current metal AM technologies by combining binder jet printing and stereolithography principles. Three dimensional objects can be printed on a powder bed system where photopolymerization takes place by selectively curing the suspensions containing metallic powder and ultraviolet curable resin in a layer-by-layer fashion. Integration of a digital light projection module allows a high-speed production with dimensional accuracy within 100 µm. Printed parts are sintered at appropriate temperatures to attain metal parts with the final density above 97% and homogenous microstructure without residual stress.

This paper explores the characteristics of a new lightweight thermoplastic composite filament filled with hollow glass beads developed for material extrusion additive manufacturing. Compounding experiments, which mix hollow glass beads with neat acrylonitrile butadiene styrene matrix, were conducted using a twin-screw extruder to prepare composite filaments. Two different types of hollow glass beads were selected as the fillers of composite filament due to their varying densities. In order to characterize the final components produced using composite filament, various specimens were fabricated by a material extrusion additive manufacturing process. In order to characterize the physical properties of the specimens, measurements of density and flexural testing were performed. To identify the thermomechanical effects of hollow glass beads on the neat acrylonitrile butadiene styrene matrix, thermal diffusivity and specific heat were obtained. Consequently, the thermal conductivity of the specimen was derived from its density, thermal diffusivity, and specific heat capacity. The microstructures of the fractured interfaces of the specimens were also observed by scanning electron microscopy. The experimental results revealed that most of the hollow glass beads survived, thus bringing about lighter weight (lower density) and thermal insulation (lower thermal conductivity), which can be useful for numerous potential applications.

In functionally graded materials (FGM), material property gradually changes within a product. To manufacture FGM by additive manufacturing (AM) using polymer powders, precise deposition of different powder materials is crucial. The powder deposition, however, is challenging, because process control and material choices are complicated. This paper presents a newly developed laser-based AM system using the direct deposit of poly-lactic acid powders on the target surface. This direct-writing AM system can facilitate material change even within a layer for superior material property variation. This study characterizes the optimal process conditions for deposition consistency by statistical methods. This study also identifies suitable statistical models by examining the model characteristics such as lack-of-fit and curvature. In addition, this study finds an appropriate statistical method to handle process abnormality such as no powder flow. Through these analyses, this study characterizes the optimal combination of process conditions and material choices for stable powder deposition, and verifies the best conditions for the new AM system. This study will help develop a new AM system with the optimal deposition for each material composition to produce novel material structure for FGM.

Magnetic-Field Assisted Finishing (MAF) is a polishing process that utilizes a slurry mixture made of ferrous and abrasive particles in a liquid medium, known as a brush. The brush attached to a magnetic tool directly interacts with the surface of a workpiece and removes any imperfections and defects in the surface giving a smooth and nice surface finish. In this study, two distinct MAF setups were applied to the surface of chromium alloyed low carbon steel sheets to achieve the surface finish. The preliminary studies were conducted on one setup to understand the polishing behavior of the sheets and the other setup was designed to polish larger areas of the sheets to mimic the practical sheet producing environment. The effect of processing conditions such as types and sizes of abrasives, brush composition, and finishing time to attain the final surface roughness of the sheets was studied. The brush with the weight composition of 4:1:1.5 (iron: 3 μm black ceramic: silicone) was found to be the optimal condition for polishing the sheet metal samples. The optimal conditions obtained were applied to the larger scaled experimental setup. The final surface roughness of 38 nm and 220 nm were achieved in these experimental setups, respectively.

In this paper, a new hybrid manufacturing process was proposed to fabricate biomimetic intestinal villi. The hybrid process consists of two steps, i.e., a micro-drilling process to make steep holes and a laser-based machining process to smoothen their geometries. Polycarbonate (PC) was used as a candidate material for mold, and villi’s scaffold was fabricated using polydimethylsiloxane (PDMS). For the hybrid manufacturing process, conditions of the micro-drilling process were optimized first and then a series of laser-based machining experiments were performed using the pre-produced micro-drilled molds. A full factorial design of experiments was conducted to investigate the effects of laser power, air, and the objective lens, and the shape of villi was observed as an output to evaluate the process performance. Experimental results demonstrated that the proposed hybrid manufacturing process is able to fabricate villi whose geometry is consistent and suitable for cell culturing. Consequently, villi scaffold with various dimensions could be conveniently built using different parameters, and it could be applied to personalized organ-on-a-chip applications in the future.

Personalization is an emerging manufacturing paradigm towards meeting diversified customer needs. This paper proposes a framework for producing personalized products efficiently. An approach for optimal mix of different module types is proposed in order to construct a proper assembly architecture. Sketch-based modeling, which facilitates easy model creation and modification by customers, is presented as a key to personalized design. A cyber physical system provides the platform for the collaborative design and co-creation of personalized products. A case study on personalized bicycles based on the proposed framework is presented. Such a framework enables open product realization through active customer participation.

Electrohydrodynamic (EHD) jet printing creates micro or nano scale patterns using a simple configuration of a printing nozzle, precision pump, voltage generator, and pressure regulator. Drawing patterns by an EHD printing system on a substrate requires continuous and precise movement of either a printing nozzle or target substrate. This requirement for precision mechanical movement increases the setup cost and limits the spatial resolution of the printing. In this study, we propose a concept of "motionless" EHD printing that can print patterns without any mechanical motion of a printing nozzle or the substrate. The motionless EHD printing utilizes an array of target micro electrodes that can be selectively connected to a voltage generator. This study focused on the vertical and horizontal range of the motionless printing by investigating how the vertical and horizontal distances between the microelectrodes and the nozzle influenced on the quality of printing patterns. Finally, this motionless EHD printing was used to create patterns of biodegradable polymer/model drug mixtures for controlled drug delivery and their release performance in vitro was demonstrated. Display Omitted Motionless electrohydrodynamic (EHD) printing is proposed.Printing location is controlled without movement of both a nozzle and substrate.Motionless EHD printing covers a lateral distance of 1.2 mm from a printing nozzle.Printing pattern decreases down to 3µm for reduced gap between nozzle and substrate.

With the rapid development of sensing, communication, computing technologies, and analytics techniques, today&rsquo, s manufacturing is marching towards a new generation of sustainability, digitalization, and intelligence. Even though the significance of both sustainability and intelligence is well recognized by academia, industry, as well as governments, and substantial efforts are devoted to both areas, the intersection of the two has not been fully exploited. Conventionally, studies in sustainable manufacturing and smart manufacturing have different objectives and employ different tools. Nevertheless, in the design and implementation of smart factories, sustainability, and energy efficiency are supposed to be important goals. Moreover, big data based decision-making techniques that are developed and applied for smart manufacturing have great potential in promoting the sustainability of manufacturing. In this paper, the state-of-the-art of sustainable and smart manufacturing is first reviewed based on the PRISMA framework, with a focus on how they interact and benefit each other. Key problems in both fields are then identified and discussed. Specially, different technologies emerging in the 4th industrial revolution and their dedications on sustainability are discussed. In addition, the impacts of smart manufacturing technologies on sustainable energy industry are analyzed. Finally, opportunities and challenges in the intersection of the two are identified for future investigation. The scope examined in this paper will be interesting to researchers, engineers, business owners, and policymakers in the manufacturing community, and could serve as a fundamental guideline for future studies in these areas.

Multilayered ultrasonic welding (USW) is widely used in joining of electrodes or tabs in lithium-ion batteries. To achieve quality joints and enhance the welding process robustness, an improved understanding of the joint formation is highly desirable. In this paper, USW of four-layered Ni-coated Cu is studied to investigate the joint formation at a single interface and joint propagation from interface to interface under both ambient and preheated conditions. The results indicate that joint formation involves three major mechanisms: Ni–Ni bonding with minimal mechanical interlocking, Ni–Ni bonding with moderate mechanical interlocking, and a combination of Ni–Ni bonding, Cu–Cu bonding, and severe mechanical interlocking. Results also show that joints propagate from the interface close to the sonotrode side to that close to the anvil side. It is further observed that the joint formation can be accelerated and the joint strength can be improved with process preheating, especially at the interface closest to the anvil. The effect of preheating is most significant during the early stage of the process, and diminishes as process progresses. The favorable effects of preheating improve the robustness of multilayered USW.

Magnetic field-assisted finishing (MAF) is a surface quality enhancing process that utilizes a flexible brush composed of ferrous metal and abrasive particles. This paper experimentally and statistically investigates the characteristics of a MAF process with nano-scale solid lubricant. A new MAF tool was developed by integrating iron and abrasive particles, and nano-scale solid lubricant. In this experiment, the optical microscopic images of the surface are obtained to measure the surface roughness resulting from MAF processes with varying the content of abrasive particles and the presence of nano-scale solid lubricant. Furthermore, spatial statistics techniques are used to quantitatively evaluate the quality of the surface resulting from each combination of MAF parameters. It is demonstrated that the size and type of abrasive particles mainly affect MAF process and the newly developed MAF tool with nano-scale solid lubricant can improve the final surface quality.

Multi-layered ultrasonic welding (USW) is widely used in joining of electrodes or tabs in lithium-ion batteries. To achieve quality joints and enhance the welding process robustness, an improved understanding of the joint formation is highly desirable. In this paper, USW of 4-layered Ni-coated Cu is studied to investigate the joint formation at a single interface and joint propagation from interface to interface under both ambient and preheated conditions. The results indicate that joint formation involves three major mechanisms: Ni-Ni bonding with minimal mechanical interlocking, Ni-Ni bonding with moderate mechanical interlocking, and a combination of Ni-Ni bonding, Cu-Cu bonding, and severe mechanical interlocking. Results also show that joints propagate from the interface close to the sonotrode side to that close to the anvil side. It is further observed that the joint formation can be accelerated and the joint strength can be improved with process preheating, especially at the interface closest to the anvil. The effect of preheating is most significant during the early stage of the process, and diminishes as process progresses. The favorable effects of preheating improve the robustness of multi-layered USW.

A reduction in silicon material consumption in the photovoltaic industry is required for cost reduction. Development of ultra-thin crystalline silicon (c-Si) solar cell (

Due to the sudden increase of energy consumption from modernization and civilization, energy efficiency has become an important issue in engineering devices. Much research effort has been made to enhance the performance of individual thermal devices. However, enhanced thermal devices are usually components in a larger thermal system such as an energy network connected by pipe networks to circulate an energy-carrying medium. Even when each component operates at maximum efficiency, the general system may not work in harmony to a full extent. Thus optimizing the full thermal system would increase the energy utilization efficiency even further and ultimately decrease the amount of CO2 emission. In this paper, we developed a numerical model for estimating heat flow and temperature variation in a complex energy network system using Simulink in Matlab. Emphasis has been made on heat pump's intermittent operation, where the system can be shut down for specific periods of time. A special thermal routine for the pipe was devised where the conduction becomes major heat transfer mode during the night. The code we developed was validated by comparing experimental data, and detailed analysis on system components' temperature variations and energy flow characteristic are provided.

This paper investigates a new technology to create functionally graded material (FGM) by additive manufacturing (AM). In particular, this paper focuses on creating graphene-polymer composite FGM by laser-based sintering processes. Graphene-polymer composites have received high attention in AM due to their excellent electrical conductivity, thermal stability and mechanical strength. However, AM of the graphene-polymer composites has a huge challenge to overcome. The heterogeneous materials should be mixed properly, and it is not easy to achieve the desired composite characteristics solely by changing the mass ratio of graphene. This paper shows a newly developed laser-assisted AM system for the graphene-polymer composite FGM by laser-based sintering processes. The paper also describes two methods of material integration: mixing graphene and polyethylene powders before sintering, and depositing the different material powders separately and sintering them. This study identified that the two methods led to different mechanical and electrical properties of the created parts. Thus this paper demonstrates the possibility to create quite useful hybrid (mechanically and electrically) FGM composites.

The functionally graded material is characterized by its gradual change in material compositions and properties over the volume of a component to optimize its functional value. To fabricate functionally graded material parts by additive laser material processing, appropriate powders are critical in term of their size, shape, and mechanical properties. This paper presents new methods to mass produce polycaprolactone powders, a type of biodegradable polymer, with deliberately modified properties as well as to fabricate functionally graded material parts using the modified powders by laser material processing. To modify the properties of the biodegradable polymer powder, this research used two different approaches: recrystallization and spraying. The two different modification methods enabled the significant change of the polycaprolactone powders’ molecular weight that strongly affects mechanical properties. This controlled molecular weight change enabled the gradual variation of the mechanical properties in functionally graded material. By the two different modification methods, the raw materials with irregular shape and size were changed into powders with a round shape and similar sizes, so that they became more suitable for the laser material processing. We verified the modified powder properties such as the size distribution, shape, crystallinity degree, thermophysical properties, and molecular weight by using a variety of methods. The modified polycaprolactone powders with varying mixture ratios were sintered by Nd:YLF laser irradiation with 349-nm wavelength, and the different mechanical properties were verified by micro-tensile tests. As an application of functionally graded material, a biomedical trigger capsule was fabricated and its performance evaluation demonstrated the desired results according to three-dimensional functionally graded material design.

Thermal warpage of a glass substrate after a flash lamp annealing process for crystallization of amorphous silicon thin-film is critical to subsequent fabrication processes for manufacturing large-scale displays. This phenomenon is understood through the structural mismatching of hypothetical two-layers in a homogeneous glass structure: thermally softened and uninfluenced, and is mechanistically different from that induced by the mismatch in coefficients of thermal expansions among heterogeneous thin-film structures. Thin subsurface region experiencing the intensified heating is softened, the stress in the region is relaxed, and finally the softened region is shrunk laterally, while uninfluenced part of the substrate remains as it is. The model assumes that the shrunk subsurface layer, of which the thickness is proportional to the thermal penetration, is bonded to the uninfluenced part completely. Due to structural mismatching the substrate is deformed considerably and warped towards the light source (the flash lamp) according to the curvature-flash duration relationship, γ = C2η(1 − C1η1/2). This relationship is confirmed by numerical simulation results based on a viscoelastic model and by experimental observations.

In order to reduce the cost per watt of photovoltaic power generation, reducing the thickness of the crystalline silicon solar cell is a promising strategy. However, with a thinner silicon wafer, the bowing depth induced by two distinctive thermal expansion rates between the silicon substrate and the aluminum layer in the rear side grows exponentially. Excessive bowing can cause damage such as breakage and microcracks to the silicon wafer, eventually resulting in ruining the cell. The detail understanding of the bow phenomenon is undoubtedly significant in thin crystalline silicon solar cell fabrication. In this study, we worked on developing an accurate numerical technique that can calculate the correct deformation of the bow, especially for an ultra-thin silicon solar cell with

To reduce the cost per watt of photovoltaic power, it is important to reduce the cell thickness of crystalline silicon solar cells. As the thickness of the silicon layer is reduced, two distinctive thermal expansion rates between the silicon and the aluminum layer induce bowing in a solar cell. With a thinner silicon layer, the bowing distance grows exponentially. Excessive bowing could damage the silicon wafer. In this study, we tried to measure an irregularly curved silicon solar cell more accurately using a 3D image scanner. For the detailed analysis of the three-dimensional bowing shape, a least square fit was applied to the point data from the scanned image. It has been found that the bowing distance and shape distortion increase with a decrease in the thickness of the silicon layer. An Ag strip on top of the silicon layer can reduce the bowing distance.

A three-dimensional hydrogel scaffold has been proposed for the effective production of biomimetic intestinal villi to reduce ethical and cost problems caused by animal testing in pharmaceutical development. This study explores an experimental approach to develop a new technique based on laser machining and microdrilling processes to produce a plastic mold for the fabrication of a three-dimensional hydrogel scaffold. For process optimization, both the laser machining and the microdrilling experiments are conducted by varying the experimental conditions, and structural characterization of the mold and intestinal villi were performed using SEM (scanning electron microscope) and OM (optical microscope) images. Polycarbonate (PC) was used as a candidate material. The experimental results show that intestinal villi can be fabricated by both laser and microdrilling machining processes.

This paper investigates the methodology to modify biodegradable polymers having random size, shape, and molecular weight into particles appropriate for selective laser sintering (SLS), which is a powerful technique to build arbitrarily complex objects. Polycaprolactone (PCL), which has recently drawn significant attention as biodegradable polymer for potential application in bone and cartilage repair, was used in this study. PCL powders with various sizes, shapes, and molecular weights were modified by chemical processes and resultant shape, size distribution, degree of crystallinity, and thermophysical properties were observed by optical and scanning electron microscopy (OM and SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The modified PCL as well as raw material were sintered by CO2 laser irradiation with 10.6-im wavelength, and specimens for tensile testing were fabricated. By simple design of experiment (DOE) method, macro and micro structures of the fabricated parts were observed depending on various processing parameters related with SLS. Finally, micro tensile tests were conducted, and tensile properties as a function of molecular weight and particle shape were obtained. All the procedures attempted in this study can be extensively applied to other biodegradable polymers. Since SLS has an advantage to deposit multiple materials spatially, the obtained mechanical properties can be referred to generate functionally graded material (FGM), which incorporates deliberately designed transition in materials composition and properties within a component, by SLS.

Outdoor digital information display (DID) installed near public areas has become a very popular medium of communication. Cooling performance of an outdoor DID system has become a critical issue from increasing system temperature due to heat generation at the back panel, in addition to irradiation from the sunlight. Gap distance between the heating plate and glass could control the main heat transfer rate considering its positive or negative effect on the pressure and temperature gradient at the wall. Additional reduction of maximum surface temperature can be achieved using tapered geometry with increased inlet gap distance, as well as guide vane installation at the system exit to lower pressure loss. Full system optimization has also been performed, including correlation for tapered geometry and guide vane effect. With system optimization, we can find the optimal gap clearance of parallel or tapered geometry for best performance.

This article presents a novel technique to estimate the mechanical properties of the aluminum composite layer on silicon solar cells by using a hybrid 3-dimensional laser scanning force measurement (3-D LSFM) system. The 3-D LSFM system measures the material properties of sub-layers constituting a solar cell. This measurement is critical for realizing high-efficient ultra-thin solar cells. The screen-printed aluminum layer, which significantly affects the bowing phenomenon, is separated from the complete solar cell by removing the silicon (Si) layer with deep reactive ion etching. An elastic modulus of ~15.1 GPa and a yield strength of ~35.0 MPa for the aluminum (Al) composite layer were obtained by the 3-D LSFM system. In experiments performed for 6-inch Si solar cells, the bowing distances decreased from 12.02 to 1.18 mm while the Si layer thicknesses increased from 90 to 190 μm. These results are in excellent agreement with the theoretical predictions for ultra-thin Si thickness (90 μm) based on the obtained Al composite layer properties.

Received 10 September 2012; received in revised form 6 November 2012; accepted 7 November 2012ABSTRACTThis paper investigates the tolerance stack-up in a commercial sliding-type mobile phone modeldeveloped by a Korean electronics company, with focus on the dimensional quality of the gapbetween the sliding top and the main body. The tolerance analysis in this study is done using acommercial software package, which runs Monte Carlo simulations to produce the statistical dis-tributions of the gap size at desired locations. Such an analysis revealed that the original designdid not yield the desired dimensional quality of the gap. Through a series of systematic analy-ses and syntheses, an improved design is proposed for the nominal dimensions and tolerances ofselected features of the parts. The proposed design was validated, through tolerance analysissimulation, to meet the desired requirement of the gap quality.Key words:Computer-Aided Tolerancing (CAT), Datum Flow Chain (DFC), Gap, Mobile phone,Tolerance analysis, Tolerance design

) T : 온도 (K) t : 시간 (s) v : 기판의 처짐 (m) x : 두께 방향 거리 (m) 그리스문자 β : 열팽창률 (m/m-K) Key Words: Flash Lamp Crystallization(플래시 램프 결정화), Amorphous Silicon on Glass(유리기판위 비정질 실리콘), Large-Window Display(대면적 디스플레이), Thermal Deformation(열변형) 초록: 플래시 램프 열처리(Flash lamp annealing, FLA) 공정은 저온폴리실리콘의 생산을 위한 기술로써 대면적 기판용 실리콘 결정화 기술로 기대 받고 있는 기술이다. 본 연구에서는 FLA 공정 중 기판에 발생하는 변형의 원인에 대하여 이론적인 해석과 이를 토대로 시뮬레이션을 수행하였다. 상용 FEM 해석 프로그램에 고온에서의 유리의 점성에 대한 모델을 적용하여, 고온에서 유리의 구조적인 수축과 응력이완으로 인한 영구변형을 수치적으로 재현하였다. 0 세대 실험시편(2cm x 2cm)의 경우 중력의 영향이 미미하여서, 실험 결과와 일치하는 ‘U’모양의 변형이 남는 것을 확인하였고, 4 세대 기판(74cm x 94cm)의 경우 중력으로 인하여 ‘M’모양의 변형이 발생하는 것을 시뮬레이션하였다. Abstract: The flash lamp annealing (FLA) process has been considered highly promising for manufacturing low-temperature polysilicon on large-scale backplanes. Based on a theoretical estimation, this study clarifies the critical mechanisms of glass backplane deformation during the FLA process. A simulation using a commercial FEM code with viscoelastic models shows that the local region, whose temperature is larger than the glass softening point, undergoes permanent structural shrinkage owing to stress relaxation. For larger backplanes (4th Gen), structural shrinkages and gravitational deflection are critical to deformation in the FLA process, resulting in an “M” shape; in smaller backplanes (0th Gen), the latter is negligible, resulting in a “U” shape.

A 532nm Nd:YAG laser was applied to crystallize amorphous Si thin films in order to evaluate the applicability of Nd:YAG laser to low-temperature polycrystalline Si technology. In this study, we aim at enhancing uniformity as well as crystallinity. In order to achieve the goal, a new optical system called as a diffusing system was used to enhance the uniformity of irradiating beam profile, consequently improving the quality of crystallized microstructures. Optimal processing parameters for high crystallinity and uniformity were developed by design of experiments (DOE). To investigate crystallinity and uniformity, Raman spectroscopy and optical microscopy were utilized. Therefore, the effectiveness of Nd:YAG laser is suggested as a feasible alternative that is capable of crystallizing the amorphous Si thin films.

The in-mold labeling (IML) process has become a popular choice for the exterior decoration of many mobile devices due to its capability of rich color representation with a relatively easy manufacturing procedure. A molten polymer is injected into a cavity where pre-decorated film has been initially inserted. A heterogeneous characteristic of involved material coupled with various processing parameters can induce defects of the final product such as film delamination, wash-out, and flow-mark. In this study, major controlling parameters for the deformation of the final product have been identified with the design of experiment (DOE) method using several nondimensional quantities of temperature, material property, and thickness ratio. MOLDFLOW and ABAQUS software has been simultaneously used to simulate the injection process and thermal impact process, respectively. We found that the thickness ratio is a critical factor on final deformation, and the material property ratio has a relatively minor effect.

This paper addresses the optimization of a micro-grinding process using compressed air to minimize specific grinding forces and surface roughness while maximizing specific material removal rate (MRR). The design-of-experiments (DOE) approach and response surface methodology (RSM) are introduced to obtain the optimal grinding conditions. In the DOE approach, a central composite design approach is used for experimental design. Micro-grinding experiments are conducted, and the experimental results are used to obtain response surface models of specific grinding forces and surface roughness in terms of depth of cut, feed rate and air temperature. Multi-objective optimization is then conducted by introducing desirability functions, and the optimal values of depth of cut, feed rate and air temperature are obtained for minimum specific grinding forces and surface roughness and maximum specific MRR. The experimental results under the optimal grinding conditions are similar to those estimated from the response surface models, and thus the validity of the models is verified.

Surface-based control of melt crystallization of ibuprofen (IBU) is reported. The substrates in the present study included glass, flat Au, and laser-patterned Au. The IBU crystal morphologies were regulated depending on the surfaces where IBU crystallization was induced, and spherical, sunflower-like, and dendritic morphologies were obtained. Especially, the dendritic morphology of a large surface area was observed on the novel laser-patterned surfaces. Three-dimensionally tortuous Au structures were achieved by a 532 nm Nd: YAG laser, of which Gaussian beam profile was reshaped into a flat-top contour using a custom-designed diffusing system. Also, the effect of poly-ɛ-caprolactone was analyzed as a crystallization modulating additive to fine-tune the IBU crystal morphologies. The IBU crystallization behaviors as well as the laser patterning processes are described as a part of the ongoing efforts to develop a general strategy to utilize heterogeneous nucleation and directional growth to control the crystallization of important organic compounds, such as active pharmaceutical ingredients.

In this study, we developed a method to predict the residual stress distribution and thermal deformation caused by in-mold labeling (IML) processes. IML is one of the injection molding processes for injecting a material into a cavity and subsequently inserting a decorated film. The IML process can yield products with decorations of outstanding excellent quality in only one working step. Although the IML process has various advantages, it causes defects such as film delamination, wash-out, and flow marks. In particular, deformation is considered to be a major concern in terms of delamination. To validate the model, the deformation predicted by using a numerical model was compared with experimental results, and both results showed good agreement. We verified that the developed method can be used to obtain the design guidelines for preventing delamination in the initial design stage of the IML process.

This article investigates the fabrication of polycaprolactone (PCL) composites filled with different volume fractions (10-30%) of tricalcium phosphate (TCP) by selective laser sintering (SLS) for tissue engineering scaffolds. Optimal processing parameters for each composition were developed by design of experiments (DOE). To investigate optimal structure with the ordered porosities for tissue engineering scaffold, specimens with four different geometries were generated and compressive mechanical tests were conducted. Furthermore, the experimentally measured compressive moduli for solid specimen were compared with moduli predicted by Halpin's theoretical model, and were found to be in excellent agreement. The results of this study can provide invaluable information for further developing and fabricating tissue engineering scaffolds with adequate mechanical load-bearing function and desirable porosity for applications.

Selective laser sintering (SLS), a layered manufacturing-based freeform fabrication approach was explored for constructing three-dimensional structures in functionally graded polymer nanocomposites. Here, we report on the processing and properties of functionally graded polymer nanocomposites of Nylon-11 filled with 0–10% by volume of 15 nm fumed silica nanoparticles. SLS processing parameters for the different compositions were developed by design of experiments (DOE). The densities and micro/nanostructures of the nanocomposites were examined by optical microscopy and transmission electron microscopy (TEM). The tensile and compressive properties for each composition were then tested. These properties exhibit a nonlinear variation as a function of filler volume fraction. Finally, two component designs exhibiting a one-dimensional polymer nanocomposite material gradient were fabricated. The results indicate that particulate-filled functionally graded polymer nanocomposites exhibiting a one-dimensional composition gradient can be successfully processed by SLS to produce three-dimensional components with spatially varying mechanical properties.

Solid immersion lenses (SIL) facilitate high numerical aperture (NA) and consequent sub-wavelength diffraction limited focusing in near-field optics based systems. Such systems are in commercial and research use for various applications including near-field scanning optical microscopy, ultra-high-density magneto-optic data storage and near-field nanolithography. Here, we present a novel manufacturing method using SIL-based near-field optics for laser-induced patterning on silicon wafers. The near-field effect of SILs was investigated by using hemispherical lenses made of three different materials (BK7, Sapphire, LaSFN9) to superfocus an incident Q-switched, 532 nm Nd:YAG laser beam transmitted through a focusing objective. This optical arrangement achieved a laser-processed feature resolution near the diffraction limit in air. Results of experiments that were conducted at various processing conditions to investigate the effects of varying incident laser power (with peak pulse power less than 1 W), pulse width, number of pulses and size of SIL on processed feature size and resolution are presented. Experimental results are compared with numerical simulations using the simplified model.

This article investigates the fabrication of functionally graded materials (FGMs) by selective laser sintering (SLS) of Nylon-11 composites filled with different volume fractions of glass beads (0–30%). The investigation involved a combination of experimental studies, theoretical modeling and numerical analysis. Optimal processing parameters for each composition were developed by design of experiments (DOE). These parameters were then compared with parameters predicted by numerical modeling. Specimens for tensile and compressive testing for each composition and for a 1D FGM composition were fabricated and tested. The experimentally measured tensile and compressive moduli were compared with moduli predicted by Halpin's theoretical model and were found to be in excellent agreement. The results showed that the tensile and compressive modulus increases while strain at break and strain at yield decreases as a function of glass bead volume fraction. A finite element model for the compressive properties of the 1D FGM specimen showed good agreement with experimentally measured values. Finally, to demonstrate the SLS-based FGM approach, two components exhibiting a one-dimensional functional gradient of particulate-filled polymer composites were fabricated.

We present a 1-D heat transfer, melting, vaporization and resolidification model describing the interaction of a scanning continuous-wave laser with a metal surface wherein the beam power is constant. A physical model based on the Stefan problem is developed with appropriate boundary conditions. The effects of processing parameters on process variables are investigated numerically by varying beam diameters, scan speeds and substrate temperatures for Nickel. Relations are derived for the times to initiate melting, to initiate vaporization, to reach maximum melting depth, for melting-resolidification, and for maximum melting and vaporization depths. Surface temperatures are compared with approximate closed form solutions.

This paper reviews the state-of-the-art research related to the dimensional accuracy in additive manufacturing (AM) processes. It is considered that the improvement of dimensional accuracy is one of the major scientific challenges to enhance the qualities of the products by AM. This paper analyzed the studies for commonly used AM techniques with respect to dimensional accuracy. These studies are classified by process characteristics, and relevant accuracy issues are examined. The accuracies of commercial AM machines are also listed. This paper also discusses suggestions for accuracy improvement. With the increase of the dimensional accuracy, not only the application of AM processes will diversify but also their value will increase.Copyright © 2014 by ASME

Injection molding process is a widely used manufacturing technique to massively produce the components of mobile device with various sizes and complicated geometries. However, the final part quality, especially dimension or geometry, referring to the original design specifications is not often acceptable due to various reasons. This study aims at developing the numerical model to predict the final part quality and subsequently identifying the critical reasons for existing problems. moldflow and abaqus software have been simultaneously used to simulate the injection molding process and thermal deformation arising after ejection step from the mold. In order to validate the model, the deformation predicted by the developed model was compared with experimental results, and both results showed good agreement. We also carried out design of experiment (DOE) to investigate the effect of various processing parameters that affect the final deformation of injection molded product. The developed model and information derived from DOE are expected to provide useful resources to the initial stage of mobile device design.