Draft Angle Research Articles

An engineering approach to optimal metallic bipolar plate designs reflecting gas diffusion layer compression effects

GDL (Gas diffusion layer) intrusion into gas feeding channels narrows the effective channel cross-sectional area and eventually results in performance degradation of PEFCs (polymer electrolyte fuel cells). Therefore, cross-sectional channel design of metallic bipolar plates should be optimized to resolve this problem. In this study, effects of the cross-sectional configuration of metallic gas channels on pressure drops are numerically investigated for the comprehensive fluid dynamic analysis of channel flow. Multi-physics numerical systems combining solid mechanics and fluid dynamics are applied to figure out the GDL behavior. First, static structural analysis is performed to determine elastic deformation of GDLs under clamping forces. Subsequently, computational flow analysis in the deformed regions is conducted to visualize flow patterns and estimate corresponding pressure drops. Four cross-sectional parameters are selected: channel to rib width ratio, draft angle, inner fillet radius and clamping pressure. Results are validated against experimental data. The GDL intrusion is found to be greatly affected by draft angle and channel to rib ratio. Cross-sectional area is reduced down to 45% in the most shrunk channel, leading additional pressure drop of 0.12 bar. It is suggested that fluid dynamics should be combined with solid mechanics for better accuracy in computational fuel cell modeling.

The effect of material characteristics and mould parameters on the thermoforming of thick polypropylene sheets

Two grades of 5 mm thick polypropylene (PP) sheets, one having linear polymer chains (PP-TF-1) and the other having long-chain branches (PP-TF-2), were drape formed, using moulds of different parameters. Single-sided heating of sheet was found to be suitable only at lower depths of draw. Double-sided heating gave good part shape conformance at all depths of draw. PP-TF-2 was found to have lower crystallinity than PP-TF-1, suggesting that it would have a lower sagging tendency and would give parts with more uniform wall thickness distribution. This was confirmed in formability studies. At higher depths of draw, an increase in draft angle was found to give more uniform wall thickness distribution, maintaining reasonable values of wall thickness. At lower depths of draw, draft angle was found to have no influence on product quality. Irrespective of material characteristics and other mould parameters, only moulds with generous values of corner radii gave strong corners.

Optimization of a Reinforcing-Rib Design for ABS and High Glossy Surfaces of Plastic Parts

The goal of this study is to determine the optimum value of design variables in mixed conditions of the thickness, height and draft angle of reinforcing ribs within an objective limit in ABS resin and a high glossy surface. For this purpose, we investigated the actual depths of sink marks on the surface of the specimen that was manufactured with an injection mold specifically for this study. A response surface methodology with the Box-Behnken design was used to analyze the real depths with combinations of the thickness, height and draft angle of the ribs. The result shows that the most influential factor to increase the shrinkage is the thickness of ribs and that the optimum value of the rib thickness is a multiple of 0.31 of the section thickness. It was found that the rib height and rib draft angle are not factors that can change the sink amount.

The Numerical Simulation of Multi-Directional Forging EQ153 Steering Knuckle

This paper centers on EQ153 steering knuckle multi-directional forging forming, and applying Deform-3D to simulation the deformation process. According to temperature, effective strain, load prediction and final forging shape to illustrate in such a process a near-net-shape forming with no flash and little draft angle and lower pressure is been formed.

Design and Optimization of Forged aluminium Tension strut

Suspension system of an automobile plays an important role in ensuring the stability of the automobile. Although it has been achieved to a considerable extent, another major aspect of suspension system is passenger car. Now a day in automobile Industries every supplier is trying to give a good product with cheap price to the customer. By considering the customer requirement I am designing Forged aluminium Tension Strut which will satisfy the customer requirement. Tension Strut is the part of Linkages system which is link between the Chassis and Wheel assembly with specific ball joint at one side and Bushing at another side. In SUV (sport utility vehicle) the strength requirement of tension strut is always in higher demand and shape should not be more bulge. Due to this requirement most of the suppliers are prefer to use “Steel” material for forged tension strut. In this project I am designing the Tension strut in 3D software Catia V-5 by providing the different types of shapes or Sections and will optimize the 3D model in FEA by applying the aluminium material for Static Load cases.FEA in V-5 will give 90% 95% accuracy of result but it will take very less time as compare to other FEA software. For FEA(Finite Element analysis) we are having option to do in V-5 using GPS licence. For use of GPS we need to consider Boundary condition at bushing and ball joint. We need to check 3D model for manufacturing feasibility i.e. minimum draft angle and radius for forging process in V-5 before doing analysis. We will get the final optimized model in good shape or geometry with lighter in weight and also will be having a higher strength per customer requirement. Weight reduction of components in car plays a major role which may affect for cost reduction of car also. Keyword: Aluminium forging,CAD-Catia V-5,Finite Element Analysis-Catia V-5.

Influence of developer temperature on the shape of structures fabricated by deep X-ray lithography

This paper describes the fabrication of poly(methyl methacrylate) (PMMA) microstructures with three-dimensional (3-D) sloped sidewalls using synchrotron-radiated (SR) deep X-ray lithography (DXRL). Here, the developer temperature was varied to produce variations in the inclination angle of the sloped sidewalls. We found that the PMMA sidewall inclination angle and height were controlled by the dosage, development time, and development temperature. When the development temperature was low, the inclination angle was nearly 0°, regardless of dosage amounts or exposure time. When the development temperature was high, microstructures with sloped sidewalls were fabricated; as the dosage amount and development time increased, the inclination angle increased. The ability to control the PMMA sidewall inclination angle suggests the application of this technique to microstructure fabrication technologies, such as 3-D microelectromechanical system (MEMS) device components, in which the inclination angle becomes the draft angle for moulding processes.

마이크로금형 구배각 제어를 위한 절삭가공조건 예측모델에 관한 연구

, Tae-il Seo*AbstractIt is very difficult to determine suitable cutting conditions in order to obtain accurate cutting profiles because machining errors caused by tool deflection depend upon cutting conditions. In this study the relationship between real cutting profiles (inclined shapes and machining errors) and cutting conditions was modeled in order to fabricate draft angle on micro molds. CCD (Central Composite Design) of DOE (Design Of Experiment) and RSM (Response Surface Method) were applied in order to model the relationship between cutting conditions and machining errors. In order to use CCD the range of radial depth of cut was chosen by 10-90㎛ and the range of feedrate was chosen by 200-300mm/min, and 9 points of cutting conditions were chosen inside determined ranges. Then, actual cutting processes were carried out as respect to 9 points of cutting conditions, draft angles and real cutting profiles were measured on cutting profiles, each response surface function was determined by conducting response surface analysis and the functions were represented by 3-dimensional graphs, contour lines and 101×101 matrices. Consequently it is possible to determine suitable cutting conditions in order to obtain arbitrary given draft angles and cutting profiles by using modeling. To validate proposed approach in this study suitable cutting conditions were determined by modeling in order to obtain arbitrary given draft angle and cutting profile, and actual cutting processes were carried out. About 95% of good agreement between predicted and measured values was obtained.

유한요소해석과 다구찌방법을 이용한 단조피스톤의 성형조건 연구

본 연구에서는 다구찌 방법을 이용하고 유한요소해석을 통해 알루미늄 피스톤 제조에 큰 영향을 미치는 설계변수의 적합한 조건을 도출하였다. 단조 최대 성형하중을 목적함수로 하고 설계변수로서 예비성형체, 소재온도 및 빼기구배를 선정하였으며 마찰을 잡음인자로 하는 직교배열표를 작성하고 시뮬레이션별 유한요소해석을 통해 하중을 평가하였다. 이를 통해 설계 변수들이 미치는 영향을 분석한 결과를 바탕으로 설계변수의 최적조합조건은 제안하였다. 이러한 방법은 여러 가지 금속성형공정에서 최종 단조품 전단계에서 여러 예비성형체에서 적합한 예비성형체를 결정할 때 도움을 줄 수 있으며 특히, 최적의 설계조합을 결정할 때 쉽게 적용할 수 있을 것이다. This paper presents design methodology to determine the design parameters that affect the manufacture of aluminum forging piston using the FE simulation and the Taguchi method. Maximum forging load is used as the objective function, and preform, material temperature and draft angle are selected as the design parameters. Their combinations are implemented by orthogonal array, and forging load is evaluated through the simulation. From the analytic results of design parameters to minimize the load using signal to noise ratio, their optimal combinations are proposed. The proposed design methodology will be able to help in selecting proper preform among preforms and to be used in determining the optimal combination of the parameters in metal forming process.

Adding draft angle to [formula omitted]-spline and NURBS surfaces

B-spline and NURBS surfaces are the most prevailing parametric surfaces in current CAD/CAM systems. Used for mould and die representations, they need sufficient draft angle in manufacturing processes. This paper tries to add draft angle to B-spline and NURBS surfaces with minimum changes in their control nets and weights in the least square sense. An enhanced sufficient condition for B-spline surfaces is introduced based on the convex combination, so as to improve the existing algorithm for adding draft angle to such surfaces. The draft angle distribution is visualized by a terrain, whose area under a certain level means that the corresponding part of the surface is too steep. Adding draft angle to this part can be expressed as a constraint on optimization. This idea is successfully applied to NURBS surfaces. Five examples demonstrate the effectiveness of the proposed methods.

Molded Pulp Material Structure Parameters on the Performance of the Buffer

This paper analysis the cushion performance of the bucket unit for molded pulp material model, which based on the ANSYS software to simulate the compression test and study the effect variety of the draft angle and the height on the model.

Influences of fillet radius and draft angle on local loading process of titanium alloy T-shaped components

In order to study influences of geometric parameters on the T-shaped components local loading process, a new mathematical model considering the fillet radius and draft angle was established by using the slab method. The results obtained by the mathematical model agree with the data form experiment and numerical simulation, and the results are closer to the experimental and simulation results. The influence of draft angle may be neglected under the forming conditions used. The influence of fillet radius is notable, especially in the case that the ratio of fillet radius to rib width is less than 0.75.

The Numerical Simulation of Conductive Body Forming Process and Mould Design

T2-copper conductive body is a important part used in high voltage switch, it has poor machining process due to the complex shape. Through Deform numerical simulation, conductive body was formed by open-die forging and closed die forging. In the open-die forging simulation，heat transfer coefficient between blank (880°C) and open-die (200°C) is 11, the surrounding environment temperature is 20°C, friction factor is 0.3. The main open-die forging process parameters is: outer draft angle α=6.5°; inner draft angle β＝10°; bridge width b＝5、8、11mm. punching skin and cylindrical blank. Simulation results show that forging can meet the requirement while properly adjusting mould parameters. The main size of closed-die forging working parts is designed according to the conductive body graph, no draft angle and ring blank of external diameter Φ111mm and inside diameter Φ93mm with the same volume of conductive body. The simulation results shows that forging can be formed using open-die forging, and it is difficult to form product by the process of the closed-die forging for ring blank because of the restriction of solid state metal liquidity, many regions of the filling is not sufficient. Open-die forging and casting blank-closed die forging are both used in actual production. The casting blank-closed die forging is a more reasonable forming process compared with the open-die forging as metal volume of distribution is solved, higher utilization rate of material, more simple process in following work and the like. To make it more suitable for practical production, appropriate adjustments of some parameters was made in the mold design process based on the numerical simulation. Keywords: open-die forging; casting blank–closed die forging; numerical simulation

Aero-optical characteristics of supersonic flow over blunt wedge with cavity window

The optical rays that form the image of an object and propagate a supersonic flow over a vehicle are refracted by the density variations. A numerical analysis of the aero-optical characteristics of supersonic flow over blunt wedge with a cavity window is carried out. A hybrid method of Reynold averaged Navier-Stokes and direct simulation Monte Carlo (RANS/DSMC) is employed to simulate the flowfield. Refraction factor is introduced to evaluate the flowfield’s aero-optical characteristic. The results show that mean flow’s aero-optical effects are mainly caused by the shock wave, the expansion wave and the turbulent boundary layer. Fluctuation flow’s aero-optical effects are mainly caused by the turbulent boundary layer and the shock wave induced by the cavity window. The aero-optical effects at the leading side of window are caused by the mean density variations, while the effects at the trailing side are caused by the density fluctuations. Different draft angles of the cavity window are investigated. The airborne optical devices of supersonic vehicle should be mounted in the middle of the cavity window with a large draft angle.

Microthermoforming of microfluidic substrates by soft lithography (µTSL): optimization using design of experiments

We present a detailed analysis of microthermoforming by soft lithography (µTSL) for replication of foil-based microfluidic substrates. The process was systematically optimized by design of experiments (DOE) enabling fabrication of defect-free lab-on-a-chip devices. After the assessment of typical error patterns we optimized the process toward the minimum deviation between mold and thermoformed foil substrates. The following process parameters have most significant impact on the dimensional responses (p < 0.05): critical temperature before start of evacuation, molding temperature, pressure of pre-stretching and duration of pre-stretching as well as duration of molding pressure. The most relevant parameter is molding temperature with >40% relative impact. The DOE results in an empirical process model with a maximum deviation between the prediction and experimental proof of 2% for the optimum parameter set. Finally, process optimization is validated by the fabrication and testing of a microfluidic structure for blood plasma separation from human whole blood. The optimized process enabled metering of a nominal volume of 4.0 µl of blood plasma with an accuracy deviation of 3% and a metering precision of ±7.0%. The µTSL process takes about 30 min and easily enables the replication of 300 µm wide microchannels having vertical sidewalls without any draft angles in a well-controllable way. It proves to be suitable for multiple applications in the field of microfluidic devices.

Design and Manufacture of Vacuum Forming Moulds

This paper presents an investigation of the positive vacuum forming process. Previous research has indicated requirements of a draft angle of at least two to five degree and a depth to width ratio of not greater than 1:1. For specific formed geometry that required smaller draft angles and greater draw depths these limitations may make the positive vacuum forming process not applicable. The overall aim of this work was to allow the process to become more versatile. This work focused on three prototype moulds which were designed, manufactured, tested and analysed with a view to over come the present process limitations. Moulds were made of wood with a size of 68 x 68 x 75mm. Air holes of 1 and 10mm diameter were drilled in to these moulds in different positions. Polypropylene terephthalate glycol (PETG) materials was used to make the final product via the vacuum process. To release the product from the mould a constant 8bar pressure was applied. Proper time to make the final products and the quality of the final product were investigated. It was found that moulds with air holes opening in all surfaces resulted in shorter cycle times, lower air pressure and better quality of formed parts. It was also found in this work that a zero draft angle and as well as 1:1.1 draw depth was possible to achieve in the vacuum forming process.

Predict and Analysis of Fold in Steering Knuckle Forging Based on Numerical Simulation

The steering knuckle was hard to be formed because of complex shape and high quality requirement. This paper predicted fold defect in forging based on numerical simulation. The whole process was reviewed and the cause of fold and evolution was analyzed. Further more, the effect of different fillet radius as well as draft angles on fold was compared. Accordingly, the measures were presented. Finally, the process tryout was done at site. This was quite in accord with the results of simulation. As a result, the optimum analyzed technical parameters were obtained and the fold was avoided.

Fabrication of metallic bipolar plate for proton exchange membrane fuel cells by rubber pad forming

In this paper, the rubber pad forming process is used to fabricate the metallic bipolar plate for a proton exchange membrane (PEM) fuel cell, which has multi-array micro-scale flow channels on its surface. The rubber pad forming process has the following advantages: high surface quality and dimensional accuracy of the formed parts, low cost of the die because only one rigid die is required, and high efficiency. The process control parameters (rubber hardness, internal and outer radii, draft angle) of the rubber pad forming are analyzed by the finite element method using the commercial software Abaqus. After that, the rubber pad forming process is used to manufacture a metallic bipolar plate of SS304 stainless steel with perfect flow micro-channels. The results of this effort indicated that the rubber pad forming process is a feasible technique for fabricating the bipolar plates of PEM fuel cells.

RESEARCH ON THE FORMING ANGLE OF A1050-H14 ALUMINUM MATERIAL PROCESSED BY USING SINGLE POINT INCREMENTAL FORMING TECHNOLOGY (SPIF)

Single Point Incremental Forming - SPIF is the recent manufacturing process of metal sheet forming by drafting a non-cutting edge sphere-tip tool on a clamped metal sheet. The formability of metal sheet in SPIF is considered by the forming angle (ψ)- the maximum draft angle so that the material is not torn. The experimental research on A1050-H14 aluminum sheet on Bridge Port VMC500-16 CNC milling machine in C1 workshop of the HCMUT in order to find out the regression equations to predict the maximum forming angle in the relation with four most important technology parameters in SPIF: size of the step down z, forming feed vxy, spindle speed n, forming tool diameter d.

Sufficient conditions for draft angles on general B-spline surfaces

Many manufacturing processes, e.g. casting, forging, moulding, require that components must have a sufficient draft angle. Ensuring this when using general B-spline surfaces is a difficult task, often requiring iterative modeling. In this paper a theorem is presented that provides sufficient conditions to ensure draft angle on B-spline surfaces. The theorem is used to develop a simple algorithm that was used to add a draft angle to two surfaces.

Fabrication of Glassy Carbon Molds Using Hydrogen Silsequioxane Patterned by Electron Beam Lithography as O2 Dry Etching Mask

Glass is a good candidate material for optical devices because of its enhanced optical properties, the technique of die machining has not been established for the hot embossing of glass. In this study, we used the glassy carbon (GC) mold for the hot embossing of glass. An inductively coupled plasma reactive ion etching (ICP–RIE) using oxygen plasma was employed for the submicron structuring of the GC mold. Hydrogen silsesquioxane (HSQ) is a negative-type electron beam (EB) resist used to be resistant to oxygen plasma. HSQ patterns drawn by electron beam lithography (EBL) were used as the O2 dry etching mask. The etching selectivity between HSQ and GC was 35. The average of the extent of side etching was 40 nm at a depth of 300 nm. The side etching functioning as the draft angle was caused mainly by oxygen radicals, because HSQ patterns remained even after GC patterns were side-etched. We confirmed that the GC mold fabricated by O2 dry etching can be used for glass hot embossing. Since the mold lubricant was not rubbed on the mold surface, GC is the appropriate mold material for Pyrex glass.