Draft Angle Research Articles

Investigation of Bipolar Plate Forming with Various Die Configurations by Magnetic Pulse Method

Bipolar plates are a major part of fuel cells, which are a clean and recyclable energy source. This study was carried out with two dies for a bipolar plate forming investigation with the magnetic pulse method: a bipolar plate die and a 10-channel die. With the bipolar plate die, the forming of bipolar plates with a Cu110 sheet and a Grade 2 Ti sheet indicated that the bipolar plate die needed optimization for a full replication. The obtained maximum average depth percentage was 86% for a Cu110 sheet, while it was 54% for a Grade 2 Ti sheet in this study. A further increase of the depth percentage is possible but requires a much higher capacitor bank energy. The increase of the capacitor bank energy would result in severe tearing, while the depth percentage increase was little. The primary current and flyer velocity were measured at various capacitor bank energies. With the 10-channel die, the die parameters’ effect on metal sheet forming was investigated with a Cu110 sheet and an SS201 sheet. The draft angle had a significant effect on the replication of the die surface. The full replication was achieved for channels with proper parameters with both a Cu110 sheet and an SS201 sheet. Therefore, the bipolar plate die could be optimized based on the 10-channel die results.

Glass molding of all glass Fresnel lens with vitreous carbon micromold.

An all glass Fresnel lens (AGFL) was fabricated by glass molding with a vitreous carbon (VC) micro mold. In the glass molding process, a glass plate was heated up to its softening temperature and pressed against to the VC mold to replicate the Fresnel pattern. The VC molds having negative shape Fresnel profile were fabricated by carbonization of replicated Furan precursor using a diamond turning machined nickel master. During the carbonization process, the Furan precursor shrank due to the thermal decomposition, and this shrinkage must be compensated to obtain a precise AGFL. In this study, we examined the shrinkage ratio during the carbonization process using a preliminary experiment using the commercially available PMMA Fresnel lens as the master, and fabricated a nickel master with an enlarged Fresnel profile for shrinkage compensation. To verify the compensation method, the surface profiles of the fabricated VC mold and molded AGFL were measured and compared with the designed profile. The deviations between measured and designed profiles were less than 4 μm. In addition, the tip radii of the grooves and draft angle of the molded AGFL were within the acceptable tolerance for CPV applications.

Precipitation hardening stainless steel produced by powder bed fusion: influence of positioning and heat treatment

Additive Manufacturing (AM) technologies are nowadays of interest in the most varied production sectors, first and foremost in the aerospace, automotive and biomedical sectors. Those technologies, essentially tooling-free, are appealing as it is possible to design a component independently on the specific processing route (e.g. undercuts, draft angles, internal channels with sharp edges or blind holes) and shape, with excellent geometrical and dimensional tolerances. 15-5 PH alloy is a precipitation hardened stainless steel, mainly applied for aircraft components and high-pressure pumps or valves manufacturing. The present work involved the production of L-PBF 15-5 PH specimens, subsequently tested on a laboratory scale for microstructural and mechanical characterization. Starting from experimental results, LPBF-experimentally derived properties have been compared with those of an analogous alloy, obtained by conventional manufacturing processes. Particular attention has been paid to the evaluation of the effect of heat treatment on mechanical properties and metallurgical features, to obtain equivalent or better performances with respect to literature reference values. For this reason, the material was tested in the as-built condition and in all the most used thermal treatment applied for solid parts (in accordance with reference Standards ASTM A564/A564 M and AMS 2759).

Multi-objective optimization of WEDM process parameters for taper cutting of AISI D2 tool steel

Wire electrical discharge machining (WEDM) process is one of the most popular method for the producing complex geometries in hard and wear resistant materials such as those used in tooling industry. This taper cutting involves in making of inclined surface, and it is particularly significant in the manufacturing of tooling that requires draft angles. In the present paper, experiments were conducted in order to find the effect of process parame- ters such as taper angle, geometrical thickness and servo voltage on response variables such as angular error and cutting speed on AISI D2 tool steel using statistical design of experiments. The experiments were planned using Central Composite design (CCD) which is part of Response Surface Methodology (RSM) – involving three variables with five levels. Multi objective optimization was conducted for maximizing the Cutting speed and minimizing the angular error using genetic algorithm. The optimization procedure leads to creation of non-dominated optimal points which gave an insight regarding the optimal operating conditions of the process.

A study on joining magnesium alloy high pressure die casting components with thread forming fasteners

Abstract With tremendous weight saving potential, magnesium alloy high pressure die casting components have been widely used for automotive applications. Magnesium fastening technology is thus becoming increasingly important to design engineers. Joining as-cast holes of magnesium high pressure die casting components with thread forming fasteners provides significant advantages for the assembly process, overall cost benefit and joint integrity. This type of joint is thus preferred for structural applications. Designing the thread forming fasteners with as-cast holes follows the general rules for designing for the machined holes, including carefully designing the variables such as the assembly torque range, the length of thread engagement, the hole diameter and required failure mode. In addition, special attention needs to be paid to the draft angles of the magnesium cast components that are required for the die casting process. In this paper, the effects of above key factors, individually and combined, on the joint performance of thread forming fasteners with as-cast blind holes of AM60B magnesium components are studied. A joint design philosophy was proposed to optimize both joint performance (the prevailing torque, the failure torque and the failure mode) and manufacturing easiness (the hole diameter and corresponding draft angle). The detailed design considerations for as-cast holes of magnesium HPDC are discussed and explained through a hypothetical example.

Seakeeping Performance Estimation of the Container Ship under Irregular Wave Condition Using Artificial Neural Network

In the current study, sea keeping performance of the S-175 container ship is estimated under irregular wave conditions by using numerical calculation and artificial neural networks (ANNs). For this purpose, strip theory is employed to calculate of the response amplitude operator (RAO) and wave resistance. Then, the RAO of heave, pitch, and roll motions and added resistance are used in the considered ANN. In our calculation, the ship dimensions are changed at the same displacement and body form. By comparing the RAO diagrams and according to survey seakeeping criteria, optimum hull is determined for seakeeping performance. In addition, predictive equations based on length of vessel (L), the breadth (B), draft (T) and wave encounter angle (μ), are presented to estimated of seakeeping performance by using ANN.

Experimental Study on Pitching Motion Mode of a SWATH-USV

The importance of the research about ship motion model has become more prominent with the improvement of economic level. Mastering ship motion model is a necessary basis for studying ship's divisibility. The hydrodynamic parameters obtained by parameter identification methods are more precise, which is dissimilar from the parameters obtained by classical methods. In this paper, a SWATH-USV was taken as the research object to accomplish a series of pitch decay tests on the condition that the SWATH-USV was in different drafts and tilts angles in the hydrostatic state. And a mathematical model by the method of system identification based on genetic algorithms has been established, adopting VB language to program a systematic identification software. With this, the author obtained the pitch motion differential equations, and the changing regularities of hydrodynamic coefficients with draft and initial tilt angle of the model in different drafts and initial tilt angles and their kinematic equation. Using this equation to predict, the results are proved to be well matched with the experimental results. And the feasibility of the identification method is also confirmed. The analysis results and methods can provide essential technical support for the in-depth analysis of the wave resistance and the design of the boat.

Model Design for a Hydraulic Clutch Actuation System

This paper derives an accurate dynamical model of an indirectly controlled hydraulic actuation path for a wet friction clutch. The considered setup exhibits a relatively low pressure range, which necessitates to account for the variable compressibility of the hydraulic fluid due to entrained air. In addition, the model design accounts for the complex valve geometry as well as the draft angles of the valve housing due to injection moulding. The relevant hysteresis phenomena of the valves are modelled via Prandtl-Ishlinskii and LuGre operators, respectively. Simulation results show the accuracy of the model with an average error of 0.9% (180 mbar) compared to measurements. In addition, the necessity to respect the entrained air is verified by a counter-simulation with constant bulk modulus.

Effect of tool geometry on the velocity and strain rate fields in continuous rotary extrusion of magnesium AZ91 alloy

The Continuous Rotary Extrusion (CRE) process is also known in literature under Conform TM name and it is mainly used for the continuous extrusion of aluminum and copper alloys. In the CRE process a feedstock in the form of rod, powders or chips, is fed into the groove of the rotating wheel. CRE has lot to offer when compared to other more conventional extrusion processes such as low energy input, no limit for billet length because it is a continuous process as well as improved material physical properties due to plastic deformation under constant parameters. Therefore, the CRE process is of our interest in forming Mg alloys. In the presented study, the effect of tool geometry on the velocity and strain rate fields in the deformation zone are investigated by FEM simulation of the CRE extrusion of magnesium alloys AZ91. The FEM process model was developed in commercially available DEFORM 3DTM software. The flow stress data for AZ91 magnesium alloy were obtained from reported literature. The metal flow predictions for two different feeder plate and presence of draft angle in exit die have been presented.

Die-casting of product with thin fins by Al-25%Si

Casting of aluminium alloys, which have excellent fluidity but solidification difficulty, was investigated using a vertical type high-speed twin-roll caster. The results showed that Al-25% exemplifies these characteristics. The fluidity of the Al-25%Si was better than that of A383, which is a popular aluminium alloy for die casting. It is estimated that its large latent heat contributes to the good fluidity. Die casting of a model heat sink with thin fins was achieved using Al-25%Si. The thickness of the fin top was 0.5 mm, the draft angle was 0.5° and the height was 50 mm. The heat sink model cast from Al-25%Si had smaller thermal resistance and lighter weight compared with the conventional type heat sink model cast from A383.

Defect analysis and design optimization on the hot forging of automotive balance shaft based on 3D and 2D simulations

Defects analysis and tool optimization of the hot forged automotive balance shaft were conducted based on 3D and 2D finite element (FE) simulations in order to improve forging quality and productivity. In practice, folding was observed on the forgings. 3D simulation of the whole forging process was implemented to observe the defect morphology, which was consistent with the actual. Meanwhile, the formation and thickness of folding were analyzed by using 2D simulation. According to the results, the metal flow folded into the closed ring at the stiffened rib when the metal transited through the cavity. The folding location was determined by large temperature gradient, big rotation angle, high damage value, and low metal flow velocity. The thickness of the folding was less than 5 mm. Finally, the forging tools were redesigned by increasing draft angle and fillet radius on preforging dies. Forgings without defects were obtained in simulation and practice.

Design of a piston forging process using a hybrid Taguchi method and multiple criteria decision-making

In the process of hot forging aluminum pistons, many factors must be considered. In this study, the goal to which was to design the process parameters of the piston in forging, material temperatures, friction coefficients, draft angle, and preform type were major control factors. To determine the optimization of multiple performances, considering forming load and die stress as affected by the control factors in the piston forging process, a hybrid of Multiple criteria decision-making (MCDM) and the Taguchi method was employed. For the application of this hybrid method, a Multiple-objective performance index (MOPI) was used to solve the aluminum piston forging process with multiple performance characteristics. A finite element simulation analysis was conducted to investigate multiple performances. Through the application of the Taguchi method based on MOPI that can be referred to as the Signal to noise (SN) ratio, the relatively important influences of major factors are examined and the design parameters for the piston forging process are optimized. The results are presented in order to demonstrate the effectiveness of this approach.

Proposal and evaluation of a selection procedure for cast parts

The design of casting components is a complex activity, which is usually based on guidelines scattered in the literature, or based on the designer’s accumulated experience. A single failure in the casting process selection can increase design and production time and, in critical cases, result in a collapse of the manufacturing and assembly of components. Nowadays the selection is made by prioritizing the features of the casting process, but this action could be carried out during the product development stage, assisting the designer. This could allow the project to adjust to a more viable casting process. In this context, our goal is to propose a selector for casting processes to be used during the early stages of the embodiment design. It was achieved through the use of quality function deployment and design for manufacturing (DFM) principles. Our proposal relates the component’s main functions with each process characteristic (mass, minimum section thickness, draft angle, surface finish, dimensional tolerances, minimum lot and lead time) through a correlation matrix, resulting in importance indexes for these characteristics. Furthermore, the importance indices obtained are related to the capability of each casting process discussed, providing a process rating. A checklist based on DFM principles is also provided to guide the designer when a need for improvement is observed or no processes are suited for producing the desired part. For validation, two ferrous and two nonferrous cast parts were analyzed. The results were compared with other selectors described in the literature and with processes actually used in the industry. Thus, they have shown a good relation with the other methods, especially regarding the quantitative classification determined by the proposed selector.

Automatic Recognition and Construction of Draft Angle for Injection Mold Design

In the injection molding process, plastic products are difficult to demold due to friction force between the cavity and products, thus, finished products might be deformed or damaged. Therefore, designers should add a draft angle to the geometric surface of products, which is parallel to the unloading direction, in order to help the products eject smoothly from the cavity. This study uses CAD software as the main architecture to develop the function of automatic draft angle recognition and construction. The study is divided into three stages. First, the geometric features of products are identified in the CAD model by induced algorithm, then the quilts to be added in the draft design are determined and classified. Finally, draft angles are created in different ways according to different surfaces. An algorithm suitable for automatic draft recognition and construction, as well as the constraints of automatic creation of draft angle, is proposed. The feature recognition algorithm of this study can automatically inspect 90% of the surfaces to be drafted, and the automatic creation of draft features can economize 80% of required mouse clicks, thus, effectively increasing draft angle design efficiency, and preventing errors in mold design and manufacturing.

Cross-sectional shape optimisation for thin-walled beam crashworthiness with stamping constraints using genetic algorithm

The energy absorption capacity of thin-walled beams (TWB) is important to reduce the occupant injury in the collision of automobile structure. At the conceptual design stage, engineers mainly depend on their intuition and experience when determining the cross-sectional shape of TWB. This paper presents the crashworthiness design and optimisation for the TWB with complex cross-sectional shapes under axial impact load using a genetic algorithm. The optimisation model is formulated to determine the optimal cross-sectional shape of TWB, which is to minimise the mass of TWB constrained with energy absorption and maximum peak force. Moreover, four stamping constraints, including minimal segment, draft angle, chamfer radius and assembly, are together considered to promote the complex cross-sectional shape in practice. A numerical example verifies the effectiveness of the optimisation model and shows powerful ability to obtain the optimal cross-sectional shape of TWB.

Injection Mold Design Parameters Calculation Using Pro/Plastic Advisor for Spur Gear

Injection molding is one of the technique and methodology to create mold of various complex shapes with more detailed structure. The techniques involve various parameters to be checked for effective output. This should be done on design stage itself. We have come up some suggestion on how to approach an injection molding process. Simplified design the problems which may occur in the development phase of the product are solved in the design phase itself. Aim of the work is to calculate the injection mold parameters using pro/plastic Advisor. Using diametral method 3D model of the spur gear is created in PRO/E system. The 3D model spur gear is imported in the Pro Plastic Advisor to perform Numerical simulation. The physical Mold orientation, the dimensions for each of the element in the Mold, the location of the gate, runner, requirement of insert, draft angle requirement, shrinkage factor, location of cooling channels were calculated using Pro Plastic Advisor. Pro Plastic Advisor results give confident to designers to ensure the quality components. The correct Injection molded parts can be molded by concentrating on these areas of plastic technology is proper design and material selection included with material processing.

Stacking with cylindrical spots in lamination of stamped electrical steel sheets

Abstract The rotors and stators of motors (or generators) as well as the cores of transformers are produced by progressive stamping coupled with stacking. Failure in stacking leads to rotor/stator/core misalignment during winding or loss of lamination after crashes. Proper embossing depth of cylindrical spots and clearance between the punch and die are essential for achieving high-quality lamination. In this work, the proper embossing depth was determined and the effect of the punch/die clearance on stacking quality was investigated. Three electrical sheets with various iron losses (H470, H600, and H1300) were used. The sheet thickness was 0.5 mm. The punch/die clearance ranged from 1% to 4% of the sheet thickness. DEFORM 2D was used for the finite element analysis. The piercing test shows that the proper embossing depths for the H1300, H600, and H470 sheet metals are 0.39, 0.37, and 0.36 mm, respectively. The draft angle of the joined interface increases with punch/die clearance. A small clearance is favorable for the stacking with cylindrical spots. Poor stacking occurs when the clearance is larger than 4% of the sheet thickness.

Integration of finite element analysis and design of experiment for the investigation of critical factors in rubber pad forming of metallic bipolar plates for PEM fuel cells

In the present study, rubber pad forming process of metallic bipolar plates of PEM fuel cells is investigated. A 3D finite element model of the process with damage initiation criterion is developed. Design of Experiment (factorial design method) is used to find the key parameters of the forming process and their optimal levels. The required input data of the factorial design method is provided by the output results of the finite element model. The finite element results show that the thickness distribution in the formed bipolar plate is not uniform. Also, the corners of the micro-channels are the regions in which the damage initiation criteria (the von Mises stress and the plastic strain) reach maximum values. The design of experiments shows that the outer corner radius, draft angle, and the friction coefficient are the most critical parameters in the forming process. The optimal values for the draft angle, the outer corner radius, and the friction coefficient are found as 40°, 0.4 mm, and 0.05, respectively. Finally, some experimental tests are performed to validate the results of the finite element simulations and the design of experiments.

Influence of die parameters on the deformation inhomogeneity of transitional region during local loading forming of Ti-alloy rib-web component

The deformation inhomogeneity of transitional region plays a great role in both the macro and micro forming qualities in the local loading forming. In this work, the dependence of deformation inhomogeneity of transitional region on the die parameters in the local loading forming of Ti-alloy rib-web component was studied based on finite element (FE) simulation. To evaluate the deformation inhomogeneity, an area-weighted strain inhomogeneity index was employed, which is calculated through the user subroutine of FE software (DEFORM-2D). It is found that there exist two kinds of strain concentration areas contributing to the deformation inhomogeneity of transitional region. One kind is the almost symmetric strain concentration area at the non-partitioned ribs, which is essentially related to the filling of rib. Another kind is the slant strain concentration area at the partitioned rib, which is caused by the multi-step loading during local loading forming. Besides, the effects of die parameters on the deformation inhomogeneity of transitional region were studied by the combination of orthogonal experiment design and FE simulation. The results suggest that the draft angle of the right rib is the most significant factor for both the deformation inhomogeneities of the partitioned rib region and whole transitional region. And, these two deformation inhomogeneities both decrease with the draft angle of the right rib decreasing. Furthermore, the relationship between die parameters and deformation inhomogeneity of transitional region is developed using the response surface methodology (RSM). Based on the RSM model, the die parameters were optimized to improve the deformation homogeneity of transitional region. The results will provide basis for the design of die parameters to improving the deformation and microstructure homogeneities in the isothermal local loading forming of Ti-alloy rib-web component.

Cross-sectional shape design and optimization of automotive body with stamping constraints

At conceptual design stage, automotive body is usually simplified as a frame structure, which consists of thinwalled beams (TWBs). Therefore, the most important issue is to determine the cross-sectional shape of TWBs under the requirement of mechanical properties. However, design engineers mostly depend on their experience or repeated modification to design the cross-sectional shape of TWBs. So this paper presents a rapidly cross-sectional shape design and optimization method to satisfy the demand of mechanical properties and meanwhile minimize the weight of TWB. Firstly, cross-sectional mechanics property formulations are summarized. Especially, the torsional rigidity formulation of three-cell cross section is derived for the first time in this paper. Secondly, the shape optimization model is created to minimize the weight of TWB and improve the mechanical properties, which is solved by genetic algorithm. Moreover, three stamping constraints, draft angle, chamfer radius and assembly, are introduced to promote the cross-sectional shape more practice. Lastly, numerical examples verify the effectiveness of the optimization model and show the application in structural modification of automotive frame.