Die Face Research Articles

Experimental Study of the Airflow Field and Fiber Motion in the Melt-Blowing Process.

The melt-blowing process involves high velocity airflow and fiber motion, which have a significant effect on fiber attenuation. In this paper, the three-dimensional airflow field for a melt-blowing slot die was measured using the hot-wire anemometry in an experiment. The fiber motion was captured online using a high-speed camera. The characteristics of the airflow distribution and fiber motion were analyzed. The results show that the melt-blowing airflow field is asymmetrically distributed. The centerline air velocity is higher than that around it and decays quickly. The maximum airflow velocity exists near the die face, in the range of 130-160 m/s. In the region of -0.3 cm < y < 0.3 cm and 0 < z < 2 cm, the airflow has a high velocity (>100 m/s). As the distance of z reaches 5 cm and 7 cm, the maximum airflow velocity reduces to 70 m/s. The amplitude of fibers is calculated, and it increases with the increase in air dispersion area which has a significant influence on fiber attenuation. At z = 1.5 cm, 2.5 cm, 4 cm, and 5.5 cm, the average fiber amplitudes are 1.05 mm, 1.71 mm, 2.83 mm, and 3.97 mm, respectively. In the vicinity of the die, the fibers move vertically downward as straight segments. With the increase in distance from the spinneret, the fiber appears to bend significantly and forms a fiber loop. The fiber loop morphology affects the velocity of the fiber movement, causing crossover, folding, and bonding of the moving fiber. The study investigated the interaction between the fiber and airflow fields. It indicates that the airflow velocity, velocity difference, and dispersion area can affect the motion of fiber which plays an important role in fiber attenuation during the melt-blowing process.

Intelligent template based die face design method for process reuse of automotive panel

Die face design of automotive panel is a tedious repeated process and depends heavily on experience of engineers, which leads to increase of lead time and production costs. An intelligent template based die face design method is presented for process reuse of automotive panel. In this method, the new part is extracted as feature parameters to match the existing process in the template library automatically and the similar process model is applied to the new part adaptively. Finally, a process reuse system for die face is developed and a typical automotive panel is employed to verify the effectiveness of the proposed method. The results show a favourable effectiveness and practicability in reducing design period and reliance on experience.

Air jet impingement cooling for hot stamping dies

The strength of panel sheets can be increased by 2–3 times after hot stamping, and for high quality of hot stamped sheets, uniform cooling rate on the die face to quench the panel is needed. However, it is difficult for cooling water channels, commonly used for hot stamping dies, to dissipate heat evenly. In addition, dies are easily corroded by contact with water at high temperature. Thus, this study considers air cooling for the quenching process. The airflow can be applied to the sheet directly during the forming stage to cool and quench, eliminating difficulties with cooling channel design and providing more uniform cooling. Simulations and experiments were used to test the feasibility of air cooling for hot stamping with CSC-15B22 steel. A simple hot stamping tool with flat die face and either water or air cooling channels was used for testing, and results show that the both direct and indirect airflow can be used for hot stamping. With indirect air cooling, the cooling rate is sufficient for complete martensite transition, though the cooling rate is 40% lower than with indirect water cooling. To improve cooling efficiency of the air cooling system and obtain more uniform cooling, an air jet impingement cooling system (direct airflow cooling) was also tested. Results show that a similar cooling rate can be obtained in both indirect water cooling and the air jet impingement cooling. Thus, it is possible for air jet impingement cooling to provide hot stamping superior to water cooling. These results can be a reference for the design of new cooling systems for hot stamping dies.

Failure Investigation &amp;amp; Analyses of AISI D3 Dies Used in Tableting Machines for Pharmaceutical Application

AISI D3 material finds wide use as Dies in Tableting Machines for Pharmaceutical applications owing to its good strength, toughness and moderate corrosion resistance combined with cost effectiveness. However, 10-15% of AISI D3 Dies used in rotary Tableting Machines were found to fail within 4-6 months of service resulting in frequent disruption of regular production and loss in overall productivity besides having potential long-term risks such as metal contamination in the output product. Visual examination of the failed Die showed 180o crack across the top Die face with rust marks, but no such crack was found on the bottom face. Also, the crack on the top Die face had a jagged morphology and those cracks on the Outer Diameter (OD) surface oriented in the axial direction were found to be straight and sharp. Macro-examination of Die sectioned diametrically and perpendicular to the crack on the Die face revealed jagged axial cracks on the Internal Diameter (ID) surface. Cluster pitting marks centered around mid-height of the Die were observed on the ID surface and the cut open sections of the Die along the crack revealed extensive corrosion. While microstructural examination of samples taken on the ID surface showed presence of banded carbides oriented axially in tempered martensite matrix, the same examination carried out on samples taken on Die face revealed fine needle like carbides in tempered martensite matrix. Fractography analysis conducted in the cluster pitting zone on the ID surface clearly showed presence of micro-cracks having multiple points of origin with clear indications of propagation into the cross section of the Die. Scanning Electron Microscopy (SEM) carried out in the aforementioned zone near ID surface also showed the presence of multiple micro-cracks. The SEM-EDX analysis in the referred zone at specific locations in the vicinity of microcracks confirmed inadequate Chromium oxide content leading to lack of corrosion resistance in the material. Based on the investigation &amp; analyses and the detailed study of the Tableting Process in rotary Tableting Machines that revealed the nature of applied load to be cyclic, a comprehensive failure mechanism was arrived at, and it was inferred that the predominant mode of AISI D3 Die failure was Corrosion Fatigue. Finally, recommendation has been proposed to prevent such failures during service.

Fiber spinning with airfields enhanced by airfoil louvers

Airfields are used in common polymer fiber spinning processes, such as melt blowing and spunbonding. A pair of louvers was installed in the air flow field of a melt blowing slot die. Previous research work has shown that, with louvers in place, the air velocity along the fiber threadline is higher than the velocity when louvers are not used. Since the air velocity is what drives the spinning process, the presence of louvers was expected to increase the attenuation of the molten filaments and thus improve the melt blowing process. Melt blowing runs were made with variable louver size (chord), louver separation, louver distance from the die face, the angle of the louvers relative to the die face, and air flow rate. Fibers were collected and fiber diameters were measured.

On the die face design for stamping an automotive engine hood

Since the engine hood is mainly manufactured in the drawing operation, the die addendum design is the key to the success of manufacturing a defect free product. In this study, the existing die addendum designs corresponding to those engine hoods were reviewed and the design parameters were constructed. The preliminary study was then performed to examine the influences of the stamping die angle, binder surface shape, and die open line shape on the defects occurred in the part. Based on the simulation results, the optimum design for the die addendum face was then investigated and a systematic design guideline was proposed. In order to validate the proposed design guideline, actual engine hoods were stamped according to the finite element analysis and the production part shapes, thickness distributions, and the stretch at the central region were compared with those obtained from the finite element simulations. The consistent agreement between the product parts and the simulation results confirms the validity of the design guideline proposed in the present study for stamping an engine hood.

Hole Making Process of Metal and Composite Sheets by Impact Hydraulic Pressure

Abstract Hole making process of metal and composite sheets using impact hydraulic pressure is investigated. The sheet is mounted in contact with the die face that locates at the bottom end of the cylinder. The piston at the top end is impacted by a drop-hammer with 10 m/s velocity, by which very high pressure is put on the sheet face to induce shear force at die edge. The die hole is circular, square or rhombic. The test materials are pure aluminum and its alloy, pure titanium, stainless steel and carbon fiber reinforcement plastic (CFRP) sheets. The cut surface is rather rough and the shear drop is larger compared with that in conventional punching. Burr generation is successfully suppressed for the metallic materials. Interlaminar fracture of CFRP sheet occurs in the hole vicinity. Corner radius of the square and rhombic holes is rounded. Counter punch in the die cavity is useful for improving shape accuracy.

Computational Fluid Dynamics Simulations and Experiments of Meltblown Fibrous Media: New Die Designs to Enhance Fiber Attenuation and Filtration Quality

The meltblowing process employs high-speed hot air jets to attenuate polymer streams injected from a die head. In this study, we examine design strategies to control the air flow field below the polymer injection point to achieve higher fiber attenuation and meltblown webs with smaller fiber diameters. Computational fluid dynamics (CFD) simulations for new die configurations show that vertical or inclined air constrictors around the primary air jets keep the centerline air velocity and temperature at their maximum values for 10–15 mm longer below the die face than the reference die. Polymer streams are kept near their melting temperatures at higher air velocities for a longer period, resulting in higher fiber attenuation. The underlying mechanisms leading to such behavior are discussed. Experimental results show reduction in fiber diameter and pore size, validating the simulation. Improved filtration properties are also obtained from the nonwovens webs.

Fabrication of micro‐meltblown filtration media using parallel plate die design

ABSTRACTMeltblown fibers are typically produced using a die technology based on the slot concept, an extension of the sheet die technology with a series of holes substituting the center rectangular slot of the sheet die. While this prevalent technology has met with considerable success, an economical, facile design would be desirable. In this study a new parallel plate die concept to fabricate micro‐meltblown fibers that offers simplicity, ease of use, and low cost was examined. The new die concept had parallel plates forming channels for polymer melt to flow through with a set of air holes surrounding them. This die design produced meltblown fibrous media with fibers in the range of 3–10 μm with pore size between 20 and 60 microns. The underlying mechanisms leading to such large fiber size formation and its implication in air filtration performance has been discussed. While conventional meltblown die generates fibers of smaller diameter and webs with higher filtration efficiency than the parallel plate geometry, design modifications could enhance the parallel plate meltblown die performance and make it a viable alternative. These die adaptations that include reducing air flow resistance, increasing the number of air nozzles around the polymer nozzles, recessing the polymer spinnerets above the die face, and having inclined air channels to increase the drag force on the fibers has been discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42998.

알루미늄 판재의 다단계 드로잉에 있어서 원통컵의 치수 정밀도 비교

Deep drawing of cylindrical cups is one of the most fundamental and important processes in sheet metal forming. Circular cups are widely used in industrial fields such as automobile and electronic appliances. Some of these cups are formed by a one-stage process, others such as battery cases and beverage cans are made by a multi-stage process. In the current study the multi-stage deep drawing of aluminum sheet metal is examined. The process consists of two deep drawing operations followed by two ironing operations. The press die, which can be used for the four-stage forming process, was manufactured allowing punch and die components to be easily changed for various experiments. The rolling direction of both the sheet and the drawn cups was always positioned toward the horizontal x-direction on the die face to minimize experimental errors during the progressive forming. The dimensional accuracy of the cylindrical cups formed at each stage and the earing defect due to the anisotropy of sheet were investigated. The influence of anisotropy on the thickness distribution was also examined. Both the thickness and the outer diameter of the cups were measured and compared for each set of experimental conditions. It was found that the dimensional accuracy of cups rapidly improves by employing the ironing process and also by increasing the amount of ironing.

Spring-Back Control in Automotive Door Inner Panel Stamping

The spring-back defect of the front door inner panel is a major technical issue during the automotive body manufacturing processes. The primary purpose of this study is to control the spring-back value of the door inner panel by optimizing geometric parameters of addendum surface and selecting appropriate forming process. The Inverse Approach is employed to analyze the formability of the panel and to acquire rapid amendment of the die face design. Two kinds of forming processes are conducted, respectively, one-step forming method and two-step forming method. The results show that the one-step forming process combining with the optimized addendum surface can reduce the spring-back amount of side wall regions on door panel less than 2mm. The proposed optimizing scheme was verified by multiple trial-producing.

Investigation of static zones and wall slip through sequential ram extrusion of contrasting micro-crystalline cellulose-based pastes

The shape and size of static regions in the extrusion flow of a viscoplastic material through axisymmetric square entry dies was studied experimentally using a simple flow field analysis technique. A white micro-crystalline cellulose/water paste was extruded sequentially with a graphite-stained black analogue paste, revealing static regions in the corners of the system extending less than 30% of the barrel radius into the centre of the channel. Slow (relative to the bulk) slip flow along the die face was evident in the experiments, implying the existence of a stick-slip transition on this surface.Finite element simulations using the Papanastasiou regularised Bingham plastic viscosity model and the linear Navier wall slip law were found to reproduce the experimental results poorly, capturing only separately the slip dominated bulk flow and the static corner region for different values of the slip coefficient β. The effect of severe wall slip was to reduce the distinction between unyielded and yielded material making the definition of the yield surface challenging. Investigation and implementation of a stick-slip wall condition is believed to be required for further work in this area.

Experimental Investigation into a New Melt-Blowing Die for Dual Rectangular Jets

In this work, online measurements of turbulent air flow field in the melt-blowing process for the slot die with inner stabilizing pieces and the corresponding blunt die were carried out with a hot-wire anemometer. The experiment results reveal that the inner stabilizing piece has an important impact on the flow field below the die face. The new modified die is aerodynamically superior, should contribute to produce much finer melt-blowing fibers and require less energy than the corresponding blunt die.

A Geometry Method for Calculating the Fiber Diameter Reduction in Melt Blowing

Melt blowing is one of the important methods for producing ultrafine fibers. The production of melt blowing is the nonwoven. Fiber diameter has crucial effect on the property of the nonwovens. In the melt-blowing process, many achievements have been published on the fiber diameter distribution along the spinning line. Note that all the results were obtained by methods of mechanical analysis, online measurements through high-speed photography and offline measurements from the production of nonwoven. In this study, a new method for calculating the fiber diameter distribution along the spinning line near the die face was revealed. This method was based on the geometry of the fiber path in the melt-blowing process. The fiber diameter reduction was calculated by this method and then compared with the experimental results obtained by other researchers. The results show that the proposed method is feasible.

Precise Die Face Design of Drawing Dies for Stamping Process Based on Point Cloud

Low cost, short cycle and high quality are the goals of the automobile manufacturing. The auto die is one of the key equipments in automobile industry. For the die manufacturing process is very complicated the trial-and-error method is still used in the tryout process especially the die face tryout. The computer aided engineering becomes more and more important for the new die development. In this paper the precise die face design process based on the blank drawing and die structure simulation for automobile die is studied in detail. The precise die face is generated by the cloud of simulation nodes distribution. The industrial application shows that the precise die face design method based on point cloud generation for automobile die is an efficient way for decreasing the die manufacturing cycle and an accurate method for die tryout process.

Experimental and simulation studies of springback in rubber forming using aluminium sheet straight flanging process

Rubber forming is very widely used in aircraft manufacturing. Springback of rubber forming process is an important and decisive parameter in obtaining the desired geometry of the part and design of the corresponding tooling. In this research, the rubber forming of aluminium sheet was conducted. To investigate the springback, the straight flanging was employed in die design. The deformation process was studied by preparing the sheets with different thicknesses and different die radii. The influence of process parameters (time and pressure) on the rubber forming process was studied. Based on the analysis of experimental results, it was found that springback of straight angle decreased with the increase of blank thickness t, whilst increased with the increase of the die radius r. The springback can be eliminated with the bending ratio r/t<2. The increase of forming pressure and time of rubber forming had little effect on the springback when the blank coincided with the die face. Springback of flanging in rubber forming process was smaller than that of stamping. In the jogged flanging, a better shape was formed by using the polyurethane.

Precision Analysis of Parametric Modification of the Die Face Based on Reverse Engineering

The conventional precision analysis method of modification and design is qualitative, laborious and time consuming. The precision of reverse parametric modification have direct influences on the quality of the reversed products. In this paper, a quantitative analysis method based on a reverse parametric approach and precision control concept is proposed. Combining with the ATOS scanner system, analyzing every aspect of the precision control and the error distribution, including data acquisition process, reverse reconstruction process and parametric process. In the process of the product reverse parametric modification, general error distribution is mainly composed of data acquisition error, reverse reconstruction error and parametric error. The method of precision control during the reverse parametric modification process is analyzed, according to this method, the total error of parametric modification for die face is 0.089mm, is lower than the accuracy requirement of 0.10mm in the reverse parametric modification process, the reverse modification of the die face of the blade based on precision control is realized. Validity and effectiveness of the method has been confirmed by case studies.

Study on the Formability Rules with Precise Die Face for the Inner Clutch Shell of Automobile

The ultimate goal of the metal forming industry is to form components made of a specific material into a required shape without experiencing wrinkling, bifurcation and spring-back. This study is devoted to develop the whole process by making rules of precision for specific part geometry. For inner clutch shell a computer simulation system and the general procedure of dynamic simulation in sheet metal forming are presented. Finally compute all simulation results with reference to the original part property and recommend the appropriate process flow to produce the part, the comparison with tryout results shows that the formality simulation of thick panel with precise die face is reliable and accurate.

Modifying Air Fields To Improve Melt Blowing

An advanced model for melt blowing was used to predict the effects of modified air fields on fiber formation. The model, which was developed previously, involves the simultaneous solution of the momentum, energy, and continuity equations. Crystallization effects were included. The model equations were solved numerically. Simulations were done for two classes of modified air fields. The first class of modified air field has a plateau of constant velocity and temperature. For wide plateaus placed near the die face, the effect of the plateau is substantial. Fiber diameters are reduced (by up to two times) versus diameters for when there is no plateau. The second class of modified air field has a quench (or a plateau-quench). Quenching was simulated as a step drop in air temperature. The simulation showed that quenching can enhance online crystallinity, though fiber attenuation is reduced when quenching is used.

Accurate Prediction of Die Face Coloring Rate for Short-Period Manufacturing of Automotive Drawing Dies

In this paper, the thinning rate and die elastic deformation under large forming force are investigated by finite element simulation with experimental validation focused on the problem of coloring rate between die and panel in automotive die manufacturing. The study suggests that when the panel is formed, the thinning rate of panel has little influence on the coloring rate and the die elastic deformation under large forming force is the main influence factor. The definition of high contact pressure area is proposed by the comparison between the simulation and industrial experiment results. The definition greatly benefits the predication of die face coloring rate. The method that die face is compensated reasonably is also proposed. It can reduce the die polishing workloads obviously compared to the traditional method of die face equivalent offset. This paper has a guide for comprehensive understanding the influence factors of coloring rate and greatly reducing the die tryout period.