Movable Die Research Articles

Freeform bending tool design for rectangular profiles and its influence on the process

Abstract Freeform bending offers a wide range of possibilities in terms of component geometries, material grades and profile cross-sections. In the field of circular solid and hollow profiles, the design of the tool is determined by the circular shape of the profile used. When using rectangular profiles, the cross-section of the tool cannot be easily obtained by an offset of the profile cross-section. The large tolerance ranges of the profile standards require compromises with regard to the shape and tolerances of the tool. Tests have shown that the design of the tool has a great influence on the quality of the component. Furthermore, the trade-off in the tool design can lead to unsuitable tool shapes leading to defects and damages on the profile. These are mainly wrinkling, cross-sectional deformations and strongly deformed profile corners, which in some cases form cracks in the material. In this paper, the influences of the tool design on the bending result and the defects of the profiles are investigated. For this purpose, several tool designs with different variants and combinations of the movable die and the fixed die are compared with each other.

Movable Die and Loading Path Design in Tube Hydroforming of Irregular Bellows

Manufacturing of irregular bellows with small corner radii and sharp angles is a challenge in tube hydroforming processes. Design of movable dies with an appropriate loading path is an alternative solution to obtain products with required geometrical and dimensional specifications. In this paper, a tube hydroforming process using a novel movable die design is developed to decrease the internal pressure and the maximal thinning ratio in the formed product. Two kinds of feeding types are proposed to make the maximal thinning ratio in the formed bellows as small as possible. A finite element simulation software “DEFORM 3D” is used to analyze the plastic deformation of the tube within the die cavity using the proposed movable die design. Forming windows for sound products using different feeding types are also investigated. Finally, tube hydroforming experiments of irregular bellows are conducted and experimental thickness distributions of the products are compared with the simulation results to validate the analytical modeling with the proposed movable die concept.

Flexible bending of rectangular profiles: numerical and experimental investigations

The rectangular cross-section copper profiles are widely used in various industries. These tubes and profiles are formed in a small radius to decrease the weight and occupied space. The smaller bending radius, the higher the probability of defects, especially when the cross-sectional area of the tube is non-circular. Because by decreasing the bending radius, it is possible to create fold defects in the inner radius of the bend, excessive thinning of the outer wall, and changing the cross-sectional shape. In these situations, conventional tube bending techniques cannot produce these bends with optimal quality. Therefore, it is necessary to provide innovative, and new methods for the production of small radius bends in non-circular tubes. One of the most reliable and suitable bending methods for tubes and the profiles are flexible bending. In this study, a flexible bending machine has been fabricated based on a novel approach. Also, the key parameters in flexible bending of rectangular copper profiles such as: feeding speed, clearance between the die and profile, offset (u), guide fillet radius, the distance between the fixed die and movable die (v) and friction with ABAQUS finite element method software have been investigated. The numerical results have been compared with experiments. Experimental results showed good compatibility with simulation results.

Study of Large-Expansion-Ratio Tube Hydroforming with Movable Dies

In this paper, finite element codes LS-DYNA and DYNAFORM are used to analyze the plastic flow pattern of a tube hydroforming into a product with large expansion ratio and eccentric axes. Tube hydroforming with a movable die is proposed to enhance the forming capacity of tube hydroforming technology. The relative speed of the axial feedings to the movable die for obtaining a sound product is determined by a geometric analysis. The whole forming processes are divided into two stages. At the first stage, an internal pressure is applied on the inner surface of the tube and two axial feedings and a movable die move forward simultaneouly. At the second stage, one of the axial feedings keeps moving forward, whereas, the movable die moves backward. With this forming schedule for the axial feedings and movable die, products with more uniform thickness distributions are obtained. Finally, experiments of tube hydroforming with a movable die are conducted. Low-carbon steels are used as the tube specimen in the experiments. The simulation results of the product shape and thickness distributions are compared with experimental results to verify the validity of the finite element modeling and the proposed forming schedules.

An investigation of the variable cross-section extrusion process

In this work, a flexible extrusion process which involves extruding the materials via one fixed and one movable die was studied. The novel extrusion process is termed as variable cross-section extrusion which can produce near net shape bars or tubes with variable cross sections along the length. During the extrusion process, the key is accurately and dynamically adjusting the geometry and size of die hole. Based on the “equivalent volume theory,” a novel motion control model was proposed for the movable dies. Besides, a numerical calculation method and a program for the model were also presented. By using the program, the motion parameters of movable dies were calculated for extruding a typical variable cross section. Finite element method (FEM) simulation and experimental work were carried out to analyze the precision and accuracy of the control model. According to the simulation results, the shapes of extrusion parts agree well with the designed shape. However, the measured dimensions of the FEM extrusion part are always smaller than the designed curves with absolute deviation of 0.81 mm. According to the experimental results, the dimensional tolerances are 0.35 and −0.22 mm when the movable die is moving upward and downward, respectively. These-dimensional tolerances are associated with the instant transformation of moving direction of the movable die, which were driven and controlled by an electrohydraulic servo system. All results have shown the motion control model has enough precision and accuracy and can be used in the processes of design and parameter calculation.

Tube Hydroforming of Fuel Filler Pipes with Movable Dies

Tube hydroforming is a relatively new approach to manufacture light weight metal structures. As the manufacturing technology became advanced, demands of lighter and stronger metal structures are also increasing. This research is to use tube hydroforming to expand the tube of a fuel filler for cars. The pipe material is JIS G3141. The product has a large expansion ratio at the edge of the pipe. Traditional tube hydroforming is difficult to achieve this large expansion ratio of a metal product. Tube hydroforming with movable dies is proposed to enhance the capacity of tube hydroforming technology. With movable die design, product with more uniform thickness can be obtained, and the forming pressure becomes lower than that needed in tube hydroforming without movable dies. A finite element code DEFORM-3D is used to analyze the plastic flow pattern of the tube. The loading paths of internal pressure, axial punches and movable dies for obtaining a sound product are determined by an adaptive simulation algorithm. The thickness distributions of the product for different loading paths are discussed.

The Pier’s Deformation and Load Capacity Calculation of Bridges in Construction with Movable Die Carrier

A large horizontal force will be generated to the pier when the movable die carrier walks to the next span, especially for the high-pier bridges. thus a horizontal deflection will be produced as well as cracks developed. With solid degenerated virtual laminated element program, considering both geometrical and material nonlinearity, the mechanical performance of the pier under a horizontal force on the top of the pier is simulated and illustrated, and the cracks emerged at the bottom part of a high pier in the process of the movable die carrier walking to the next span is analyzed. The results show that when the cracks emerged, the stress of the bars and the stress of the concrete in the compression zone is quite small, hence the safety of the bridges in the construction stage is confirmed.

Casting Die Designing for Drive Cover

The driving covers casting with complex shape belongs to irregular casting. According to the requirements of size and performance of the thin-walled castings, the expanding-type runner of the trapezoid shape section was adopted, conducive to the production of thin-walled castings. The parting surfaces of the die-casting die are the interface of the movable die and fixed die and that of left and right slider. The left and right slider would be reset by spring. Proved by actual production, the mold operated smoothly, without clamping stagnation, and the production of die castings meet delivery requirements.

Less Loading Tube-Hydroforming Technology on Eccentric Shaft Part by Using Movable Die

Eccentric shaft parts, such as crankshaft and camshaft, fabricated by thick-wall tube hydroforming are increasingly used in industries, especially air-conditioner and automotive industry. In hydroforming those thick-wall components, the very high internal pressure and incomplete filling of the die corner make the forming process become difficult. In this paper, a new less-loading hydroforming die with movable sleeve is introduced to form the tube-like eccentric shaft workpiece. The characteristic of less loading hydroforming is illustrated by comparing with the conventional one by using FE simulation. Some typical loading paths and defects in the new hydroforming process are also investigated. The results obtained from this paper demonstrated the internal pressure, die closing force and die stress can be significantly decreased, as well as the qualified tube-like eccentric shaft workpiece can be formed by using the new movable die hydroforming.

Evaluation of the effects of a movable tool in the hydroforming process

In this paper, the production of stainless steel hemi-toroidal parts has been investigated using three different processes: the conventional stamping, the standard sheet hydroforming and the hydroforming adopting a movable die (MD) which can have a vertical stroke and whose shape completes the female die cavity. Tests adopting the MD were performed at Aalborg University using a specific experimental equipment; numerical simulations were performed using ABAQUS\Explicit and were aimed at investigating the effect of the friction condition of the MD tool on the blank deformation. The friction coefficient was varied on both the whole surface of the MD tool and locally (in the region of the MD corner radius). The role of the MD in the hydroforming process was thus studied by comparing results in terms of thickness and strain distributions on the final part obtained adopting the same geometry of tools, but different forming techniques. Simulations put in evidence that a moderate increase of the friction can be successfully used for reducing thinning if the MD is adopted; in addition, the friction in the region of the MD corner radius shows to play a key role in forming sound parts.

Recent developments in sheet hydroforming technology

In this paper, recent developments in sheet hydroforming technology are summarized, several key technical problems to be solved for the development of sheet hydroforming technology are analyzed, and varied sheet hydroforming technologies are discussed. Compound deformation by drawing and bulging is the main direction for the development of sheet hydroforming technology, in which it is advantageous to increase the feeding of materials, and the ratio of drawing deformation (drawing in of the blank flange) to bulging, enabling the forming limit of a sheet blank to be increased. It is also advantageous to increase the local deformation capacity for sheet hydroforming, to increase the range of application of the process. Press capacity is one of the important factors restraining the range of applications. As one of the flexible forming technologies that is still under development, it has much potential for innovative applications. Its applications have been increasing remarkably, recently in automotive companies. A breakthrough in the technology will be obtained by the development of novel equipment. A new sheet hydroforming technology using a movable die is proposed in this paper, which has been developed recently by the authors.

Technology of sheet hydroforming with a movable female die

An improved sheet hydroforming process is proposed and investigated experimentally and numerically. A movable female die keeps in contact with the deformed area of the sheet blank so that further deformation of the deformed area is restricted. Under the sealing, the sheet blank under the flange can be drawn in. So the hydroformed part has less thinning than the hydrobulge formed part only, and the limit drawing ratio of the sheet can be remarkably improved. This process is especially suitable for forming of small batch production of sheet metal parts with complicated shapes. The female die can be replaced with other female die of various shapes, and can also be made of very cheap materials such as plaster and hard wood instead of metal when the part number is very small. Thus complex-shaped sheet parts can be formed with less expensive tool systems. In this paper, the hydroforming processes of part A (without a movable die) and part B (with a movable die) were investigated by experiment and by elastoplastic FEM. The effects of various process parameters on the deformation of the sheet blanks were investigated. The forming conditions affecting wrinkling and rupture have been analyzed. The effects of friction and contacting force acting on the experimental results are also discussed.

On the machinability of Al-Si-Cu alloy for die casting

As Al-Si-Cu alloys, which are used in many fields for the die casting aluminium alloy, that is, copper silumin, apt to be embrittled, especially to grow the hardspot and get worse the machinability when the iron content exceeds 2%, so much attention is paid to the iron content in casting. On the other hand, if the iron content is too little, it is said that the durability of the movable die is very affected because the die is liable to be seized. In this paper, the alloys, which are equivalent to JIS ADC12 and ADC13 and have four sorts of iron content in the range of 0.31-2.05%, are cast as the test specimen for the purpose to examine the influence of iron content on the machinability of alloy. 9.5mmφ rods are made for the turning specimen by the cold chamber 80CT type die casting machine (Toshiba Machine Tool Co.)The high speed steel (SKH4) side tool has been used and the side rake angle is changed in the range of 0°-30°. And the RAMO-type high speed precision lathe has been used in the turning conditions as follows: the cutting speed is 75m/min, the cutting depth is 1mm, the feed is changed in the range of 0.06-0.25mm/rev and the dry cutting method is gone. The influence of iron content on the machinability of alloy is discussed by the cutting force, the unit net horsepower, the roughness of turning surface and others in this paper.