The effect of die half angle in tube nosing with relieved die

This research concentrates on rotary nosing using cone shape dies, in particular using “relieved dies”. “Relieved die” is a cone-shape die with contact surfaces and grounddown relieved surfaces. The objective of this research is to improve the forming limit by reducing the necessary force during the process. The present research focuses attention on the effect of die half angle. Die half angle is important parameter because the angle of nosing depends on the angle of the die in press and rotary nosing. According to the previous research, the forming limit is highest when the number of contact areas is three [1]. Therefore, this paper researched on the effect of die half angle by experiment and calculation, FEM, under the condition that the number of contact areas is three. It is revealed that the optimum contact angle changes depending on the die half angle

Characteristics of micro incremental in-plane bending of sheet metal using tiltable punch

Incremental forming methods have gained interest in recent years as a forming technique for micro and fine components. This paper presents a newly developed incremental in-plane bending with tiltable punch for micro-metal sheets whose thickness is less than 1mm. The punch has two unique points. Firstly, it has a joint which enables the punch tilt freely according to the contact pressure. Secondly, the punch "sole" has a trapezoidal shape, where the toe is thin and the heel is wide. With increase of indentation, the toe bites deeper into metal than the heel resulting in the thickness distribution. As a result, the thin sheet metal is bent without any difficulty of punch positioning. Among the conditions of incremental bending, the effects of the toe angle of the punch sole during contact on the bending radius are examined by experiments, calculations and analysis. As a result, incremental forming with a tool with a toe angle of 30 degrees results in the largest sheet-metal curvature

Examination of working condition for reducing thickness variation in tube drawing with

The present research carried out a series of analyses using the finite element method (FEM). The analyses investigated the effect of working condition on thickness variation after drawing a tube with initial thickness distribution. As a result, it was notably revealed that application of dies with small half angle below 5 degrees was prominently effective for levelling the thickness variation. This effect was strengthen by employing tubes with thicker walls and larger diameters. Moreover, the mechanism of levelling the thickness variation was also examined. The small die angle affects the contact length at die approach, and the contact length at thinnest side becomes longer than that at the thickest side. The difference of the contact lengths equalizes the thicknesses of the thinnest and thickest sides. The analyses also predicted the thickness variation should almost be zero under an optimum condition

An extrusion method of tube with spiral inner fins by utilizing generation of spiral outer fins/grooves

This paper presents a new extrusion method for fabrication of a tube with spiral inner fins. The spiral fins are formed by utilizing the generation of spiral outer fins or grooves, which drive the metal to circumferentially move with twist deformation. The effect of the outer fins/grooves is examined for realizing the circumferential metal flow. The position of the mandrel has an ability to flexibly control the spiral angle. This method would drastically enhance the productivity and reduce the manufacturing cost, as the tube would be manufactured directly from a billet through only one process

Evaluation of water film by reynolds' equation in deep drawing using high-pressured water jet

The authors had proposed a deep drawing method using high-pressured jet waters as lubricant. This method aimed to suppress the usage of oil or other chemical lubricants, which might require some additional processes for lubricant removal and become a nuisance in environment. The conditions had been determined through trial and error approach without knowing water behaviors as lubricant. As a result, some scars and dimples were observed on the surface of deformed cup. In the present paper, a numerical model was composed for the evaluation of the water behaviors as lubricant. Darcy-Weisbach equation was used for evaluation of pressure drop between nozzle exit and pump, while Reynolds' equation was used for the thin film of fluid between the die and blank. The data of blank deformation in FEM was considered for the determination of the thickness distribution of the fluid film. The characteristics of the water were evaluated by the composed numerical method, and the results were used for examination of lubrication characteristics in experiments

Analysis of spinner straightening utilizing the finite element method

This paper presents analysis methods utilizing the Finite Element Method for spinner straightening, and shows a guideline for optimum conditions. Two types of analysis methods were composed. Model [F-Expl], “full actual model with explicit scheme”, considers the rotational movement of dies as the actual process using the explicit scheme. Model [BndCr], “a model carrying out fundamental analysis on one cross section based on simple bending in the Finite Element Method (FEM)”, uses the FEM only for calculation of simple bending without rotation for obtaining the deformed bar shape. A series of experiments were conducted in an actual production line as well as the analyses by Model [F-Expl] and [BndCr]. The examination mainly focused upon the effect of straightening intensity by changing the die positions. The experimental and analytical results show some mechanism of straightening and a basic guideline for the optimum working condition

Finite element analysis of tube drawing process with diameter expansion

This paper presents a tube drawing process with diameter expansion for producing a thin-walled tube effectively. In this proposed process, the tube was flared by a plug pushing into the tube, and then the tube was expanded by drawing the plug in the tube axial direction with chucking the flared tube edge. Optimum plug shape, such as the plug half angle and the corner radius, was investigated by a series of analyses using the finite element method (FEM) for improving the forming limit and the dimension accuracy. At first, a friction coefficient was determined to 0.3 by a comparison of the flaring limit between the analysis and the experiment of the tube flaring. As a result of the analyses in the drawing with the diameter expansion, the forming limit was high when the plug half angle was set to 18~30°. The thickness reduction ratio increased with an increase in the expansion ratio and the plug half angle. In addition, the overshoot, which is a difference between the plug diameter and the tube inner diameter after the drawing, was prevented by using the plug with the corner radius of 20 mm

Effect of temperature in formability of composite composed of overlapped fibre bundle, thermoplastic resin and metal

A structure for a composite of fibre-metal laminate (FML) has been proposed, hich is composed of reinforcing fibre bundles, thermoplastic resin as the matrix and metal plates. The reinforcing fibre bundles are discontinuous, and are intentionally overlapped in the longitudinal direction. The resin including fibre bundles was sandwiched between the metal plates. The application concept for the industry is composed of three stages. At the 1st stage, FML is fabricated by lamination of reinforcing fibre bundles, thermoplastic resin and metal plates. At the 2nd stage, FML is formed into the final shape of the product by secondary forming processes, such as stretching or bending under a heated condition which melts the thermo resin. At the 3rd stage, the formed product is expected to have high strength. In the present paper, the effect of heating temperature on the deformation of FML at the 2nd stage was clarified. Firstly, the numerical examination was shown on the effect of overlap length on the fracture mode and the reinforcing mechanism in the proposed FML. Based on the result, the minimum bare length for the overlapped part for the discontinuous fibre bundles was determined so that the tensile strength might be as high as that with FMLs with continuous fibre bundles at the 3rd stage. Finally actual FML was experimentally fabricated, and subjected to all though the 1st to 3rd stages to verify the efficiency of the FML. In particular, the effect of heating temperature was focused upon to realize the forming process at the 2nd stage

Development of Twisting Method of Sheet Metal using Taper Roll

Twisted shape of metal, like a propeller or screw, are usually manufactured by machining. However, machining processes generate many metal chips, resulting in yield loss. This paper proposed a new processing method called, “twist rolling”, which uses a pair of tapered rolls to obtain a continuous twisted shape. The effect of taper and skew angles on twist angle was investigated. The finite element analyses (FEA) and experiments were conducted for clarifying the effect of taper and skew angles. A commercial code, ELFEN, was used for the FEA, and a prototype machine was built for the verification using aluminium sheet metals. The FEA and experimental results were qualitatively in good agreement. The twist angle increased with the increase of the taper and skew angles. The sheet metal angle increased with the decrease of the sheet thickness. This study successfully verified the feasibility of the proposed method, “twist rolling”

Two-step forming for improvement of forming limit in rotary nosing with relieved die for fabrication of axisymmetric and eccentric nosed tubes

This paper presents application of two-step forming for improving the forming limit in rotary nosing with a relieved die. Nosing is one method which is used for reducing the diameter of a tube tip. “Two-step nosing” is composed of two stages and different dies are applied for the two stages. The die shapes are determined based on the occurrence tendency of defects in “one-step nosing”, where only one die is used through the whole process. In this research, a series of experiments and numerical analyses of one-step nosing was carried out for investigating the mechanism of the occurrence of defects. As a result, it is revealed that the occurrence of defects was highly relevant with the contact area between the die and tube. Based on the result of one-step nosing, the optimum die shapes were determined for the two stages, and then “two-step nosing” improved the forming limit 9% higher than one-step nosing under the optimum condition. Furthermore, “two-step nosing” was experimentally applied for forming eccentric nosed tubes, and its superiority was verified