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

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

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

Molding of wood powder with a natural binder

International Conference on the Technology of Plasticity, ICTP 2017, 17-22 September 2017, Cambridge, United KingdomThis paper describes the molding of wood powder using sucrose as a natural binder, as a means of fabricating products based on natural resources. The conditions, such as the temperature and binder content of the wood powder, were optimized in order to produce compacts successfully in the molding process. In experiments, the plasticization temperature of sucrose was initially investigated by thermogravimetric/differential thermal analysis for the prediction of the thermal flow temperature of the wood powder combined with sucrose. In addition, flow behavior of the mixture was evaluated for the temperature and the binder content by capillary flow tests. Based on these data, molding test of wood powder with sucrose was conducted to evaluate the injection moldabilty. As a result, the plasticization point of sucrose was found to be approximately 176 ºC, with a mass reduction onset at 200 ºC due to decomposition to volatile products. Wood powder mixed with sucrose flowed at temperatures above 180 ºC, although flow was restricted above 220 ºC due to the effect of gases evolved from the sucrose. The minimum sucrose content required for flow was 30 wt% within the temperature range of 180 to 200 ºC. The mixture was found to fill a mold under optimized conditions, forming compacts with good surface texture at a sucrose content of 30 wt% and 200 ºC. This method allows the fabrication of products from naturally occurring materials with minimal environmental impact

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

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”

Fabrication of a ring groove on tube-inner surface by ironing from outer surface using displacement control of tube bottom end

This paper presents a improving method in a press forming for transferring convex shapes of an inner plug projection onto the tube-inner surface by applying outer-die ironing from the tube-outer surface. The previous study found that the concave shape was not perfectly formed and some “Non-filled-area” appeared around the upper and lower parts of the plug projection. This study tried to verify the effect of applying the reaction force on the tube-end surface by the finite element analysis (FEA) and experiment. The FEA showed the suitable amount of the reaction force and the optimum timing for reducing the force. The analytical results were verified by the experiment and the “Non-filled-area” was successfully reduced by the proposed method