A flexible shear spinning of axi-symmetrical shells with a general-purpose mandrel

https://doi.org/10.1016/j.jmatprotec.2007.04.008Get rights and content

Abstract

An experimental study is conducted to survey the technological possibility of the shear spinning of truncated hemispherical shells with a cylindrical mandrel for general purposes using A1050-H and A1050-O commercially pure aluminum sheets of 1 mm thickness. It is found that there exist forming limits to prevent the occurrence of wall fractures and flange wrinkles during the spinning process of truncated hemispherical shells. It is also found that the sine law is not realized exactly in shear spinning of truncated hemispherical shells with a cylindrical mandrel for general purposes due to the spring back of the workpiece.

Introduction

The shear spinning process is sometimes called spin forging or shear forming in the literature. The process of shear spinning is characterized by the fact that the radial position of any element in the blank remains the same radial position during deformation. This demands that the initial thickness of the blank t0 and the final thickness of the axi-symmetrical shell tf are related by the sine law for the tangential angle in the meridian plane of the axi-symmetrical shell α: tf = t0 sin α [1].

While the recent spinning technology including conventional spinning, shear spinning and tube spinning has been reviewed elsewhere [2], it has been considered that the outer shape of the mandrel should be identical with the inner shape of the product to be formed in shear spinning. In the ordinary process of shear spinning, a mandrel whose outer shape is identical with the inner shape of the product has been used as shown in Fig. 1.

On the other hand, the path of the forming roller 0–1–2–3–0 as shown in Fig. 2 can also form a conical shell supported on the end of a cylindrical mandrel that rotates with the main spindle of a spinning lathe [3]. If a workpiece has the rigidity that is sufficient to maintain the shape of shell to be formed during the process, an ironing process between the forming roller and the mandrel is not so essential to the shear spinning process. In other words, there is no need to use a mandrel that has an identical outer shape with the inner shape of the product to be formed if the workpiece has sufficient rigidity to maintain the shape of the shell to be formed during the process. If the path of the forming roller is controlled to satisfy the sine law corresponding to the product to be formed, various axi-symmetrical shells can be spun by a combination of a forming roller and a cylindrical mandrel for general purposes. This flexible process will be applicable to form axi-symmetrical shells of a great variety and small-batch production if various axi-symmetrical shells can be manufactured practically with a certain degree of accuracy.

In the earlier papers [3], [4], an experimental study was conducted to survey the technological possibility of the shear spinning of truncated conical shells with a cylindrical mandrel for general purposes. There exist forming limits to prevent the occurrence of wall fractures and flange wrinkles as shown in Fig. 3 [3]. The sine law is also realized in shear spinning of truncated conical shells with a general-purpose cylindrical mandrel as shown in Fig. 4 [4]. While a sudden change in the wall thickness is observed in Fig. 4, the thinning phenomenon of the wall thickness at an early stage of shear spinning can be prevented by the use of a non-linear path of the forming roller to allow a gradual change in the wall thickness from the initial value to the final value, as shown in Fig. 5 [4].

This paper deals with an experimental study of the technological possibility of the shear spinning of truncated hemispherical shells with a general-purpose mandrel.

Section snippets

Experimental procedure

A scheme of shear spinning of truncated conical shells with a general-purpose mandrel is shown in Fig. 2. A circular blank disk of outer diameter D0 = 120 mm and thickness t0 = 1 mm was supported on the end of a cylindrical mandrel of outer diameter dM = 50 mm. The cylindrical mandrel rotated at a constant number of revolutions N = 187.5 rpm with the main spindle of a spinning lathe. A forming roller of outer diameter of dR = 74 mm and round-off radius of ρR = 2 mm was fixed to a tool post on an XY-table. The

Performance of shear spinning operation

Based on the results of preliminary experiment, experiments of shear spinning of truncated hemispherical shells with a cylindrical mandrel for general purposes were carried out under various working conditions listed in Table 2.

Typical experimental results under the working condition of a residual flange width of 10 mm for A1050-H and A1050-O aluminum sheets are shown in Fig. 7. The abscissa of Fig. 7 denotes the value of radius R of the hemispherical shell to be formed. The symbols × and + in

Conclusions

Truncated hemispherical shells can be manufactured practically by shear spinning with a cylindrical mandrel for general purposes. However, the dimensional accuracy of the spun product in shear spinning of truncated hemispherical shells with a general-purpose mandrel is not so high as in shear spinning of truncated conical shells.

References (4)

There are more references available in the full text version of this article.

Cited by (0)

View full text