A cold forging process for producing thin-walled hollow balls from tube using a plastic insert

Abstract

This paper investigates a cold forging process for producing hollow balls made of an aluminium alloy. The forging with an outside diameter of 30 mm is formed from a tube section with a 2-mm wall thickness. Preliminary tests have shown that in traditional die forging, the use of a billet with such a small relative thickness not only limits the range of applicable geometric parameters but also causes buckling. The authors propose to solve this problem by using an additional tool that has an active effect on the inner surface of the workpiece, and thus makes it possible to control the forging process conditions. The tool is a plastic insert, i.e., an additional flexible core made of a low-melting alloy. Theoretical and experimental results presented in this paper provide a considerable insight into the cold forging process for thin-walled hollow balls. The effects of the plastic insert geometry and dimensions on the forging process are also examined. A solution is proposed to ensure that the forged part meets all requirements.

Selected aspects of a cold forging process for hollow balls

“…The primary objective of experimental testing is to verify and validate the numerical model. It is worth mentioning that similar studies were successfully conducted and their results were reported in previous works [7,19]. Moreover, results presented in this paper are a continuation of previous studies.…”

“…An interesting technological solution for hollow balls is a forging process performed with the use of flexible inserts. This technique was proposed by Samołyk et al [19]. A general scheme of this concept is shown in Fig.…”

“…During the forming process, both the workpiece and the core are deformed in such a way that it has a positive effect on process stability. In a previous study [19] it was proposed that the core had a specifically defined shape and was put inside the billet. A different solution for producing the core is proposed on the Russian Patents website [21].…”

“…The coefficient value complies with the lubrication conditions that were ensured in experimental testing. A method for determining this value (upsetting of ring samples) was discussed in more detail in previous studies [7,19]. In the simulation, the tube was assigned the properties of AlMgSi0.5 aluminium alloy in an annealed state (EN Al6060-O, in compliance with EN 573-1: 2004).…”

Theoretical and Experimental Analysis of a New Process for Forming Flanges on Hollow Parts

“…An alternative to hydroforming is forging with the use of special elastic or plastic inserts. One example of such processes is the forging of hollow balls with the use of a low-melting alloy core to affect the inner wall of the workpiece [39].…”