Forming of rail car axles in a CNC skew rolling mill
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(2020) 20:69
ORIGINAL ARTICLE
Forming of rail car axles in a CNC skew rolling mill Zbigniew Pater1 · Janusz Tomczak1 · Konrad Lis1 · Tomasz Bulzak1 · Xuedao Shu2 Received: 25 February 2020 / Revised: 26 April 2020 / Accepted: 28 May 2020 © The Author(s) 2020
Abstract This study relates to an innovative method for forming rail car axles by skew rolling in a CNC 3-roll mill. The rolling mill was constructed at the Lublin University of Technology. The use of this machine makes it possible to produce elongated axisymmetric parts that are up to 55 mm in diameter and up to 1000 mm in length. Experimental rolling tests are performed (in 1:5 scale) using this machine. Two types of axles are analysed: one manufactured in accordance with North American standards (AAR Class E) and one manufactured in compliance with European standards (BA302). Diameters of produced axles have a dimensional accuracy of ± 0.4 mm. Produced axles are free from internal cracks, and their surface defects (shallow helical grooves) can easily be removed by machining. The major shortcoming of the proposed method is the presence of chucking allowance. To eliminate this allowance, it is proposed that the forming process should be performed in two operations: rolling extrusion and skew rolling. Results of a numerical analysis were performed using the Simufact.Forming program confirms that rail car axles can be formed by the proposed method. Keywords Skew rolling · Rail car axle · CNC rolling mill · Experiment · FEM
1 Introduction Rail car axles are large-size parts manufactured in batches of up to thousands units [1, 2]. These parts are currently produced by open die forging and rotary swaging processes. The open die forging of rail car axles is performed in hydraulic forging presses having a load range between 8 and 15 MN that are coupled with two forging manipulators. In open die forging, car axles are formed from forging ingots with circular or square cross sections, and the manufacturing of a single axle takes several minutes. The duration of the rotary swaging process is shorter (approx. 4 min) due to the use of swaging machines, which also helps reduce machining allowance. The rotary swaging of car axles is performed using rotary swaging machines with 4 dies, each having a load of 6.5 MN [3]. To make the manufacturing of car axles more efficient and less energy-consuming, extensive research is * Zbigniew Pater [email protected] 1
Lublin University of Technology, 36 Nadbystrzycka Str, 20‑618 Lublin, Poland
Faculty of Mechanical Engineering and Mechanics, Ningbo University, Ningbo 315211, People’s Republic of China
2
conducted on the production of these parts by rolling processes. The research focuses on cross-wedge rolling (CWR), a method which is effectively used for producing stepped axles and shafts in the automotive industry [4–6]. Nevertheless, well-known rolling techniques cannot be directly applied to producing rail car axles, as this would require the use of large rolling mills equipped with tools of up to 3 m in diameter [2
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