Forming of rail car axles in a CNC skew rolling mill

Shen

et al. 2021

Preprint

To meet the requirement of lightweight, there are increasing solid shafts being designed to be hollow in transportation industry. In this study, a novel method of flat-knifing cross-wedge rolling (FCWR) with single guide is proposed including a modified roller, a horizontal mill and a single-guide structure, and its key problems are studied by numerical simulations and experimental tests. A mathematical model of FCWR roller is established, which reveals the wedge length of rollers is effectively reduced by modifying knifing wedge from normalized roller. Further, a horizontal multifunctional mill is invented and constructed to carry out the FCWR experiment with single guide. According to the results from the numerical simulations and corresponding experiments, it is observed that the typical defects of hole expansion and knifing groove are absolutely avoided because the improved flat-knifing wedge produces a radial force to shrink the inner hole and avoid the deformation concentration of the outer surface during knifing stage. Moreover, the single guide rolling performed in the horizontal mill efficiently improve rolling stability because the workpiece is restricted into a smaller workspace. To the authors’ knowledge, all these integrated improvements of FCWR roller, single guide rolling and horizontal mill are innovative, which are of great engineering significance to manufacture hollow shafts on account of the advantages of avoiding forming defect, reducing roller diameter, improving rolling stability and simplifying mill structure.

Section: Fig Relationship Between Wedge-length Reduction and Process Parameters 3 Parameter Ranges And Research Schemesmentioning

confidence: 69%

Producing Hollow Shafts in a New Horizontal Mill by Novel Flat-Knifing Cross-Wedge Rolling With Single Guide

Shen

et al. 2021

Preprint

“…The FE projects were performed in Simufact.Forming software, which has been successfully employed in numerical analysis of CWR process [25,26] and skew rolling process [27,28], and their FE results have a good agreement with experimental results.…”

Section: Fig 6 Contact Model Of Roller Mandrel and Workpiece At The Stretching Stagementioning

confidence: 69%

“…The friction coefficients between tools and workpiece were modeled by Shear model (two rollers were 0.8, guide and mandrel were 0.2. [28] The temperature of tools (rollers, guide and mandrel) was constantly maintained at 300 °C [28]. The initial temperature of workpiece was 1050 °C and the coefficient of heat transfer between tools and workpiece was 10 kW/m 2 K [28].…”

Section: Fig 6 Contact Model Of Roller Mandrel and Workpiece At The Stretching Stagementioning

confidence: 99%

“…[28] The temperature of tools (rollers, guide and mandrel) was constantly maintained at 300 °C [28]. The initial temperature of workpiece was 1050 °C and the coefficient of heat transfer between tools and workpiece was 10 kW/m 2 K [28]. Besides, the mesh of billet was created by ringmesh mesher, whose element size equals to 1.4 mm, and will be automatically reconstruected if the eff ective strain increases by 0.4 [28].…”

Section: Fig 6 Contact Model Of Roller Mandrel and Workpiece At The Stretching Stagementioning

confidence: 99%

See 1 more Smart Citation

Producing hollow shafts in a new horizontal mill by novel flat-knifing cross-wedge rolling with single guide

Int J Adv Manuf Technol

Shen

et al. 2021

To meet the requirement of lightweight, there are increasing solid shafts being designed to be hollow in transportation industry. In this study, a novel method of flatknifing cross-wedge rolling (FCWR) with single guide is proposed including a modified roller, a horizontal mill and a single-guide structure, and its key problems are studied by numerical simulations and experimental tests. A mathematical model of FCWR roller is established, which reveals the wedge length of rollers is effectively reduced by modifying knifing wedge from normalized roller. Further, a horizontal multifunctional mill is invented and constructed to carry out the FCWR experiment with single guide. According to the results from the numerical simulations and corresponding experiments, it is observed that the typical defects of hole expansion and knifing groove are absolutely avoided because the improved flat-knifing wedge produces a radial force to shrink the inner hole and avoid the deformation concentration of the outer surface during knifing stage. Moreover, the single guide rolling performed in the horizontal mill efficiently improve rolling stability because the workpiece is restricted into a smaller workspace. To the authors' knowledge, all these integrated improvements of FCWR roller, single guide rolling and horizontal mill are innovative, which are of great engineering significance to manufacture hollow shafts on account of the advantages of avoiding forming defect, reducing roller diameter, improving rolling stability and simplifying mill structure.

“…This defect leads to the waste of the material, but does not affect the quality of products. Actually, all these observed defects are the typical imperfections in skew rolling 230 [2,17,21] and cross-wedge rolling [22,23,24] and can be removed in later precision machining, so do not affect the quality of produced shaft.…”

Section: Forming Precisionmentioning

confidence: 99%

Manufacturing large shafts by a novel flexible skew rolling process

Zhou

et al. 2021

Preprint

When manufacturing large shafts with multi-specification and small-batch production, both the conventional forging and rolling process bring a high tooling cost due to heavy forging press or large-size specialized roller. In this study, a novel flexible skew rolling (FSR) process is proposed by adding degrees of freedom to the rollers as compared to the typical skew rolling process. Since each of the FSR rollers has three degrees of freedom (circle rotating, radial rotating and radial feeding), the FSR process can be divided into four stages: radial rolling, rollers inclining, skew rolling and rollers levelling. Therefore, the FSR process can produce various shafts with same rollers via programming different movements. To verify the feasibility of FSR process, a physical investigation corresponding with a numerical simulation for a single-step shaft is undertaken with a Φ80×390 mm C45 steel billet. According to the results from physical experiments and numerical simulations, the FSR formed shaft has a maximum deviation of 0.99 mm, and its microstructure and properties have been improved obviously. Moreover, although there is a tendency of center crack in FSR products as predicted by numerical results, both the transverse and longitudinal section of the physical shaft are free from central cracking. The major forming defects existed on the rolled shaft are knurled pockmarks, surface threads and side cavity, which are the typical defects of the conventional skew rolling and cross-wedge rolling and can be removed by machining. To the authors’ knowledge, this novel process has a good combination of flexible production and less loading, which will be of great engineering significance to reduce the tooling cost in large shafts manufacturing.