TPT November 2020

T UBE BEND I NG , END FORM I NG & SWAG I NG

Multiple-point bending technology for square and rectangular hollow sections

IN general, there are two types of technology for the forming of square hollow sections and rectangular hollow sections: ‘direct forming technology’ and ‘traditional forming technology’. In direct forming the steel strip is bent into the shape of the SHS and RHS before welding, while in the traditional forming method the steel strip is rolled into the shape of a circular tube and will then form to SHS or RHS with the assistance of rolls after welding. In the traditional forming method, several sets of rolls will be required in the ‘circular section forming’ stage alone, which will result in high tooling cost and reduced production efficiency due to frequent roll changes. Each size of tube will require a set of rolls specifically designed for that size. A roll change is required whenever a different size of tube is produced, resulting in discontinuation in production and high

labour cost. This forming technology is recommended for producing small- sized tube when the required variety of tube sizes is minimal. The usage of SHS and RHS has been gaining popularity, and there has been increasing demand for heavy-wall tube with good cross-section quality. Forever Machinery has developed and produced a tube mill that utilises direct forming technology to produce SHS and RHS. By adopting multiple- point bending technology, the machine is capable of producing tubes in a variety of sizes without changing the rolls, which translates to a claimed cost saving of 70 per cent of the tooling. The machine also incorporates a quick- change system for the rolls, saving the time required for roll change. Based on past experience, the R&D department at Forever Machinery has also developed a new set of rolls

designed specifically for direct forming technology. Over the years, the company has optimised its design for different tube sizes by in-depth research into forming technology, roll profile design, forming characteristics, forming contour design, welding technology, seam guide roll, squeezing roll, ironing roll and side rolls. The forming section uses the concept of straight edge flexible forming, enabling the sizing section to share one set of rolls for all different tube sizes. This design feature also increases the precision of the finished products. The company’s most advanced tube mill also incorporates servomotors for the adjustment of rolls, to further improve the efficiency of the machine. Shijiazhuang Forever Machinery Co Ltd www.pipemill.cn

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NOVEMBER 2020