TPT July 2019

T E CHNOLOG Y

SHS and RHS tube forming technology

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 size. This design feature also increases the precision of the finished products. The company’s most advanced tube mill also incorporates servo- motors for the adjustment of rolls, to further improve the efficiency of the machine. Adopting a differ- ent bending radius for each stand improves the ‘weak corner’ issue associated with old direct forming technology. Integrating Siemens PLC, HMI and a control system specifically designed for the tube mill allows fully automatic control and operation of the machine. With more than 100 set points for the PLC program, the automatic roll-adjustment system is able to position the rolls accurately for each tube size. The forming, welding, sizing and turks head sections are able to communicate with each other

IN general, there are two types of technology for forming of SHS (square hollow sections) and RHS (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

via Profibus and Profinet protocols, in order for the line to work reliably. Each stand is equipped with Siemens servo control system together with absolute value encoder position control system, enabling real-time monitoring of the machine. The Siemens S7-1500 PLC is capable of collecting and processing all the feedback signals from the motors and other electrical components. All parameters are keyed in from the HMI, which can also be used to monitor the running status of the line. Rolls can be automatically adjusted based on the tube size input into the PLC. Manual adjustment is also possible from the HMI to fine-tune the rolls. With the help of the automatic roll adjustment system, all the real-time information including power loads, roll positions and any fault signals will be presented on the HMI for the operators. This is not only more convenient for the operators to observe the current status of the machine, but also reduces the time required for fault detection and troubleshooting, ensuring the reliability and efficiency of production. Shijiazhuang Forever Machinery Co Ltd – China Fax: +86 311 83839990 Email: mao@frv.cn Website: www.pipemill.cn

SHS and RHS tube forming

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JULY 2019