The world’s largest billet inspection line machine,
destined for a Chinese steel mill, Dalian Steel,
contains components supplied by Tectra Automation
to H. Rohloff. The R16-million machine uses
thermography to accurately detect defects.

Tectra Automation has supplied components to H. Rohloff for the design and manufacture of the world’s largest billet inspection line. The machine, currently awaiting factory acceptance by the client, is destined for a Chinese steel mill, Dalian Steel. The machine is valued at R16 million and uses thermography to accurately detect defects.

Dalian Steel employs 50,000 staff and produces 11 million tons of steel per year. The company supplies to international markets and previously had no method of inspecting the billets.

H.Rohloff designed and manufactured a Billet InspectIR inspection line consisting of six computers, a control desk, a 19 inch signal processing cabinet, induction heater, pre-wetting station, camera box station and marking station. The line was designed to inspect 360 mm bar.

According to Louie van der Walt, Project Engineer, H. Rohloff, the company once again partnered with Tectra Automation in order to ensure world-class components for a world-class machine. “Tectra Automation has worked with us on the development of our two previous Billet InspectIR lines which were supplied to ArcelorMittal and a steel manufacturer in Germany. The Tectra team is ideal because of their expertise, product quality and service back-up.

“We worked with Tectra Automation from the design phase to ensure that we developed a sophisticated machine that met all of our client’s requirements.”

Van der Walt notes that the inspection line will be installed in the production line and is unique in that it can inspect round bar from 40mm to 360mm and square bar up to 250mm. “The line features 11 Bosch Rexroth servo motors which are responsible for positioning the billets. Once the parameters are programmed into the machine, it automatically adjusts according to the size of billet being inspected.”

All 11 servo motors are controlled with a single controller and drive – the Bosch Rexroth Indradrive MI – and are connected via a single cable. The IndraDrive MI is compact in design and takes up to 70 percent less space in the electrical panel and needs up to 85 percent less wiring. It features a single hybrid cable that connects up to 20 motors in series.

“The Indradrive also enables all motors to move at the same time which ensures that the inspection process is quicker and more efficient because the machine can automatically adjust to the size of the billets,” says van der Walt.

The steel manufacturer is located in a coastal city and as a result, the high levels of humidity needed to be catered for. The H. Rohloff team selected Bosch Rexroth aluminium and stainless steel profiles for the line due to their robust nature and ability to cope with the environmental conditions. In addition, Profibus was selected as the line’s communication protocol and is used in conjunction with a Bosch Rexroth L40 PLC that is responsible for the motion control of the 11 IndraDive MI servo axes, Profibus nodes and the machine sequencing. This ensured the inspection line offered plug and play functionality and ease of installation.

The Billet InspectIR uses four infrared focal plane array (FPA) cameras to identify defects in the billets with one camera covering a quarter of the billet. The round or squared billet is fed into the wetting station where it is sprayed with a fine mist. It then is fed into the camera box where defects, if any, are identified by raising the temperature of the bar by 20 degrees using an induction heater. Defects are shown to be hotter than the surface of the billet. All data is streamed in real time to the operator for reporting and quality control. A sophisticated signal processing system analyses the data and defects are identified and classified according to orientation, length and depth.

The defects are marked with quick drying ink to an accuracy of within 20mm. Defective billets are removed from the line and the defects can be removed through grinding.

Van der Walt notes that the system’s operator interface is in both Chinese and English and was designed to be easy to use. “The system is incredibly user friendly as a result of the excellent work the Tectra team completed on its programming. In addition, the interface is fast and through the use of Profibus, installation should be just as quick and easy.”

The five ton inspection line will be assembled at H. Rohloff’s manufacturing facility and shipped as is to site. Once on-site, it will also be installed in the production line in order to streamline efficiency and enhance quality control.

Tectra Automation is the sole distributor of Bosch Rexroth products in sub-Saharan Africa.