Automation Reinforcement Steel Mats Automatically Shaped

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FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

The construction industry requires many diligent hands, as manual labor remains standard in many areas. Terhoeven has automated the cutting of reinforcement steel mats using Mitsubishi Electric technology and Orgassa's expertise.

In the production of welded wire mesh, steel wire is first uncoiled and straightened. During this process, the wires also receive their characteristic ribbing. An automated machine then welds the wires into a mesh with transverse and longitudinal rods. To achieve optimal machine utilization, the welding machine produces the meshes in the maximum format. Since smaller formats are typically used on construction sites, the meshes must be cut to the appropriate size. In the past, this process was very labor-intensive as there was no automated solution.

Up to six people are needed to lift the heavy meshes and position them on the cutting machine. During subsequent stacking, every second mesh must be flipped to reduce the stack height. It is becoming increasingly difficult to find personnel for this strenuous and monotonous work. The company van Merksteijn International B.V., which processes 3,400 tons of concrete steel daily, therefore sought an automated solution.

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Mechanical Engineer Specialized in Reinforcement Steel Mats

The company found its solution with Terhoeven GmbH & Co. KG, which offers solutions for this sector under the hambi Maschinenbau (engl.: Mechanical engineering) brand. Originally founded in 1908 as a village smithy, the company is now run by Stephan Terhoeven in its fourth generation. He explains: "Since 2006, we have focused entirely on mechanical engineering and have given up our other business areas in agricultural and farming technology." With around 30 employees, hambi offers various machines for handling, cutting, and bending welded wire mesh. The range extends from small bending benches used on construction sites to large machines for rebar bending facilities and mesh manufacturers.

On behalf of van Merksteijn International, the machine manufacturer developed a system that fully automates the handling, cutting, and stacking of welded wire mesh. The ASA (Automatic Cutting System) first separates the top mesh from the stack, lifts it, and transports it to the feeder unit. The feeder unit pushes the mesh into the guillotine until the set length is reached. The guillotine then cuts the mesh, and the mesh discharge transports the cut section to the mesh turner. In the final step, the system stacks the mesh. The mesh turner rotates every second mesh during this process. This rotation minimizes stack height by interlocking the sections.

Separating and Lifting the Mats as a Challenge

Lifting the top mesh from the stack initially seems relatively simple. "For automation, however, this step is a major challenge," explains Stefan Broeckmann, responsible for design and development at Terhoeven. The manufacturing tolerances of welded wire mesh are in the centimeter range, but handling requires an accuracy of less than a millimeter. Additionally, the individual meshes are not neatly stacked. For the automation process, the company commissioned Orgassa GmbH. "We share a long-standing, trusting collaboration," says Terhoeven. The first crucial step is determining the actual position of the mesh and, thus, the gripping points where the grippers can lift the mesh. Marc Orgassa, managing director of Orgassa, explains the procedure: "A combination of image processing with modern camera technology and laser sensors detects the actual position of the gripping points, allowing the meshes to be grabbed with precision." The 3D image processing used for this was entirely programmed by Orgassa.

When the six grippers lift the welded wire mesh, the next challenge arises. As the mesh is lifted, it bends, creating horizontal forces on the lifting devices. "To compensate for this," explains Orgassa, "the distances between the individual gripping points need to be adjusted." Therefore, three separately operating drives are required for each of the six points to move the grippers in all three spatial directions. During operation, the drives must be precisely and synchronously controlled.

Drive and Automation Technology from a Single Source

To compensate for the deformation of the meshes during lifting, 18 drives are required for the lifting mechanism, along with four additional drives for transporting the meshes within the system and for turning them before stacking. Servo drives from Mitsubishi Electric, along with corresponding servo amplifiers, are used for this purpose. The motors of the MR-J5 series are very compact and offer high dynamics. The associated servo amplifiers can be linked via intermediate circuits—allowing the braking energy of one drive to be directly used by another. The servo amplifiers also enable power regeneration back into the grid. This achieves a high level of energy efficiency in the system overall. "With the Motion Controller, we can optimally implement the required synchronization of the drives," says Orgassa, highlighting an important reason for choosing this system.

All other components of the automation technology also come from Mitsubishi Electric. In addition to the servo-equipped drives, frequency inverters of the FR-E800 type are used for simple conveyor tasks. A safety PLC from the MELSEC iQ-R series controls all processes in the system. This is complemented by three C-Controllers equipped with a Linux operating system. These separate CPUs primarily run the image processing that, using cameras and sensors, determines the gripping points of the welded wire meshes. "The communication via CC Link IE TSN is particularly important for us," explains Orgassa, "as it ensures the synchronization of the various system components and the controllers with the drives."

This is an important prerequisite, as the image processing naturally requires the exact positions of the grippers. The CC Link IE TSN protocol is used, which enables both real-time capability and the necessary safety-oriented communication. With the gigabit bandwidth provided by the open CC-Link IE TSN standard, the communication of control, motion control, and safety can easily be integrated into one network. The electrical supply protection for the entire system is also ensured with a component from Mitsubishi Electric: a contactor of the SD-T100 type is used here.

Work Safety is a Top Priority

When handling the heavy welded wire meshes, the automation technology must ensure the safety of the operating personnel. Therefore, all components of the drive and automation technology are used in safety versions. This applies not only to the safety PLC but also to the servo drives, which are also monitored for safety. In the event of a power failure in the system, the drive will remain in a safe position in any case. The position is additionally monitored with encoders—also in safety versions. The same applies to the compact digital I/O modules of the NZ2GN type, which connect various switches and sensors in the system to the PLC. To prevent potentially dangerous access to the system during operation, a safety fence, including a safety door and two light curtains, has been installed. "Overall, with all safety measures, we achieve Performance Level c and, in some areas, Performance Level d," emphasizes Broeckmann.

Operation by one Person

The operation of the ASA is carried out via a GOT operating device from Mitsubishi Electric. In addition to the touch display, it also integrates some buttons and switches to facilitate operation with gloves. The programming of the user interface and visualization was done by Marc Orgassa in the iQ Works programming environment. The software package enables efficient cross-system programming of all automation components, from the drives and safety PLC to the operating device. "Only the software for image processing was programmed in C," notes Orgassa as an exception.

The user interface offers four different levels for various users. In addition to using the active program and operating in routine mode, there is a setup mode for entering parameters for a new mesh size. In the fourth level, basic settings can be adjusted or errors can be diagnosed. Retrofitting the system, for example, to accommodate a new mesh size, is very simple with the GOT operating device. Only a few tasks need to be performed manually during setup, such as adjusting the width stop in the storage area or changing the grippers for two different rod diameter ranges. To operate the system within the safety fence during setup or troubleshooting, a mobile GOT operating device is provided. This allows the system to be moved only in safe operation at reduced speed.

System Successfully Commissioned

After a development period of nearly two years, the first system was commissioned at the customer's site in spring 2024. "The ASA is 6 meters high and over 40 meters long," emphasizes Stefan Broeckmann, highlighting its impressive dimensions. When explaining why they chose Mitsubishi Electric for the drive and automation technology, Terhoeven states simply, "We have been using Mitsubishi Electric products in our machines and systems for many years and have consistently had good experiences." Orgassa adds, "Using all components from a single source is, in our experience, very practical. With Mitsubishi Electric's current portfolio, we can easily implement real-time communication, drive synchronization, and safety requirements."

After presenting a world-first with the successful automation of cutting welded wire mesh, the machine manufacturer is already working on the next steps. A machine is planned that can bend welded wire mesh into cages of various geometries and sizes, which are used on construction sites for the production of columns, beams, or lintels—once again fully automated. "For the automation technology, we will certainly rely on Orgassa and the systems from Mitsubishi Electric again," says Stephan Terhoeven. (st)

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