AWL builds fully automatic production line for manufacturing fences

For a large manufacturer of fencing systems in the United Kingdom, AWL has designed and built a fully-automated production line with very high output. The project was a challange due to the multitude in functionality and the integration of the various processes and manufacturing technologies.

The company
The company is focused on the production of temporary fencing systems that are most commonly used in or around construction sites for keeping workers and the general public away from construction hazards. There are also a number of other common applications such as: Site Perimeter Fencing at pop concerts, fairs and exhibitions as well as traffic containment at road works, temporary car parks etc.

Impact
As the client used to weld these fences semi automatic in various steps, the change over to a fully-automated welding line has had a huge impact on the production process and the number of employees required. By changing over to the fully-automated production line labour costs were cut significantly! Because of the high customer demands for output and required product and process quality, at the start of the project single welding processes were validated by AWL. The entire installation was developed with some main key aspects in mind: suitable for mass production, minimum of required operators, process reliability, high autonomy and, last but not least, fulfilment of product quality requirements.

Why choose AWL?
According to customer requirement specifications, many process disciplines and technologies needed to be integrated in the entire customized production line. Standard solutions available in the market could never have fulfilled those requirements. In such projects AWL, as a first-class system integrator, is the smart and reliable partner for customized solutions.

The entire AWL project team, consisting of the departments: engineering, mechanical, electrical and process controls, is managed by experienced project managers and focuses on high performance, high quality and reliability.

Installation philosophy and description
The installation was developed for several variants of temporary fences; the three main variants being Round Top panels and Temporary fence panels (with or without corner plates). The installation was also prepared for fences with two variants of meshes: Anti-climb HD mesh and Standard mesh.

According to customer requirements regarding the number of operators and variety of products, special attention was paid to “autonomy” and the “variant change over during production” process during development.

In general the tubes are buffered in several tube buffer devices which can be loaded by forklift trucks. After separation of the tubes mechanical processes, like swaging the tube ends, are executed. For Round Top panels the tubes are first automatically fed into a bending station. To ensure the quality of the bend and (later on) the weld, the seam welds of the tubes are detected by a seam-detecting device. The prepared (swaged or bended) tubes are transported automatically to the assembly station.

In the assembly station the final frame is welded by resistance-projection welding. In the welding of galvanized tubes all welding units are equipped with medium-frequency welding systems.

To ensure the welding quality of the welds an extra testing station is integrated. Clamping cylinders press the welded frame with adjustable force near to the welds. Only frames with optimal welding quality are passed to the next station. Welding failures are indicated by the process control and can be removed from the production line.

After the frame is welded in the assembly station it is transported to the station for welding the corner brackets (stiffeners for the corners of frames). The corner brackets are stocked in buffers outside of the installation. The separated corner brackets are placed automatically into the welded and positioned frames and welded by spot-welding units.

The welded mesh is automatically transported from two mesh-welding machines and stacked into a mesh buffer. Finally the welded frame and mesh are welded together by a welding gantry. Once the fence is completed by the resistance-welding process at the welding gantry some customer-specific labels are mounted automatically on the fences. The assembly and joining of the labels into the fences is executed by a clinching process.

Complete welded and assembled fences are stacked (in different patterns) in a buffer zone (conveyor belt). The stacked fences are lifted in an upright position and transported out of the production line automatically and are finally ready for unloading by forklift trucks.

Unique features 

• All single parts of the fences are stacked in buffer devices. Stacking of buffers can be executed while the production line is running, which means that loading buffers will not disturb the entire process. 
• Because of the high required output of the production line in combination with several product variants, the installation can change over without stopping the process / installation. 
• Welding process (by medium-frequency welding): all welds are tested mechanically to ensure the requested welding quality. 
• Seam-weld detection (before bending): to ensure high bending and welding quality, seam welds in the tubes for Round Top variants are detected. 
• The welding controllers are connected to the PLC, enabling service from a distance through VPN connection. This way AWL can intervene directly in the machine control in case of an emergency. The whole production process is easy for operators to run as the controls are made visual via the HMI and data handling also takes place. 
• The production line is equipped with multiple disciples such as: bending, detecting, checking, welding MF, diameter reduction, testing, automated feeding, buffering, labeling, logistics and handling; all of which are needed to create a high-quality fence in a short cycle time.
• The production line is connected to the mesh welding machine and has a buffer station, making sure the process continues to run smoothly when the mesh welder is changed over for different wire thickness.