Multi-spot welders for steel meshes made of smooth or ribbed reinforcement bars are among the specialised equipment produced by Przedsiębiorstwo Aparatury Spawalniczej ASPA S.A. The meshes are used in the building and mining sectors. The construction of the welders is suited to specific tasks and parameters identified by customers.
Components of a multi-spot welder:
- welding unit with transformers and welding part (Photos 2 and 3),
- moving supports to be placed under lengthwise bars (Photo 4),
- mesh moving mechanism (Photo 5),
- mesh collecting table (Photo 6),
- lengthwise bars pushing and positioning feeder (Photo 7),
- crossbar feeder (Photo 8),
- control cabinet (Photo 9).
The welder body has a gantry construction. The top beam is featured with a guide with pressure assemblies. The assemblies are fixed so that they can be easily moved and removed in order to prepare the machine for welding meshes with different spacing of the lengthwise bars. A guide with 25 moving bottom holders with electrodes and a unit to set the position of the crossbar is fixed to the bottom beam. ASPA welding transformers are installed below the electrodes base.
Moving supports for lengthwise bars
The supports for the lengthwise bars form a framework composed of two spans connected with cross beams. On the beams, there are guides of lengthwise bars that allow a wide adjustment range of the bars position and spacing.
Mesh moving mechanism
The mesh moving mechanism uses Rexroth linear drive connected with pneumatic mesh clamping units. The device grasps a heated crossbar and moves the welded mesh from under the electrodes by the set mesh size. A pre-programmed linear drive facilitates welding of meshes with different spacing of crossbars. When the cycle is completed, the welded mesh is removed from the welding area and rests on the collecting table beams.
Mesh collecting table
The mesh collecting table is a spatial steel construction located behind the welder body. The mesh moving mechanism and crossbars feeder is fixed to the table components.
Lengthwise bars pushing and positioning feeder
The bar feeder moves the bars under the welder electrodes.
The crossbars feeder enables automatic feeding of single bars between the electrodes. The feeder may be featured with several chambers to feed different bar diameters. It may also come with elements supplying several bars at a time to weld several meshes simultaneously.
The welder power system is composed of power circuits and automation and control circuits placed in a standalone control cabinet. The main components of the power circuit include ASPA welding transformers. The master controller, which connects all automation circuits, is the main element of the automation system. ASPA microprocessor systems controlling the welding parameters are used to control the thyristors. The control cabinet also includes the mesh moving mechanism controller.
The welding cycle is semi-automatic. The operators put the crossbars into the feeder and place the lengthwise bars in the guides manually. By pressing START, the automatic part of the process is initiated. The pushing table pushes the lengthwise bars under the welder electrodes, the feeder places a crossbar between the electrodes and a seam is welded. The mesh moving clamps hold a heated crossbar and move the mesh by the set mesh size. The feeder provides another crossbar and the process is repeated. When the last crossbar is welded, the mesh is ready. It is removed from the welding area and rests on the collecting table beams. Then the operator takes the mesh. When all the operations have been completed, the welder is ready to start a new cycle.
The paper was published in “Spajanie” magazine