A welding carriage is a welding automation that carries the torch along the seam on a rail at a constant speed. It is also called a welding tractor or rail welding robot, and it is most used on long seams in tanks, silos, pipes and ships. In this article we explain its parts, the processes it is used with and what to check when buying one.
Parts of a welding carriage
- Rail: The track the carriage runs on. Rigid rails suit straight seams, flexible rails suit cylindrical shells. Rails are usually fixed with magnetic feet.
- Carriage and drive: The body that moves along the rail via a motor and gear or chain; it sets the travel speed.
- Torch holder: Adjusts torch height, lateral position and angle.
- Weaving (oscillation): Swings the torch side to side to fill wide joints; not every carriage has it.
- Control unit: Where speed, weaving and start/stop are set.
- Seam tracking: The sensor system that keeps the torch on the real seam. Classic carriages lack it; DKT carriages do it with a camera and 2 laser sensors.
Which welding processes is it used with?
Welding carriages are most commonly used with MIG/MAG and flux-cored welding; submerged arc welding is common on thick plate and long seams. The carriage carries the torch and the welding machine supplies the current, so carriage and welding machine compatibility must be considered from the start. At DKT the welding machine is chosen according to the customer’s preference.
7 things to check when buying a welding carriage
- Part dimensions: Plate thickness and shell diameter define the rail.
- Seam length and position: Horizontal, vertical or circumferential seams need different setups.
- Process and machine compatibility: Torch type and connection to the welding machine.
- Rail type: Rigid for straight seams, flexible for cylindrical shells.
- Speed and weaving: An adjustment range that suits your joint width.
- Seam tracking: The key feature that stops the operator having to intervene constantly on long seams.
- Service and spare parts: A supplier you can reach when something breaks.
With and without seam tracking
A carriage without seam tracking runs blind along the rail. If the rail is not exactly parallel to the seam or the plate waves, the torch slowly drifts off and the operator stands by the carriage correcting it with the adjustment knobs. With seam tracking, the system does this correction itself and the operator only supervises. On DKT’s machine-vision welding carriage the camera scans the weld zone and corrects drift, and 2 laser sensors keep the torch distance constant. For a comparison of methods, see our weld seam tracking article.
Summary
- A welding carriage carries the torch on a rail at constant speed; it is the most practical automation for long seams.
- Rail type, welding process and machine compatibility must be chosen right from the start.
- On long seams, seam tracking is what frees the operator from the carriage.
For tank and silo applications see our tank welding robot page, and for cost items our welding robot price page.