They select and set up welding equipment. When the welds are done, welders check that they meet standards. Some welders have more limited duties. They perform routine welds that someone else planned out. These jobs do not require knowledge of all welding techniques.
Some welders operate automated welding machines.
These are used in industries where the work is repetitive and the items to be welded are about the same size. Operators set up and operate the machines as specified in layouts, work orders, or blueprints. They monitor the machines during welding and check that the welds meet standards. Automated welding is used more and more in making products. A machine or robot does the welding tasks while a welding machine operator watches the production.