Spot welding system

A spot welding system comprising:

• a robot-side system having a robot and a robot-side controller;
• and
• a welder-side system having a welding gun mounted to the robot, and a welder-side controller,
• wherein the robot-side system includes:
• a storage, the storage configured to store in advance appropriate thickness information regarding a difference between a thickness of a welded part at a time of welding start and a thickness of the welded part at a time of welding completion in spot welding;
• a welded-part thickness measurement unit that measures thicknesses of the welded part for the spot welding based on positions of electrode rods of the spot welding system that sandwich the welded part at a time of a welding start command and at a time of a welding completion command;
• and
• a comparative determination unit that determines quality of the welding by comparing thicknesses of the welded part at a time of a welding start command and at a time of a welding completion command, and comparing a difference between the measured thickness at the time of the welding start command and the measured thickness at the time of the welding completion command with the stored appropriate thickness information of the welded part, and
• wherein the spot welding system puts together a plurality of welded parts into one set, performs welding work of the plurality of welded parts, and measures overall welding time of the plurality of welded parts of the set to judge existence/absence of abnormality.