Spot welding system and method with the ability to make a pressing force exerted on an object to be pressed constant

摘要

Spot welding system (10, 70), comprising: a spot welding gun (30, 80) having a counter electrode (44), a movable electrode (48) arranged to be movable relative to the counter electrode along the gun axis (O), and a driving part (52) which controls the movable one Electrode (48) drives comprises; a position detecting part (54) configured to detect a position of the movable electrode (48) along the gun axis (O); and a portion configured to calculate a pressure change (56) established based on a first position of the movable electrode (48) along the gun axis (O) which is detected when the drive member (52) is set in accordance with a first pressing force command value ( P ₀ , P ₁ ) is driven to press an object (W) to be pressed with the movable electrode (48) in a state in which the spot welding gun (30, 80) is disposed at a predetermined first position, on a second one Position of the movable electrode (48) along the gun axis (O), which is detected when the drive part (52) according to the first pressing force target value (P ₀ , P ₁ ) is driven to the object to be pressed (W) with the to press the movable electrode (48) in a state in which the spot welding gun (30, 80) is arranged in a second position which is different by an angle (Θ) than the first position, and on the first pressing force set value (P ₀ , P ₁ ) ,, a change amount (δ _Θ ) between a first pressing force (F ₁ ) exerted by the movable electrode (48) on the object (W) in the first position and which coincides with the first pressing force set value (P ₀ , P ₁ ) , and a second pressing force (F ₂ ) calculated by the movable electrode (48) applied to the object (W) in the second position.