US 11,904,402 B2
Spot welding machine
Anders Bergström, Västra Frölunda (SE); and Tony Hedlund, Arboga (SE)
Assigned to Car-O-Liner Group AB, Västra Frölunda (SE)
Appl. No. 17/058,990
Filed by Car-O-Liner Group AB, Västra Frölunda (SE)
PCT Filed Jun. 10, 2019, PCT No. PCT/SE2019/050539
§ 371(c)(1), (2) Date Nov. 30, 2020,
PCT Pub. No. WO2020/009635, PCT Pub. Date Jan. 9, 2020.
Claims priority of application No. 1850844-0 (SE), filed on Jul. 4, 2018.
Prior Publication US 2021/0252628 A1, Aug. 19, 2021
Int. Cl. B23K 11/24 (2006.01); B23K 11/11 (2006.01); B23K 11/25 (2006.01); B23K 11/28 (2006.01)
CPC B23K 11/24 (2013.01) [B23K 11/115 (2013.01); B23K 11/256 (2013.01); B23K 11/257 (2013.01); B23K 11/258 (2013.01); B23K 11/28 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A welding machine adapted for performing a spot welding process on a workpiece, wherein the welding machine comprises:
a welding gun including a pair of opposed electrodes for receiving the workpiece, the pair of electrodes comprising at least one movable welding tip portion;
a transformer having a primary input side and secondary output side, the secondary output side connected to the pair of electrodes;
a distance detector arranged to detect the distance moved by the movable welding tip portion; and
a control unit adapted to control the spot welding process,
wherein the control unit is further adapted to:
control the transformer for applying, prior to performing the spot welding process, a first welding pulse portion to the workpiece using the welding gun,
receive, from measurement means arranged at the secondary output side of the transformer, an indication of a first voltage and a first current applied in relation to the first welding pulse portion,
determine a first resistance value based on the indication of the first voltage and the first current,
compare the first resistance value with a predetermined resistance threshold, wherein the predetermined resistance threshold is based on a thickness of the workpiece determined using information received from the distance detector,
control the transformer for applying, prior to performing the spot welding process, a further second welding pulse portion to the workpiece using the welding gun if the first resistance value is above the predetermined resistance threshold, and
initiate the spot welding process if the first resistance value is below the predetermined resistance threshold.