Welding of can bodies

A method of controlling a welding station used for welding seams extending along cylindrical can bodies, the welding station comprising a pair of welding rolls and a calibration unit for causing a desired cylinder overlap during welding, the calibration unit being adjustable along at least three different adjustments axes, the method comprising:

• monitoring welded seams and providing an electrical signal indicative of the weld thickness at a series of predetermined points along a seam length;
• generating one or more control electrical signals in response to said electrical signal indicative of the weld quality of welded seams;
• and
• providing the one or more control electrical signals to one or more of a plurality of adjustment mechanisms configured to adjust the calibration unit relative to one or more of the three adjustment axes, to cause the desired cylinder overlap.

A method of controlling a welding station used for welding seams extending along cylindrical can bodies, the welding station comprising a pair of welding rolls and a calibration unit for causing a desired cylinder overlap during welding, the method comprising:

• monitoring welded seams and providing an electrical signal indicative of the weld thickness at a series of predetermined points along a seam length;
• generating one or more control electrical signals in response to said electrical signal indicative of the weld quality of welded seams;
• and
• providing the one or more control electrical signals to one or more of a plurality of adjustment mechanisms configured to adjust the calibration unit relative to one or more of the three adjustment axes, to cause the desired cylinder overlap,
• wherein the adjustment mechanisms are responsive to the control signal(s) in order to adjust:
• a radial position of a roller of the calibration unit relative to a direction of movement of cylinders through the weld station;
• a longitudinal position of the calibration unit along an adjustment axis perpendicular to a line passing through a centre of each welding roll;
• a combination thereof,
• wherein one of the adjustment mechanisms adjusts the radial position of a roller of the calibration unit using a co-operating dual-thread system operable using an encoded motor and gearbox.