(1) Visual Inspection of Weld Appearance

During production, operators visually inspect the welds inside and outside the cans as part of quality control. Visual inspection can only identify obvious defects, such as weak weld spots, cold welds, burn-through, overheating, uneven weld spots, missing welds, splatter, insufficient or excessive overlap at the can start or end, and other major defects.

(2) Weld Strength Test (Spherical Tester)

The test method is as follows: place a sample can on the spherical tester, align the ball in a straight line with the weld, and move the ball along the weld on the can body. Expand the weld outward by 1–2 mm (adjustable). Remove the can from the tester and inspect the weld for any cracks or fractures.

(3) Tear Test

The test method is as follows: take two sample cans. On the first can, use scissors or pliers to cut 5 mm at one end of the can body, then bend the cut edge upward. Place the can on the test spindle, grip the cut edge with pliers, and pull upward at a 45° angle along the weld evenly (do not pull abruptly). Repeat the process with the second can from the opposite end. Visually inspect the removed weld strip: if the weld tears cleanly along its length and feels smooth when shaken between the fingers, the weld quality is good. If the weld breaks at any point, the welding current is too low. If the torn edge is uneven or rough to the touch, this indicates splatter, overheating, or excessive welding current. The removed weld strip should bend without breaking, and twisting or knotting it should not cause it to snap. Brittle or broken welds indicate excessive welding current. This method is particularly useful for detecting cold or hot welds.

(4) Conical Test

The main purpose is to check the ductility of the welds at the can’s front and back. Place the test can on the conical tester and insert a proportionally sized cone at a constant speed into the welded can body to expand it into a conical shape. Remove the can and observe the expansion: an expansion of more than 20% indicates good flanging performance; 10–20% is acceptable; 10% or less is considered unqualified.

(5) Weld Flanging and Curling Test

The main purpose is to check the ductility of the welds at the front and back. Remove one can from the welding machine, fix it on the corresponding mold on the test base, and place the can on the flanging test mold. Operate the piston valve to push the pressure plate against the can body and perform a flanging curl of about 10 mm. Remove the can and check for any cracks in the flanged area. Cracking indicates failure.

(6) Pre-Weld Overlap and Weld Width & Thickness Inspection

The overlap width before welding and the weld width after welding are generally measured using a magnifier with scale or a projector. Weld thickness is measured with a pointed micrometer.

(7) Can Inner Diameter Inspection

Measure with an internal caliper. The difference between the front and back can diameters should be less than 0.10 mm.