A Study of Welding Current Control for Spot Welders
1969 Volume 38 Issue 2 Pages 164-170
Details
1969 Volume 38 Issue 2 Pages 164-170
The fluctuation of the welding current caused by the fluctuation of the source voltage or the secondary impedance variation of the spot welder reflects upon the strength of weld, so from the stand point of heat control it is necessary to control the welding time for improvement of the tensile shear strength.
For the above mentioned reason, we used both the ∫10 In dt=const. welding time control method and the welding current control method with feed-back loop (n 2).
From the spot welding experiment of mild steel sheet of 1.6 mm to 3.2 mm thickness, the following results were obtained.
(1) In comparison to the welding time and current setting methods without feed-back loop, these control methods could improve the consistency of the tensile shear strength at the decreased welding current to normal welding current, and could increase the reliability of the tensile shear strength.
(2) By using both the ∫10 I2 dt=const. welding time control method and the welding current control method thod with feed-back loop, the tensile shear strength at the welding current about 40 percent less than normal welding current was kept nearly equal to the tensile shear strength of normal welding current specified by R.W.M.A.
(3) The setting of the welding time and current in these control methods can be applied to the welding condition specified by R.W.M.A., and no particular difficulty of welding depending on the thickness of mild steel sheet to be welded was observed in the case of above mentioned control methods with feedback loop.
(4) In the case of the ∫10 I2 dt=const. welding time control method, it was possible to obtain the tensile shear strengthat the welding condition of A class specified by R.W.M.A. even with a welding current about 30 percent less than normalwelding current.
By way of example, the most suitable values of I2⋅t replaced ∫10 I2 dt=const. were in the following range
plate.thickness 1.6 mm: (10-30)×108 (A2. cycle)
plate thickness 2.3 mm: (40-60)×108 (A2. cycle)
