Gap between sheets

What are the factors to cause unstable welding production? Gap between sheets is one of the causes. Understanding the effect of the gap would help to improve production stability and weld quality consistency. Here we present an idea to find optimal parameters for welding sheets with gaps.

Welding issues

Early splash between sheets
Splash(expulsion) - Early splash could happen due to bad contact resulted from the gap.
Gap closing failed after squeeze time
Gap is not closed after squeeze time due to too large gap or too low force.

The gap between sheets could happen due to alignment errors or stamping tolerances. When the sheets with gaps are spot welded, the gaps can lead to early splash or no weld.

The effect of gap on the weld lobe

We ran a set of simulation with different gaps (no gap, 0.2mm, 0.5mm, & 1.0mm) to investigate their effect on the weld lobe. The material used in this simulation is DP600 in 1.0mm. The AC machine is selected and weld time is set to 8 cycles. The weld lobes are generated by  SORPAS 2D.welding v14.4.

weld lobe for spot welding without gap
Weld lobe without gap
weld lobe for spot welding with 0.2mm gap
Weld lobe with 0.2mm gap
weld lobe for spot welding with 0.5mm gap
Weld lobe with 0.5mm gap
weld lobe for spot welding with 1.0mm gap
Weld lobe with 1.0mm gap

By comparisons of weld lobes with different gaps simulated by SORPAS® 2d.welding, we can see the gap between sheets has significant effect on splash limit.

  • To get a stable production, choose optimal parameters in the overlapped area of the lobes covering all possible gaps.
  • In general, the process window is larger with higher force. But it should be compromised with consideration of electrode life.
safe zone of weld lobes for covering all possible gap