A number of factors contribute to resistance welding inconsistency, including:
- Inconsistent heat control
- Electrode force variations
- Part geometry/contact area variations
- Material hardness variations
- Oil on the part
- Other surface condition variations
Conventional controls that apply the same heat regardless of what combination of prevailing conditions exists, result in inconsistent welds. When variations are severe enough, a conventional control can degrade and even damage the tooling. Monitoring can detect these sources of weld variation, and keep poor-quality and inconsistent welds from leaving the factory. But manufacturers can still end up with a very high, very expensive reject rate. Also, monitoring alone will not improve the consistency of the welds that are not rejected and allowed to pass through production.
In order to begin to understand how adaptive welding can improve the consistency of all welds and reduce the number of rejected welds produced in the first place, it is necessary to understand the different stages of the lead resistance welding process that progress as each weld is being formed.