Projection Welding Controls & Monitoring
A number of factors contribute to inconsistent set-down of projection-welded parts, including:
- inconsistent heat control
- electrode force variations
- part projection geometry 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 all of 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.
An adaptive projection weld schedule effectively compensates for these sources of variation by automatically adjusting the heat during each weld to obtain consistent set-down of each projection. If after making these adjustments the set-down target is still not reached by the end of the heat application, the adaptive schedule can extend the heat as needed to achieve the set-down target.
The Adaptive schedule is also able to recognize when serious tooling and part stack-up problems exist that would prevent a satisfactory weld from being produced. The adaptive schedule instantly cuts off the heat the millisecond such a problem is detected, and alerts the operator about the problem. In an automatic welding operation the adaptive control automatically rejects the problem part without causing any halt to production. This avoids unnecessary tooling wear or damage, maximizes production throughput and minimizes down time.
Adaptive projection schedule applied to projection nut welding: the adaptive schedule automatically detects missing nuts, upside-down nuts or incorrect nuts, and immediately notifies the operator or robot about the problem.