Expulsion is the molten metal ejected from the nugget under pressure, burning in the air with bright light and loud noise. Because the loss of liquid metal from the nugget expulsion always produces poor quality weld and it also consumes more than three times the energy needed to make a low temperature solid state weld. Majority of welding professionals believe you have to melt the metal in order to produce a nugget. I can easily prove this is untrue in the accompanying video. Fusion weld nugget and solid state nugget are different. The low temperature weld has invisible join line, no HAZ (heat affected zone) and is much stronger.
High temperature nugget has three parts: low temperature, medium temperature and the center high temperature weld. To produce an expulsion you have to go through low temperature weld, medium temperature weld and high temperature weld. If we calculate the nugget temperature in real time, we can terminate the weld when it just reaches the coalescence temperature; every weld will be a quality low temperature weld.
My weld controller has three wire connected to a Bosch Rexroth MFDC inverter.
1. 24V on/off signal.
2. 0-5V current control signal (2V=10kA)
To program this controller set the auto/manual switch to manual and capture/store switch to capture and make a few good welds. Then switch the capture/store switch to store the weld schedule and switch the auto/manual switch to auto now you can start to weld tens of thousands of good welds similar to your test welds. Because this controller welds by temperature the weld cap size change is compensated. Using the auto mode I have made 1,240 welds with only one expulsion. The only expulsion weld is number 1,123.
Let's assume the average energy consumption at the tip wire is 4,000 Joules (low temperature weld) and the expulsion weld consume 3 times the energy or 12,000 Joules which gives us 8,000 Joules per weld saving. Let also assume the overall system efficiency is 25%, so the actual saving at the kWh meter will be 8,000J/0.25=32,000J. Average car has 5,000 welds so the energy saving per car will be 32,000J*5,000=160x106J or 44.44kWH. Statista projects 77.73 million cars made worldwide this year. This makes total worldwide energy saving to be 3.454 billion kWh. According to PG&E carbon footprint calculator 1kWH=0.524 lbs of CO2. The total saving of CO2 will be 1.81 billion pounds per year.
Intelligent Resistance Welding Consortium claimed in 1995 there is $1.1 billion business in new equipment sale alone worldwide. According to Money Times $1.00 (1995) =$1.61 (2017). According to Statista estimate there will be 77.73 million cars made 2017, during 1995 only 39.2 million. MFDC welding system with servo motor is about 1.5 times the cost of an AC system with air cylinder.
Service and training equals the sales of the systems.
Total market potential=1.1*1.61*(77.73/39.2)*1.5*2=10.54 billion per year.