EQUIPMENT FOR RESISTANCE WELDING-Measurements
Measurement of the parameters are important while fixing the parameters or testing a machine. Resistance welding instrumentation system which record the various parameters simultaneously with respect to time are now available in the market. Also, instruments for accurate measurement of the secondary current, pressure, the deflection of the electrodes, vibration of the electrodes for huge resistance welding machines are available in Indian market. The resistance welding instrumentation system developed by WRI can measure secondary current and weld time for spot / projection welding applications.The primary current can be measured using current transformers connected to pointer stop type ammeters or storage oscilloscopes.The primary voltage or secondary voltage can be readily measured using an ordinary voltmeter (preferably pointer stop type). If a wattmeter is also included in the circuit (primary) the power factor can be calculated.Time can be conveniently measured using stop watches in seam or flash welding. In spot welding, cycle counters are used. In many sophisticated machines, calibrated timers with displays are used in their sequential control circuits.Pressure is measured using strain gauges but location of these require ingenuity on the part of the operator. Now a days, pressure transducers which are provided with flanges for connecting in the fluid line are available for up to 800 kg / cm2. Static electrode force can be measured by means of deflection gauges. This force can be calculated from the pressure by multiplying it with the area of cross section of the electrode surface.The load cell developed by WRI can measure the load directly between the electrodes for spot / projection welding machines.