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Table 6.7 - Dip resistance dispersion with different sampling frequencies
Run SO Freq. Nw V.. I. Di R. Di RSD
Di rl 12 4032 512 19.61 163.5 24.7 4.3
Di r2 14 4032 512 19.71 157.2 26.6 4.4
Di r3 16 4032 512 19.71 153.6 28.6 4.6
Di r4 18 4032 512 19.80 148.2 30.6 4.4
Di r5 12 8065 1024 19.60 164.6 25.1 4.2
Di r6 14 8065 1024 19.71 159.1 26.8 4.2
Di r7 16 8065 1024 19.71 154.2 28.9 4.3
Di r8 18 8065 1024 19.77 149.2 30.8 4.6
Di r9 12 12500 2048 19.66 162.0 25.0 4.0
Di r10 14 12500 2048 19.73 158.1 27.1 4.4
Di rl1 16 12500 2048 19.75 151.9 28.9 4.5
Di r12 18 12500 2048 19.76 148.4 31.0 4.7
Diprl3 12 2000 512 19.62 166.2 24.4 4.5
Di rl4 14 2000 512 19.69 159.3 27.3 4.5
Di r15 16 2000 512 19.69 154.8 28.4 4.0
Di r16 18 2000 512 19.78 148.6 30.6 4.2
Di r17 12 4032 1024 19.61 167.8 25.0 5.3
Di r18 14 4032 1024 19.61 159.4 27.1 4.4
Di r19 16 4032 1024 19.71 154.5 28.8 4.3
Di r20 18 4032 1024 19.76 148.0 31.0 4.4
SO: stand-off [mm], Freq.: sampling frequency [Hz]
DipR,,.,,: dip resistance (run average) [nL ], Nw: number of samples in a window
DipRsD: standard deviation of dip resistance (run average) [mS)]
WFS = 6.0 m/min, V, d = 21.5 V, Sw = 0.5 m/min, Weld length = 200 mm
In order to develop models to estimate the stand-off based on the measured
values of dip resistance, a good understanding of the variables involved in the
measurement of such resistance is necessary. Figure 6.13 shows a schematic diagram
of the welding voltage and current measurement pick-up points. Figure 6.14 shows
the equivalent electrical circuit, outlining the various resistance components in a
lumped form. It is assumed that the level of current drained by the voltage
measurement system (signal conditioning and analog to digital converter) is negligible.
Hence, it is assumed that there is no resistive voltage drop in the voltage sensor leads.
The measured resistance will therefore include only the series combination of the
resistance components due to the torch cable, the contact tip, the wire stickout, the
welding arc, the weld pool and the solid workpiece and fixturing.
The torch cable, the weld pool and the solid workpiece/fixturing contributions
can be considered as constants which depend on the materials involved and on the
temperature in the steady state. The contact tip contribution depends on the wire
surface condition, the contact-tip wear and the contact-tip temperature. The wire
stickout contribution depends on the wire material, the cross sectional area, the
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