LIBRARY ı6ıul 0) - Cranfield University

during the controlled welding trials. More consistent bead appearances
were observed
to be produced from the dip transfer trials (see Figures 7.23 and 7.25). Reduced levels
of spatter were also observed to occur. In the spray transfer trials, a considerable
reduction in the levels of defects was obtained. The porosity was eliminated
completely and the undercut largely reduced (see Figures 7.27,7.29,7.31). Also,
consistent penetration levels were obtained through-out the welds. The stand-off was
controlled to ±2.5 mm in all welding trials. Table 7.5 shows the bead geometry
measured from the weld beads produced in the voltage and stand-off controlled trials.
Table 7.5 - Bead geometry along the welds produced in the voltage and stand-off
controlled flat position fillet welding trials
Run Measured feature Position alon the weld mm Geometry feature
mm 30 65 100 135 170 Min. R uired Expected
SV2 4.85 4.56 4.58 4.78 4.59 4.00 4.46
Pen,, 0.58 0.63 0.53 0.56 0.55 0.32 0.57
Max. Undercut 0.0 0.0 0.0 0.0 0.0 0.0 0.0
SV3 Le 5.95 5.87 5.91 6.03 5.83 6.00 6.41
peng 1.00 1.14 1.07 0.93 1.01 0.32 1.21
Max. Undercut 0.0 0.0 0.0 0.0 0.0 0.0 0.0
SW Le 4.08 4.11 3.98 4.07 4.19 4.00 4.54
Pen., 1.32 1.25 1.40 1.27 1.33 0.32 1.26
Max. Undercut 0.37 0.25 0.37 0.32 0.30 0.0 0.0
SV5 Le 5.73 5.39 5.55 5.63 5.53 5.00 5.40
Pen., 1.70 1.90 1.92 1.85 2.08 0.32 1.70
Max. Undercut 0.0 0.0 0.0 0.0 0.0 0.0 0.0
SV6 Le 4.82 4.73 4.99 5.21 5.12 5.00 5.43
Pen., 2.22 2.31 2.12 2.20 2.14 0.32 1.86
Max. Undercut 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Note the improvement on the penetration profile obtained in the spray transfer
trials. The finger-like penetration was greatly reduced and in some cases even
eliminated.
Some bead misalignment was observed to occur in some welds, even though
the robot was carefully programmed on-line to ensure good alignment. This was
believed to occur due to some joint movement allowed in the welding jig (see Figure
5.1) during the joint fit-up. Also, the cast of the wire together with differences in the
heat sink characteristics provided in both sides of the joint were believed to affect the
symmetry of the bead profiles relative to the joint bisection plane. These observations
confirm the already mentioned necessity of a means to ensuring the alignment of the
wire relative to the joint line, which could be provided by a proper seam tracking
facility.
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