Tweco 281 Thermal Arc Fabricator - Manual (Page 51)

FABRICATOR 281
April 10, 2006 4-13
Distance from the MIG Gun Nozzle to the Work Piece
The electrode stick out from the MIG gun nozzle should be between 5/64" (2.0mm) to 13/64" (5.0mm). This distance
may vary depending on the type of joint that is being welded.
Contact
Ti
p
Gas
Nozzle
Solid Wire Flux Cored Wire
.023”
(.6mm)
1/4” (6.4mm) 5/16” (7.9mm) 3/8” (9.5mm)
9/16”
(14.3mm)
11/16”
(17.5mm)
.030”
(.8mm)
.035”
(.9mm)
.035”
(.9mm)
.045”
(1.1mm)
Art # A-07186
Wire Diameter
Distance: ±1/16”
Figure 4-14: Optimum Contact Tip to Work Distances
Electrode Wire Size Selection
The choice of electrode wire size in conjunction with shielding gas used depends on:
- Thickness of the metal to be welded,
- Type of joint,
- Capacity of the wire feed unit and power supply,
- The amount of penetration required,
- The deposition rate required,
- The bead profile desired,
- The position of welding and
- Cost of the electrode wire.
Weld metal deposition rate is proportional to current density. Current density is defined as the current per cross
sectional area of the electrode wire and is normally expressed as amps per mm
2 . An example is in Table 4-3 below.
Electrode Wire Size Current (Amps) Current Density(Amps/mm2) Deposition Rate(lbs/hour)
.035”( 0.9mm) 200 314 7.0
.045”(1.2mm) 200 177 6.2
Table 4-3: .035"(0.9mm) , .045"(1.2mm) wire deposition rate