Tweco PWH-M 2A - Manual (Page 19)

Operation 3-1 Manual 0-2005
OPERATION
3.1. PRE-OPERATION SET-UP
The selection of specific parameters for a given weld-
ing application depend on the type of material, con-
figuration of the joint and type of weld desired. Proper
settings for a given joint have to be developed on the
job.
Table 3-A gives the maximum operating range of the
various tips. These values are for a stiff collimated arc
with the electrode setback at its maximum. A softer,
less constricted arc can be obtained by decreasing the
electrode setback (see Fig. 3-A). The minimum setback
is with the electrode point flush with the face of the tip
(see Fig. 3-B). By decreasing the electrode setback the
plasma gas flow can be decreased while maintaining
the higher current ratings of the tip. This gives a wider
weld bead and in most cases allows for faster travel
speeds.
Max Setback
Figure 3-A
The electrode gauge values given in Table 3-A will re-
sult in maximum electrode setback for the given tip.
This setback, when used with the given values for cur-
rent and plasma gas flow will produce a stiff collimated
arc that results in a narrower weld bead.
CAUTION
Decreasing the electrode standoff can only be
done with tip orifice diameters of 0.046 or larger.
This procedure should be followed at the beginning of
each shift:
WARNING
Check to be sure the main disconnect switch is
open.
1) Check the torch to be sure that it has the proper
components (see Section 4.1) and is adjusted
properly (see Table 3-A).
2) Close the main disconnect switch supplying
power to the welding system.
Min Setback
Figure 3-B
When the electrode is at minimum setback (flush with
tip face) the plasma gas flow rate can be reduced be-
low the levels given in Table 3-A while maintaining the
given current levels. This produces a softer arc that re-
sults in less depth of penetration, giving a wider weld
bead, and allowing faster travel speeds.