Miller Electric OM-842 - Manuel (Page 23)

OM-842 Page 19
In this mode, time values are not de-
fined for initial current, initial slope,
weld/peak current, and final slope.
The operator uses the Start/In-
crease and Decrease push buttons
to vary the weld current level once
initial current starts.
The first momentary closure of the
Start/Increase push button starts the
sequence. Following start level,
each time the Start/Increase push
button is pressed and held weld out-
put increases at a rate calculated by
the microprocessor control. The rate
of increase depends on the pro-
grammed initial current level, weld/
peak current level, and initial slope
time. Each time the Decrease push
button is pressed and held, weld out-
put decreases at a rate calculated by
the microprocessor control. The rate
of decrease depends on the pro-
grammed weld/peak current level, fi-
nal current level, and final slope
time. The weld output will maintain at
the level that exists when either the
Start/Increase or Decrease push
button is released. The programmed
values that normally define the weld/
peak current level define the upper
limit that the Start/Increase push but-
ton can command.
The weld output level can be in-
creased and decreased indefinitely
until the operator decreases the
weld current down to the pro-
grammed final current level. At this
point the sequence enters final cur-
rent and then postflow. If the weld
current never exceeds the pro-
grammed final current value, the op-
erator must decrease the weld cur-
rent to zero, at which time postflow
will begin.
If Stop Button Detect is enabled in
the weld program, pressing the Stop
push button stops program execu-
tion and starts postflow. If Stop But-
ton Detect is disabled, pressing the
Stop push button has no affect.
Postflow starts if the arc is manually
broken.
Ref. SB-139 983
A: Momentary closure of Start/Increase push button starts sequence.
B: Maintained closure of Start/Increase push button increases weld out-
put; maintained closure of Decrease push button decreases weld
output.
C: Release of Start/Increase or Decrease push button sets weld/peak
current (output remains at level existing when push button released).
D: Maintained closure of Decrease push button decreases weld output to
programmed final current level; final current starts.
Preflow: Time programmed/Volume set by gas meter.
Start Level (Not Shown): Time & level programmed.
Initial Current: Time undefined/Level programmed.
Initial Slope: Controlled by Start/Increase and Decrease push buttons/
Slope rate of change calculated by microprocessor control.
Weld/Peak Current: Time undefined/Level determined by weld output level
when Start/Increase or Decrease push button released.
Final Slope: Controlled by Start/Increase and Decrease push buttons/
Slope rate of change calculated by microprocessor control.
Final Current: Time & Level programmed.
Postflow: Time programmed/Volume set by gas meter.
Weld/peak current can be increased or decreased during welding.
Stop push button functions throughout sequence if Stop Button Detect is en-
abled in the program.
A
Initial
Current
Weld/Peak
Current Initial
Slope
Final
Slope
Final
Current
Preflow Postflow
C
B
D
Figure 4-4. Semi-Automatic 4 Mode Sequence