CHAPTER 6: ADVANCED WELD FUNCTIONS
MODEL HF2 2 kHz HIGH FREQUENCY RESISTANCE WELDING POWER SUPPLY
6-12
990-057
DUAL PULSE (Figure 6-25)
Dual Pulse combines the best features of
Up/Downslope with Quench/Temper. Use Dual
Pulse for best welding control of flat-to-flat, round-
to-round, or round-to-flat small parts that may or
may not be plated.
Adding Up Slope to the front of each weld period
allows a reduction in electrode force, resulting in a
cleaner appearance by reducing electrode
indentation, material pickup and electrode
deformation. Up Slope will also help to displace
plating and/or oxides, reduce flashing and spitting,
or reduce thermal shock when welding parts
containing glass-to-metal seals.
Figure 6-25. Dual Pulse
In the normal application of Dual Pulse, the Weld1 Period provides sufficient heat to displace the plating
or oxides, seat the electrodes against the base metals, and force the parts into intimate contact. The Cool
Period allows time to dissipate the heat generated during the Weld1 Period.
The Weld2 Period completes the structural weld. The Weld2 Period weld current should be greater than
the Weld1 Period weld current by a factor of 2 or 3 since the first bond significantly reduces the
resistance of the interface between the parts. The only use for the Down Slope Period following the
Weld2 Period is to control grain refinement in brittle parts by slowing reducing the Weld2 Period weld
current to zero during the Down Slope Period.
Dual Pulse can be used with Unitek Peco Force Fired Manual or Air Actuated Weld Heads. For
Manually Actuated Weld Heads, weld current begins when the Force Firing Switch closes. For Force
Fired Air Actuated Weld Heads, weld current begins when both levels of a two-level Foot Switch are
closed and the Force Firing Switch in the Air Actuated Weld Head closes.
When Dual Pulse is used with a Non-Force Fired Air Actuated Weld Head, the Squeeze (SQZ) Period
must be used to allow sufficient time for the electrodes to close and apply the required weld force to the
parts before the Weld Period begins. Weld current begins when the Squeeze Period ends and both levels
of a two-level Foot Switch are closed.
When Dual Pulse is used with any type of Air Actuated Weld Head, the Hold Period can be used to
automatically keep the electrodes closed on the parts after weld current has terminated for the purpose of
providing additional heat sinking or parts cooling. Squeeze and Hold Periods have no meaning with
Manually Actuated Weld Heads and do not appear on either the weld schedule Program or Run screens.
