Controls and/or timers for resistance welding are simple, "in order" timers. They
control, or time, the events of the process. Here is a list of extra control features
that are possible with different makes and models. This list is far from
complete. In the application of Resistance Welding, we assume that production
speed and equipment up time in making quality parts are the most important issues to people using the
process. If it is the only "control" on the machine (no PLC or other master control) as is the case for
stand alone machines, then it should be called the control. It is refered to here as the
timer to make things simpler. Many of these listed extras can also be accomplished with PLCs.
The timer has wired options and programmed options. These can be different for
different makes and models. One feature common on all modern timers is the
ability to have many weld schedules available for different welds. The weld
schedule number is normally visable on the front and can be used to quickly
change the schedule settings. Often in robotic spot welding or automatic
multi-spot locations or cross wire welding, the user may want to have
different settings/schedules on the same part. This may be an option that
is programmed into the unit, wired into the unit, or both. To try to assist
the end user, the list below is seperated into programmed vs. wired but is not
accurate for all timers available.
Below are the definitions of the above listed
items. We have made a huge effort to ensure they are accurate and
usefull. If you feel they are not, or you have thought of, or have, a better
idea or explination please e-mail us from
the bottom of this page. Our intention is to provide you with useful help,
and helpful information on resistance welding, spot welding, cross wire welding,
and nut welding.
Squeeze: This is the time from the initiation of the air valve, or force
mechanism, to the time of the weld. It should be long enough for the FORCE of
the process to develop to an acceptable level. If the timer has a pressure
switch or simalure input then the signal is in this event and waits for the
satisfaction prior to continuing.
Weld Time: This is the duration of TIME in which the CURRENT flows. The weld
TIME is very important in the physics of heating the weld nugget. The shorter
the WELD TIME the better.
The Percent Current is also a time but in a different sense. It is the time
at which the CURRENT is allowed to flow after the "zero cross over point" is
detected in the individual half cycle of the process voltage. It controls the
amps, or amount of amps, in the RW welding process on a per cycle basis.
Hold: This is the time after the welding TIME and CURRENT flow for the
FORCE to remain in place while the weld nugget(s) solidifies or strenthens. It
should be about 2-3 times the weld TIME due to thermodynamics. If a weld
checker is built into the timer, release of the FORCE may be an input at this
location as a quality matter.
Off: Off time is after hold and prior to re-initiation of the air valve
in Repeat Mode. This is used in conjuntion with repeat and can help speed the RW
process in production when multiple welds are made, with the same settings,
and can be operator dependent.