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The Invisible Repair

Bringing a collision-damaged car back to preaccident condition in a fast, quality-oriented manner while still making a reasonable profit is the goal of every modern body shop today.

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Dealership "program" cars, auction cars and used-car inventory
cars must all pass the critical telltale damage-repair test in
order to prevent the dreaded "diminished value" scenario.

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But what is diminished value?

It’s the loss of market value in a vehicle due to an accident
or collision damage and repair. Two things affect diminished value:
as stated, the loss in market value from a collision and the loss
due to substandard repairs.

But a diminished-value scenario can be avoided.

Keep Welds Hidden with S-TRSW

One of the most obvious damage-repair clues is evidence of the
welding method used in the restoration process. Statistics indicate
that 80 percent of collision repairs are front and back perimeter
panels or quarter-panel replacement. In front areas, the highly
visible core support, when repaired using MIG-welding techniques,
is highly detectable as a collision repair.

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With Squeeze-Type Resistance Spot Welding (S-TRSW), however, a
shop’s welds can duplicate factory welds in both strength and
appearance. That same core support can be completely accomplished
and ready for paint in a fraction of the time, and it doesn’t
draw attention to a collision repair.

Besides core supports, body panels and quarter panels are other
specific areas where S-TRSW techniques lend themselves to significant
improvement in repair practices.

Using S-TRSW, there’s also a conservative 50 percent productivity
improvement over MIG welding for a given job. The average metal
man will save approximately eight to 10 hours a week, or 35 to
40 hours a month, depending on the number of body men and the
mix and type of work done.

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Is It a Factory Weld or S-TRSW?

Consider this example of how S-TRSW welds imitate factory welds:

An independent Northwest body shop specializes in work for a Mercedes-Benz
dealership in its area. Repair work was being done on a nearly
new MB-600, having a retail value in the neighborhood of $140,000,
and the dealership insisted on the repair work being done according
to the MB repair manual.

The damage was such that replacement or repair of the rear quarter
panel was indicated, along with repair of some inner structure.
Due to the value of the automobile, the dealership insisted on
replacement, in lieu of repair, and the insurance company approved
the decision.

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Prior to painting and detailing by the body shop, the vehicle
was returned to the dealership for mechanical work. At this point,
the insurance adjuster stopped by the dealership to check the
progress and was appalled to find what appeared to be a repair
instead of the aforementioned replacement of the rear quarter
panel. The welds appeared to be factory welds, leading the adjustor
to believe the panel hadn’t been replaced; it appeared that the
expensive job the insurance company had approved had been replaced
with a lower-cost operation.

Needless to say, the insurance adjuster was quite irate – and
he immediately began throwing about phrases such as "fraud"
and "underhanded short-cuts," etc.

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The shop owner patiently waited for the adjuster to wind down,
and then showed him the old, damaged panel and the new S-TRSW
equipment used to duplicate the factory welds. With the evidence
in front of him, the insurance adjuster was quite contrite and
apologized for his accusations.

Details on S-TRSW

European car manufacturers have recommended spot welding as the
accepted and preferred method of collision repair for a long time,
but the European S-TRSW equipment didn’t lend itself to use in
the United States due, primarily, to the difference in electrical
power here and abroad; spot welding requires very high amperage,
and it wasn’t until a unit was designed to operate in our electrical
environment that earlier equipment problems were overcome.

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But don’t confuse S-TRSW with other types of spot welding. S-TRSW
is a held-pressure and welding process. The welding of two pieces
of metal is accomplished by the application of pressure and heat,
and nothing is added to the welding process – no welding rod,
wire or gas, and no deposit of filler weld or metal. The welding
process literally melts the two pieces of metal together, requiring
a very high temperature of approximately 1,300 degrees F.

The design requirements of a proper S-TRSW unit are fairly complex.
Proper pressure must be applied in a controlled manner, squeezing
the work pieces together. The weld function also must be controlled
so proper electrical energy is sent to the electrode tips to accomplish
a predetermined weld density. The weld must continue to be held
for a period of time to allow the weld nugget to cool under pressure,
and some method of controlling electrode-tip temperature must
be used to ensure weld consistency and to keep production flowing.
These hold, weld, wait and reset functions also must be compatible
with modern shop-production requirements.

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More specifically, one manufacturer uses compressed air for holding
and incorporates liquid cooling for the electrode tips to provide
continuous welding without any deterioration in weld strength
or nugget size from heat build-up in the unit.

As the trigger switch is actuated, the electrodes compress. The
electrode pneumatic pressure is preset on the control panel, and
a two-second delay is built in to allow maximum pressure to be
reached prior to the weld cycle. After two seconds, the weld cycle
automatically actuates. The density of the weld is determined
by the current setting on the control panel, which has been set
by the technician.

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When the weld cycle is completed, the hold cycle remains to keep
the electrodes compressed for two seconds. The weld and hold cycles
are automatic and will cycle through even if the trigger button
is released. The purpose of this hold cycle is to let the high
temperature in the weld cool down under pressure, allowing the
weld nugget to harden.

The wait cycle then engages, releasing the electrodes, and a red
light comes on for two seconds, indicating the equipment is resetting
for the next weld.

The total elapsed time is eight seconds.

Advantages of S-TRSW

The advantages of S-TRSW over other welding methods include:

  • The extremely high temperature generated during the welding
    process is confined to the small area of the electrode tips, thereby
    not weakening the metal;
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  • The equipment functions without smoke or fumes;
  • The operator can use clear safety glasses to better observe
    and control the welding process;

  • The equipment is capable of welding through primers, sealers
    and corrosion-protection coatings and of giving a consistent 6-mm
    weld nugget from the first to the last nugget. The time-consuming
    grinding and dressing of the weld has been virtually eliminated.

    I-CAR recently performed tests and confirmed that one manufacturer’s
    S-TRSW welds are many times stronger than MIG welds and equal
    to factory welds, comparing nugget size to nugget size. I-CAR
    continues to recommend MIG welding, but now endorses S-TRSW when
    it’s recommended by a vehicle manufacturer.

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    Speaking of vehicle manufacturers, the Nissan-Infinity repair
    manual states: "… resistance spot welding is superior to
    other welding processes. In addition, it features a low amount
    of thermal strain, a short welding time and finishing is unnecessary.
    For these reasons, it is recommended that resistance spot welding
    be used whenever possible. Further, use of MIG welding is recommended
    for locations where resistance spot welding cannot be utilized."

    Toyota, BMW, Mercedes-Benz, Volvo and Saab all have taken positive
    positions on S-TRSW, and their respective repair manuals go into
    great detail to educate collision repair technicians on the welding
    process. The emphasis comes from Europe, where resistance spot
    welding is the rule and not the exception.

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    An Invisible Repair

    S-TRSW is here to stay. More and more manufacturers are recommending
    it, and progressive shops – which added this new equipment early
    on – swear by it. It saves time, improves production and reduces
    the chances of diminished value. S-TRSW makes a noticeable difference
    when striving for unnoticeable collision repair.

    J. M. (Mike) McEniry is a media consultant and freelance writer
    who’s worked more than six years in the collision repair industry.

    Check It Out

    One of the most obvious damage-repair clues is evidence of the
    welding method used in the restoration process.

    • Using S-TRSW can help avoid a diminished-value scenario because
      a shop can duplicate factory welds in both strength and appearance.

    • The S-TRSW process literally melts two pieces of metal together,
      requiring a very high temperature of approximately 1,300 degrees
      F.

    • The extremely high temperature generated during the welding
      process is confined to the small area of the electrode tips, thereby
      not weakening the metal.
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  • The equipment functions without smoke or fumes.
  • The equipment is capable of welding through primers, sealers
    and corrosion-protection coatings and of giving a consistent 6-mm
    weld nugget from the first to the last nugget.

  • I-CAR continues to recommend MIG welding, but now endorses
    S-TRSW when it’s recommended by a vehicle manufacturer.

  • Toyota, BMW, Nissan, Mercedes-Benz, Volvo and Saab all have
    taken positive positions on S-TRSW.

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