Basic Nitrogen Welding Process – TAPAS

Basic Nitrogen Welding Process – TAPAS

The first thing we’ll do is learn
the basic welding technique. Once you learn the basics, then we’ll turn
our attention to the trickier applications. There are five major variables
in the nitrogen welding process. We’ll abbreviate them TAPAS: Temperature,
Airflow, Pressure, Angle, and Speed. The temperature will be around 450 to 900 degrees
Fahrenheit, depending on the type of plastic. The airflow for thin plastics will range
from 7 to 15 liters per minute. Pressure refers to the downward
pressure on the welding rod. You should press down on the rod with
about a half pound of downward pressure as you make your pass to make sure
the rod and the plastic fuse together. Angle refers to the angle between
the torch and the plastic. It should generally be about 45 degrees
with the airflow pointed toward the area where the rod and bumper meet. Finally, the speed should be
about 4 to 6 inches per minute. It’s common for people to go too
fast and not get sufficient fusion. The temperature is set with a hot
air welding temperature control dial. It has settings ranging from 1 to 8. 8 is a maximum temperature and it’s not
recommended to run at this level for long. Set it at about 6 initially and
adjust it up or down as needed. See the literature that came with your kit
for recommended temperature settings depending on the type of plastic. Once you switch the flow over to nitrogen,
adjust the fine flow control to between 7 and 15 liters per minute on the flow gauge. Lower flow is used on very thin plastics. The thicker the plastic, the
greater the flow you will need. Don’t keep the flow below 10 for very long;
it may burn out your heating element. Make sure the air flow is about 15 when the welder
is turned to the air side so the element is protected. The angle of the torch to the work is also important. Generally, you want the angle to be about
45 degrees so you’re blowing hot nitrogen on both the bumper and the rod. However, if the bumper is very thin, you may want to focus most of the heat on the rod and not the bumper, or if the bumper is thicker than the rod, you
may need to focus more heat on the bumper. It will take some practice before you
get the feel of where to direct the heat. Pressure is the downward pressure
of the welding rod onto the surface. You need to apply about half
pound of pressure down on the rod so that the two plastics fuse
together as you make your pass. Speed is the last variable. You need to control your speed to
about 4 to 6 inches per minute. The natural tendency is to go faster than this. You will need to slow yourself down to make sure
the plastics have time to melt and fuse together. Let’s take a look at a basic weld keeping TAPAS in mind. After the plastic’s been cleaned and roughed up, we
start by blowing the hot nitrogen gas on the bumper. Notice that the plastic starts to
turn glossy as the surface melts. Lower the rod down and pre-heat
the end of it at the same time. You’ll need to heat for about 10 seconds. Touch the rod to the bumper. When it sticks, apply pressure
and fold the rod forward slightly so that the first quarter inch of
welding rod sticks to the surface. Keep the torch at a 45 degree angle and focus the
heat where the rod and bumper come together. You want to pre-melt the top surface
of the bumper in front of the rod and also pre-melt the bottom surface of the rod
before it comes down to meet the bumper. Once you get it going, you should have a small
puddle of melted plastic in front of the rod. Some melted plastic should
extrude out the sides as well, leaving a furrow of plastic along the edges of the rod. Keep a steady downward pressure on the rod. The rod should naturally fall onto the bumper
as everything gets to the right temperature. Again, you want to control your speed
to about four to six inches per minute. Continue welding until you want to end the weld bead. At that point, fold the rod down to the bumper, focus
the heat on the top of the rod until the rod turns clear, then you can nip it off using the torches’ nozzle. This demonstrates the proper way to do a basic weld. Now, let’s look at a few common errors. First, don’t try to go backwards. You want to move the rod toward
the torch as you make your pass. Second, don’t lay it down and try to melt it from the top. You can’t get any good fusion between
the rod and the bumper this way. Third, don’t go too slow to the point
that the rod has no structure. If you see the rod getting totally clear
like this, it won’t have any strength, and you can’t get any downward
pressure on the bumper. The bottom surface of the rod should
be melted, but the top shouldn’t, so that it can support your downward
pressure as you make your pass. We recommend that you practice
on the backside of a scrap bumper so you get the feel of doing this basic welding process. The coordination of these five variables
takes practice to get the feel of. The more you practice, the better you’ll get. Before we move on, let’s take a look at using the TAPAS method using the eighth inch diameter round rod. This is one of our most popular profiles. It’s great for tucking into tight areas and
to weld cracks that are not quite straight. After cleaning the plastic and
grinding the v-groove with a die grinder, pre-heat the plastic and the end
of the rod to begin the weld. Here, you can see that the angle of the torch is
a little flatter with more heat focused on the rod. This rod is thicker than the ribbon, so it will
need to get a little more heat to get it melted. Once the plastics get to the proper temperature,
touch the rod down and start welding. Just as with the ribbon, keep the heat focused
where the rod meets the bumper pre-melting the rod and the bumper, and fusing them together with downward pressure as you make your pass. You won’t be able to see a puddle in front
of the rod as you did with the ribbon, though. We also have a wide ribbon for maximum
strength on backside reinforcements. Here, use the same method as on the narrow ribbon. Pre-heat the bumper and the end of the rod. Touch the rod down, get it folded over, and
control your speed so the rod and bumper are both pre-melted before the pressure
exerted by the rod fuses them together. With the wide ribbon, you will need to
move the hot nitrogen flow in an oval motion to melt the ribbon all the way across. Note the puddle of plastic in front of
the ribbon as you make your pass. Note that if the ribbon has tapered edges like this, you probably won’t get a furrow of plastic on each
side of the rod as you did with the narrow ribbon. Get some practice doing welds with the TAPAS
method on a scrap bumper before you graduate to repairing an actual tear in the bumper. When you’re ready, go to the next section of the DVD, and we’ll cover how to repair a
basic tear to the edge of the bumper.

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