of a role, but for larger bots it can be extremely useful.
There are many types of welding but generally, there are
three things that are required: an electrode which causes
an arc which heats up the metal you are welding to a
molten state; a shielding gas which protects the molten
metal from contamination; and filler material that you
add to the molten puddle to form the weld. Three specific
types of welding that you will find useful are: stick welding,
MIG welding, and TIG welding.
Stick welding involves using a consumable welding rod
or electrode with a flux coating. The flux coating creates a
shield of inert gas to protect the weld from contamination.
A high electric current is passed through the electrode
which causes an arc, thereby heating up the metal. The
electrode also acts as the filler material as it melts from the
arc. This method is one of the most simple and common
welding methods. It is typically used to weld steel but
also can be used to weld raw iron, aluminum, nickel, and
MIG (metal inert gas) welding is perhaps the easiest
type of welding. In this method, a welding “gun” is used,
through which a wire electrode is fed through the gun
along with an inert gas. This type of welding is usually
compared to using a hot glue gun. This method can be
used for welding steel, aluminum, and other metals.
FIGURE 7. The drill bit is
pushed against the Lexan
(in blue), causing it to
flex downwards into the
center of the hole,
allowing you to line up
with the holes in your
part (in black).
40 SERVO 05.2008
FIGURE 6. This type of part is a perfect example of when to
make a hole template using a thin piece of Lexan.
TIG (tungsten inert gas) welding is a more versatile
type of welding but is also more difficult. It uses a
non-consumable tungsten electrode to produce the arc.
The welder controls the electrode with one hand, while
they add filler metal from a welding rod with the other.
There is also a foot pedal that controls the power going
through the electrode. This type of welding requires the
most experience, but it allows you to make much cleaner
and controlled welds. Materials that can be welded
using this method include steel, titanium, aluminum,
Tricks of the Trade
After almost six years of building combat robots, there
are a number of tricks that I have learned that help in the
robot building process. These allow me to work more
quickly with less precision, yet still obtain the same results.
There are better ways that involve a lot more time and
effort to set up, but I’ve found these tricks will get you
about the same results.
There are many times when you need to drill a pattern
of holes into a sheet of metal or plastic (such as a base
plate) so that they line up with holes in a frame or other
part such as shown in Figure 6. If the sheet isn’t clear —
and often times it isn’t — this can lead to a very long and
arduous process of measuring out the placement of each
hole. This can take hours to do properly. There is a trick,
however, that I have used many times that — if done
carefully — will result in all of your holes lining up perfectly.
It requires a piece of sacrificial Lexan, usually about .063”
thick, to be used as a template.
1) First, cut out the Lexan so that it will cover all of the
holes in the part. Next, clamp it to the part that the holes
need to match up to. Mark where the part is in relation to
your Lexan; I usually do this by making a pen mark around
the perimeter of the part on the Lexan.
2) Use a hand drill with a drill bit slightly smaller than the
holes in the part. Place the drill bit over the center of the
hole, so that the bit is on top of the Lexan and the hole is
under the Lexan. Slowly push down and start the drill
so that the Lexan deflects into the hole and the bit
auto-centers. See Figure 7 for an illustrated example.
3) Drill through the Lexan being careful not to hit any
threads in the part underneath. If you are mounting to
something you made, then just don’t tap it before this step
to avoid messing up the threads, then you can use the
same drill size. Repeat this procedure for all of the holes;
you should finish with something that looks like Figure 8.
With all of the holes drilled, you can unclamp your