2004-Tips for beginners.
In progress – Almost ready.
If you haven't read the other pages I suggest you go the page one and read them as well.
Push or Pull.
There are differing opinions on when to
push or not. Pushing is usually recommended with MIG but some say
pull when doing thin work unless it is Aluminum. I've found my
best Aluminum weld were done by pulling.
I haven't seen the
reason for pushing explained – I'm sure it is in a research
paper somewhere. My theory is it is all about the convection
currents produced by the hot weld. If you pull the shielding gas
get sucked away into the convection current rising from the job –
you are blowing the gas right into it. If you push the gas has to
turn around to get sucked up and the gun is partly blocking the
path. This the “pushing” rule might not apply is some
cases – welding up a vertical surface for example.
Surface preparation.
As I've said above I usually
don't prepare the surface at all. MOG can cope better with dirty
surfaces than MIG/MAG. What I've been doing is not rocket science.
If I build a rocket I'll be more careful. Having a good surface to
weld is a good thing - it just isn't worth while for what I've
been doing. Welding a galvanized surface won't be as good as bare
metal and the burnt zinc can be hard to see through sometimes. Not
all galvanizing is created equal, this is obvious just by looking
at it. Some galvanized surfaces have big crystals/flakes while
other don't. Weld mesh for example seems to have very little zinc
on it and it welds quite well.
The painted tubes I use can be
welded fairly well with MOG without preparation, MIG/MAG doesn't
do as well. I've found just taking off a small amount of paint to
give initial contact makes a big difference (photos in the sample
section later on). The paint is quite thin and the welding wire
seems to be able to poke through it to strike an arc. The paint
burns into a gray layer which is easily wire brush off. Your local
steel may have a different type of paint on it than mine.
MIG/MAG/MOG.
This could possibly be sung to the tune
of “Bill and Ben”.
MIG - I believe originally stood
for “metal inert gas”. The term continued to be use
even when the gas was not inert so some said it mean “metal
in gas”. Then you had gas-less MIG which made no sense.
This
has now been corrected by using three different acronyms.
MIG is still has the original meaning and the gas is
usually argon.
MAG stands for “metal active gas”
and usually applies to CO2, or mixes containing CO2 or O2.
I'm
not certain what MOG stands for - possibly “Metal
withOut Gas”. It has also been suggested the “O”
could be “Ohne” German for without. Anyway it means
using flux cored or gas-less wire.
In my opinion the thing
which set these welders apart isn't the metal and isn't the gas –
it is the wire feed and calling them “wire fed welders”
or something like that would have been clearer.
When it was
first invented in the 1940 is was called gas shielded metal arc
welding (GMAW) – doesn't exactly roll off the tongue but I
guess I could live with it.
This is a quote from Welding.com
MIG (GMAW or Gas Metal Arc Welding) - An arc welding
process which joins metals by heating them with an arc. The arc is
between a continuously fed filler metal (consumable) electrode and
the workpiece. Externally supplied gas or gas mixtures provide
shielding. Common MIG welding is also referred to as short circuit
transfer. Metal is deposited only when the wire actually touches
the work. No metal is transferred across the arc. Another method
of MIG welding, spray transfer moves a stream of tiny molten
droplets across the arc from the electrode to the weld puddle.
Consumables: contact tips, shielding gas, welding wire.
Which to use?
My limited experience has been that
MIG/MAG produces a nicer weld when it is working properly but MOG
has been far more consistent. MOG seem more forgiving of incorrect
voltage or feed rate and of dirty surfaces. I have often welded
the undersides of work pieces with MOG but have had little luck
doing this with gas. (later – I fixed the speed problem and
could weld undersides - more or less). MOG is noisier and
splatters and the welds are rougher. I'm having trouble with the
speed controller on my welder and this make MIG/MAG very
difficult. Being in Australia and coming into summer MOG has the
advantage that it can tolerate drafts, I don't fancy closing up my
shed in 40 Deg heat to stop my shielding gas blowing away. My
welding work has mainly been “in situ” if I was
working under better conditions gas would be more practical.
Having finished three small rolls of MOG I bought a 4.5 Kilo roll
of it.
Breathing MOG fumes seems to give me a dry throat –
it can't be good for you.
Tips (clues for beginners).
“How to mig weld”
is the most frequent search term used to find my web site. People
are obviously after help. Five years ago I looked to the web for
help myself and couldn't find a thing. Things have improved since
then and there are some interesting sites out there but still no
really basic stuff. I've found more on stick welding basics than
MIG.
My first page said “Written by a Novice for those
who know even less.“ and this still applies to some extent.
My total experience amounts to melting a half a mini-spool of
aluminum wire onto 3mm aluminum extrusion and 1.5 spools worth of
MOG onto mainly 1.5mm galvanized iron. I'm no expert but I've
worked out which end makes the sparks.
Some of what I say
maybe obvious to you but we all sometimes miss the obvious so I
have to say it. Some of what I say may be wrong – decide for
yourself.
Obvious tip number one is don't pull your new MIG
out of the box and expect to do real work with it straight away. I
had MIGed before and I still went through most of the sample roll
experimenting and practicing. My problem (and I've heard this from
others as well) was having enough “scrap” on hand to
stick together.
If you don't have one already buy an
electronic welding mask. They cost a bit (mine was about Au$135)
but they are worth every cent. Not only is it easier to get the
weld started but for the majority of us who would use their hand
to place the (manual) visor in place – this frees up a hand.
Preferably get one which take common, cheap, largish batteries
(not button cells) and has an auto-shutdown – variable
density (darkness) is nice too. Get some clear protective “lenses”
for it. I use some cheap reading glasses with mine, there are flat
magnifying (protective) lenses made to fit my mask – haven't
tried them but they seem like a good idea. I sometimes have
trouble with the reading glasses fogging up.
Get good
gloves and other protective gear, if you do a lot you will need
protection from the UV (sunburn) and well as heat and sparks.
Get comfortable, it is hard to weld if you are straining
to stay steady, perhaps even arrange an armrest or a rail you can
slide your arm along to remain steady. Use both hands if possible.
Think about it like you are writing – small writing at arms
length without support is hard to do. I've welded in all sort of
positions, on ladders, laying on the ground etc – it worked
but it wasn't as tidy.
Make sure the polarity is correct. I've been caught a few times with this. Most MIGs I've seen let you choose the polarity of the tip (ie positive or negative). This has to be tip negative for MOG and positive for MIG/MAG.
Nothing kinky. It is easy to get the wire tangled up when replacing spools. If you try to untangle it you are likely to be left with some kinks in the wire. These kinks are likely to get jammed in the tip.
If you can't make it work try to have someone experienced test your setup. When Phil and I bought the WIA150 second hand we were able to try it out first - all set up for steel. Setting it up for aluminum involve new gas, new wire and new settings. It didn't work, Phil's neighbor was a professional welder and soon noticed we had the wrong sized tip fitted. Having someone set the gear up and test it will help identify where the problems are. Is it you, is the welder, is it the setup or the material you are trying to weld?
Read the manual.
Fire.
This
hasn't happened to me once or twice, it has happen frequently. The
welder can throw sparks for quite a distance. I've had 3 grass
fires, many cases of dry leaves or sawdust burning and one case of
hessian (sp) under-felt burning. I was totally unprepared this
first time and beat the fire out with my gloved hand. Since then
I've kept a bucket of water nearby. Today I took the precaution of
spraying the area first with a water using a weed sprayer. When
you are welding you won't see or hear the flames and you won't see
the smoke. You may smell the smoke or feel the heat if you a close
enough. Usually you don't notice until you stop welding or the
fire is large. This of course doesn't just apply to MIG. A friend
set a car alight with a stick welder – it was parked under a
house at the time. Be careful.
Feed Rate, Voltage
etc.
Once the work material and wire type etc has been
fixed you have three main variables to adjust. These are the tip
voltage, wire feed rate and the rate at which you move the tip.
The three interact and there will be many combination that work
and many more that don't. The voltage setting is the main control
for penetration but the other two parameters have some effect. The
feed rate sets the arc length. Your movement controls the smooth
transfer on metal to the work piece. The first two parameters are
a compromise because the ideal “settings” will usually
vary from part of the weld to another. You can vary your motion to
compensate to some extent. Low voltage will mean low penetration
and the weld will sit on the job instead of soaking in. Too much
voltage will mean penetrating right through and making a hole.
Most MIGs have very little choice (if any) voltage wise so you can
try them all if you have too. Having fixed the voltage we now
adjust the feed rate. The easiest is to drag the gun along some
scrap of similar thickness to the work piece and adjust till you
get a smooth arc. If you can hear it - you don't even need to
watch it. I start fast and slow it down. When the rate is fast you
get a series of pops. The wire hits the job and short-circuits
without maintaining an arc. The wire then melts and the process
repeats when the new piece hits the metal. It doesn't seem to do
any harm. Having it too slow on the other will cause the arc to
burn back to the tip and quite often fuse the wire to it – I
think that does do harm. There will be a range of speeds were you
have a steady arc. You will have to experiment a bit. I think a
short arc is better but I'm still learning too. (later) I've found
with MOG as least too slow a feed can cause popping also. This is
different though. Too fast and the whole length of wire to the tip
glows and melts with little or no arc. Too slow and a portion of
the wire at the end disappear in a bright arc.
Move
along.
Once the voltage and feed are set you have work to
do. You have to coax the liquid metal into the correct place and
at the correct rate. Almost all the welding I do is using a zigzag
weave pattern. Joining two pieces with a straight weld is possible
is some cases but generally a weave is a better option. For most
work you have to keep moving or bad things happen. When you start
the wire will melt into a little ball, this may happen too quickly
to watch as your eyes are adjusting. The ball should attach itself
to the work piece – it should not sit on top of the work
piece. You may see the surface of the work melt - sort of like the
surface has been eaten away – like acid does. In that split
second I'm usually trying to see where I am and that isn't always
easy, the dazzle of the arc can make it hard to see where the join
is, the smoke and other problems can make it impossible sometimes.
You can't wait too long or you will start making holes or have
lumps of metal where you don't want any. Chances are the
ball/puddle formed on one side of the join or maybe it has already
bridged the gap. Either way you have to move, zigzag or whatever
your going to do along the join. The puddle should grow into a
seam each zigzag extending the seam as always bonding to the work
piece. Move to slow and your likely to get holes, too fast you may
not form a continuous weld or it may be hollow – bridging
the gap but not filling the gap.
A straight weld is sometimes
used to build up the thickness of the edges before stitching them
together. If you make a hole it is probably best to keep going –
maybe move a little faster. Small holes can be filled, I've found
I can close them up by just circling around them till they fill.
I've been mainly using MOG so I wait till I've finish the weld,
let it cool a little and then clean of the flux before closing the
holes.
I've sometimes done a weld and found it was too light
and gone over it again. One thing to be careful of is working one
area too much and making it too hot (as in glowing) this can cause
the work to sag or distort.
(later) I've found using gas that
something the welding goes into a different mode. Instead of the
wire disappearing into the melt with a short arc at the boundary –
the wire forms into drops which hover above the melt and drip into
it. The weld can still be ok but it is off-putting to watch. The
welding.com quote about “short circuit transfer”
verus “spray transfer” might be relevant
here.
Weaving.
Even a simple side to side zigzag weave has
a lot of possible variations. Speed, width and amount of travel
per cycles being the obvious ones. Then you can vary the speed for
parts of the weave or taken to extreme stop in places. For example
when joining two piece of different thicknesses you might move
faster over the thin piece. The same applies if the pieces are the
same thickness but one is more prone to melting through –
for example when joining two pieces of flat to form a 'T”
the edge of one piece is welded to the middle of another –
the edge is more likely to melt through than the other piece
because it has less metal sucking heat away. The corners will be
the worst for the same reason. Starting on a corner (or edge)
isn't so bad because the metal is cold but ending on the
corner/edge is likely to melt it through.
The other weave I
sometimes use is a cycloid – that is moving is circles while
advancing. For some reason this seems to be less prone to burning
through. I think it spreads the heat out better. One several
occasions when I've done this I've burned a hole on the advancing
edge and filled it in one the back of the circle – so there
was a hole moving along with me. Another pattern worth trying is a
triangular pattern. You lead on the on the sides and lag in the
middle.
MOG
on Galvanized tube.
MOG
on Painted tube.
