The Shed – September-October 2019

Troubleshooting

Over time, at occasions such as Fieldays
and customer evenings, I have spoken
to many owners of small MIG welding
machines who are having problems,
and the most common by far is with
the wire feed.

Wire-feed problems
Common symptoms

• The end of the wire seems to pulse
  up and down.


• The speed and sound of the motor
  changes when welding.


• The wire slips between the feed
  rollers.


• The wire tangles into ‘birds’ nests’
  in the rollers and guides.


• At low amps, it is hard to get a
  consistent arc.


• The wire burns back into the tip.

Some ways to address these
problems
Liners
Many of these small MIG machines
come with a very soft nylon or
PVC-type liner. I would recommend
changing this to a steel, black Teflon, or
carbon liner. These much stiffer liners
create far less friction, or drag, on the
wire. The machine we are using in the
photos here comes with a steel liner and
feeds beautifully without any wire drag.
A good way of checking drag is to unclip
the roller and pull the wire through
from the gun end. If you need too much

energy to pull it, then the little feed

motor is going to struggle too.

I prefer the black liners, as they

are easy to fit into most small MIG

torches and can usually be bought by

the metre or in short lengths. These

black liners are also excellent for

aluminium wires.

Roller tension

Avoid over-tensioning the rollers.

This is so common. When the feeding

problems start, the normal response

is to give the wire more tension.

More is certainly not better, as too

much pressure can cause the wire to

‘pigtail’, or twist into a spiral, a bit like

a spring inside the liner. It is hard to

see, as the spirals are quite long, but

cut off a metre or so of wire out of

the torch and throw it on the ground.

Misunderstood feed problems have

condemned many good MIG machines

of all shapes, sizes, and brands to the

back of the shed. If you need a lot of

tension, the chances are your liner

is blocked.

Wire size

A trap many fall into is to buy really thin

wires for doing panel work. This can be

a big step back for your little MIG. The

0.6mm solid wire can be a nightmare

to feed because it is so thin and soft.

Any amount of drag and, hello, bird’s

nest in the rollers. The 0.8mm gasless

wire can also give similar problems,

and if the brand of machine won’t feed

smoothly at low amps, you’ll have more

problems. But a lot of this is all about

roller tension. Many times problems

with the wire feed will go away when

you move up to the next-size wire. The

0.9mm flux-cored gasless and 0.8mm

solid wires are fine for panel work.

Whether you choose solid wire using a

shielding gas or flux-cored wire, neither

is superior over the other. They have

different characteristics and properties

which work differently on certain jobs

and applications. Both types of these

wires will produce good-quality welds

with good weld appearance if welded

correctly and used with half-decent

settings and torch angles.

Other problems

Terminals

Many welders also forget about small

things like maintaining the terminals.

If your terminals are frayed or worn,

the leads will overheat and the result

will be a drop in power.

Cleanliness

Don’t forget cleanliness. Remember

all of the yield and tensile-strength

numbers that manufacturers measure

are tested on clean plates, not a rusty,

galvanized, 20-year-old trailer chassis

that has last week’s cow poo still stuck

to it. Don’t be lazy; clean it up first.

Preparing to weld with gasless wire which
is more forgiving of surface rust

Welding with flux-cored wire. The weld

direction is backhand or dragged