Page 161 - CITS - Welder - Trade Theory

WELDER - CITS

All guides must be as close as possible to the drive roller to prevent the possibility of the wire bunching up.
Wire feed controls

The wire feeder will have its own built-in control system. The number of controls that will be built into the feeder
will depend on the type of feeder but the most common are
Wire speed - this control is the adjustment for how fast the drive rollers will turn and as stated earlier, the faster
the wire speed for each wire size the more amperage the power source will produce. The wire speed controls
can be labelled as wire speed, eg ipm (inches per minute) or mpm (metre per minute), or as a percentage from
the slowest speed being zero to the highest speed being 100%. Usually mpm will be the range of 1 m/min to 25
m/min.

The amperage being set by the wire speed setting will also have an effect on the speed of travel and the deposition
rate of the wire (how fast the weld metal is being put onto the weld piece); with the advantage of, the higher the
amperage the thicker the material that can be welded.

Burnback - Burnback is the setting of the degree that the wire electrode will melt back towards the contact tip at
the completion of the weld. If there is too much burnback the wire electrode will melt back onto the contact tip,
possibly damaging it. If there is not enough burnback set, the wire electrode will not melt away from the weld pool
and can be left stuck to the weld metal.
Spot timers or stitch modes are to be found on some feeders. These controls normally control the time the drive
roller will turn for after the trigger contactor has been activated
Purge switch - Some feeders have a purge switch. This is to allow the gas flow setting to be set on the gas
regulator without turning of the wire feed roller or without any welding power being turned on.
Welding Gun- types, description of parts functions and

maintenance.

Objectives: At the end of this lesson you shall be able to
• describe the MIG welding Gun.
• explain the MIG gun part function
• explain the MIG gun maintenance.

Introduction
MIG/MAG torch connection The torch connection is the system in which the MIG torch is connected to the wire
feeder. There are various types of MIG torch connections. Different manufacturers can use any one of many
systems to connect their torch to the wire feeder. When ordering a new Torch tell the supplier the type of torch you
need, including amperage rating the type of connection on the feeder so the torch can be supplied to match the
connection The Torch connection is also the area where the wire electrode, welding current and welding gases
are passed on to the welding torch. This means these components should be checked for damage or leaky seals
etc, so the connection will do its job correctly.
MIG/MAG torches
The MIG Torch is connected to the wire feeder, and its job is to deliver the wire electrode, shielding gas and the
electrical welding current to the welding area. There are a lot of different shapes and styles of MIG Torch out in
the marketplace but they all have things in common. (Fig 1 & 2).
1 Aircooled (less than 200 Amps) or water cooled (above 200 Amps) (Fig 1)
2 Current rating : The operator must select the correct size Torch. Using a torch that is not sufficiently rated
for the machine may result in the Torch overheating. This may result in a poor weld and damage to the torch.
A Torch with an excessive rating will be larger and heavier than the smaller Torch, which could result in
discomfort for the operator.

3 They all have parts that will wear out (consumables eg liners, tips, diffuser, nozzle, etc.) Let’s take a look at
each part (Fig 3)

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CITS : C G & M - Welder - Lesson 49 - 60