Mma Operation - Impax IM-MIG120 Instruction Manual

MMA OPERATION

Inspect the job carefully. With a correct
combination of electrode size and current
setting the area of weld should be complete
fusion of the electrode and parent metal/s. Any
slag which forms on the surface should be
chipped away with the pick/brush supplied.
If the resultant weld looks messy and irregular,
this is an indication of porosity or slag
contamination, and you have almost certainly
failed to achieve the correct combination. This is
a common problem, so do not worry as practice
will quickly cure this.
When welding material up to 7mm in thickness
place the pieces 2-3mm apart, run the welding
bead along the join. A second bead can go
along the underside for extra strength (Fig.33).
Fig 33
2-3mm
When welding material from 7mm to 30mm thick
prepare the material as shown in Fig.34 filling up
the space with several layers of weld.
Fig 34
60º
2-3mm
5
3
When welding together material over 30mm in
thickness prepare the material as shown in
Fig.35 filling up the space with several layers of
weld, welding each side in turn with each
welding pass.
7mm
>30mm
6
4
2
1
Fig 35
Disconnect the Welding Power Supply from the
mains supply before changing or removing
electrodes. Use pliers to remove used
electrodes from the electrode holder or to move
the welded pieces.
The Manual Metal Arc Process
When an arc is struck between the metal rod
(electrode) and the workpiece, both the rod and
workpiece surface melt to form a weld pool.
Simultaneous melting of the flux coating on the
rod will form gas and slag which protects the
weld pool from the surrounding atmosphere. The
slag will solidify and cool and must be chipped
off the weld bead once the weld run is complete
(or before the next weld pass is deposited).
The process allows only short lengths of weld to
be produced before a new electrode needs to
be inserted in the holder. Weld penetration is low
and the quality of the weld deposit is highly
dependent on the skill of the welder.
Types of Flux/Electrodes
Arc stability, depth of penetration, metal
deposition rate and positional capability are
greatly influenced by the chemical composition
of the flux coating on the electrode. Electrodes
can be divided into three main groups:
• Cellulosic
• Rutile
• Basic
35
60º
>30mm
2-3mm