Impax IM-MULT160-K Instruction Manual page 37

MMA OPERATION
Do not hit the electrode on the workpiece as
this may damage the electrode. Withdraw with a
clean movement at the end of the welding run.
Note: This is the most difficult aspect for most
beginners. It is recommended that you practice
on some scrap material in order to get a feel of
the operation.
If the electrode is not withdrawn quickly enough
once the arc is primed, there is a possibility that
the electrode will weld itself to the workpiece.
Should this happen, give it a sharp tug to free it,
and try again. If this fails to free it, turn off the
machine immediately as it will quickly overheat.
If you withdraw the electrode too far once the
arc is primed, you will lose the arc and have to
try again.
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.28).
Fig 28
2-3mm
When welding material from 7mm to 30mm thick
prepare the material as shown in Fig.29 filling up
the space with several layers of weld.
Fig 29
When welding together material over 30mm in
thickness prepare the material as shown in
Fig.30 filling up the space with several layers of
weld, welding each side in turn with each
welding pass.
Fig 30
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.
7mm
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.
36
60º
>30mm
2-3mm
6
5
4
3
2
1
60º
>30mm
2-3mm