Jasic MIG 250C, Operator'S Manual

Page: 19 / 50

19
GUIDE TO MMA WELDING
Before starting any welding activity ensure that you have suitable eye protection and
protective clothing. Also take the necessary steps to protect any persons within the welding
area.
Notes for the welding beginner
This section is designed to give the beginner who has not yet done any welding some information to get
them going. The simplest way to start is to practice by running weld beads on a piece of scrap plate. Start
by using mild steel (paint free) plate of 6.0mm thick and using 3.2mm electrodes. Clean any grease, oil
and loose scale from the plate and fix firmly to your work bench so that welding can be carried out.
Make sure that the work return clamp is secure and making good electrical contact with the mild steel
plate, either directly or through the work table. For best results always clamp the work lead directly to the
material being welding, otherwise a poor electrical circuit may create itself.
Welding position
When welding, ensure you place yourself in a comfortable position for welding and your welding
application before you begin to weld. This maybe by sitting at a suitable height which often is the best
way to weld ensuring you
’ re relaxed and not tense. A relaxed posture will ensure the welding task
becomes much easier.
Please ensure you always wear suitable PPE and use suitable fume extraction when welding.
Place the work so that the direction of welding is across, rather than to or from your body. The electrode
holder lead should always be clear of any obstruction so that you can move your arm freely along as the
electrode burns down. Some elders prefer to have the welding lead over their shoulder, this allows
greater freedom of movement and can reduce the weight from your hand.
Always inspect your welding equipment, welding cables and electrode holder before each use to ensure it
is not faulty or worn as you may be at risk of an electric shock.
MMA process features and benefits
The versatility of the process and the skill level required to learn, basic simplicity of the equipment make
the MMA process one of the most common used throughout the world.
The MMA process can be used to weld a wide variety of materials and is normally used in the horizontal
position but can be used in vertical or overhead with the correct selection of electrode and current. In
addition, it can be used to weld at long distances from the power source subject to the correct cable
sizing. The self shielding effect of the electrode coating makes the process suitable for welding in
external environments. It is the dominant process used in maintenance and repair industries and is used
extensively in structural and fabrication work.
The process is well able to cope with less than ideal material conditions such as dirty or rusty material.
Disadvantages of the process are the short welds, slag removal and stop starts which lead to poor weld
efficiency which is in the region of 25%. The weld quality is also highly dependent on the skill of the
operator and many welding problems can exist.