Lincoln Electric IM710 SP-170T - Manual (Page 22)

Fumes and slag generated from
Innershield type electrodes recom-
mended for use with this welding
machine can be toxic.
• Avoid contact with eyes and skin.
• Do not take internally.
• Keep out of reach of children.
• Follow all safety precautions
found in this operating manual.
B-7 B-7 LEARNING TO WELD
WARNING
OVERLOAD PROTECTION
OUTPUT OVERLOAD
The SP-170T is equipped with a circuit breaker which
protects the machine from damage if a severe over-
load occurs. The circuit breaker button will extend out
when tripped. The circuit breaker must be manually
reset.
THERMAL PROTECTION
The SP-170T has a rated output duty cycle of 30%. If
the duty cycle is exceeded, a thermal protector will
shut off the output until the machine cools to a rea-
sonable operating temperature. This is an automatic
function of the SP-170T and does not require user
intervention. The fan continues to run during cooling.
ELECTRONIC WIRE DRIVE MOTOR
PROTECTION
The SP-170T has built-in protection for wire drive
motor overload.
LEARNING TO WELD
No one can learn to weld simply by reading about it.
Skill comes only with practice. The following pages
will help the inexperienced operator to understand
welding and develop this skill. For more detailed infor-
mation, order a copy of “New Lessons in Arc Welding”
listed at the end of this manual.
Electronic Components
Hinges
Bearings
THE ARC-WELDING CIRCUIT
The operator’s knowledge of arc welding must go
beyond the arc itself. The operator must know how to
control the arc, and this requires a knowledge of the
welding circuit and the equipment that provides the
electric current used in the arc. Figure B.7 illustrates
the welding circuit for a typical welding machine. The
circuit begins where the gun cable is attached to the
welding machine. Current flows through the gun
cable, gun, and contact tip, to the wire and across the
arc. On the work side of the arc, current flows through
the base metal to the work cable and back to the
welding machine. This circuit must be complete for
the current to flow.
This machine’s welding circuit has a voltage output of
33 volts DC maximum. This voltage is quite low and is
only present when the gun triggers depressed.
To weld, the work clamp must be tightly connected to
clean base metal. Remove paint, rust, dirt or oil as
necessary and connect the work clamp as close as
possible to the area you wish to weld. This helps pre-
vent current from going through an unwanted path.
Avoid allowing the welding circuit to pass through
hinges, bearings, electronic components, or similar
devices that can be damaged. See Figure B.8. Always
disconnect electrical devices before welding upon
them.
FIGURE B.8
The gun and cable assembly is held by the operator
who guides the automatically fed wire along the joint,
maintaining a contact tip to work distance of about 3/8
to 1/2 inch (10 – 12 mm). This is called electrical
stickout. This electrical stickout (ESO) must be prop-
erly maintained by the operator. The electric arc is
made in the gap between the work and the tip end of
a small diameter wire. When the power source is
properly set, the arc gap is maintained automatically.
Arc welding is a manual skill requiring a steady hand,
good physical condition, and good eyesight. The
operator controls the welding arc, and, therefore, the
quality of the weld made.
SP-170T