Systematics MP140 - INTRODUCTION; THE MIG PROCESS; SHORT ARC OR DIP TRANSFER

2 Systematics , Inc. 1025 Saunders Lane West Chester, PA. 19380
INTRODUCTION
The Systematics MP140 is a com-
bination welding power source,
wire feed unit, MIG torch and
accessory package. It operates on
115 volts AC input current and is
designed to meet the requirements
of auto body repair shops and light
fabrication. The MP140 produces
fusion welds by the Gas Metal Arc
Welding process (GMAW or MIG), on
steel up to 1/4" thick(aluminum 3/
16") , using .023" through .045"
steel wire and 3/64" aluminum
wire(Optional liners and contact
tips must be purchased to cover
given wire sizes). Heavier sec-
tions can be easily welded using
slightly different techniques. Con-
sumable MIG Spot/Stitch Welding on
steel can be performed with the
Optional SSTP-2 module installed.
The number of controls on the
unit have been reduced to assist
inexperienced operators learn MIG
welding. This facilitates rapid
set up for welding different thick-
nesses of material requiring vari-
ous heat inputs. The VOLTAGE con-
trol adjusts the welding voltage
and the WIRE SPEED control adjusts
the speed of the wire drive motor.
THE MIG PROCESS
AS APPLIED TO THE MP140
The MIG process uses a bare,
consumable electrode in the form of
spooled wire, which is fed by a
controllable speed feed unit through
the cable and torch to the weld. The
emerging wire and the weld are
shielded by a stream of CO2, Argon,
or a mixture of the two, which
prevents oxidation of the molten
weld puddle. The gas shield enables
high quality welds to be made
without the use of flux, eliminat-
ing the need for slag or flux
removal after the weld is com-
pleted.
The consumable electrode wire is
melted and transferred to the weld
puddle by the "short arc" or "dip"
transfer mode.
POWER SOURCE
WIRE SPOOL
FEED
ROLLS
WORK
MIG
TORCH
+
REVERSE
POLARITY
(STD.)
_
SHIELDING GAS
SHORT ARC OR DIP TRANSFER
Short arc transfer occurs at 12
to 22 arc volts (voltage while
welding), depending on wire size.
Welding commences as the arc is
struck and a weld pool is formed.
The tip of the electrode wire dips
into the pool and causes a short
circuit. The short circuit current
flow causes a rapid temperature
rise in the electrode wire and the
end of the wire is melted off. An
arc is immediately formed between
the tip of the wire and the weld
pool, maintaining the electrical
circuit and producing sufficient
heat to keep the weld pool fluid.
The electrode continues to feed and
again dips into the pool.
FIG. 1. SCHEMATIC OF MIG PROCESS
This sequence of events is re-
peated up to 200 times per second.
Short arc transfer is suitable for
positional welding. The heat input
to the workpiece is kept to a
minimum which limits distortion
and makes possible the welding of
thin sheet material.
FIGURE 2. SHORT ARC TRANSFER
ELEC-
TRODE
WORK