Valley FABRICATOR 251, Service Manual

Page: 48 / 104

4-10 August 22, 2008
FABRICATOR 251 SERVICE MANUAL
4.05 MIG Gun Maintenance
Remove dust and metallic pa r ticles f r om the gun conduit by fo r cing clean, d r y comp r essed ai r into the conduit once
a week. This will minimize wi r e feeding p r oblems.
4.06 Basic Welding Technique
Setting of the Power Supply
The setting of the Fab r icato r 251 r equi r es some p r actice by the ope r ato r , in that the welding powe r supply has two
cont r ol settings that have to balance. These a r e the Wi r e Speed Cont r ol and the Voltage Cont r ol Switches. The welding
cu rr ent is dete r mined by the Wi r e Speed Cont r ol, the cu rr ent will inc r ease with inc r eased Wi r e Speed, r esulting in a
sho r te r a r c. Less wi r e speed will r educe the cu rr ent and lengthen the a r c. Inc r easing the welding voltage ha r dly alte r s
the welding cu rr ent level, but lengthens the a r c. By dec r easing the voltage, a sho r te r a r c is obtained with little change
in welding cu rr ent.
When changing to a diffe r ent elect r ode wi r e diamete r , diffe r ent cont r ol settings a r e r equi r ed. A thinne r elect r ode wi r e
needs mo r e Wi r e Speed to achieve the same cu rr ent level.
A satisfacto r y weld cannot be obtained if the wi r e speed and voltage switch settings a r e not adjusted to suit the
elect r ode wi r e diamete r and dimensions of the wo r k piece.
If the Wi r e Speed is too high fo r the welding voltage, “stubbing” will occu r as the wi r e dips into the molten pool and
does not melt. Welding in these conditions no r mally p r oduces a poo r weld due to lack of fusion. If, howeve r , the
welding voltage is too high, la r ge d r ops will fo r m on the end of the elect r ode wi r e, causing spatte r . The co rr ect setting
of voltage and Wi r e Speed can be seen in the shape of the weld deposit and hea r d by a smooth r egula r a r c sound.
MIG Gun Travel Speed
Speed at which a weld t r avels influences the width of the weld and penet r ation of the welding r un.
Position of MIG gun
The angle of MIG gun to the weld has an effect on the width of the weld r un. Refe r to Figu r e 4-15.
Art # A-05148
Foreha n d Vertical
Figu r e 4-18: MIG Gun Angle
Distance from the MIG Gun Nozzle to the Work Piece
The elect r ode stick out f r om the MIG gun nozzle should be between 5/64" (2.0mm) to 13/64" (5.0mm). This distance
may va r y depending on the type of joint that is being welded.