Tweco A120 CutMaster - Manual (Page 37)

CUTMASTER A120
Manual 0-4989 OPERATION 4T-3
4T.04 Cut Quality
NOTE
Cut quality depends heavily on setup and param-
eters such as torch standoff, alignment with the
workpiece, cutting speed, gas pressures, and
operator ability.
Cut quality requirements differ depending on application. For
instance, nitride build - up and bevel angle may be major fac-
tors when the surface will be welded after cutting. Dross - free
cutting is important when finish cut quality is desired to avoid
a secondary cleaning operation. The following cut quality
characteristics are illustrated in the following figure:
Kerf Width
Cut Surface
Bevel Angle
Top Edge
Rounding
Cut Surface
Drag Lines
Dross
Build-Up
Top
Spatter
A-00007
Cut Quality Characteristics
Cut Surface
The desired or specified condition (smooth or rough) of
the face of the cut.
Nitride Build - Up
Nitride deposits can be left on the surface of the cut when
nitrogen is present in the plasma gas stream. These build-
ups may create difficulties if the material is to be welded
after the cutting process.
Bevel Angle
The angle between the surface of the cut edge and a plane
perpendicular to the surface of the plate. A perfectly per-
pendicular cut would result in a 0° bevel angle.
Top - Edge Rounding
Rounding on the top edge of a cut due to wearing from the
initial contact of the plasma arc on the workpiece.
Bottom Dross Buildup
Molten material which is not blown out of the cut area
and resolidifies on the plate. Excessive dross may require
secondary cleanup operations after cutting.
Kerf Width
The width of the cut (or the width of material removed
during the cut).
Top Spatter (Dross)
Top spatter or dross on the top of the cut caused by slow
travel speed, excess cutting height, or cutting tip whose
orifice has become elongated.
4T.05 General Cutting Information
!
WARNING
Disconnect primary power at the source before dis-
assembling the power supply, torch, or torch leads.
Frequently review the Important Safety Precautions
at the front of this manual. Be sure the operator
is equipped with proper gloves, clothing, eye and
ear protection. Make sure no part of the operator’s
body comes into contact with the workpiece while
the torch is activated.
CAUTION
Sparks from the cutting process can cause dam-
age to coated, painted, and other surfaces such as
glass, plastic and metal.
NOTE
Handle torch leads with care and protect them
from damage.
Piloting
Piloting is harder on parts life than actual cutting because
the pilot arc is directed from the electrode to the tip rather
than to a workpiece. Whenever possible, avoid excessive
pilot arc time to improve parts life.
Torch Standoff
Improper standoff (the distance between the torch tip and
workpiece) can adversely affect tip life as well as shield cup
life. Standoff may also significantly affect the bevel angle.
Reducing standoff will generally result in a more square cut.
Edge Starting
For edge starts, hold the torch perpendicular to the work-
piece with the front of the tip near (not touching) the edge
of the workpiece at the point where the cut is to start.
When starting at the edge of the plate, do not pause at the
edge and force the arc to "reach" for the edge of the metal.
Establish the cutting arc as quickly as possible.