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Cut quality
NOTE!
Cut quality depends heavily on setup and parameters such as torch standoff, alignment with the workpiece, cutting speed, gas
pressures, and operator ability.
Cut quality requirements may differ depending on application. For instance, nitride build-up and bevel angle may
be major factors 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:
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 some materials to be welded after the cutting process.
Torch Standoff -
Edge Starting - For edge starts, hold the torch perpendicular to the workpiece 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.
Direction of Cut - In the torches, the plasma gas stream swirls as it leaves the torch to maintain a smooth
column of gas. This swirl effect results in one side of a cut being more square than the other. Viewed along the
direction of travel, the right side of the cut is more square than the left.
To obtain a more square cut along the internal diameter of the circle, the torch must move in the counter-
clockwise direction or around the circle. To maintain a square edge along when cutting along the external
diameter, the torch must move in the clockwise direction.
28
Kerf Width
Top
Spatter
Bottom Dross
Build-Up
Smooth or Rough
Cut Surface
Drag Lines
Figure 5.22 - Cut quality characteristics
90
Left Side
Cut Angle
Figure 5.23 - Side Characteristics Of Cut
Cut Surface
Bevel Angle
Top Edge
Rounding
Excessive Dross
Build-Up
Right Side
Cut Angle
A-00512
0-5584
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