Tweco PCM-62 Machine Torch - Manual (Page 23)

Manual 0-2817 4-3 OPERATION
E. Bottom Dross Build-up
Molten material which is not blown out of the cut
area and re-solidifies on the plate. Excessive dross
may require secondary clean-up operations after cut-
ting.
F. Kerf Width
The width of the cut (or the width of material re-
moved during the cut).
G. 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.
4.06 General Cutting Information
WARNINGS
Disconnect primary power at the source before dis-
assembling the power supply, torch, or torch leads.
Frequently review the Important Safety Precau-
tions in Section 1. Be sure the operator is equipped
with proper gloves, clothing, eye and ear protec-
tion. 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 damage
to coated, painted, and other surfaces such as glass,
plastic and metal.
NOTE
Handle torch leads with care and protect them from
damage.
A. Piloting
Piloting is harder on parts life than actual cutting be-
cause the pilot arc is directed from the electrode to
the tip rather than to a workpiece. Whenever pos-
sible, avoid excessive pilot arc time to improve parts
life.
B. 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 gener-
ally result in a more square cut.
C. Edge Starting
For edge starts, hold the torch perpendicular to the
workpiece with the front of the tip near (not touch-
ing) 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.
D. Direction of Cut
Inside the torch, 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.
Right Side
Cut Angle
Left Side
Cut Angle
A-00512
Figure 4-3 Side Characteristics of Cut
To make a square-edged cut along an inside diam-
eter of a circle, the torch should move counterclock-
wise around the circle. To keep the square edge along
an outside diameter cut, the torch should travel in a
clockwise direction.
E. Dross
When dross is present on carbon steel, it is commonly
referred to as either “high speed dross", "slow speed
dross", or "top dross”. Dross present on top of the
plate is normally caused by too great a torch-to-plate
distance. "Top dross" is normally very easy to remove
and can often be wiped off with a welding glove.
"Slow speed dross" is normally present on the bot-
tom edge of the plate. It can vary from a light to heavy
bead, but does not adhere tightly to the cut edge, and
can be easily scraped off. "High speed dross" usu-
ally forms a narrow bead along the bottom of the cut
edge and is very difficult to remove. When cutting a
troublesome steel, it is sometimes useful to reduce
the cutting speed to produce "slow speed dross". Any
resultant cleanup can be accomplished by scraping,
not grinding.