Tweco PCM-120 Machine Torch - Manual (Page 28)

OPERATION 4-8 Manual 0-2698
Travel speed also affects the bevel angle of a cut.
When cutting in a circle or around a corner, slowing
down the travel speed will result in a squarer cut.
The power source output should be reduced also.
C. Piercing With Machine Torch
To pierce with a machine torch, the arc should be
started with the torch positioned as high as possible
above the plate while allowing the arc to transfer and
pierce. This standoff helps avoid having molten metal
blow back onto the front end of the torch.
When operating with a cutting machine, a pierce or
dwell time is required. Torch travel should not be
enabled until the arc penetrates the bottom of the
plate. As motion begins, torch standoff should be
reduced to the recommended 1/8 - 3/8 inch (3 - 9
mm) distance for optimum speed and cut quality.
Clean spatter and scale from the shield cup and the
tip as soon as possible. Spraying or dipping the shield
cup in anti-spatter compound will minimize the
amount of scale which adheres to it.
A standard shield cup is recommended for most ma-
chine cutting applications. Do not allow an exposed
torch tip to contact the workpiece or output current
will fold back to 35 amps..
A method called “running start” is recommended
when piercing with a machine mounted torch. The
torch should be positioned far enough off the cutting
line to allow the pierce to be complete before the cut-
ting line is reached. This allowance depends on the
thickness of the material and the torch travel speed.
Piercing the plate is not recommended on plates hav-
ing a thickness greater than 3/4 inch (19 mm).
Blowback from the piercing operation can shorten the
life of torch parts. All piercing should therefore be
done as quickly as possible and at maximum amper-
age (120 amps) and maximum standoff.
Pierce off the cutting line and then continue the cut
as needed. Clean spatter and scale from the shield
cup and the tip as soon as possible. Spraying or dip-
ping the shield cup in anti-spatter compound will
minimize the amount of scale which adheres to it.
4.09 Recommended Cutting Speeds
Cutting speed depends on material, thickness, and the
operator’s ability to accurately follow the desired cut line.
The following factors may have an impact on system per-
formance:
• Torch parts wear
• Air quality
• Operator experience
• Torch standoff height
• Proper work cable connection
• Alloy content of material
NOTE
This information represents realistic expectations
using recommended practices and well-maintained
systems. Actual speeds may vary from those shown
in the charts depending on the alloy content of the
selected material.
Refer to Appendix 1, Cutting Speed Charts, for complete
chart data.
4.10 Gouging
WARNINGS
Disconnect primary power to the system before
disassembling the torch, leads, or power supply.
Be sure the operator is equipped with proper gloves,
clothing, eye and ear protection and that all safety
precautions at the front of this manual have been
followed. Make sure no part of the operator’s body
comes in contact with the workpiece when the torch
is activated.
Sparks from plasma gouging can cause damage to
coated, painted or other surfaces such as glass, plas-
tic, and metal.
Check torch parts. The torch parts must correspond
with the type of operation. Refer to Section 4.04,
Torch Parts Selection.
A. Recommended Gases
Refer to the following table for characteristics of rec-
ommended gases when gouging with the Torch: