Operator’s Ready Reference
What is plasma?
Plasma is a gas heated to an extremely high temperature and ionized so that it becomes
electrically conductive. Plasma arc cutting uses the plasma as an electrode to transfer a
electrical arc to the work piece. The heat of the arc melts the work piece and the force of the
plasma and shield gases blow away the molten metal to cut the work piece.
Different metals react differently to plasma cutting. Carbon steel can be oxidized, and is usually
cut with a plasma containing oxygen to take advantage of the exothermic process. Higher
levels of oxygen in the plasma result in higher heat and higher rates of oxidation. The result is
a faster and cleaner cut. Stainless steel and aluminum are not subject to rapid oxidation and
depend entirely on the plasma’s heat for the cutting process. Because plasma produces much
higher heat than the oxygen-fuel cutting process, plasma can cut stainless steel and aluminum
quickly and cleanly.
Choosing a plasma process
Thermal Dynamics systems offer a variety of plasma cutting processes for precision and general
purpose cutting. Ultra-Cut systems offer precision cutting as well as conventional cut options.
Auto-Cut O2 systems offer high speed oxygen cutting, precision non-ferrous and conventional
cut options. Auto-Cut systems offer conventional mild steel and precision non-ferrous options.
Process
Plasma Shield
O
2
O
2
N
2
Air
O
2
H2O Precision Non-Ferrous
Mild Steel Precision 50-300 Amps
and High Speed Oxygen Process
Mild Steel Precision at 30 Amps Weld Ready Cut Surface
Used For Advantages
Weld Ready Cut Surface
Best Cut Quality on Stainless
and Aluminum to ¾”
Better Parts Life Than Air
N
2
N
2
Conventional Thin Non-Ferrous
Better Cut Surface Than Air on
Non-Ferrous
Thicker Non-Ferrous
H35 N
2
>¾” Aluminum
>¾” Stainless
Air Air Conventional Mild Steel
Faster Cutting on Thicker SS and
Aluminum
Weld Ready Cut Surface
H35=65%Ar/ 35%H
Economical Cost of Operation
Good Cut Quality
Air Air Conventional Non-Ferrous Economical Cost of Operation
page 2
2
Cut charts
Cartridge
21-1020
Electrode
21-1068
Plasma
Gas Distributor
21-1040
Tip
21-1050
Shield Cap
21-1024
Shield Cup
21-1016
Art # A-06768
Shield
Gas Distributor
21-1082
Thermal Dynamics provides a cut parameters chart for every process and output current combination.
Material
Mild Steel
Current
Level
30A
O2 Plasma / O2 Shield
Process
Consumable Parts
Material
Thickness
(ga) (in) inch (PSI) Ball (PSI) Ball (PSI) Volts
20 0.036 60 22 120 21 120 128 0.050 130 0.120 0.2 0.058
16 0.060 60 22 120 21 120 143 0.050 60 0.120 0.3 0.070
14 0.075 60 22 120 21 120 145 0.070 45 0.120 0.3 0.072
12 0.105 60 22 120 21 120 148 0.110 40 0.150 0.3 0.074
10 0.135 80 22 120 21 120 154 0.130 30 0.150 0.3 0.085
3/16 0.188 80 22 120 21 120 154 0.120 25 0.150 0.4 0.075
Gas Control
Settings
Material
Thickness
(mm) (Bar) Ball (Bar) Ball (Bar) Volts
1 4.1 22 8.3 21 8.3 130 1.3 3050 3.0 0.2 1.5
2 4.1 22 8.3 21 8.3 145 1.9 1130 3.1 0.3 1.8
3 4.1 22 8.3 21 8.3 150 3.0 910 3.8 0.3 2.0
4 5.5 22 8.3 21 8.3 154 3.2 710 3.8 0.3 2.1
5 5.5 22 8.3 21 8.3 155 3.0 640 3.8 0.4 1.9
Pre Flow
Pressure
(Air)
Pre Flow
Pressure
(Air)
30A Mild Steel (O2/O2)
Cut Flow Rates /
Pressures
Plasma (O2) Shield (O2)
Cut Flow Rates /
Pressures
Plasma (O2)
Shield (O2)
Torch
Height
(in)
Travel
Speed
(ipm) (in) (sec) (in)
Arc
Voltage
Working
±0.005
Arc Voltage for
Torch Height Control
Travel
Torch
Arc
Voltage
Working
Height
(mm)
±0.1
Speed
(mm/
min)
Initial
Initial
Pierce
Delay
Pierce
Delay
@ Rec.
Speed
Width
@ Rec.
Speed
Piercing
Height
Piercing
Height
(mm) (sec) (mm)
Kerf Size
Kerf
Width
Kerf
Pierce
Data
Plasma Marking
Parameters
15A Arc Current
Burn-through
thicknesses
< 1/16” (0.063”) /
may
occur on
1.6 mm
Pre Flow
Pressure
(N2)
20psi
1.4 bar
Marking (with 30A Mild Steel Parts)
80 psi
5.5 bar
Arc
Voltage
145
Cut Flow Rates /
Pressures
Plasma
Pressure (N2)
Ball Press Ball Press Volts
40 psi
20
2.8 bar
Shield
Pressure N2)
70
page 3
Torch
Working
Height
In ±0.005 /
mm ± 0.1
0.1
2.5
Travel
Speed
ipm /
mm/min
300
7600
Initial
Piercing
Height
In ±0.005 /
mm ± 0.1
0.1
2.5
Pierce
Delay
(sec)
0
Marking
Quality
Degrades
as
Thickness
Decreases.
Consumable parts
Cartridge Covers
Upper O-Ring
on Torch Tip
Shield Cap Protrudes
0.063-0.083" (1.6 - 2.1 mm)
Electrode
Plasma Gas
Distributor
Tip
Shield Gas
Distributor
Shield Cap
Upper O-Ring
on Tip
1: Stack Parts
2: Press Cartridge onto Stacked Parts
4: Check Shield Cap Protrusion
Art # A-04716
No Gaps
Between Parts
3: Thread Shield Cup onto Cartridge
Shield Cap
Shield Cup
Parts selection
Consumable parts are specifically designed to perform in specific conditions. Using the
wrong consumable parts will result in short parts life and poor cut quality. Use the cut charts to
determine which consumable parts to use in any specific application.
Installing consumable parts
The XT torch is a precision instrument. Take care when installing consumable parts to keep the
parts clean and free from any contamination that might cause a gas or coolant leak inside the
consumable parts cartridge.
Assembly Sequence, 30-150 Amp Consumables
7.04 Torch Consumables Installation
Do not install consumables into the Cartridge
while the Cartridge is attached to the Torch Head.
Keep foreign materials out of the consumables and Cartridge.
Handle all parts carefully to avoid damage,
which may affect torch performance.
1. Install the consumables as follows:
WARNINGS
Art # A-03887
page 4
Tip
Electrode
Plasma Gas
Distributor
Shield Cap
Shield Gas
Distributor
Shield Retainer
Shield Cup
Assembly sequence:
Cartridge
1
2
3
4
Art # A-07424
Assembly Sequence, 200/300 Amp Consumables
To ensure proper assembly of the torch cartridge:
1. Place the cartridge assembly on a clean, flat surface
2. Assemble the consumable parts from electrode to shield cap.
3. Install the consumable parts in the cartridge
4. Install the shield retainer to complete the cartridge assebly.
page 5
Consumable Parts Life
Tips and electrodes wear under normal usage. Tips and electrodes should be
changed before failure to avoid damaging the other consumable parts or the material to be
cut. Optimum life will vary according to specific cutting conditions. Keep a count of cuts
per set of tip and electrode in a given application to establish the most effective time to
change consumable parts sets. The pilot arc is more erosive to the tip and electrode than
the cutting arc is, so an application that demands more pilot and pierce sequences will erode
consumable parts faster than an application that uses longer cuts but fewer arc starts.
Tip – Tips wear as the arc erodes the tip orifice. When the tip is no longer round or has
become enlarged, it should be replaced. Tip life is best when cuts are made at optimum
speed. Cutting too fast or too slow causes the arc to bend and biases erosion, resulting
in an orifice that is oval shaped.
Electrodes – The electrode wears from the hafnium or tungsten insert at the end of the
electrode. The face of the insert is liquefied by the heat of the arc and droplets erode from
the insert as cutting progresses. Proper gas flow will support longer electrode life.
An electrode should be replaced when the electrode insert is pitted to a depth of 1/16 inch
(see chart below).
Replace the Gas Distributor if it is charred or cracked
Replace the Gas Disributor if the flange is damaged in any way
Replace the tip and/or electrode if they are worn
Torch
Electrodes
Good Tip
Worn Tip
Good Electrode
page 6
Worn Electrode
Art # A-04745_AB
Amperage Plasma Gas Recommended Wear Depth
for Replacement
30
50
70
100
Inch mm
O2 0.04 1
Air 0.04 2
O2 0.04 1
Air 0.08 2
O2 0.04 1
Air 0.08 2
O2 0.04 1
H35 0.08 2
Art # A-04704_AB
Cut characteristics
Kerf Width
Cut Surface
Bevel Angle
Top
Spatter
Top Edge
Rounding
Dross
Build-Up
Cut Surface
Drag Lines
Cut Surface – Cut surface is influenced by process and positioner precision more than by other
parameters. For smoothest cut face on different materials, use: mild steel – oxygen plasma
Direction of cut – The plasma has a clockwise swirl as it exits the torch tip. Considering the
direction of torch travel, the right side of the cut will always show less bevel and top edge
rounding than the left side. Program cuts so that the right side will be on the finished part and
the left side will be scrap.
A-00007
stainless < ¾’ – nitrogen / WMS
> ¾” – H35 / nitrogen
aluminum < ¾’ – nitrogen /WMS
> ¾” – H35 / nitrogen
Left Side
Cut Angle
Right Side
Cut Angle
A-00512
Clockwise
Scrap
Counter-
Clockwise
Scrap
Workpiece
Art # A-04182
Top edge rounding – Caused by the heat of the plasma arc at the top surface of the cut.
Proper torch height control can minimize or eliminate top edge rounding. Excessive top
edge rounding is often a sign that torch cutting height should be lower.
Top spatter – Top spatter is caused by fast cutting or by too high a torch height setting.
Reducing cut speed or lowering torch cutting height will reduce top spatter. Top spatter is
easy to remove.
Bottom dross – Molten metal may build up on the bottom of the plate. Faster cut speeds
reduce bottom dross as less material is melted. Bottom dross that is easy to remove is an
indication of slow cutting speed. Bottom dross that is difficult to remove or requires grinding
is an indication of too fast cut speed.
page 7
Kerf – Kerf width is specified in the cut charts and can be calculated into cut programs.
The kerf width is related to tip orifice size and higher current cutting will produce a wider kerf.
Higher torch height will also result in a wider kerf.
Bevel angle – Precision cut processes produce bevel angle in the 0-3° range. Conventional
plasma cutting will produce larger bevel angles. Proper torch height control will produce the
smallest bevel angle, as well as improved kerf width and minimal top edge rounding. A slower
cut speed can be used when cutting circles and corners to reduce bevel.
Effect of Height Control Settings – General Purpose Cut
Correct Voltage
High Voltage
Positive Bevel
Wide Kerf
Top Dross
Minimal Bevel
Normal Kerf
Low Voltage
Negative Bevel
Wide Kerf
Nitride contamination – Air plasma cutting will produce nitride contamination of the cut face
on carbon steel and stainless steel. Nitride contaminated surfaces will require grinding before
welding to eliminate weld porosity. The depth of the contamination will be close to the Heat
Affected Zone, between .005 and .010” in depth.
Nitride contamination can be eliminated by using a process other than air plasma;
oxygen plasma for carbon steel, H35 or nitrogen/WMS for non-ferrous materials.
Cut speed – Cut charts specify a cut speed that will produce high quality cut performance.
Any plasma system can cut at faster or slower speeds, but cut performance will be affected.
Cut speed should be reduced for corners and tight curves to reduce bevel and corner rounding.
Optimum cut speeds produce a trailing arc which will be visible in the slight arc lines
visible in the cut face. Arc lines are useful for evaluating cut speed on mild steel, but less so
for aluminum and stainless steel. Arc lines that trail at less than 15° indicate that cut speed is
in the optimum range when air or oxygen plasma processes are used. Optimum cut quality in
precision cutting processes will result in arc lines that are near vertical. A slow cut speed may
show arc lines that angle forward and a fast cut speed will show arc lines at a sharper angle
relative to the top of the plate.
page 8
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