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A
plasma cutter cuts metal by sending air or an inert gas through a
plasma torch, sparking an electrical arc, and then forcing plasma
through the torch tip to cut metal. The arc of a plasma cutter can
reach temperatures of 45,000 degrees F and provide one of the fastest
ways to cut metal.
Plasma cutters have an on/off switch and an
amperage setting that determines how much power to use for cutting.
Provided the plasma cutter has enough power to cut through the metal
workpiece, plasma is often a very safe, efficient, and clean way to cut
metal.
While many mention the advantages of plasma over
oxy-fuel cutting, a plasma cutter requires a significant up front
investment. Though a plasma cutter will certainly pay off in the long
run with its speed and low operating costs if you need to cut a lot of
metal, it can be daunting to
select the right plasma cutter for your business or home workshop
needs.
The following guide will introduce some major factors
to consider when purchasing a plasma cutter as well as some helpful
links to the Baker's website where you can learn more about plasma
cutters and related products.
Match Your Plasma Cutter to Your Work
As
with purchasing a welder, the kind of plasma cutter you select will be
determined by the kind of work you do. Unlike oxy-fuel cutting, a
plasma cutter is capable of cutting just about every kind of metal.
Therefore, the main consideration when choosing a plasma cutter is the
thickness and amount of metal you plan on cutting. Below are some key
questions to ask when trying to match a plasma cutter to your work:
- Are you cutting thick metal?
- How often will you use your plasma cutter?
- Do you need a portable unit?
- Are you willing to adapt your power outlets for your cutter?
- Do you have a generator you plan to use with your plasma
cutter?
- Will your electrical current fluctuate?
As
you review your plasma cutter options, these questions will
narrow
down your choices. While certain units will stand out for your
particular needs, it's likely that choosing between brands will come
down to what you're used to or what's recommended to you. The main
difference between brands is that one manufacturer's standard feature
may be an extra on another brand's machine.
There
also are combination units that include a plasma cutter with a stick
and TIG welder. If you just want a plasma cutter for the occasional
job, this may be a great option provided you can find a unit that meets
your TIG or stick welding needs.
If you do decide
to look into a portable unit that is light and runs off a generator,
look for a unit that can handle the fluctuating power of a generator.
Explore
Plasma Cutters
Choosing a Plasma Cutter's Output Power
The
output power of a plasma cutter will determine what it can cut. For
example, 12 amps of output power from a 120V machine will be able to
cut most 1/8 inch metal, while 60 amps of output power from a 230V
machine will be able to cut most metals that are 7/8 of an inch thick.
There also are inverter-based plasma cutters available that
provide high
cutting output power, yet weigh much less than regular cutting machines
that offer the same cutting capacity.
Explore
Miller's Guide to Output Power and More
Choosing a Plasma Cutter's Cutting Speed
The
cutting speed for plasma cutters is typically noted as Inches Per
Minute (IPM). Your work flow and priorities will determine what you
need, but keep in mind that while two plasma cutters may be able to cut
through a 1/2 inch of metal, one may cut through the metal in a minute,
while the other could take as long as four or five if it has a slow
cutting speed. Choosing a machine with the right cutting speed can make
the difference between a sound investment and a dip in your
productivity.
Choosing a Plasma Cutter's Duty Cycle
The
duty cycle of a plasma cutter is the amount of time it can operate
continuously within a ten minute span before needing to cool off. A
five minute duty cycle means a plasma cutter can run for five minutes
before needing to cool off for five minutes. If a machine is run at a
lower power, the duty cycle may be extended, though excessively hot
operating conditions may shorten it. Using a machine beyond its duty
cycle will cause it to overheat.
A longer duty cycle will be
ideal for making long cuts or deep cuts on large pieces of metal, while
a shorter duty cycle is ideal for a home shop where a series of small
cuts are made regularly.
Choosing the Right Torch for a Plasma Cutter
There
are two common types of plasma cutting torches. The most common torches
are the high-frequency starting systems that create a spark with
a high-voltage transformer, capacitors, and spark-gap
assembly.
High frequency torches have the advantage of not using any moving parts
and therefore remain fairly dependable. However, they do require
occasional maintenance and may create electric noise that can interfere
with computers and other nearby electrical equipment in your office,
shop, or home.
Another option is the contact start torch that
uses a moving electrode or nozzle in order to produce a spark that
lights the pilot arc. This kind of torch does not create inference with
other electrical items and turns on instantly without a pre-flow cycle.
An excellent feature to explore in a torch is a drag shield
that attaches to the cup of the torch and holds the tip at the ideal
1/16 to 1/8 of an inch from the metal being cut--this distance is known
as the "stand off." The torch can be operated at full capacity with a
constant standoff. The standoff distance is based on the thickness of
the metal and the amount of amperage used to cut it, with low amperage
cutting requiring little to no standoff distance.
If you plan
on working on thin metal, you will most likely only need a single flow
torch that works with limited amperage and does not require an extra
flow of shielding gas in order to cool the torch. For larger cutting
operations or users who plan on cutting thick metal, a dual flow torch
with a shielding gas will make it possible to cut thicker metal at a
high amperage.
Regardless of the way a torch ignites the
plasma arc or utilizes a drag shield, choose a torch design that fits
your hand well, especially if you plan on using it for extended periods
of time.
Explore
Plasma Cutter Torches
Choosing Your Consumables for a Plasma Cutter
After
making the initial purchase of a plasma cutter, the most important
ongoing cost will be the cutting tips and electrodes. Therefore, before
you pick up a plasma cutter, learn as much as you can about how fast
your machine will use these items. A damaged tip from poor technique or
a worn out electrode will either slow your cutting speed or reduce the
quality of your cuts, and it's often recommended to change the tip and
electrode together in order to achieve best cutting
performance.
David
Cook of The Fabricator suggests the following equation for
determining the ongoing cost of plasma cutting units:
"Consumable
cost, or the total consumable cost divided by the consumable life in
hours of arc-on time per hour, is the most useful measurement. For
example, if the cost of a nozzle is $4, the cost of the electrode is
$6, and together a set lasts 2.5 arc hours, then the cost per hour, or
CPH, is ($4 + $6)/2.5 = $4."
Explore
Plasma Cutter Consumables and Parts
What Else to Consider for a Plasma Cutter
As
with any large piece of machinery, it's important to test out a plasma
cutter or to at least make sure the retailer offers a good return
policy if the cutter does not live up to its promises. In addition, a
reliable warranty will ensure your investment in a new cutting system
will be a sound one for the long term.
Explore
Plasma Cutter Accessories
Read More About Plasma Cutters
Written Exclusively for Baker's Gas and Welding by Ed Cyzewski
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