Difference between HF and Pilot arc
Difference between HF and Pilot arc
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What is plasma?
In order to explain what plasma cutter machine is, we must
know what kind of material is plasma.
As somebody said once, “plasma is the fourth state of
matter” together with the other three forms, which are solid, liquid and a gas.
Plasma forms artificially when heating a neutral gas or put it under strong
electromagnetic field.
The same is the principle under which plasma cutter
machines are functioning.
In these types of machines the plasma forms when specific
gases, for example oxygen, argon or hydrogen, are forced through a nozzle
inside a torch and then arc appears into this high pressure gas flow.
Then the
result is something known to the science with the term “plasma jet”. The plasma jet quickly reaches
very high temperatures. Exactly this substance, called plasma jet, is used in
plasma cutter machines, which nowadays are widely used in the industry and as
well as at home.
How HF plasma cutter machines & pilot arc plasma cutters work
HF plasma cutter machines and pilot arc plasma cutters are used to
cut metals and other materials having electrical conductivity.
Cutting
different materials with plasma cutters turns out to be much faster, quite easy
and rather more precise compared to the usage of traditional cutting tools,
like angle grinders for example.
As we mentioned at the beginning, the plasma used in this
type of cutter machines is a gas, which is highly ionized and is warmed up to a
very high temperature.
This gas transfers the power of the arc to the workable
material.
Then the great heat induces melting and bloating of the workpiece,
which leads to its cutting via the plasma arc.
After the compressed air enters the plasma cutter, the
built-in air chamber distributes two separate fluxes – one for the plasma gas,
and the other for the subsidiary gas.
Plasma gas arc serves as a melted metal and the subsidiary
gas cools the various parts of the cutter and blows the melted metal.
During the years this technology was developed and now on
the market there are two types of plasma cutters – HF plasma cutters and arc
plasma cutters.
What is HF plasma cutter machine and how it functions
First, let us explain what “HF” in plasma cutter machines
means.
It is an abbreviation for “high frequency”, which makes clear that these
type of machines use high frequency circuit to ignite the pilot arc.
Imagine
this process similar to a usual everyday activity – something like when you get
into your car and turn the key or press a button to start the engine.
Then the
spark plugs deliver an electric current from the ignition system to the cylinder
of the engine, where the compressed fuel is ignited.
In the case of HF plasma cutter machines, the electrode and
the nozzle are in a fixed position.
The HF plasma cutter arc jumps the gap and
the air blows the arc out of the nozzle.
The high intensity spark inside the torch, used to heat the
plasma gas in HF plasma cutters, is obtained by high voltage high frequency AC.
The discharge is transmitted to the torch through wires. Most of modern industrial
plasma machines use the high frequency method, because it is considered to be
the more reliable, especially concerning the high duty industrial environment.
It can guarantee better, faster and more precise cutting quality, which is mandatory
for business and professional use
Some pilot arc plasma cutting machines that use contact start have
a moving electrode inside the torch.
Then the main DC power is activated in the
plasma torch, and just a few moments later the gas flow starts in the torch.
This quickly creates a short circuit spark, which ionizes the gas flow through
the torch.
A significant part of modern plasma cutters on the market
today use this technology for hand and mechanized cutting machines
The reason for this wide usage is that this type of
equipment is a way too customer-friendly –pilot arc plasma cutters can start the arc
without touching the workpiece.
The other main advantage is that the pilot arc can
be started on almost any kind of metal surfaces, no matter if they are painted,
greasy, rusty, etc. And one of the other big advantages is that it
can be used with
CNC machines – computer numerical control machines, where the
built in computer software can accurately control the position and the velocity
of the details.
Plasma cutting torches
From the time when first plasma cutting machines were
invented, the torches they used then evolved significantly till nowadays.
Now
those torches differ significantly because of the mechanism which starts the
plasma arc – if it is HF plasma cutter or pilot arc plasma cutter.
In the most widely spread small hand-held cutting machines
with maximum 100A the torch can handle easily most of the jobs that have to be
done.
One of the most common one used in custom tasks is the 75-degree or
90-degree torch, which has the form of the letter “L”.
Another commonly used torch is the so called “15-degree”.
Obvious from its name, it has a 15 degree angle, which actually is slight,
which directs the torch in almost upright position.
This kind of angle provides
the operator of the machine a greater visibility and better control over the
arc.
This type of torch is suitable for cutting corners, for example.
On the market there is a wide variety of torches, but the so
called “Long Torches” are 45 and 90 degree.
They are longer than the 75, 90 and
15 degree torches and can be used when the operator of the machine for a
various reasons doesn’t want to be close to the material he is working over.
With this kind of torches there is no need the worker to bend over.
Long
torches are perfectly suitable for cutting objects, which are placed higher
above the operator, so he doesn’t need to use ladder.
Apart for the commonly used torches, there are various other
types, including ones for mechanized cutting.
180 degree full length machine
torch can be used on portable tools and most type of CNC tables.
The other one
– 180 degree mini machine torch is used when the common torch is too long,
because as its name states, it’s a bit shorter.
Robotic torches are used in big industrial enterprises,
where they can be put quickly in a robotic arm and can perform holes, clamps,
etc.
Like all other torches they vary in shapes and angles, depending on their specific
purpose and the needs of the operator of the machine.
Manual plasma cutters
For years now, manual plasma cutters, which use maximum 100A,
are well known on the market and sold by many dealerships and big chains in
most of the countries around the globe.
There are many various brands, which
have one in common – all of them are portable and lightweight.
All these manual plasma cutters produce torch, which is much
smaller than the models, using higher current.
Anyway, they can efficiently cut
steel and have many advantages, compared to the more powerful machines of this
kind.
The main advantage, as already mentioned above, is that they
are portable and not heavy, so can be easily transported.
It is not necessary those
machines to be positioned and fixed firmly at one place, without the
possibility to move them.
Using such a plasma cutter with maximum 100A to a big extent
decreases the risk of distortion.
That means that the metal is highly unlikely
to change its shape during the cutting process.
Nevertheless, this type of
equipment provides rather precise cuttings and is capable of working in all
positions.
With manual plasma machines the process of cutting the
metal is fast and it works on various types of metals.
On materials such as
stainless steel and aluminum the cuts are slag-free. And least, but not last –
one other main advantage is that no gas cylinders are required at all for this
manual arc plasma cutters to function.
Disadvantages
And as we mentioned the advantages, it will be pretty fair
to mention and the disadvantages, which are just a few compared to the pluses.
If not operated properly, there is a risk of electrical
shock for the operator of the arc plasma cutter.
This condition is dangerous
and life-threatening. Always have in mind that these types of machines needs
two essential conditions to function properly – clean air source and
electricity.
When buying such a machine one must have in mind that it is
not cost effective for very thick steel over 40 mm but anyway it can cut the most
commonly used materials.
Plasma cutting consumables
Having high quality consumables for your plasma cutter
are vital for the good work and perfect cuts on the
material.
Even the smallest faulty or low quality component can cause a severe
damage on the work piece and can influence the efficiency of the machine and
its entire performance.
So, for successful cuts with manual plasma cutting machines,
one has to watch strictly the four essential consumables.
These four are the
ceramic shield, the swirl ring, the nozzle and the electrode.
No one can give exact time frame how much time consumables
will last.
But in all cases, the operator has to be careful and to watch if they
are properly maintained.
The durability of the consumables can very different,
especially when hand-held systems are involved.
Their durability depend on many
factors, including the skills of the operator of the machine, his work experience,
the thickness of the materials, the type of the material itself, etc.
The best advice from professionals is that the consumables
must always match to the application.
It is neither a good idea, nor recommended
lower or higher amperage consumables to be used.
Only the stated in the user’s
manual consumables have to be used, which guarantees proper and safe
functioning of the arc plasma cutter.
Protection while working with plasma cutters
Before first use, read carefully the manual of the
machine.
If you don’t understand something or the manual is not quite clear,
call your local dealer and ask for a clarification.
It is recommended the plasma cutter machines to be used in a
dry place, as the wet and damp environment increases the risk of electric
shock, which is a life threatening condition, potentially lethal.
It is highly recommended the use of ear protection. Plasma cutting makes loud noise with the compressed air flow and will harm your hearing.
Flame resistant clothes are essential, especially long
sleeve shirt and long pants, covering the sensitive parts of the body.
Always wear gauntlets and auto darkening hood, set to a
darker level. Avoiding wear darkening hood can harm your eyes.
Wear safety shoes, as they are designed to protect you in
case of an accident with the plasma cutter.
Try not to breathe the air near the plasma cutter, as it is
full of dust and small metal particles.
If it is possible, mount a fan over the
place where you use the plasma cutter.
Be extremely careful.
The plasma cutter can cut everything
that conducts electricity, And can burn you very badly.