A Guide To Choose Between Manual Plasma Cutting And Mechanical Plasma Cutting

Machinery plays a vital role in our life. Our household gadgets, transport facilities and buildings are majorly made of metals. When some are easily malleable, some are not. Over the years, modern technology has developed by leaps and bounds and man has excelled in discovering and inventing methods to make life easier. One such technology is plasma cutting. This is very useful when huge volumes of metal are dealt with. Plasma cutting has allowed man create some truly amazing masterpieces.

Plasma cutting is widely used in construction industries, automotive industries and also for ornamental work like signage and art.

Plasma – An Introduction

Plasma is an ionized gas which is electrically conductive. It has the properties of a gas and produced in extremely hot conditions. It can reach temperatures up to 30,000F and has a speed of 20,000 feet per second. It is also called the fourth state of matter. It can be created by heating a gas to extreme temperatures and thereby ionizing it. Plasma has the same number of protons and electrons and by ionizing it, the number of electrons are either increased or decreased. Plasma works effectively in melting the metal which is to be cut and blows it away.

Plasma cutters were initially hand held or manually used to cut through different metals. Some metals which were very thick and those could not be cut using manual cutters needed higher speed and energy to do the task and hence mechanical plasma cutters were invented.

How is a Plasma Cutter used?

A plasma cutter contains a nozzle and an electrode inside a torch. When the device is switched on, the passing current creates the plasma and is pressurized. Usually a compressed gas is used – oxygen, air or any inert gas serves the purpose. The gas gets ionized due to the current and creates electrically conductive super hot jet of plasma. Now the electrode and nozzle which are usually in contact are pushed apart and result in a spark. This accelerates the plasma and current passes from the nozzle to the metal to be cut.

A hand held plasma cutter can cut metals like up to the thickness of 38 mm while mechanical computerized devices can cut metals up to 150 mm thickness. The thickness and the type of the metal used can determine the factors for choosing the type of the plasma cutter. Plasma welding gave birth to the idea of plasma cutting and is widely used on metals like aluminum, steel, stainless steel, copper, brass, titanium and cast iron.

Manual Plasma Cutting

Image Soure: Amazon.com

The very first plasma cutters designed in the 1960’s were massive and weighed tons and were used to cut through 6 inch stainless steel plates. The modern cutters used now are feather light despite being very powerful and are easily portable. The capacity of cutting various metals of different thickness has also been improved and one tool does it all.

The older plasma cutters used nitrogen or carbon dioxide as the plasma gas which was very expensive at that time. Nowadays shop air is used in the cutters and is very economical and the cut quality is also great for metals like aluminum and steel.

Any type of plasma cutter needs a direct current. In the earlier days, various power supplies like reactors and rectifiers were used. These proved to be expensive and tampered with the cut quality. Now  inverters and switch mode power supplies are used to provide current to the plasma cutter. Inverters are  the best for hand held plasma cutters as they are very light and portable. They are also powerful, economical and enhance the cut quality of the metal.

Mechanical Plasma Cutting – CNC method

Mechanical plasma cutting is widely used in large industries where heavy metals of higher thicknesses are required to be cut. The Computerized Numerical Control, CNC, method is faster, provides clean and sharp cuts of metals and is does not need manual intervention.

CNC has three types of configurations used. They depend on the metals used and the way they are supposed to be cut. The types are 2-dimensional, 3-dimensional and Tube and section plasma cutting.

Components of a plasma cutter

A Plasma cutter torch , irrespective of being hand held or computerized has the following components.

  • An electrode which carries the charge
  • A gas chamber to distribute the plasma
  • A nozzle to focus and deliver the plasma

The torch contains these elements and has been designed and improved over the decades. The modern designs ensure that the cutting performance is improved and the torch is more durable than the older versions. It is also ergonomically designed and checked for safety measures.

The manual cutters use either the high frequency starting method or the contact start method. The high frequency method is simple and reliable. A transformer is used to generate a high voltage spark in the torch which ionizes the plasma gas. This leads to the air flow between the electrode and nozzle creating an arc which then is used to cut the metal. One downside of the high frequency method is that it produces a lot of noise and it also needs regular maintenance.

In the contact start method, the ionized gas pushes the electrode and nozzle thus creating a spark. The spark then creates an arc for cutting the metal. These systems are less noisy than the high frequency systems.

Which one should you choose? Manual or Mechanical Plasma cutting?

  • A manual plasma cutter can cup metals of thickness of 30 mm to 40 mm whereas a mechanical plasma cutter can easily cut through metals up to 150 mm thickness.
  • A manual cutter is lightweight and portable. Mechanical CNC cutters are huge and usually fixed.
  • When you choose a manual cutter, the precision of the cut metal depends on the expertise of the user. The CNC cutters are programmed to work according to the metal and the necessity.
  • CNC cutters perform better than their manual counterparts and give sharper and cleaner cuts. Their different , flexible cutting heads provide 2-d and 3-d cuts.

Manual or hand held devices are perfect for small industries where the workload is less. But if you are looking at higher precision cuts and a huge amount of metal to be cut, the definite answer is mechanical plasma cutting.

References taken from :

www.wikipedia.org

www.thefabricator.com

  • Updated October 2, 2016