What is Plasma Arc Machining (PAW) Process: Introduction, Process and Equipment's of PAW, Applications, Advantages, Dis-Advantages.

Plasma: Once a gas or air heated at high temperatures, the amount of collisions between atoms will increase. When you heat the gas above 5000°C, it partially ionizes into positive ions, negative ions and neutral ions. When you further heat the gas above 11000°C then, it completely ionizes. Such a completely ionized gas is called as Plasma. Plasma State lies in between temperatures 11,000°C to 28,000°C.

Introduction:-

In this method, gases are heated and charged to plasma state. Plasma is that the superheated and electrically ionizing gases at close to 5000°C.

These gases are focused on the workpiece in the mode of high velocity stream.

Working principle and method (process) details are shown in Figure.

 

Process details and equipment's of PAM :-

Plasma Arc machining consisting of following equipment's:

Plasma Gun: Gases are utilized to make plasma like, nitrogen, argon, hydrogen or combination of these gases. The plasma gun consist of a tungsten electrode fitted within the chamber. The electrode conductor is asign negative polarity and nozzle of the gun is given positive polarity. The stock of gases is kept up into the gun. A powerfull arc is well-established between the two terminals anode and cathode. There is a collision amongs molecules of gas and electrons of the established arc. Because of this crash gas molecules get ionized and heat is evolved. This hot and ionizing gas known as plasma is aimed to the workpiece with high velocity. The well-established arc is controlled by the provision rate of gases.

Power Supply and Terminals: Power supply (DC) is employed to develop 2 terminals within the plasma gun. A tungsten electrode is inserted to the gun and create cathode, and nozzle of the gun is created anode. Heavy potential difference is applied along the electrodes to establish plasma state of gases.

Cooling Mechanism:Due to continious supply of hot gases through the nozzle as a result, chances of its overheating. A water jacket utilized to encompass the nozzle to keep away from its overheating.

Tooling: There is no direct visible tool applied in PAM. Focused spray, plasma state gases behaves like as a cutting tool.

Workpiece: Workpiece of various materials can be prepaired by PAM process.These materials are aluminum, magnesium, tempered steels and carbon and composite prepares. All those material which may be processed by LBM can even be prepaired by PAM process.

Application of PAM :-

• The chief application of this method is profile cutting as dominant movement of spray focus purpose is simple just in case of PAM method.

• This is also suggested for smaller machining of challenging to machining materials.

 

Advantages of PAM :-

• It gives quicker production rate.

• Extremely hard and weak metals can be machined.

• Small cavities can be machined with acceptable dimensional precision.

 

Disadvantages of PAM :-

•  Its initial cost is incredibly high.

• The process needs over safety precautions that additional enhance the initial value of the setup.

• Some of the workpiece materials are abundantly susceptible to metallurgical changes on excessive heating thus this reality imposes limitations to this process.

• It is uneconomical for larger cavities to be machined.