Laser Machining Archives

THERMIT WELDING

Welding the parts by using liquid Thermit steel around the portion to be welded is called Thermit welding. this is a type of fusion welding process. In this process, neither arc is produced to heat parts nor flames are used. high temperature is being obtained by the usage of the exothermic reaction. Welding principle is the heat of the Thermit reaction used for welding in plastic state and mechanical pressure is applied for the joint.

It depends on the chemical reaction between iron oxide and aluminium. The reaction in thermit welding is that the reaction takes place about 30sec only and the heat liberation temperature is about 2800°C. It is twice the melting temperature of steel.

Working

Thermit is a mixture of aluminium and iron Oxide in the ratio of 1:3. This is placed in a furnace and it is ignited. On heating the chemical reaction takes place. Due to this, liquid and slag are formed which are used for welding.

The Thermit welding process is classified into two types.

1. Pressure welding process

During the pressure welding process, the following steps are adopted.

· The parts to be welded are butted and enclosed in a mould. The mould can be easily removed after the welding of metals.

· The heated iron stag is poured to the mould.

· Then the aluminium oxide is poured on the parts to be welded.

· This will create the heating of parts and then the pressure is applied on the workpiece to join.

2. Non-pressure welding

In this process, the following steps are adopted.

· The parts to be welded are lined up in parallel and a groove is taken in the parts.

· The wax pattern is formed in and around the welding parts.

· Then sand is rammed around he wax pattern and mould is completed with gate, runner and riser around the joint area.

· Then the mould is heated and wax is melted, it will give a space between the joint.

· Finally, the heated iron slag and aluminium are poured into the mould after solidification of liquid metal. Thus, the joint is made.

LASER BEAM WELDING

The word laser sands for light Amplification by the stimulated emission of radiation.

Principle

Light energy is converted into heat energy. Here, the light energy is produced from the laser source like ruby rod in the form of monochromatic light.

Working

Electrical discharge from the capacitors makes the flash tube converts the electrical energy into light flashes. Then ruby rod is exposed to the intense light flash. This helps the chromium atoms of the crystal excited and pumped to a high energy level beam. This high energy level is immediately reduced to intermediate and drop to original state with the evolution of red fluorescent light.

This laser light is intense and can be readily focused without loss of intensity. The laser light is focused by the focusing lens to the work piece in the form of coherent monochromatic light.

The light energy is impacted to the work piece. This light energy gets converted into heat energy. This heat energy is sufficient to melt the materials to be welded. The various laser forms that are generally used are Liquid laser, Gas laser, Ruby laser, Semi-conductor laser.

Posted in: laser beam welding process, Non-pressure welding, Pressure welding process, Thermit Welding Process, Types of Thermit welding process, Types of Welding process, working principle of laser beam welding process, working principle of thermit welding process

Laser Machining Unconventional Machining Process

Plasma Arc Machining | Laser Beam Machining

By magnaparthi on 21/04/2020

Plasma arc machining

When a free flowing gas is heated to a very high temperature it becomes partially ionized. This ionized gas is called as plasma. In this process metal is removed from the surface of the work piece with the help of high temperature plasma. Metal is also moved as a result of electron bombardment.

This plasma arc machining has a gas chamber which is fitted with a copper nozzle at the bottom. A tungsten electrode is held vertically in the gas chamber. The tungsten carbide is connected to the negative terminal of the D.C supply d the nozzle is connected to the positive terminal of the power supply.

When the power supply is given, an arc is produced between the tungsten electrode and the copper nozzle. A di-atomic gas is passed through the gas chamber. Hydrogen, nitrogen, oxygen are the generally used di-atomic gases. This gas is permitted through the arc. The arc heats up the gas and it gets ionized due to high temperature. This ionized gas flows out of the nozzle in the form of a flame known as plasma flame. This plasma flame is forced on to the surface of the work piece. The high temperature of the plasma flame melts down the metal. As a result of the action of bombardment of the ions on the surface of the work piece the metal is eroded.

The metal removal rate is controlled by controlling the flow of the di-atomic gas. Vast using of the tungsten electrode in the same position leads to the erosion of the electrode so it has to be frequently adjusted. Ware of the nozzle is minimized by cooling with the help of water.

It is used for cutting stainless steels and aluminium alloys. Profile cutting and slitting in hard materials can be done using this method.

Laser beam machining

Laser is an electromagnetic radiation. A beam of same wavelength is focused by a lens on a very small spot on a work piece. The laser beam emits high heat which can melt and vaporize any type material.

This equipment consists of a ruby crystal. The crystal is placed inside a flash lamp coil. The flash lamp is filled with xenon gas. When the flash lamp is switched on it gives high intensity light. The ruby crystal is stimulated and it emits the laser beam. By using a lens the beam is focused on the work piece. The work piece is fed past the beam. The portion of the metal is melted and vaporized.

This type of machining is also known as micro machining method. Which is used for producing very fine and minute holes. It is also used to machine very hard materials. Holes in surgical needles,oil or gas orifice are drilled using this method. Complex profiles in thin materials like ceramic can be cut using this machine.