Applications of laser: welding, drilling and cutting

APPLICATIONS OF LASER: WELDING, DRILLING & CUTTING

Let us discuss some of the basic applications of laser in industry.

Laser Heat Treatment

We know laser is a light beam of very high intensity, directionality and coherence. So, when laser light is focused on a particular area, even of micrometer size, for a very longer time, then that particular area alone will be heated and the other area will remain as such. This is called thermal effect (or) Laser heat treatment. In this process the light energy is converted into heat energy.

Instrumentation technique

Principle

The technique of laser heat treatment is used in Engineering applications like surface hardening, coating, glazing, alloying, cutting, welding, drilling and perforating holes in the materials and hence this process is called material processing. In general ruby laser, Nd‒YAG Laser and CO₂ laser are used for this purpose.

Instrumentation

The instrumentation for materials processing consists of a laser source to produce laser beam, shutter to control the intensity of the laser beam and an assembly of lenses to effectively focus the laser onto the specimen as shown in Fig. 10.21.

Apart from these instrumentation, separate control arrangements are made for removing the molten materials, smokes, fumes etc., with the help of a shielding gas jet, which consist of the assisting gases such as air, N₂, O₂, Ar etc. The powder feeder is used to feed the metal powder, wherever necessary.

Processing

Laser source is switched ON. The light reflected by the plane mirror is made to pass through the shutter. The intensity of the laser beam is controlled by the shutter and the controlled laser beam is allowed to fall on the focussing lens assembly. This lens assembly focusses the light effectively onto the window and is made to incident on the specimen.

Now the specimen gets heated, giving rise to smokes, fumes and molten materials. These smokes, fumes and the molten materials are removed immediately by blowing the assisting gas from the shielding gas jet and this inturn. makes the laser beam to continuously fall on the specimen, thereby increasing the cutting rate. Thus the materials can be drilled, cut, put holes etc. using this technique, effectively and easily.

In case of alloying, cladding, molding, welding etc. the power feeder will be used to spray the metal power over the specimen, during the focussing of laser beam onto the specimen.

Applications

Laser in Microelectronics

Laser plays a vital role in micro‒electronic applications, such as making photo masks (photo sensitive substrates on ICs), writing/ reading CDs and DVDs, designing thin film circuits, etc. as follows.

(i) Thin film technology

As the laser beam is highly directional, these beams are used to trim off a portion of metal (or) semiconductor film deposited on the dielectric substrate, by evaporation technique. Also, we can itch any number of microcomponents over the dielectric substrate to form an IC. Thus, by using as accurately controlled laser beam we can prepare thin‒film circuits including resistors, capacitors, etc.

(ii) CD/DVD

High power laser is used to write the data in the CD/DVD by creating pits (0's) and lands (1's) and low power laser can be used to read the data.

Laser Cutting

Laser is used as a tool to cut thin metal sheets by properly focusing the laser onto any particular area to be cut, for a longer time. Thus due to thermal effect the sheet is cut as shown in Fig. 10.22.

Laser Drilling and perforating holes

The same technique as used for cutting will be adopted for drilling and perforating holes, even upto 0.2 to 0.5 μm of thickness.

Thus, using thermal effect, with extremely high precision we can drill or perforate holes in any desired position.

Laser Welding

We know in ordinary welding process heat will be made to fall on the area to be welded, so that the material in that area will go to molten state. This on cooling will join the material. In this process the heat will spread all over the surroundings and will affect the other areas of the material and hence the material gets damaged.

To avoid this difficulty, laser is used for welding. Due to its high directionality, it is focused onto that particular area alone, even of very small size and the other area remains unaffected. Thus due to thermal effect the parts can be welded. This process is also called Micro‒Welding.

Advantages of Material Processing

1) There is no damage to the materials.

2) Time consumption is less

3) There is no need of machining after the processing i.e., after welding we can use the materials directly.

4) There is no need of vacuum, as needed in electron beam material processing.