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A Guide to Shot Blasting / Shot Peening

Shot peening (also known as shot blasting) is a surface conditioning process carried out after various manufacturing processes. In simple terms it increases/improves the surface finish. Shot peening is done with the help of small balls which are streamed out in the form of a jet at very high velocity, accelerated and directed toward a work piece. Compressive force is applied when they strike the surface of the work piece one after the other. The point of application of each shot is slightly different from the other as one shot hit will slightly overlap the area of others shots around it.

Shot blasting machine

Description of shot blasting process

As we mentioned above, shot blasting is a surface conditioning process.  Small metal ball, called the shots, are used to induced the residual stress on the surface of the work piece. The process is described as a cold rolling process. Plastic deformation of a work piece is achieved by the help of compressive force applied by the high velocity shots. These produce a series of small dimples overlapping each other. Residual stresses induced on the work piece surface increases its fatigue resistance due to a compressed top layer.

The process uses what is called a peening chamber which has a turn table at the bottom. The workpiece is placed on the table which can only rotate around its axis. A shot nozzle is placed on the top of the peening chamber which can move forward and backward – a ventilation duct is placed on the top opposite to the nozzle. The table rotates to enable the shot peening of different sides of the same surface. The nozzle moves around the shot peen area between the centre and outer most edges of the work piece.

 

Applications

Materials used in shot blasting

Metal parts before and after shot blasting.

Most ductile materials can easily be produced using this process as it requires plastic deformation to get the output. However, brittle materials are more difficult to process but can still be processed to a certain extent. Some particular materials which can utilise this process include:-

Mechanical Design Guidelines

Process Variations

Economics of the Process

Advantages of shot blasting

Disadvantages