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What is sandblasting? What is shot blasting?

The sandblasting (or shot blasting) is a mechanical cleaning process through which it erodes the surface of a product by abrasion due to a jet of abrasive material, removing rust, paint, encrustations from any surface without damaging it, bringing it back to the original state.

Are used two main techniques: the compressed ait sandblasting (through the use of sandblasting machines) or the wheels shotblasting (through the use of shotblasting machines).

During the sandblasting with compressed air, with an air jet individual grains of abrasive material are projected at high speed on the surface to be cleaned. The small size of the grain increase the specific pressure on the point of impact, removing the layer you want to remove and by reducing it in powder form. At this point the granule, deflected by the impact, moves away from the blasted object in one or more pieces. This process results to be quite rapid because it allows an high machining speed, enough for the average of common mechanical operations. The speed of execution is very much influenced by the hardness and thickness of the layer to be removed, but also by the hardness of the underlying material.

Sandblasting: sandblasting and shotblasting machines  
  Nozzle for sandblasting with compressed air

To improve performance, you can take action on three parameters, the nozzle size, the type of grit, the size of the grit. Depending on the abrasive material and the type of shot that is used, surface finishes or textures, this procedure can also be applied to a piece for decorative purposes (glass sandblasting or marble sandblasting), or to prepare the surface for painting , also at powder.

Both the sandblasting and the shot blasting appear to be both an intermediate process to the working cycle of the product (it is one of the preferred processes for preparing the piece at a subsequent painting), and a finishing operation.

Some examples of removed layer may be oxide, paint, calcifications, a galvanic coating or plastic, etc.. At the end of the operation the underlying material to the removed layer is completely uncovered and with roughness dependent on the size of the grit used and by the pressure of the jet.


Sandblasting machines

The sandblasting machines are devices that, thanks to the action of the compressed air, pneumatically projecting the necessary abrasive for the treatment of materials, direct with regulators on the component. The sandblasting machines using a shooting system in depression or under pressure. The different applied technology enables the treatment of pieces by the characteristics of resistance, conformation and sizes, and allows to achieve results consistent with the requirements of the customer.

Shotblasting machines

The shotblasting machines (wheels) directly transform the energy of an electric motor in kinetic abrasive energy, making possible the movement of a wheel. Through this system, the shotblasting machine is capable of projecting a considerable amount ` of abrasive material at high speed, allowing the machining of a resistant layer, also of large size or large surfaces, such as, for example, rust, flakes, ground, or burrs.

Wheel for shotblasting  
  Glass beads for sandblasting and shotblasting

Abrasive for sandblasting and shotblasting

Plastic grit
The grit of plastic, it is mainly used for paint stripping aeronautical pieces, the deburring of electronic components, and the cleaning of molds.

Steel grit
The steel grit is the result of a series of operations that allow it to retain unchanged its quality over time. Thanks to this property, the metal grit can be used numerous times during the process of blasting. Can be used mainly two types of metallic grit: the spherical grit and the angular grit.

- Spherical grit: is the result of a merger operation, followed by a series of heat treatments that give it resilience and resistance to stress.

- Angular grit: is the result of a series of operations of crushing of the spherical granules. Subsequently is subjected to heat treatments that give it a structure suitable for the purpose.


Corundum (crystalline aluminum oxide)
The corundum or, otherwise known as crystalline aluminum oxide, appears to be resistant to wear and impact and is used in blasting for surface treatments for cleaning and blasting and / or shot peening. The corundum shape is broken and has a rough surface, what determines the removal of material and affects the treated surfaces. It results to be an inert abrasive material (it does not contain free silica) and therefore does not release undesirable components during use. The accurate control of particle size of the corundum allows to obtain consistent and repetitive results. The wide range of particle sizes and types of corundum allows application versatility.

Glass beads
The beads of tempered sodium glass, otherwise also known as crystal beads in some areas of use, are resistant to wear and impact and are considered average for an abrasive blasting and peening of metal. The glass beads are used in the sandblasting for the surface treatments, in operations of peening of stainless steel or aluminum, in which the finishing of the particular to be treated covers a central role for any subsequent treatment. The glass beads have a spherical shape and smooth surface, which do not determine for removal of material and does not affect the treated surfaces. Also, such as corundum, appear to be an inert abrasive material (not containing free silica) and therefore do not release undesirable components during use.

La sabbiatura: trattamento e finitura  
  Sandblasting and impact surface treatment engineering