Shot Blasting Machine
Shot blasting is a process for the removal of contaminates and impurities from the surfaces of metals and steel. Though the term, shot blasting, is all encompassing, other words are used to describe the process such as grit blasting, abrasive blasting, peening, and media blasting. Which descriptor is used depends on the machine’s manufacturer or the main use of the machine.
There are three basic purposes for shot blasting – cleaning, enhancement, or the manipulation of the properties of a metal. Industries like ship building, aircraft maintenance, casting and foundry industries, forging, rail production, vehicle painting, and alloy wheel cleaning depend on shot blasting machines as a means of cleaning or preparing metals.
For the purposes of cleaning, shot blasting machines are an effective method for removing contaminants or roughen a surface prior to applying primer or a coating. This usage is important for metal working industries that require their products to have a coating or sealant. The blasting force removes rust and welding slag or scales to create a uniform and smooth surface for finishing or preparation for painting.
The painting of a metal surface requires it to be roughed or textured for a coating to able to adhere. To achieve a sufficient grit, the surface is treated with a shot blasting machine that uses an abrasive to add the appropriate gradation. Once the blasting process is completed, the metal can easily be painted and sealed.
A special function of shot blasting is to strengthen the material properties of a metal by applying stress to its surface. When the process is done correctly, the surface of a metal is expanded creating a layer of compressed stress while relieving its tensile stress. This form of shot blasting is referred to as peening.
It is easy to get the terms sandblasting and shot blasting confused since they seem to describe the same function. Sandblasting uses compressed air to shoot some form of abrasive against a surface. The process of shot blasting is built around the use of centrifugal force to propel media at a surface and is a far more aggressive operation than sandblasting.
Surfaces that require shot blasting are normally larger and more difficult to manipulate requiring a strong application of force with denser media material. Shot blasting demands very strict safety procedures and stringent containment. The National Institute for Occupational Safety and Health (NIOSH) and OSHA have established a set of regulations regarding shot blasting machines. The process is usually used for restoring automobile frames or cleaning large steel containers.