Shot blasting has been helpful to many industries since the first machine was used in the 1900s. This was because manufacturers sought to have better and faster surface cleaning and preparation that was better than the most popular technique at the time, sandblasting. In the article below, I will take you through a detailed guide that will explain Shot Blasting and the shot blasting process.
What Is Shot Blasting?
This is a method used to clean rust and paint off a surface or to prepare such surfaces for further work. Beads made of copper, aluminum, or steel are blasted at high speed onto a surface, and this action helps to achieve the desired results. It is an eco-conscious method that gets the job done on metal or concrete without the need to use harmful chemicals.
This sand blasting process is beneficial in numerous industries, including the automotive and aerospace industries. This sand blasting process utilizes kinetic force generated pneumatically or centrifugally to propel the media on the surface. Centrifugal force is created if the sand blasting machine has a wheel spinning at a high velocity. In contrast, pneumatic force is achieved through compressed air or fluid. While shot blasting and grit blasting are sometimes used interchangeably, it is essential to note that the former only refers to the use of spherical media, while the latter uses angular grains.
Types of Media in Shot Blasting
The term shot or media may be confusing, but this simply describes the abrasive used during blasting. Media vary based on their mineral composition, hardness, shape, and grade. Different shots will produce different results, making them a critical aspect of any sand blasting process. The various types of media that can be utilized include:
Non-Metallic Abrasives
These types of abrasives are especially useful when a project demands an even more environmentally conscious media. They are also perfect for use on sensitive surfaces because they are less aggressive to the other media used in the sand blasting process. They offer deep penetration that cleans and prepares the most demanding yet sensitive surfaces. Some examples of non-metallic media include aluminum oxide, glass beads, plastic, and garnet.
Spherical Abrasives
Round spherical media is most useful in desanding mechanical parts, preparing concrete surfaces for coating, and peening structural surfaces. Spherical abrasives are ideal when uniformity is the desired result. These abrasives can also be used for many cycles, making them the most cost-effective to use in big projects.
Angular Abrasives
These abrasives are best used on tough paints or coatings, to prepare surfaces exposed to extreme conditions before an adhesive is applied, and to remove contaminants. Angular abrasives come in various hardness degrees so that they can create a rough surface that will firmly hold coating, especially where zinc primers will be used.
Step-by-Step Blasting
Shot Blasting is a process that is quite easy to do but demands that the right steps are taken to achieve the best possible results. The key steps in the sand blasting process are:
1.Preparing the Surface
It is advisable to always start by chemically or mechanically preparing the surface to be blasted. This includes removing contaminants, debris, and oils to ensure that the treatment is even more effective. Solvents and brushes can be used in the initial surface preparation stage. It is important to note that the pre-blasting process will affect how well or not the desired effects will be achieved.
2.Set up the Equipment
Start this step by ensuring that the air compressor, blast cabinet, and abrasive media are set up correctly. Set up the blasting conditions like the media flow and air pressure that will be needed to get the job done. This may mean that after the first blast, the parameters will be adjusted accordingly to get the required results on the surface. Subsequent actions should support the sand blasting process to create better results, such as blowing compressed air, washing, and vacuuming the surfaces.
Components of Shot Blasting Tools
There are mainly six components that make up any efficient blasting tool, and these include:
1.The Media Delivery System
Enclosed centrifuges and air compression are two primary forms of delivering media during the shot blasting process.
With an air compression tool, the media is either inserted manually or mounted on the mechanical arm. Individual rotating impellers are used to eject the media at a high speed in different directions in a centrifuge-powered tool. The turbines can either move left to right or up and down. This is the most vital component of any blasting tool.
2.The Material Recovery System
One of the aspects that makes blasting equipment efficient and economical to use is that it all has a material recovery system. What this part does is to instantly collect the used shots and feed them back into the system. There is also the filter or separator section that ensures the collected media is cleaned and free from contaminants before it is reintroduced into the equipment.
The material recovery system allows for repeated use of the same media for numerous cycles. The systems of collecting, separating, and transporting media are interconnected so that the material can get back to the designated location as quickly as possible.
3.The Air Filtration System
The dust collector is an essential component in preserving air quality during the blasting process. As the media hits the surface being worked on, tiny fragments may end up in the air and compromise the air quality. It is highly recommended always to check that the dust collector is in proper condition to ensure good working conditions.
Replacing cartridges and installing baffles is a sound way to keep the dust collector working as it should and reduce the presence of substantial volumes of contaminants in the air. The dust removal system also ensures that dust does not collect inside the machine, as this might affect its effectiveness. The goal is to ensure that the dust will not affect the internal components and affect the speed of the release of the media.
4.The Blasting Area
The blasting cabinet is made from materials that significantly reduce contamination, spillage, and ricocheting of the shot during the shot blasting process. In most cases, the blasting area will be enclosed, and this will aid in reducing the air pressure and subsequently the chances of contamination of the surface being prepared or cleaned. These vibration-free blasting cabinets are usually made from hardened steel to promote durability.
5.The Transport System
Blasting machines that handle bulky work or spinner hanger machines will have a transport system. This system delivers the surfaces to be worked on inside the equipment. It ensures that it is safely and securely placed before blasting begins.
There should not be any compromises with the transport system because having the equipment operator secure the surfaces to be worked on would be time-consuming and unsafe. This carrier system ensures that large pieces are delivered to the blasting zone and moved out just as quickly to keep the process as smooth as possible.
6.The Control System
Even if the blasting machine is automated, the operators need to know how to pause, halt, and start the process. Knowing where the stop button is must-have information for any operator as it may be required to be pressed manually in case the process doesn’t stop automatically. It is good practice to understand how the blasting machines, even the automated ones, work to ensure a quick response in case an issue arises.
Applications Across Industries
Versatility is the word that best describes the shot blasting process. This type of blasting can be used across different industries and proves effective each time. Some of these industries that use this type of blasting include:
1.Construction and Infrastructure
In the infrastructure sector, this type of blasting can help to remove mill scale and rust from reinforcing bars and steel beams so that any coatings applied on them grip better and last longer. Before adhesives and epoxy coats are applied on concrete floors, it is a good idea to shot blast the surface first. This should be done using angular media to make the texture rough and more receptive to adhesive.
2.Automotive Industry
Different parts of a car need to be in excellent condition before they are used, and blasting comes in handy to ensure quality is maintained. Blasting removes rust from corroded parts and also ensures that the surfaces are free from defects that may interfere with further processes to be done on the car.
This type of blasting is not only helpful when manufacturing new cars but also in refurbishing old car parts. This process can restore such parts to a state as near the original as possible. These parts can be reused, and this saves money and is an eco-friendly way to reduce wastage.
3.Marine Industry
Corrosion thrives and accelerates in saltwater. This blasting is an excellent option for ships because it gets rid of any rust and growth quickly and thoroughly. The other added benefit of the shot blasting process makes the surface more conducive when protective coating is applied.
4.Aerospace
Safety is one of the aspects that is given great significance in the aerospace industry. Blasting fuselage panels and the turbine blades increases their useful life span and fatigue resistance. Because this process removes all the contaminants that may hinder a non-destructive test, any inspections done after the blasting are more accurate, which directly translates to increased safety.
Benefits of Shot Blasting
The benefits of using this type of blasting are extensive and include:
- This blasting is an excellent option for tough materials because it guarantees more impurity removal.
- This method can be used on concrete, metal, wood, and other surfaces.
It works more efficiently than other methods generally used for preparing surfaces. - It is a cost-effective option because the results last longer, and thus no need to replace parts regularly.
- Provides a better surface for applying adhesives, paint, and other coatings.
- Helps to reveal surface defects and is also helpful in smoothing out such issues.
- It is an environmentally sound process of preparing and cleaning surfaces without the use of harmful chemicals or acids.
- There is minor cleanup needed after the surface is blasted.
- Most of the media used is recycled, so new shots do not have to be used in each cycle.
- The dust filtration systems in the blasting equipment make it possible to work in an environment free from air pollution.
Limitations of Shot Blasting
While this blasting method has numerous benefits, it also has some limitations that are worth noting. These limitations are:
- It can only be done using specialized equipment that should only be used by trained personnel.
- Operators need to wear protective clothing because the process causes noise pollution and some of the materials removed from the surfaces may contain harmful chemicals like silica.
- It is not a method that should be used on thin materials and extremely delicate surfaces.