A complete Guide to Shot Blasting Machine, How it works and the Process of Shot Blasting?

Shot Blasting Machine

Shot Blasting Machine Manufacturers in India often use the term ‘Shot Blasting’ to define various processes such as Grit Blasting, Abrasive Blasting, Shot Peening and Media Blasting. While the process of Shot Blasting remains the same, a shot blasting machine may vary in capacity, size and structural design. 

A shot blasting machine makes use of a mechanical method of propelling abrasive using a centrifugal wheel to remove a layer of deposits and impurities from the surface of metal and steel products. There are three basic purposes that require the need to shot blast before finishing the product:

  1. To clean and de-scale a surface in metal castings & forgings.
  2. Enhance the Paint & Coatings adhesion to the surface of metal products.
  3. To change the properties of the metal or steel surface by removing the deposits & impurities.

What is a Shot Blasting Machine?

A Shot blasting machine is an enclosed equipment designed for abrasive blasting for cleaning and preparing metal, stone and other surfaces. It is a machine for shot peening, cleaning metal parts such as forging, casting parts, steel surfaces, heavy metal structures, rusted metal parts etc. Shot blasting machine uses blast media on the metal parts in an enclosed chamber to remove surface rust, welding slag and descaling, making it uniform, shiny and improve coating quality of anti rust chemicals. Shot Blasting Machine Manufacturers in Pune, Mumbai, Hyderabad, Faridabad, Punjab, Jalandhar, Jamshedpur, Jabalpur, Bangalore, Coimbatore, Chennai, India offer steel grit blasting machines in various sizes and capacity with the lowest being 80kgs load capacity.

Shot blasting machines have an enclosed chamber for shots and grit blasting purpose and has a bare wheel that continuously rotates at very high speed, blasting media such as steel shots, steel grits or cut wire shots on metal parts for surface finishing purpose. The capacity of each bare wheel goes from approximately 60 kg per minute up to 1200kg/min.

Shot blasting machine also have a dust collection system to prevent tiny particles, contaminant, dust particles etc. from escaping out of the machine into the surrounding. A dust collector connected with a Shot Blasting Machine prevents wastage of abrasives as well as prevents environment. As a leading manufacturer of Shot Blasting Machine in India, MGI manufactures highly reliable, low-cost shot blasting machine that are completely dust and pollution free.

Shot blasting machine (3D visualization)

There are various types of shot blasting machines for blasting different types of metal and steel parts such as:

  • Tumble Blast shot blasting machine (vibratory belt motion)
  • Table Type
  • Hanger Type
  • Stone Shot Blasting
  • RBM (Rotary Barrel Type)

The kind of metal part or steel part that you have to blast, its shape, design, weight and size decides the type of shot blasting machine you need.

Shot Blasting Process and application of Shot Blasting Machine

Shot Blasting is the process of cleaning a surface such as iron, steel, cast-iron parts, forgings, rusted pipes, iron bars, engine and automotive parts by blasting abrasive material such as steel shots or steel grits at very high velocity utilizing the centrifugal force generated by high speed rotating disk in a shot blasting machine. Shot blasting machine is also used to alter the mechanical properties or various components, increasing resistance to fatigue for springs, gears, etc.

Compared to sandblasting process shot blasting does not produces large amounts of dust and is much more environment friendly that’s why also called Dustless Blasting. A shot blasting machine is like a closed chamber so the dust particles generated at the time of blasting process remain inside the chamber and does not pollute the environment. Shot Blaster Machines for sale in India are available at competitive price from the best Manufacturer of Shot Blasting Machine.

How does an Abrasive Blasting Machine work?

  • Operation:

The door of the machine is opened and components are loaded onto the endless rubber belt conveyor of the machine.The rubber conveyor belt tumbles the components and ensures adequate exposure of the components. The abrasive at high velocity falls upon the tumbling components and clean them. After blast cleaning cycle is over, the blast wheel is shut off and door is opened. The components are unloaded on the trolley by moving the conveyor belt in reverse direction. Always ask the manufacturer of Shot Blasting Machine for the quality of the conveyor belt to ensure long lasting blasting capability.

Shot Blasting Machine Working Demo

  • Work Chamber/ Cabinet

The heavy duty welded cabinet is manufactured out of prime quality heavy duty steel plate and mounted on sturdy andrigid structural steel frame work. 8 to 10 mm thick manganese steel extra large size hard liners are fitted in direct blast zone of the cabinet. The interior of door and cabinet is lined with special grade rubber sheet having thickness 6 mm. This rubber sheet has special property to retard abrasion on account of ricocheting of abrasive. A horizontal door is provided having limit switch for safety purpose. Inside of the door is fully lined with rubber liner. A rubber seal is provided on the inner side of the door to prevent the escape of abrasive from cabinet. The door is fitted with limit switch and lever type lock is provided for locking the door and preventing escape of abrasives.

  •  Work Conveyor:

The endless type perforated rubber conveyor is provided. The gentle tumbling action of this rubber conveyor exposes all the surface of the components to the blast stream. The abrasion resistant grade of rubber having thickness 15 mm is used in construction of the conveyor belt. The tensioning arrangement of this conveyor belt is provided. The conveyor is driven by three number of roller through a chain drive system located outside the cabinet. The spent abrasive falls through perforation of the conveyor into the hopper of the cabinet which are guided to the boot of elevator for recirculation purpose.

  •  Wheelabrator Unit (Blast Wheel Assembly):

The blast wheel assembly is mounted on steel plate having thickness of 10 to 12 mm. The unit consists of fabricated steel casing having installation of different alloy steel liners, rotor, blades, control cage, impeller and feed spout. The rotor is made out of EN grade material duly hardened to the full depth. The drive system of blast wheel (Rotor) entails a set of self-lubricated and self-aligning pedestal bearings. The rotor is dynamically balanced. The drive shaft of blast wheel is made out of EN grade material and duly precision grinded to the finest accuracy. The latest nylon sandwiched flat belt drive system is provided for driving the rotor.This system enhances the power transmission efficiency by 15%.The fabricated casing of blast wheel assembly can be easily opened up through bolts/levers for examination of various liners and parts of wheel assembly.

  •  Abrasive Circulation System:

The rotor of blast wheel assembly unit fires abrasive down on the perforated belt. The spent abrasive from perforated belt top falls into hopper of the cabinet. The abrasive from hopper transferred to the boot of Bucket Elevator which leads abrasive to the Rotary Screen Separator/Air Dynamic Separation System (Optional Accessory). The tensioning arrangement for elevator belt is provided at the top portion of the elevator, hence no spillage of belt. The Rotary Screen Separator/Air Dynamic Separation System continuously segregates usable abrasive from unusable abrasive and debris. The usable abrasives are transferred into the storage hopper for recirculation purpose. The storage hopper entails electronic abrasive level sensor* (Optional Accessory). These sensors are connected to the abrasive replenishing hopper provided at the bottom of bucket elevator. The abrasives from storage hopper are transferred into blast wheel unit through feed funnel. The rotational movement of impeller constantly accelerates the incoming abrasive and pours them on the blades of the rotor. The flow of abrasive to the blast wheel unit is regulated by pneumatic valve operated by pneumatic cylinder and solenoid valve. The blasting media at high velocity are thrown by rotor onto the job.

  •  Fabric Bag Dust Collector System:

The fabric bag type dust collector having number of tubular filter bag is provided. The dust laden air enters the dust collector through side and passes into a settling and equalizing compartment. Through expansion in the equalizing compartment, the air velocity drops and flow is distributed over the entire settling area. The air then flows up and away from storage hopper causing the heavier dust particles to settle down, the fine particles floating upward into the filter tube. The clean air passes through the tubes and is exhausted through the blower. At certain interval the tubes are shaken mechanically/manually to remove the accumulated dust from the filter bags. The dust is collected in the tray of the dust collector. The trays are taken out periodically and emptied. The filter bags are made out of a satin woven filter cloth. The seams are multiple stitched with heavy cotton thread. The blower unit of dust collector is dynamically balanced. The dust collector is fabricated in modular design and all the joints are sealed with imported sealing compound. MGI is also known for its high quality dust collection systems and not just as a leading manufacturer of Shot Blasting machines in India.

Shot blasting machine must be used with proper safety measures in place and you find more about the industrial health and safety criteria for abrasive blast cleaning operations.

Evaluation of the operation status and the effect of shot blasting

The main purpose of the evaluation procedure is to prepare the data for the decision-making, having relevance to the process conditions, its mechanisms and the surface-cleaning performance. Hence it provides the background for actions aimed to improve the performance of shot blasting machines and to make the process more effective. The methodology outlined here stipulates the simplest methods of measurements and quantitative calculations.

Cleaning performance: The measure of the degree of the casting’s cleanliness after separating the adhering moulding mix is the surface roughness. The cleaning effect is the function of the amount of abrasive agent supplied to the turbine and the effective blasting time. The lower level of the cleaning agent in the tank, the lower the concentration of the shot column and the moulding mix removal may become less effective.

Loading of driving motors in the blast turbines: It is recommended that high loads should be applied to maintain the maximal power ratings. Depending on the power level, the shot blast rate (kg/s) should be as large as possible. The maximal power level guarantees the short cleaning time and effective separation of the moulding mix. The level of applied load is associated with the level of the tank filling with the abrasive agent.

Condition of protecting screen in the separator: Keeping the screens clean is necessary to ensure safe operation of the separating rotor, of the adapting sleeve and the blasting rotor. The layer of abrasive agent, flowing freely through clean screens forms a uniform curtain, which ensures effective dust removal from the abrasive agent. Besides, fine grains of used shots are easily removed, too. The air flow is required at the specified velocity.

Proportion of non-metallic fractions: Tests have revealed that the proportion of contaminants in the circulation system of an abrasive agent, such as shot, or shot mix, should not exceed 1%. A higher proportion of such fractions causes the durability of the machine components to deteriorate dramatically, even by 80%.

Grain size distribution in the abrasive medium: Indicators characterising the grains are used in the decision making as to whether fresh agent should be added to homogenise the mixture or to replace the used medium. The grain size distribution in the abrasive agent and its quality have to be evaluated since the presence of an abrasive material leads to the wearing and tearing of the machine components, particularly the blast blades.

Noise and vibration levels: Noise and vibrations typically appear and exceed the admissible levels when the machine components are already worn and damaged. When the rotating elements are unbalanced or the screw connections get loose, the noise and vibration levels will increase.

Shot Blasting uses in Various Industries

  • ShipBuilding and ShipYard
  • Aerospace and Aircraft Maintenance
  • Iron & Steel Castings and Other Metal Foundry
  • Aluminium Casting
  • Forgings
  • Rail
  • Foundries
  • Steel Fabrication
  • Car and Bus Painting
  • Alloy Wheels Cleaning

Shot blasting is also used to clean floors, roads and outer walls at construction sites.

Other applications of shot blasting include cleaning of under water pipes and tanks before coating or re-coating them to prevent corrosion.

When we talk about shot blasting ( Airless ) then it is important to remember that we are referring to a shot blasting machine which works by directly converting electric motor energy into kinetic abrasive energy by rotating a centrifugal wheel at a minimum of 60 kg per minute which can go upto 1200 kg per minute.

With such high amounts of accelerated blasting media a shot blasting machine is used to derust, descal, deburr, desand or clean large metal parts or surfaces that cannot be cleaned effectively through other traditional or manual processes.

Difference between shot blasting and sandblasting is simple to understand. In sand blasting compressed air is used to propel the abrasive towards the surface that needs to be cleaned and in shot blasting a centrifugal wheel is used to propel the abrasive toward the surface using an electric motor. Shot Blasting Machine Manufacturers in India for Forging components, Casting components, Shot peening, Grit Blasting Machine and iron parts cleaning.

Advantages of a Shot Blasting Machine:

  • Shot Blasting is inexpensive and time saving and also abrasive material is reusable which makes shot blasting extremely affordable.
  • Cleans and smoothens a metal surface without any damage to the surface.
  • Economical to use and environment friendly as it does not produces very less amounts of dust compared to sandblasting.
  • Prepares a surface for coating or re-coating applications effectively.
  • Smoothens a rough surface and roughens a smooth surface effectively.
  • Flexibility of using various types of abrasive materials that can be used in a shot blasting machine depending on the surface that needs to be cleaned such as glass beads, steel shots, steel grit etc. makes shot blasting the most preferred method of cleaning or preparing different metal surfaces and components.

Factors that affect the Blasting process and its effectiveness:

  • Condition of the surface or the metal part that needs to be cleaned and the contaminants deposited on the surface that need to be removed.
  • Velocity and the abrasive used to treat the surface.
  • Working Condition of the shot blasting machine.
  • Size of the abrasive.
  • Hardness of the abrasive material.
  • Level of humidity and temperature as exposure of metal surface to the environment makes it susceptible to oxidation.

shot blasting shot blast

Leading Manufacturer of Shot Blasting Machine in India and Sandblasting equipment Supplier

Maan Global Industries based in Faridabad & Jodhpur Rajasthan India has mastered the process shot blasting and sandblast for effective results in various industries from castings to forgings to fabrication to coatings. We are among the leading manufacturers of Shot Blasting Machine and Sand Blasting Machine in India for over a decade and provide various models of shot blasting machines for different applications such as Portable Sandblaster, Tumb Type Shot Blasting Machine, Blast Cabinet, Cabinet Type shot blasting machine, Spinner Hanger Type Shot Blasting Machine , Blast Room and many other models.

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References: 

https://www.mfn.li/archive/issue_view.php?id=348

https://scribd.com/document/348161410/Rangan-Report

https://www.shotpeener.com/library/pdf/1991047.pdf

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