The process makes use of an abrasive jet with high velocity, to remove material and provide smooth surface finish to hard metallic workpieces. It is similar to Water Jet Machining (WJM).
This article explains the construction and working of AJM listing its advantages, disadvantages and applications. The contents of this article are listed below:
- Schematic Diagram
- Operations performed using AJM (Applications of AJM)
A simple schematic diagram of Abrasive Jet Machining (AJM) is shown below:
The constructional requirements of Abrasive Jet Machining (AJM) are listed and described below:
- Abrasive jet: It is a mixture of a gas (or air) and abrasive particles. Gas used is carbon-di-oxide or nitrogen or compressed air. The selection of abrasive particles depends on the hardness and Metal Removal Rate (MRR) of the workpiece. Most commonly, aluminium oxide or silicon carbide particles are used.
- Mixing chamber: It is used to mix the gas and abrasive particles.
- Filter: It filters the gas before entering the compressor and mixing chamber.
- Compressor: It pressurizes the gas.
- Hopper: Hopper is used for feeding the abrasive powder.
- Pressure gauges and flow regulators: They are used to control the pressure and regulate the flow rate of abrasive jet.
- Vibrator: It is provided below the mixing chamber. It controls the abrasive powder feed rate in the mixing chamber.
- Nozzle: It forces the abrasive jet over the workpiece. Nozzle is made of hard and resistant material like tungsten carbide.
Dry air or gas is filtered and compressed by passing it through the filter and compressor.
A pressure gauge and a flow regulator are used to control the pressure and regulate the flow rate of the compressed air.
Compressed air is then passed into the mixing chamber. In the mixing chamber, abrasive powder is fed. A vibrator is used to control the feed of the abrasive powder. The abrasive powder and the compressed air are thoroughly mixed in the chamber. The pressure of this mixture is regulated and sent to nozzle.
The nozzle increases the velocity of the mixture at the expense of its pressure. A fine abrasive jet is rendered by the nozzle. This jet is used to remove unwanted material from the workpiece.
For a good understanding of construction and working of AJM, refer the schematic diagram above.
The following are some of the operations that can be performed using Abrasive Jet Machining:
- Surface finishing
- Surface of the workpiece is cleaned automatically.
- Smooth surface finish can be obtained.
- Equipment cost is low.
- Hard materials and materials of high strength can be easily machined.
- Metal removal rate is low
- In certain circumstances, abrasive particles might settle over the workpiece.
- Nozzle life is less. Nozzle should be maintained periodically.
- Abrasive Jet Machining cannot be used to machine soft materials.