Short notes on Abrasive Jet Machining for GATE Mechanical Engineering
In this article, we will study about the Abrasive Jet Machining in the form of short notes for GATE Mechanical Engineering.
The process of Abrasive Jet Machining (AJM) consists of directing a stream of fine abrasive grains mixed with compessed air or some other gas at high pressure, through a nozzle on to the surface of the work piece. These particles impinge on the work surface at high speed and the erosion caused by their impact enables the removal of metal. This process is mainly employed in such machining works which are otherwise difficult, such as thin sections of hard metals and alloy cutting of materials which are sensitive to heat damage, producing intricate holes, deburring, etching, polishing etc.
Fine grained abreasive powder is filled in a vibrating chamber, called 'mixing chamber'. The gas or air at high pressure is forced into this chamber, the pressure of the gas varying from to . The abrasive particles are contained in a suitable holding device, like a hopper, and fed into the mixing chamber. A regulator is incorporated in the line to control the flow of abrasive particles. Compressed air or high pressure gas is supplied to the mixing chamber through a pipe line. This pipe line carries a pressure gauge and a regulator to control the gas flow and its pressure. The mixing chamber, carrying the abrasive particles, is vibrated and the amplitude of these vibrations controls the flow of abrasive particles. These particles mix in the gas stream, travel further through die nozzle at a considerably high speed.
Applications of AJM:
- This process is widely used for machining of brittle materials like glass, ceramics, refractories etc. Cleaning and cutting operations on materials like germanium, silicon, quartz, mica and many other operations like etching, marking, deburring etc. Some typical applications of this process include: (1) fine drilling and micro welding, (2) Aperture drilling for electronic microscopes, (3) Machining of semiconductors, (4) Machining of intricate profiles on hard and fragile materials, and (5) Frosting and abrsing of glass articles.
Advantages of AJM:
- Intricate cavities and holes of any shape can be machined in materials of any hardness.
- Brittle materials of thin sections can be easily machined.
- Normally inaccessible portions can be machined with fairly good accuracy.
- Low capital investment needed.
- There is no direct contact between the tool and the workpiece.
- Amount of heat generated is not appreicable.
Disadvantages of AJM:
- It is not suitable for machining of ductile materials.
- Metal removal is slow.
- Machining accuracy is relatively poorer.
- There is always a danger of abrasive particles getting embedded in the work material. Hence cleaning needs to be necessarily done after die operation.
- The abrasive powder used in the process cannot be reclaimed or reused.
In the next article, we will look at the process parameters for the unconventional machining methods.