Jan 222013
 

Process Parameters of Abrasive Jet MachiningProcess parameters of Abrasive Jet Maching (AJM) are factors that influence its Metal Removal Rate (MRR).

In a machining process, Metal Removal Rate (MRR) is the volume of metal removed from a given workpiece in unit time.

The following are some of the important process parameters of abrasive jet machining:

  1. Abrasive mass flow rate
  2. Nozzle tip distance
  3. Gas Pressure
  4. Velocity of abrasive particles
  5. Mixing ratio
  6. Abrasive grain size

Abrasive mass flow rate:

Mass flow rate of the abrasive particles is a major process parameter that influences the metal removal rate in abrasive jet machining.

In AJM, mass flow rate of the gas (or air) in abrasive jet is inversely proportional to the mass flow rate of the abrasive particles.

Due to this fact, when continuously increasing the abrasive mass flow rate, Metal Removal Rate (MRR) first increases to an optimum value (because of increase in number of abrasive particles hitting the workpiece) and then decreases.

However, if the mixing ratio is kept constant, Metal Removal Rate (MRR) uniformly increases with increase in abrasive mass flow rate.

Nozzle tip distance:

Nozzle Tip Distance (NTD) is the gap provided between the nozzle tip and the workpiece.

Upto a certain limit, Metal Removal Rate (MRR) increases with increase in nozzle tip distance. After that limit, MRR remains constant to some extent and then decreases.

In addition to metal removal rate, nozzle tip distance influences the shape and diameter of cut.

For optimal performance, a nozzle tip distance of 0.25 to 0.75 mm is provided.

Gas pressure:

Air or gas pressure has a direct impact on metal removal rate.

In abrasive jet machining, metal removal rate is directly proportional to air or gas pressure.

Velocity of abrasive particles:

Whenever the velocity of abrasive particles is increased, the speed at which the abrasive particles hit the workpiece is increased. Because of this reason, in abrasive jet machining, metal removal rate increases with increase in velocity of abrasive particles.

Mixing ratio:

Mixing ratio is a ratio that determines the quality of the air-abrasive mixture in Abrasive Jet Machining (AJM).

It is the ratio between the mass flow rate of abrasive particles and the mass flow rate of air (or gas).

When mixing ratio is increased continuously, metal removal rate first increases to some extent and then decreases.

Abrasive grain size:

Size of the abrasive particle determines the speed at which metal is removed.

If smooth and fine surface finish is to be obtained, abrasive particle with small grain size is used.

If metal has to be removed rapidly, abrasive particle with large grain size is used.

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I am a mechanical engineer, an engineering designer and an article writer. I am the editor-in-chief of mechteacher.com.

  • disqus_ewIsNqT2cj

    Hi I am working on a project for my thesis on Abrasive Jet Machining, unfortunately I do not have the best background in pneumatics, is there a way to determine the minimum pressure required?

    • http://mechteacher.com/ Surjeet S

      As far as I know, minimum pressure required to remove material depends mainly on the following two parameters:

      1. Properties and strength of the workpiece.
      2. Properties of the abrasive particle used

      Other than the above two parameters, the process parameters discussed in this article will also have an impact.

      I do not know any definite formula for determining it. Perhaps, if you ask it in our forums, some other user might be able to help you :)

      • disqus_ewIsNqT2cj

        Thank you very much any help is always appreciated :)