Engineering Workshop Non-Traditional Machining Production

Ultrasonic Machining Process(USM), Water Jet Machining and Abrasive Water Jet Machining-Indetailed

11 Points to know from Ultrasonic Machining(USM) Process: It is one of the types of Non-Traditional Machining methods which produces Circular, non-Circular holes of very small size is <1mm size can be produced by using this Ultrasonic Machining Method.

When very frequency vibrations are applied on to the tool, the tool is vibrating at a very high frequency. This tool will induce impact loads on to the abrasive particles which in turn induces impact loads on to the workpiece.

ultrasonic machining
ultrasonic machining

If the workpiece is a highly brittle material and because of a very smaller size of the abrasive particles, the area on which impact loads acting is very small.

Therefore without Breaking the workpiece, the fracturing is taking place in a smaller area of the workpiece. The chips produced due to the fracturing will be moving along the abrasive slurry. From the above, the mechanism of chip formation is brittle fracturing.

Detailed Explanation of Ultrasonic Machining(USM) Process:

  • During machining, the equal and opposite reaction, impact loads produced by the workpiece will be acting on to the tool, so that if the tool is made by using the hard material, the brittle fracturing is taking place in the tool also and the tool wear becomes higher.
  • To minimize this, the tool must be made by using a material which has very high softness(ductility).

         Ex: Copper, Brass, Mild steel, etc.            

  • With an increase of grain size or abrasive particle size, the material removal rate is increasing first and then decreasing.
  • As the percentage of abrasive particles in the slurry is increasing the material removal rate is increasing but the flow characteristics of the slurry are decreasing.
  • Therefore the optimum percentage of abrasives in the slurry is 40-60%.
  • Wear ratio mainly depends on the brittleness of workpiece material i.e. the higher the brittleness, it is easy to produce the brittle fracturing. Hence, the wear ratio becomes higher.

Advantages of Ultrasonic Machining(USM) Method:

  1. Highly brittle materials can be easily machineable.
  2. Circular, non-circular of very small size is <1mm size can be produced by using this USM method.
  3. Out of all the non-traditional machining methods, ultrasonic machining requires lower specific cutting energy.
  4. No electrical conductivity of the workpiece is required.
  5. No thermal effects on the workpiece are required.

Dis-Advantages of Ultrasonic Machining(USM) Method:

6. Only brittle materials can be machinable.

7. A deeper hole is not possible to produce i.e. L/D ratio up to 3 only is produced.

8. Because of brittle fracturing, the surface finish produced is poor.

9. Because of impact loads are acting on to the workpiece, the internal residual stresses may be generated in the workpiece.

Applications of Ultrasonic Machining Method:

10. This ultrasonic machining method is mainly used for producing circular,non-circular holes in the highly brittle materials like glass, ceramics, etc.

11. The dentist uses ultrasonic machining for producing the holes in the human teeth.


Water Jet Machining Process(WJM):

In this article, I will be explaining about the few concepts of Water Jet Machining (WJM) and Abrasive Water Jet Machining (AWJM) which you must know for GATE Exam. The Apparatus for WJM and AWJM were shown in the images below. You can collect the data from the Images and the rest theory was presented below.

The points which are important are bolded in size so that you can easily take the information from this article.

difference between water jet machining and Abrasive water jet machining
difference between water jet machining and Abrasive water jet machining

Water Jet Machining Process(WJM):

  1. When very high-pressure water is passing through the convergent nozzle the pressure energy is converted into velocity energy or kinetic energy.
  2. Therefore the water is coming out from the nozzle at a very high velocity which is obtained to be 200 to 400 m per second.
  3. When this high-velocity water Jet is impinging onto the workpiece, the continuous impact load is acting onto it.
  4. Therefore very soft materials will experience plastic deformation and fracturing.
  5. From the above, the mechanism of material removal is due to plastic deformation and fracturing and also called an Etching process.
  6. In this, the Material Removal Rate(MRR) is directly proportional to the velocity of the water jet and this velocity depends on the distance between the nozzle tip and workpiece.
  7. In this, no tool is used and the only nozzle is used and to withstand higher pressures.
  8. The nozzle is made by using Tungsten Carbide.

From this,                                                               

9.Medium: Water

10. Wear Ratio: Infinity.

20 Points you must know between Water Jet Machining and Abrasive Water Jet Machining Processes
20 Points you must know between Water Jet Machining and Abrasive Water Jet Machining Processes

Advantages of Water Jet Machining:

  • Very soft materials like rubber can be easily machined
  • No electrical conductivity of workpiece is required
  • No thermal effects on the workpiece are required.

Limitations of Water Jet Machining:

  • Pressurizing the water to very high pressure is difficult.
  • This method can’t be used for machining of hard materials.
  • Developed for cutting of very soft materials like rubber.

Applications of Water Jet Machining:

  • It is used for machining or cutting reinforced plastic.
  • Use to cut stone which can reduce the dust in the environment.
  • It is used to cut hard metal like titanium, stainless steel, etc.
  • It is used in aerospace industries.
  • Used for machining PCB.

Abrasive Water Jet Machining Process(AWJM):

It is advanced of Water Jet Machining Process which includes Abrasives as a medium. The detailed explanation of Abrasive Water Jet Machining was presented below.

Abrasive Water Jet Machining Process
Abrasive Water Jet Machining Process

To overcome the second disadvantage of water jet machining, the abrasive particles will be added into the water so that the abrasive particles also comes out from the nozzle at very high velocity.

When these high-velocity Abrasive particles are impinging onto the hard work piece’s, it is possible to produce plastic deformation fracturing in the hard work materials also and this process is called as Abrasive water jet machining.

As the percentage of abrasives are increasing, the material removal also increases but the flow characteristics of the liquid mixture is coming down.

Therefore the optimum percentage of abrasives will be about 40 to 60%.

It is mainly developed for cutting of granite and marble of complex shapes.

Advantages of AWJM:

In most of the cases, no secondary finishing required

  • No heat-affected zone
  • No cutter induced distortion
  • Eliminates thermal distortion
  • Low cutting forces on workpieces
  • Localises structural changes
  • No slag or cutting dross
  • Limited tooling requirements
  • Typical finish 125-250 microns

Limitations of AWJM:

  • high capital cost and high noise levels during machining.
  • It cannot cut the materials that degrade quickly with moisture.
  • Surface finish loses at higher cut speeds.

Applications of AWJM:

  • It is highly used in the automotive, aerospace and electronics industries.

  • In aerospace industries, parts such as engine components (aluminum, titanium, and heat resistant alloys), aluminum body parts, titanium bodies for military aircraft, etc. are made using abrasive water jet machining process.

This is the complete explanation about Abrasive Water Jet and  Water Jet Machining Process in a detailed manner. These processes will come under Non-Traditional Machining Processes which carries 1 Mark for GATE Exam.

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