Ultrasonic Machining: Definition, Principle, Types, Process, Working, Advantages, Disadvantages, Applications

Introduction-

The present trend is towards the development of material removal processes that employ primarily non-mechanical energy.

‘Abrasive Jet’ and ‘Ultrasonic machining’ methods are important because of certain special characteristics with which electrochemical, chemical or thermal processes can not compete.

Welcome to Engineers Rail, Here you are going to get complete information about the Ultrasonic machining process, from scratch to end.

So, Grab your seat and feel comfortable, while I am connecting you to the mainstream of the article.

So, without further delays, let’s Get Started…

Before I start, It would be nice to have a brief overview of Ultrasonic sound and waves, So, you can connect more easily later on. So, here it is-

The term ‘Ultrasonic’ is used to describe a vibratory wave of a frequency above that of the upper-frequency limit of the human ear.

It generally embraces all frequencies above about 16kc/s.

There are two types of waves, Namely-

(I) Shear Waves

(ii) Longitudinal Waves

Where Longitudinal waves are mostly used in ultrasonic applications since they are easily generated. They can be propagated in solids, liquids and gases and can travel at a high velocity So that their wavelength is short in most media.

Now, Move to the mainstream of the article-

What is Ultrasonic Machining?-

Ultrasonic machining(USM) is a process of Non-conventional machining process, In which material is removed due to the action of Abrasive Grains.

The abrasive particles are driven in the work surface by the tool oscillating normal to the work surface at a high frequency.

Principle-

As you know, Ultrasonic is a high-frequency sound wave.
Where A receiver generates high-voltage electrical pulses and a transducer converts those electrical pulses to high-frequency ultrasonic waves.

Types of Ultrasonic Machining-

There are two types of USM

  •  Rotary Ultrasonic Machining(RUM)
  • Chemical assisted ultrasonic machining(CUSM)

(I) Rotary Ultrasonic Machining(RUM)-

It is the mixer of both unconventional ultrasonic machining and conventional Diamond grinding process get together to produce Higher metal removal rate(MRR), enhanced hole accuracy with improved surface finish.

RUM can easily remove metals even from difficult to machine materials like- Ductile materials, Hard and brittle materials, ceramics and composites materials etc.

(II) Chemical Assisted Ultrasonic Machining(CUSM)-

This machining process is the same as USM, the only difference is the Liquid media used, CUSM uses chemicals like hydrofluoric acid instead of water used in USM.

This change in phenomena helps to improve metal removing rate and overall surface finishing in general.

Process- 

The four main elements of this process parameters are

  • Work materials 
  • Tool cone and tool tip (Vibrational amplifier)
  • Abrasive slurry
  • Liquid media

(I) Work materials- 

Earlier, it is assumed that materials are removed in this process only by brittle failure and only brittle materials could be machined by this process.

But, now there is no limitation to the range of materials that can be machined, except they should not dissolve in the slurry media or react with it.

However, Soft and ductile materials are usually cut more economically by other methods.

(II) Tool cone and Tool Tip-

The tool cone (also called ‘Horn‘) amplifies and focuses the mechanical energy produced by the transducer and transmit this to the workpiece in such a way that energy utilization is optimum.

It is simply a velocity transformer with the exception that it is made slightly shorter than half of the wavelength.

The horn mechanically modifies the vibratory energy to give the required force amplitude ratio. Thus, a low gain horn gives a low amplitude with a high force capability and opposition, a high gain horn has a high amplitude and a low force capability.

Titanium is a good material for the tool cone.

(III) Abrasive slurry-

Some of the abrasives types in use are-

  • Aluminium oxide (Alumina)
  • Boron carbide
  • Silicon carbide
  • Diamond dust

Boron is the most expensive abrasive material but is the best suited for cutting tungsten carbide, tool steel and precious stones. Boron silico carbide is the new promising abrasive which has an abrasive powder of 8-12 per cent greater than that of boron carbide.

Silicon covers the maximum application of USM machining.

Alumina is the best for cutting glass, germanium and ceramics. The problem with alumina is that it wears fast and soon loses its cutting power.

Diamond and rubies are nicely cut by using diamond powder which ensures good accuracy, surface finishing and cutting rates.

(IV) Liquid media-

The abrasive is suspended in the liquid. The liquid performs many functions:-

  • Acts as the acoustic bond between the workpiece and the vibrating tool.
  • Helps efficient transfer of energy between the workpiece and tool.
  • Act as a coolant.
  • Provides a medium to carry away the worn abrasive

Parts-

The main parts or tools of Ultrasonic machine are-

  • Acoustic Head (Transducer) 
  • Tool feed mechanism
  • Abrasive feed system
  • Generator

(I) Acoustic head (Transducer) – 

The magnetostriction type of transducer which utilize the effect of longitudinal magnetostriction are now very common. These may be made of nickel, iron-cobalt or iron-aluminium.

Nickel finds maximum application because of high strength and good insulting properties of the nickel oxide film.

Fig.- general arrangement of Ultrasonic cutting machine for cutting

ultrasonic-cutting-machine

(II) Tool feed mechanism-

The feed mechanism of an ultrasonic machine must perform the following functions

  • Bring the tool very slowly close to the workpiece.
  • Provide adequate cutting force and sustain this during cutting.
  • Decrease the force at a specified depth.
  • Overrun a small distance to ensure the required hole size at the exist.

For the accurate working, it is vital that the feed mechanism be precise and sensitive.

Here are some different types of feed system-

Fig.- Ultrasonic machining feed tool

ultrasonic machining feed too

(III) Abrasive feed system-

The abrasive slurry can be supplied by hand in a small machine but for machines of higher power, a pump (usually centrifugal type) is used to supply the slurry through nozzle.

A good method is to keep the slurry in a bath in the cutting zone.

This ensures a good supply and reduces any tendency of the tool to scatter the slurry when amplitude is large.

Another effective method of supplying the slurry to the cuttig zone is via a hollow tool or holes in the workpiece.

(IV) Generator-

The main requirements of a generator are reliability, efficiency, simplicity in design and low cast. Vaccum tube generators are employed usually.

Small generator usually consist of a master oscillator, a buffer amplifier and an output stage. These have a wide tuning range but low efficiency.

Working principle of Ultrasonic Machining-

Here is step bby step working of USM-

  • First the low frequency electric current passes through electric supply.
  • This low frequency current converts into high frequency current through some electrical equipment.
  • This high frequency current passes through transducer. The transducer convets this high frequency electric signal into high frequency mechanical vibration.
  • This mechanical vibration passes through booster. the booster amplify this high frequency vibration and send to horn.
  • Horn which is also known as tool holder, transfer this amplified vibration to tool which makes tool vibrates at ultrasonic frequency.
  • As the tool vibrates, it makes abrasive particle to vibrate at this high frequency. This abrasive particle strikes to the work piece and remove metal from it.

Fig- Schematic representation Diagram of Ultrasonic machiningultrasonic machining process

Uses of Ultrasonic Machinery-

Ultra sonic machine used for removing metal from hard materials like- Diamond, boron carbide, Quartz, tempered steel, ruby, ceramics, glass, alumina, saphhire.

Are you there?

I hope you enjoying and flowing with words. If so, i will move you to the advantage, disadvantages and application of USM.

Advantages-

Here are some advantages of Ultrasonic machining process-

  • Hard material can be easily machined
  • No heat generated in work
  • Non-conductive metals can be machines
  • It does not form chips of significant size

Disadvantages-

Here are some disadvantages or limitation of USM-

  • Low metal cutting rate
  • Tool wear is high because abrasive particle affect both workpiece and tool
  • It can machine only hard materials. Ductile metals may not be machined by this method.
  • Unable to drill deep holes

Applications-

Here are some Applications of USM-

  • Cutting off of parts made from semiconductors at high removal rates compared to conventional machining methods
  • Engraving on glass as well as hardened steel and sintered carbide
  • Parting and machining of process stones including diamond

→If you have still any confusion regarding the same topic. This video guide will help you further. Give a Watch-

Conclusion

Ultrasonic Machining process is the Non-conventional machining process, where conducting and non-conducting materials can be under go through metal removal process through this method, Which I discussed in detail above.

I hope you enjoyed and gain some knowledge and added some value to your knowledge part.

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Thank you being with me till the end. I hope to see you soon.

 

 

 

Before you go, Here are some Q&A sections, You might want to gaze at !!

FAQs

Q. Which material is best suited for ultrasonic machining?

Ans. Hard and brittle materials are best suited for ultrasonic machining.

Q. Under what frequency ultrasonic machining is done?

Ans. The estimated frequency of USM is around 19-25 KHz.

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