University JNTU Kakinada

Regulation R 16

Year IV Year

Semester II Semester

Teaching Classes 3+1

Credits 3

Name of the Faculty Singuru Rajesh

Unit I- Introduction

SLIDE NUMBER 1

UN-CONVENTIONAL

MACHINING PROCESS

SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

UNIT-1:INTRODUCTION

SYLLABUS

Introduction: Need for non-traditional machining methods-classification of modern machiningprocesses – considerations in process selection, applications.

UCMP = Un-conventional Machining Process

Non-traditional machining methods

Advanced machining methods

SLIDE NUMBER 2SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

INTRODUCTION

Need for non-traditional machining methods:

High Strength to weight ratio by new industries & components, which needsdevelopment of cutting tools for these advanced materials.

Increase in hardness of work material results in decrease of economic cuttingspeed (Titanium, Stailness Steel, Nimonics etc.. High strength temp resistant,alloys, FRP, Stellites (Cobalt based alloys), ceramics & other m/c alloys)

Making of holes (Shallow entry angles, non-circular, micro-sized, large aspectratio etc..)

Accurately & easily machining can be done

Easy to m/c intricate & accurate shapes

Easily adoptable for automation

SLIDE NUMBER 3SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Classification of Advanced m/c Technologies

SLIDE NUMBER 4

ADVANCED MACHINING TECHNOLOGIES

ELECTROCHEMICAL & CHEMICAL

THERMOELECTRICMECHANICAL

AJMUSMWJM

AWJMAFMMAF

PAMLBMEDMEBMIBM

ECMChMBM

SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

ULTRASONIC MACHINING

• USM is a mechanical material removal process in which the material isremoved by repetitive impact of abrasive particles (carried in liquid medium)on to the work surface, by a shaped tool, Vibrating at ultrasonic frequency.

Elements of USM:

(1) Ultrasonic transducer

(2) Tool cone or Horn

(3) Tool tip

(4) Abrasive slurry

(5) Tool feed mechanism

SLIDE NUMBER 5SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Tool feed mechanism:

• The ultrasonic vibrations are produced by the transducer. The transducer is driven by suitable signal generator followed by power amplifier.

•The transducer for USM works on the following principle 1.Piezoelectric effect 2.Magnetostrictive effect 3.Electrostrictive effect

• Ultrasonic vibration (20,000 Hz) of very small amplitudes (0.04-0.08 mm) drive the form tool (sonotrode) of ductile material (usually soft steel)

• An abrasive slurry (Alumina or Boron Carbide or Silicon Carbide) is flowed through the work area.

• The workpiece is brittle in nature (i.e. glass)

SLIDE NUMBER 6SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Mechanism of material removal:

• In USM, the tip of the tool vibrates at low amplitude and at high frequency. This vibration transmits a high velocity to fine abrasive grains between tool and the surface of the work piece.

• material removed by erosion with abrasive particles.

• Different material removal mechanisms are

• 1. Impact of free abrasive particles on the work surface

• 2. Hammering of abrasive particles in the work surface by the tool

• 3. cavitation erosion

• 4. chemical action associated with the fluid employed

SLIDE NUMBER 7SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Hammering of abrasive particles in the work surface by the tool

~power

supply

Nozzle Abrasive

slurry

Transducer

Up-down vibration of tool

hammers the abrasive particles

against workpiece, causing cutting

~power

supply

Nozzle Abrasive

slurry

Transducer

~power

supply

Nozzle Abrasive

slurry

Transducer

Up-down vibration of tool

hammers the abrasive particles

against workpiece, causing cutting

SLIDE NUMBER 8SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Different Horns used in USM:

• The horn or concentrator can be of different shape like

1.Tapered or conical

2.Exponential

3.Stepped

• Machining of tapered or stepped horn is much easier as compared to the exponential one.

SLIDE NUMBER 9SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Advantages:

• Highly brittle materials can be easily machined

• It is a noiseless process

• High accuracy and good surface finish

• No heat generation during machining

• Capability of drilling circular and non-circular holes in very hard materials.

• No thermal effects on mechanical work piece.

• Non-conductive materials can be machined.

SLIDE NUMBER 10SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Disadvantages:

• Tool wear is high

• Low material removal rate(MRR)

• Not economical for soft materials

• Not suitable for heavy stock removal

• Abrasive slurry needs to be replaced

• Residual stresses may be generated due to impact loads

• Cost and maintenance is very high.

• Power consumption is also high (2.4kw)

SLIDE NUMBER 11SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Applications:

• Almost all the material can be machined except some soft materials• Used for machining hard and brittle metallic alloys, semiconductors, glass,

ceramics, carbides etc • USM can be used for drilling, grinding, profiling, coining, threading and

even for welding• For preparing wire drawing dies and tool room items• Used in jewellery for shaping jewels• Drilling of screw threads and curved holes in brittle materials• Cutting of internal threads in ceramics and glasses• Dentists uses USM for producing holes in human teeth(painless drilling

operation by USM drills).

SLIDE NUMBER 12SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Process parameters:

• The process parameters which govern the USM are given below

1. Amplitude of vibration (a) : 15 – 50 μm

2. Frequency of vibration (f) : 20 – 25 kHz

3. Feed force or Impact force(F)

5. Abrasive size : 15 μm – 150 μm

6. Abrasive material : Alumina or SiC or Boron

carbide

7. Contact area of the tool (A)

8. Volume concentration of abrasive in water slurry (c)

SLIDE NUMBER 13SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Relation between MRR and other parameters:

• MRR is proportional to (frequency)

• MRR is proportional to (abrasive size)

• MRR is proportional to (impact force)*3/4

• MRR is proportional to (amplitude)*3/4

• MRR is proportional to (viscosity)*3/4

• MRR is proportional to (contact area of tool)*1/4

• MRR is proportional to (volume concentration of abrasive in slurry)*1/4

SLIDE NUMBER 14SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Important point to remember:

• The major variables that controls the metal removal rate in USM are

1.Tool oscillation(i.e, frequency f)

2.Impact force (F)

3.Abrasive size(d)

SLIDE NUMBER 15SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING

Quiz:3. Increasing volume concentration of abrasive in

slurry would affect MRR in the following manner

(i) increase MRR

(ii) decrease MRR

(iii) would not change MRR

(iv) initially decrease and then increase MRR

4. USM can be classified as the following type of non-traditional machining process

(i) electrical

(ii) optical

(iii) mechanical

(iv) chemical

1. Which of the following material is not generally machined by USM

(i) Copper (ii) Glass (iii) Silicon (iv) Germanium

2. Tool in USM is generally made of (i) Glass (ii) Ceramic (iii) Steel(iv) Carbides

SLIDE NUMBER 16SINGURU RAJESH DEPARTMENT OF MECHANICAL ENGINEEING