This document summarizes a presentation on ductile mode machining of glass. It begins with an outline of the presentation topics, which include an introduction to background and objectives, a literature review, concepts of ductile mode machining of glass including experimental setup and testing. Results are discussed relating flank wear and machining time to feed rate and surface roughness. Optimal cutting conditions for achieving ductile mode machining are a moderate feed rate and axial depth of cut of 0.4μm at 80 nm/rev feed rate. Below this critical feed rate, plowing occurs while above it causes brittle fracture. References cited relate feed rate to ductile-brittle transition and stress intensity factors.

1. REVIEW OF DUCTILE MODE
MACHINING OF GLASS
Presentation by
Denny J Ottarackal
Reg No:10002637
Under the Guidance of
Prof. Mathew J Joseph
Dept. of Mechanical Engineering
Amal Jyothi College of Engineering
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2. Outline of Presentation
 Introduction
● Background and Scope of Ductile Mode Machining of Glass
● Objectives and Methodology
 Literature Survey
 Ductile mode machining of Glass
● Basic concepts
● Experimental Setup
● Experimentation
 Results and Discussion
 References
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3. Introduction
Background and Scope of Ductile Mode Machining of Glass
 Glass - a brittle material.
 Very difficult to machine material.
 Functional material for optics and electronics.
 Conventional grinding process causes surface damages.
 For better surface finish glass must be machined in ductile mode.
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4. Objectives and Methodology
 Analysis of depth of cut, feed rate, tool wear and chip thickness.
 Study of Side milling process.
 Experimental study of ductile mode machining of glass by Ultraprecision vertical
spindle multipurpose machine tool.
 To relate flank wear and machining time.
 To study the relation between feed rate and surface roughness.
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5. Literature Survey
 Arif, Rahman and San stated about the relation between feed rate and brittle
fracture. They studied about the regimes in milling[1].
 Venkatachalam, Li and Liange correlated stress intensity factor with ductile mode
machining[2].
 Arif, Rahman and San described about the transition point of ductile-brittle
conversion[3].
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6. Side Milling
 In upmilling, deformed chip thickness increases
from zero to a max value with cutter rotation.
 If the undeformed chip reaches a critical
value , brittle fracture will occur.
 If the brittle fracture point is far from the level
of final machined surface and feed rate is low ,no
brittle fracture occurs.
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Side milling process of glass (a)at low
feed per edge(b)high feed per edge.
Fig.1.

7. Plowing Effect
 Minimum chip thickness effect in milling.
 Chip thickness must be a certain minimum value for effective cutting.
 If the chip thickness is below certain value , only plowing or elastic deformation
will occur.
 Fracture propagation does not take place in particles of dimension smaller than,
dc = 10Eγ /Y2.
Here E is the modulus of elasticity, γ is the fracture energy and Y is the
yield stress of work-material.
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8. Regimes in Milling
 Three regimes in milling
● Plowing regime;
If the uncut chip thickness is less than what is
required for material removal.
● Ductile regime;
Ductile mode is achieved beyond plowing zone.
● Brittle regime;
If critical value of undeformed chip thickness reached at
some point beyond the ductile zone, brittle fracture occurs.
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Different Regimes of Milling in
Slot milling of Glass.
Fig 2.

9. Experimental Setup
 Ultraprecision vertical spindle multipurpose
machine tool is used (Fig 3).
 Movement of Y-axis executed by table.
 Movements in X and Z-axis by spindle motion.
 Digital Tachometer for spindle speed measurement.
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Vertical Spindle Multipurpose
Machine Tool
Fig 3.

10. Cutting Tool
 Super hard cemented microendmill was used.
 Cutting edge radius of cutter was at submicron level.
 Cutter with submicron edge radius is essential requirement for ductile mode machining of
glass.
Workpiece
 A rectangular piece of soda lime glass with the dimensions of
35×55×5 mm are used in the experiment.
 Cutting was performed with cutter workpiece submerged in a pool of water serving as
coolant.
 Constant spindle speed of 3000rpm was used.
 Each cutting was performed by new cutter.
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11. Cutting Conditions
 Cutting was performed with cutter workpiece submerged in a pool of water serving as
coolant(Fig 4).
 Constant spindle speed of 3000rpm was used.
 Each cutting was performed by new cutter.
Tool Wear
 Two types
● Gradual wear of cutting edge
● Abrasion at the flank face
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Cutting performed submerged in coolant
Fig 4

12. Experimentation
 Axial depth of cut and feed rate varied
according to the Table 1.
 After machining , the machined surface was
cleaned in acetone by applying ultrasonic
vibrations.
 Machined surface was observd under optical
microscope for surface characterization.
12 Test no. Axial depth
of cut(µm)
Feed
rate(nm/rev)
1 0.2 40
2 0.2 80
3 0.2 120
4 0.2 160
5 0.4 40
6 0.4 80
7 0.4 100
8 0.4 120
9 0.4 140
10 0.4 160
11 0.6 40
12 0.6 80
Cutting conditions(spindle rpm = 3000).
Table 1.

13. Results and Discussion
 Too low feed rate cause powing and high
feed rate cause brittle fracture.
 Ductile mode machining obtained at moderate
feed rate.
 A high quality machined surface was obtained
at an axial depth of cut of 0.4µm and
feed rate of 80 nm/rev,shown in fig 5 and brittle
mode surface is shown in fig 6.
Surface machined in ductile mode. Fig 5.
Surface machined in brittle mode. Fig 6.
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14. Results and Discussion
 Flank wear occours at a slow rate at the beginning
as shown in Table 2, because of characteristics of
coating material of the cutter.
 Relation between surface roughness and feed rate is
shown in Table 3.
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Machining
time(min)
Flank
wear(µm)
3 4
7 5
10 15
14 29
17 39
22 52
25 65
Relation between machining time
and flank wear.Table 2.
Feed rate(nm/rev) Surface
roughness(nm)
40 50
80 30
120 38
140 70
160 240
Variation of surface roughness with feed rate.
Table 3.

15. Results and Discussion
 At low feed rate, the average value of surface roughness is slightly higher
due to powing effect.
 At medium feed rate surface roughness is low due to ductile mode machining.
 At high feed rate surface roughness is very high due to brittle mode machining.
 Critical feed rate is between 120 and 140 nm/rev, corresponding chip thickness is between 60 and
70nm.
 This undeformed chip thickness is less than theoretical value(45nm).Due to thermal softening
effect.
 AFM images of Ductile mode with powing effect, Ductile and Brittle surfaces is shown in
Fig 5, Fig 6 and Fig 7.
Fig 5 Fig 6 Fig 7
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16. Conclusion
 Feed rate and Depth of cut – critical factors in ductile mode machining of glass.
 Tool wear has to be considerd for better surface finish.
 Should be an optimum value of chip thickness for ductile mode machining.
 Feed rate affects ductile-brittle transition.
 Optimum value of feed rate for better surface roughness.
 Energy for crack propogation is larger than that of plastic deformation.
 Crack propogation is compressed in ductile mode machining.
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17. References
 •[1] Muhammad Arif., Mustafizur Rahman., Wong Yoke San.,`Ultraprecision
ductile mode machining of glass by micromilling process’, Manufacturing
Processes,Volume 13, Issue 1,2011.
 •[2] Siva Venkatachalama., Xiaoping Li b., Steven Y. Liangc.,` Predictive
modeling of transition undeformed chip thickness in ductile-regime micro-
machining of single crystal brittle materials’, materials processing technology 2 0
9, 3306–3319( 2009 ).
 •[3] Muhammad Arif., Mustafizur Rahman., Wong Yoke San.,` Analytical model
to determine the critical feed per edge for ductile–brittle transition in milling
process of brittle materials’, Machine Tools & Manufacture, 51 170–181(2011).
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18. Thank you...