Textured Cutting Tools

Performance of electrical discharge
textured cutting tools
P. Koshy, J. Tovey
McMaster University
Canada

Lubrication in cutting
lubricant

chip

chip
tool

sliding

tool

chip

sticking

tool

Infiltration of lubricant
is controlled by
capillary action and
chip velocity-induced
shear flow
Retention of the
lubricant in the
interface is as critical
as its ingress
Lubrication may be
enhanced through
texturing the tool rake
face surface
2/18

Performance of electrical discharge textured cutting tools
P. Koshy, J. Tovey

61st CIRP General Assembly
Budapest, August 24, 2011

Femtosecond laser texturing

Texture is to be
preferably oriented
normal to the chip
flow direction
Enomoto & Sugihara (2010)
micro

nano

Kawasegi et al (2009)
3/18
P. Koshy, J. Tovey


Electrochemical texturing
metal layer
(cathode)
insulation layer

dimpled texture

anode (workpiece)

Zhu et al (2009)
4/18
P. Koshy, J. Tovey


Electrical discharge texturing
Surfaces generated in electrical discharge machining
(EDM) are isotropic and entail a positive skewness,
which predisposes them towards effectively entraining
lubricant

frequency

+ve skew

surface height
P. Koshy, J. Tovey

5/18

Objective of this work
To prove the concept of ED-textured cutting tools
Identify the envelope of EDM and cutting parameters in
which such textures are effective

cutting edge

areal texture machined
with a block electrode

rake face

linear texture machined
with shim stock tooling
6/18

P. Koshy, J. Tovey


Experimental - EDM
copper electrodes with positive polarity
oil based dielectric
average gap voltage 100 V; duty factor 50%
Pulse current <72 A; pulse on-time <133 µs

Pulse current and
on-time were varied to
alter the geometry of the
characteristic crater

7/18
P. Koshy, J. Tovey


Experimental - Cutting
In comparison to surface roughness
and tool life, machining force is a
better indicator of lubrication
effectiveness, in terms of repeatability
and resolution De Chiffre & Belluco (2000)
chip

tool

continuous & intermittent orthogonal cutting
Fc

AISI T-15 High Speed Steel ground inserts

Ff

friction angle

SPG 432 geometry with 0 rake angle
annealed 1045 steel & 6061 Al workpieces
cutting speed 2−75 m/min; feed 0.025−0.1 mm
cutting width 3 mm; oil lubricant
8/18

P. Koshy, J. Tovey


Texture parameters
relief on the
rake face to
restrict tool
chip contact

restricted rake tool

de

Texture depth was limited to
prevent the tool from functioning
as a restricted rake tool
Distance de is to be optimized
with respect to the uncut chip
thickness
Maximum force reduction
referred to the texture with a
roughness of 12 µm Ra,
generated at a current of 39 A
and an on-time of 42 µs
Texturing time is ~10 seconds
9/18

P. Koshy, J. Tovey


Effectiveness of ED-texture
lubricant application
32

textured tool
Friction angle ( )

Friction angle ( )

ground tool

28
24
20
16

32
28
24
20
16

0

30 60 90 120 150 180
Time (s)

0

30 60 90 120 150 180
Time (s)

10/18
P. Koshy, J. Tovey


Force reduction in continuous cutting
Texturing decreases the forces and the variability, with
the effect more pronounced in the feed direction

0

8
6
4
2

textured

1.5

textured

3.0

10

non-textured

4.5

Cutting force (x102 N)

12

non-textured

Feed force (x102 N)

6.0

0

11/18
P. Koshy, J. Tovey


Feed force (x102 N)

6


Force reduction in intermittent cutting
non-textured

5

4
3
2
1

textured

0
0

1

2

3

Time (s)

4

5

12
10
8
6
4
2
0
0

1

2

3

4

5

Time (s)

Feed force reduction is higher in intermittent cutting as
the lubricant is directly replenished on the tool rake face
during the non-cutting interval
12/18
P. Koshy, J. Tovey


% reduction in feed force

Effect of cutting parameters on force reduction
30

50

25

40

20
15

25 µm feed

30
20

10
5

intermittent

50 µm

0

continuous

10
0

0 15 30 45 60 75 90

0

5

10 15 20 25

Cutting speed (m/min)

Cutting speed (m/min)

Texturing is more effective at the low end of typical
cutting speeds, at fine feeds and in intermittent cutting
13/18
P. Koshy, J. Tovey


2.5

2.0
1.5
1.0

textured

non-textured

0.5
0.0


Feed force (x102 N)

Force reduction in cutting of aluminum
5

4
3
2
1
0

0

5

10

15

Time (s)

20

25

0

5

10

15

20

25

Time (s)

Forces and the associated variability were significantly
lower as the lubricant used was specifically formulated for
cutting aluminum
14/18
P. Koshy, J. Tovey


Effect of texture location
Friction angle ( )

26

de

24

h = 25 µm

100 µm 50 µm

22
20

chip

18

tool

h
0

3

6

9

12

15

18

(de/h)

Force reduction is maximized when (de/h) is ~2−3
As the tool chip contact length is typically 4−6 times the
feed h, this implies that texturing needs to correspond to
just the sliding region
15/18
P. Koshy, J. Tovey


% reduction in force

Comparison of linear and areal textures
30

25

feed force

20

areal

15

cutting force

10
5
0
0

20

40

60

80

100

% area textured
linear

Textured area was varied by altering the
pitch in the linear texture
Results confirm that the areal texture is to
be preferred over a linear one
16/18

P. Koshy, J. Tovey


Role of texture parameters on force reduction
% reduction in force

35
30

35

feed force

30

25

25

20

20

cutting force

15

15

10

10

5

5

0

0
0.0

0.2

0.4

Skewness

0.6

1.5

2.0

2.5

3.0

3.5

4.0

Kurtosis

Force reduction showed no systematic trends with respect
to either the Ra roughness or the pulse parameters
Force reduction exhibited defined maxima with respect to
skewness and kurtosis of the texture
17/18
P. Koshy, J. Tovey


Conclusions
Electrical discharge texturing has been demonstrated to
bring about a significant (15−40%) reduction in machining
force through enhanced lubrication at the tool-chip
interface
The skewness and kurtosis of the texture are good
indicators of the extent of force reduction
The concept is attractive for application in broaches, taps,
gear cutting tools and possibly forming tools
Mechanical imprinting of said texture during the
compaction phase of tool inserts (as opposed to EDM of
inserts) may be explored
18/18
P. Koshy, J. Tovey


Canadian Network of Centers of Excellence

Natural Sciences & Engineering Research
Council of Canada

Thank you
for your kind attention!

Textured Cutting Tools

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (9)

Similar to Textured Cutting Tools

Similar to Textured Cutting Tools (20)

More from koshyp

More from koshyp (11)

Recently uploaded

Recently uploaded (20)

Textured Cutting Tools