Li zhou-defense

lizhou:
lizhou:
Good morning. My dissertation topic is machining chip formation / /breaking prediction
Good morning. My dissertation topic is machining chip formation breaking prediction
WPI
PhD Dissertation Presentation
Worcester Polytechnic Institute
Manufacturing Engineering Program

Machining Chip
Breaking Prediction with
Grooved Inserts in
Steel Turning

PhD Candidate Li Zhou
Advisor Yiming Rong
MFE, WPI
December 7, 2001
1

lizhou:
lizhou:
Here is the table of contents. In this presentation I’ll first introduce chip control in
Here is the table of contents. In this presentation I’ll first introduce chip control in

Table of Contents
machining, then review previous study on chip control,which leads to existing problems.
machining, then review previous study on chip control,which leads to existing problems.
Then I’ll talk about chip breaking prediction for different types of cutting tools, and online
Then I’ll talk about chip breaking prediction for different types of cutting tools, and online
chip breaking prediction tool development.
chip breaking prediction tool development.
The last parts are summary and future work.
The last parts are summary and future work.
1. Introduction
2. Literature Review
3. Extended study for chip breaking prediction for
2-D grooved inserts
4. Chip breaking prediction for 3-D grooved inserts
5. Web-based chip breaking prediction system
6. Summary
7. Future work

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lizhou:
lizhou:

Introduction
Conventionally the concept of machining is removing metal by mechanically forcing aacutting
Conventionally the concept of machining is removing metal by mechanically forcing cutting
edge through aaworkpiece, such as turning, milling, they are all chip-forming operations.
edge through workpiece, such as turning, milling, they are all chip-forming operations.
For machining chip control study, we need to answer two questions:
For machining chip control study, we need to answer two questions:
1. How chip forms and moves in space?
1. How chip forms and moves in space?
2. How chip breaks?
2. How chip breaks?
Machining:
To answer the questions, we need to study chip flow, chip curl and chip breaking. Next I’ll talk
To answer the questions, we need to study chip flow, chip curl and chip breaking. Next I’ll talk
about ititone by one.
material removal (chip-
about one by one.

forming) process
Chip Flow
Chip Curl
Chip Breaking

3

investigate and understand the absolute direction of chip flow is the logical approach in
investigate and understand the absolute direction of chip flow is the logical approach in
developing cutting models for machining, since chip curling and the subsequent chip
developing cutting models for machining, since chip curling and the subsequent chip
breaking processes depend very heavily on the nature of chip flow and its direction.
breaking processes depend very heavily on the nature of chip flow and its direction.
Introduction - Chip Flowing
Chip flow has two basic forms:
Chip flow has two basic forms:
chip flow on the tool face ––which is called as chip side flow (much of the research dealt
chip flow on the tool face which is called as chip side flow (much of the research dealt
with the chip side flow, so ititis called chip flow)
with the chip side flow, so is called chip flow)
Chip flow viewed in aaplane perpendicular to the cutting edge ––which is called as chip
Chip flow viewed in plane perpendicular to the cutting edge which is called as chip
back flow. Chip flow toward the tool groove profile in machining with grooved tools.
back flow. Chip flow toward the tool groove profile in machining with grooved tools.
Real chip flow is the combination of the two basic forms. That is, 3D chip flow.
Real chip flow is the combination of the two basic forms. That is, 3D chip flow.
For chip flow study, we need to develop models for chip flow angle.
For chip flow study, we need to develop models for chip flow angle.

Chip side-flow Chip back-flow
ηs chip flow angle (actually chip ηb chip back-flow angle
side-flow angle)
Johnson, 1962; Jawahir, 1988

4

After chip flow out, chip will curl, either naturally or forced by obstacles.
Introduction - Chip Curl
After chip flow out, chip will curl, either naturally or forced by obstacles.
Chip curl has 44basic forms ––straight chip, side curl, up curl, and screwing curl
Chip curl has basic forms straight chip, side curl, up curl, and screwing curl
Real chip curl is combinations of the basic forms.
Real chip curl is combinations of the basic forms.
The main task of chip curl study is to find out the chip curl radius, since ititsignificantly
The main task of chip curl study is to find out the chip curl radius, since significantly
influences the chip breaking.
influences the chip breaking.
1. Side-
curling

(1, 2, 3: Jawahir 1993) 2. Up-curling

3. Straight
chip

1,2,3,4: basic chip-curling forms
Real chip-curling is the combination of the basic forms 4. Screwing-curling (Fang, 2000)
5

(ISO 3685-1977 gives aacomprehensive chip form classification)
(ISO 3685-1977 gives comprehensive chip form classification)
Introduction - Chip forms and classifications
Based on chip forms and chip breaking, chips can be classified to desired chips, which are
Based on chip forms and chip breaking, chips can be classified to desired chips, which are
broken chips, and not desired chips, which are non-broken chips.
broken chips, and not desired chips, which are non-broken chips.
C-type and ε-type Short helical
According to different chip length, the desired chip can further be classified to 44types, and
According to different chip broken chips
length, the desired chip can further be chips
broken classified to types, and
the non-desired chip can be classified to 22types.
the non-desired chip can be classified to types.
with the length
less than 0.5 in

Medium helical Long helical
broken chips broken chips
with the length with the length
between 0.5-1 in between 1 – 2 in

Desired

Not Desired
Long helical
unbroken chips
with the length Long and snarled
larger than 2 in unbroken chips
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Chip control in machining is an essential problem.
Chip control in machining is an essential problem.
Long chips bring lots of troubles. It may damage finished surface, results in poor surface quality.
Long chips bring lots of troubles. It may damage finished surface, results in poor surface quality.
It may tangle with the cutting tools or machine, interrupt the machining process, result in losing
Introduction - Importance of chip control
It may tangle with the cutting tools or machine, interrupt the machining process, result in losing
machining time, and delays in the delivery of parts.
machining time, and delays in the delivery of parts.
Efficient chip control will contribute to … … …
Efficient chip control will contribute to … … …

 Unexpected long chip may cause:
 Poor surface quality of workpieces
 Damage to cutting tools / WP / Machine
 Losing machining time
 Delays in the delivery of parts

 Efficient chip control contributes to:
 Reliability of the machining process.
 High quality machined surfaces;
 Increased productivity

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To get efficient chip control, we have to satisfy two requirements:
To get efficient chip control, we have to satisfy two requirements:
1. When the cutting tool is specified, predict if the chip breaks or not under given cutting conditions.
1. When the cutting tool is specified, predict if the chip breaks or not under given cutting conditions.
2. Optimize cutting tool design and cutting condition design under chip breaking condition.
2. Optimize cutting tool design and cutting condition design under chip breaking condition.
Introduction - Objectives
Our purpose is for optimizing ………
Our purpose is for optimizing ………
The objectives in this research are to … and …
The objectives in this research are to … and …

 Objectives
 Develop chip-breaking prediction model
 Develop a Web-Based Chip Breaking Prediction Expert System
For
 Machining processes design
 Tool selection
 Tool design
 Online chip breaking control

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In most cases chips break by contacting with obstacles, which include workpiece, cutting tools, chip
In most cases chips break by contacting with obstacles, which include workpiece, cutting tools, chip
breakers.
breakers.
We have several ways to achieve chip breaking: … … …
We have several ways to achieve chip breaking: … … …

Introduction - Chip Breaking
Due to the limitations of the machining process, we often have no freedom to change the cutting
Due to the limitations of the machining process, we often have no freedom to change the cutting
conditions. Therefore optimize the design of the cutting tool geometry and the chip breaking groove are
conditions. Therefore optimize the design of the cutting tool geometry and the chip breaking groove are
the practical way to improve chip breakability.
the practical way to improve chip breakability.

Ways chip breaks:
• Chip breaking by chip/workpiece contact
• Chip breaking by chip / tool flank surface contact
• Chip breaking forced by chip breaker / chip breaking groove

To break the chip:
• Change cutting conditions
• Change cutting tool geometric features, e.g. nose radius
• Design and use chip breaker / chip breaking groove
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To help chip break, most commercial inserts have chip breaking groove or chip
To help chip break, most commercial inserts have chip breaking groove or chip
breakers. According to the type of the groove or chip breaker, the cutting tool can be
breakers. According to the type of the groove or chip breaker, the cutting tool can be
classified to 44types: … … … …
Introduction - Cutting Tools Classification
classified to types: … … … …
2D …
2D …
3D … itithas variable groove width along the cutting edge. This is the most popular
3D … has variable groove width along the cutting edge. This is the most popular
insert type used in the metal cutting industry.
insert type used in the metal cutting industry.
…
…
…
…

3D grooved tool
2D grooved tool: straight cutting edge,
chip groove with constant groove width

Grooved tool with Complicated Cutting tools with block
modifications: Pimples, dimples, type chip breaker
waviness on rake face and cutting edge 10

lizhou:
lizhou:
Cutting conditions have essential influence on chip breaking. This table lists their
Cutting conditions have essential influence on chip breaking. This table lists their
Introduction - Cutting Conditions and Chip Breaking
influences. …………
influences. …………

Chip breakability
Increase
Cutting Speed
Decrease
Depth of Cut

Feed Rate

Changing cutting conditions to break the chip is usually not
feasible due to the requirements of the machining processes

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lizhou:
lizhou:
We can get aachip breaking chart by the feed rate and the depth of cut.
We can get chip breaking chart by the feed rate and the depth of cut.
Introduction - Chip breaking limits
Generally the chip breaking curves are like this. When change cutting speed, the curve will
Generally the chip breaking curves are like this. When change cutting speed, the curve will
move forward or backward, but keep similar shape.
move forward or backward, but keep similar shape.
The chart shows there is aacritical feed rate and aacritical depth of cut, when …… chip will
The chart shows there is critical feed rate and critical depth of cut, when …… chip will
break, otherwise not. Z. Li presented the chip breaking limits theory in 1990.
break, otherwise not. Z. Li presented the chip breaking limits theory in 1990.
The fcr exists in up-curl dominated part. Dcr exists in side curl dominated part.
The fcr exists in up-curl dominated part. Dcr exists in side curl dominated part.
To predict chip breaking, we only need to predict the chip breaking limits. The most
To predict chip breaking, we only need to predict the chip breaking limits. The most
complicated part: the combination of up-curl and side-curl doesn’t need to be considered.
complicated part: the combination of up-curl and side-curl doesn’t need to be considered.
Therefore our work is greatly simplified.
Therefore our work is greatly simplified.
Based on chip breaking limits theory, Z. Li presented aasemi-empirical chip breaking
Based on chip breaking limits theory, Z. Li presented semi-empirical chip breaking
model, which we’ll discuss in detail in the literature review.
model, which we’ll discuss in detail in the literature review.

[Z. Li, 1990]
Chip breaking criterion:
1. Up-curl dominated part AB -- Critical feed rate When f > fcr, d > dcr
2. Side-curl dominated part CD -- Critical depth of cut chip will break;
3. Transitional part BC Otherwise will not break

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lizhou:
lizhou:
WPI
Next I’ll review previous work on chip control.
Next I’ll review previous work on chip control.

2. Literature Review

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People have done lots of work on chip formation mechanisms. And presented
People have done lots of work on chip formation mechanisms. And presented
many models of chip flow and chip curl.
many models of chip flow and chip curl.

Chip Formation Mechanisms – Chip Flow Direction
For chip flow, our main concern is chip flow angle.
For chip flow, our main concern is chip flow angle.
Here are the models of chip flow angle.
Here are the models of chip flow angle.

Model 1: Colwell 1954
• Chip flow perpendicular to the major axis of the projected area of cut
Model 2: Okushima & Minato, 1959
• Chip flow invariant with cutting speed
• Summation of elemental flow angles
over the entire length of the cutting edge.
Model 3: Stabler, 1951 & 1964
• Chip flow proportional to inclination.

Other Models: Armarego, 1971; Young,
1987; Wang and Mathew, 1988
• Based on above models
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For chip curl, our main concern is chip curl radius.
For chip curl, our main concern is chip curl radius.
Here are the models of chip curl radius.
Here are the models of chip curl radius.

Chip Formation Mechanisms – Chip Curl Radius
To calculate the chip curl radius
• Up-curl

Wn  lc l c2  [Z. Li, 1990]
• RC = 1 − 2
 cos γ n + 2 
2 sin γ n  Wn Wn  
• Side-curl
• Nakayama 1990: (only for rε ≤ 0.25 )
d
1 0.75 0.09
= −
R0 bch hch
bch K 2 hch + ( bch − bD )
2 2
• Huang, 1987 R =
K 2 hch + ( bch − bD ) − Khch
0 2 2

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lizhou:
lizhou:
Chip breaking have also been studied in detail. The chip breaking study can be classified to 44
Chip breaking have also been studied in detail. The chip breaking study can be classified to
methods:
methods:
…
… Chip Breaking Study
…
…
…
… 1. Material stress analysis – to find the chip breaking strain εB
…
…
• Chip curl analysis of chip formation and breaking, the FEA results
Due to the extremely complicated process (Nakayama, 1962; Z. Li, 1990)
Due to the extremely complicated processof chip formation and breaking, the FEA results
doesn’t match experimental results very well.
doesn’t match experimental results very well.
• FEA too time and labor consuming. is 1980; setup and maintain big
The database system is (Kiamecki, 1973; Lajczok,difficultto setup and maintain1985)
The database system istoo time and labor consuming. ItItis difficult toStrenkowski, aabig
machining database.
machining database.
2. Experimental work
The chip curl analysis is an efficient way to analyze chip breaking.
The chip curl analysis is an efficient way to analyze chip breaking.
Next I’ll discuss Nakayama’s work and Z. Li’s work in detail, which are the basis of the work of
•
Next I’ll discuss Nakayama’s work and Z. Li’s work in detail, which are the basis of the work of
this dissertation. Database-based prediction (Jawahir, 1990)
this dissertation.
• Tool designer – cutting tests
3. Industry application: special devices designed and applied in
some cases

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lizhou:
lizhou:
Nakayama presented aachip breaking criterion in 1962. ItIthas become the common chip
Nakayama presented chip breaking criterion in 1962. has become the common chip
Literature Review - Common Chip Breaking Criterion
breaking criterion in research.
breaking criterion in research.
In this model, chip flows out with an initial curl radius. After meet obstacles, the chip curl
In this model, chip flows out with an initial curl radius. After meet obstacles, the chip curl
radius becomes bigger and bigger, until ititbreaks. A new chip is then coming out and
radius becomes bigger and bigger, until breaks. A new chip is then coming out and
repeat this process.
repeat this process.
[Nakayama, 1962]
The chip material strain can be described as functions of the curl radius and the chip
The chip material strain can be described as functions of the curl radius and the chip
shape and thickness.ε B
shape When ε >
and thickness. chip will break
and ε B = αhc (1 / Rc − 1 / RL )

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lizhou:
lizhou:
We have talked about the chip breaking limits theory. Nakayama’s chip breaking criterion
We have talked about the chip breaking limits theory. Nakayama’s chip breaking criterion
Literature Review - The Chip Breaking Limits
and chip breaking limits theory are the basis of semi-empirical chip breaking model
and chip breaking limits theory are the basis of semi-empirical chip breaking model
presented by zhengjia liliin 1990.
presented by zhengjia in 1990.
Zhengjia Li developed models of the critical feed rate and the critical depth of cut to
Zhengjia Li developed models of the critical feed rate and the critical depth of cut to
predict chip breaking.
predict chip breaking.

Chip breaking criterion:
When f > fcr, d > dcr
chip will break;
Otherwise will not break

[Z. Li, 1990]

1. Up-curl dominated part AB -- Critical feed rate
2. Side-curl dominated part CD -- Critical depth of cut
3. Transitional part BC

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Here is the theoretical equation of the critical feed rate. ItItis applied in up-curl dominated
Here is the theoretical equation of the critical feed rate. is applied in up-curl dominated
chip breaking region.
The function disclose the fact that the critical feed rate is determined by the workpiece
The function disclose the fact that the critical feed rate is determined by the workpiece
(1) The critical feed rate
material, the cutting tool and chip breaking groove geometry, and the cutting speed.
material, the cutting tool and chip breaking groove geometry, and the cutting speed.

• Up-curl dominated region.
• Broken area: up-curled C-type chips;
• Unbroken area: snarling type chips.
• Critical feed-rate existing.

ε B ChWn K R lc
f cr = ⋅ ⋅ (1 − 2 cos γ n )
2α sin κ r sin γ n Wn
Workpiece Cutting ratio: determined by cutting speed
material property and work piece material properties

[Z. Li, 1990] 19

Here is the theoretical equation of the critical depth of cut. ItItis applied in side-curl dominated
Here is the theoretical equation of the critical depth of cut. is applied in side-curl dominated
The critical depth of cut is also determined by the workpiece material, the cutting tool and chip
The critical depth of cut is also determined by the workpiece material, the cutting tool and chip
(2) The critical depth of cut
breaking groove geometry, and the cutting speed. But the nose radius of the cutting tool has
breaking groove geometry, and the cutting speed. But the nose radius of the cutting tool has
the most significant influence on the critical depth of cut. In most cases, the critical depth of cut
the most significant influence on the critical depth of cut. In most cases, the critical depth of cut
is around the value of the nose radius.
is around the value of the nose radius.
[Z. Li, 1990] Complex 3-D chip curling.
Side-curled spiral type
continuous chips or oblique-
curl spiral type continuous
chips.
Critical depth of cut existing
and mostly determined by
insert nose radius.

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The Bridge

Chip control Basis of modeling:
is important Mechanics of chip flow 2D modeling

Expand
Difficulties
• Too many factors
Practical Application involved
• low reproducibility 3D modeling
Researches
Big
Semi-empirical Bottleneck
Gap
Very model
time/money/labor 3D modeling Academic Research
consuming Approaches

••• •••
New Problems: New material, new tools,
new fluid, ultra high speed, fine turning

21

Zhengjia li’s work on chip breaking limits show that the chip breaking limits are determined by
Zhengjia li’s work on chip breaking limits show that the chip breaking limits are determined by
the material, the cutting speed and the cutting tool geometry. Therefore he presented this
the material, the cutting speed and the cutting tool geometry. Therefore he presented this
model for chip breaking prediction.
model for chip breaking prediction.
Literature Review - Semi-empirical Chip Breaking Model
Here the critical feed rate and the critical depth of cut are presented in this way. The f0 and
Here the critical feed rate and the critical depth of cut are presented in this way. The f0 and
the d0 are the ……
the d0 are the …… Chip will break, when:
The kft Materialcuttingtool modificationInsert
The kftis the cutting tool modificationcoefficient. zhengjia f lidescribed ititdasthe function of the
is the Speed coefficient. zhengjiali ≥ f cr and as d cr function of the
described ≥ the
nose radius, the main cutting edge angle, and the groove width.
nose radius, the main cutting edge angle, and the groove width.
the kfv is the cutting speed modification coefficient, =itis K function of the cutting speed.
the kfv is the cutting speed modification coefficient,it fisaafT K fv K fm of the d = d speed. K
f cr function cutting K K
0 cr 0 dT dv dm
the kfm is the material modification coefficient determined by material properties.
the kfm is the material modification coefficient determined by material properties.
Critical feed rate
so do the kdt, kdv, and kdm. K fT = K frε ⋅ K fk r ⋅ K fWn K dT = K drε ⋅ K dk r ⋅ K dWn
so do the kdt, kdv, and kdm.
K fV = coefficients, so that thechipF (breaking
Zhengjia developed the equations of the modification F (V )
K = V)
Zhengjia lilideveloped the equations of the modification coefficients, so that thedVchipbreaking
limits can be predicted under any given conditionswithout( doing cutting test. K dm = F ( m )
limits can be predicted under any given conditionsK withoutm )
= F doing cutting test.
Chip breakability fm
Compared with database system, ititsaves lots of time and labor on experimental work. The
Compared with database system, saves lots of time and labor on experimental work. The
semi-empirical model only need aasmall number of cutting tests to develop the equations of
semi-empirical model only need small number of cutting tests to develop the equations of
the modification coefficients, then ititcan predict chip breaking without more experimental
• f0 and d0 : more experimental
the modification coefficients, then can predict chip breaking withoutthe standard
work.
work. Critical depth of cut chip breaking limits under
pre-defined standard
condition
Material Speed Insert
[Z. Li, 1990]
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Zhengjia li’s approach has great advantages, but ititalso has some limitations.
Zhengjia li’s approach has great advantages, but also has some limitations.
……
……
…… Advantages of the semi-empirical model
……
In this dissertation li’sonly awillbe extended to include more importantto develop the
1. Need model small number of cutting tests geometric
In this dissertation li’smodel will be extended to include more importantgeometric
features of the 2D grooved inserts. Then semi-empirical model for 3D grooved
empirical equations
inserts will also be developed. They are then be integrated to aaweb-based expert
inserts will also be developed. They are then be integrated to web-based expert
system for online chip breaking prediction.
2. Bridge the theoretical study and the industry applications
The system developed in this research is based on aaproject cooperated with Ford
The system developed in this research is based on project cooperated with Ford
Motor company in the last 33years, and the system developed in this research is
Motor company in the last years, and the system developed in this research is
running on Ford powertrain branch.
Existing Problems
1. 2D model not complete – some important geometric
features not considered
2. No model for 3D-grooved tools
3. No applicable chip breaking prediction tool for industry
application
23

Zhengjia li’s approach has great advantages, but ititalso has some limitations.
Zhengjia li’s approach has great advantages, but also has some limitations.
……
……
…
…
…
…
My Work Extended 2D
Extended 2D
Model
Model
In this dissertation li’s model will be extended to include more important geometric
In this dissertation li’s model will be extended to include more important geometric
1. Extended Zhengjia Li’s 2D
inserts will also be developed. They are then be integrated to aaweb-based expert
inserts will also be developed. Theyto include
predictive model are then be integrated to web-based expert
The system developed in this research isfeaturesaaproject cooperated with Ford
The systemimportant geometricisbased on that
developed in this research based on project cooperated with Ford3D Model
Motor company in the last 33years, and the system developed in this research is 3D Model
not considered previously;
Motor company in the last years, and the system developed in this research is
2. Developed a semi-empirical chip
breaking prediction model for
3D-grooved tools
3. Integrated the models into a Web-based Chip
Web-based Chip
Breaking Prediction
Breaking Prediction
web-based chip breaking System
System
prediction expert system for
industry application
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lizhou:
lizhou:
In this research the semi-empirical model for 2D grooved inserts are extended to include
In this research the semi-empirical model for 2D grooved inserts are extended to include
more geometric features of the cutting tool.
more geometric features of the cutting tool.

3. Extended Chip Breaking Model
for 2-D Grooved Inserts

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lizhou:
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O
Geometric Features
This figure shows the geometric features of 2D grooved inserts.
This figure shows the geometric features of 2D grooved inserts.
Rc
The rake angle, …, …, and … they are not included in zhengjia li’s model, their influence
on chip breaking limits will be studied here.
on chip breaking limits will be studied here. of 2-D grooved inserts
The rake angle, …, …, and … they are not included in zhengjia li’s model, their influence

h

γ0

Tool feed direction
Wn

• Rake angle γ0 γ 01 γ0

• Back-wall height h br1

• Land length br1

• Land rake angle γ01 Wn

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lizhou:
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Through chip curl analysis, we can get the new theoretical equation of the critical feed rate
Through chip curl analysis, we can get the new theoretical equation of the critical feed rate
Theoretical Analysis Result - fcr
as below
as below
ItItis still the function of the work piece material, the cutting speed, and the insert geometric
is still the function of the work piece material, the cutting speed, and the insert geometric
features. Compared with zhengjia li’s equation of fcr, this equation take the rake angle, the
features. Compared with zhengjia li’s equation of fcr, this equation take the rake angle, the
backwall height, the land length and the land rake angle into consideration
backwall height, the land length and the land rake angle into consideration

 2 cos(γ 01 − α ) 
 W + h + l f − 2l f (W cos γ 0 − h sin γ 0 + br1
2 2
) 
 cos(γ 0 + α ) 
+
ε b ch k r  2(W sin γ 0 + h cos γ 0 ) 
f cr = ⋅ 
2 sin κ r  cos(γ 01 − α ) 2 cos(γ 01 − α )
2

 br1 cos(γ + α ) (W cos γ 0 − h sin γ 0 ) + br1 cos(γ + α ) 2 
 0 0 
 2(W sin γ 0 + h cos γ 0 ) 
 

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lizhou:
lizhou:
We can also get the theoretical equation of the dcr;
We can also get the theoretical equation of the dcr;
Theoretical Analysis Result -d
These items are close to zero, so that the critical depth of cut is close to the nose radius.
These items are close to zero, so that the critical depth of cutcr close to the nose radius.
is

 
 2 arcsin − p + p + 0.12q − arcsin f
2
d cr = rε − rε cos 
 0.12ξ1rε 2rε 
 
when d ≤ rε (1 − cos κ r ) , f ≤ 2rε
d cr ≈ rε
( )
2
f 1
− p + p 2 + 0.12q sin ( κ r − Ψλ )
2
d cr = rε − rε − +
4 0.06ξ1
when d ≥ rε (1 − cos κ r ) , f ≤ 2rε
 p = ( ε B k − 0.25)ξ 2 a + 0.03c
where 
q = 0.25ξ 2 ac
 rε (1 − cos Ψλ ) + f sin ( κ r − Ψλ ) when d ≤ rε (1 − cos κ r ) , f ≤ 2rε
a =   sin ( β − Ψ ) 
r 1 −
  + f sin ( κ r − Ψλ ) when d ≥ rε (1 − cos κ r ) , f ≤ 2rε
λ
  ε
  sin β 
c = f cos( κ − Ψ )
 r λ
and  1  r − d cr f 
    arccos ε + arcsin  when d ≤ rε (1 − cos κ r ) , f ≤ 2rε
  2 rε 2rε  
 Ψλ = 
 κ − arccot cotκ + rε tan κ r + f 
  when d ≥ rε (1 − cos κ r ) , f ≤ 2rε
 r  r
2 2d cr 

   d cr  28

lizhou:
lizhou:
Then we can develop the new semi-empirical model as below.
Extended Semi-empirical Chip breaking model
Then we can develop the new semi-empirical model as below.
The modification coefficients kfv, kfm, kdv and kdm keep the same, but the cutting tool
coefficients2-D changed to include more geometric features.
for are grooved inserts
The modification coefficients kfv, kfm, kdv and kdm keep the same, but the cutting tool
coefficientsare changed to include more geometric features.
To get the new modification coefficients, experimental work are conducted
To get the new modification coefficients, experimental work are conducted
Semi-empirical Model

f cr = f 0 K fT K fv K fm
K fT = K frε × K fW n × K fκ γ × K fγ 0 × K fγ 01 × K fh × K fbγ 1
K fV = F f (V )

K fm = F f (m)
d cr = d 0 K dT K dv K dm
K dT = K drε × K dW n × K dκ γ × K dγ 0 × K dγ 01 × K dh × K dbγ 1

K dV = Fd (V )
K dm = Fd (m)

29

lizhou:
lizhou:
In the experiments design, every geometric features were designed as 44levels. Sixteen
In the experiments design, every geometric features were designed as levels. Sixteen
customized inserts are made by ourselves to do the cutting tests.
customized inserts are made by ourselves to do the cutting tests.
Experiment Design
ItItis difficult to manufacture the designed inserts. We cooperated with the harbin university
is difficult to manufacture the designed inserts. We cooperated with the harbin university
of sci. and tech. to make the inserts. They have good equipment and developed tool
of sci. and tech. to make the inserts. They have good equipment and developed tool
geometry measurement system and software along with us.
geometry measurement system and software along with us.
Inserts parameters design in the cutting tests:
4 parameters, and 4 levels for every parameter

Rake angle: 10°, 14°, 18°, 22°

Backwall Height: 0.1mm, 0.2mm, 0.3mm, 0.4mm

Land Rake Angle: -5°, -10°, -15°, -20°

Land Length: 0mm, 0.1mm, 0.2mm, 0.4mm

16 Inserts had been made and used in the tests

30

lizhou:
lizhou:
From the cutting tests, we got the modification coefficients as shown here.
From the cutting tests, we got the modification coefficients as shown here.
ItItis noted that the rake angle, the land length and the backwall height both have significant
Results
is noted that the rake angle, the land length and the backwall height both have significant
influence on the critical feed rate, but the land rake angle has very slight influence on the
influence on the critical feed rate, but the land rake angle has very slight influence on the
fcr. All parameters have almost no influence on the critical depth of cut. The cutting results
fcr. All parameters have almost no influence on the critical depth of cut. The cutting results
shows the critical depth of cut is mainly determined by the nose radius.
shows the critical depth of cut is mainly determined by the nose radius.

K fγ 0 = 1.32 − 0.0208γ 0 K dγ 0 = 1
K fbγ 1 = 0.696 + 1.52bγ 1 K dbγ 1 = 1
d cr ≈ rε
K fγ 01 = 1 K dγ 01 = 1

K fh = 1 − 1.84h K dh = 1

31

lizhou:
lizhou:
This table shows the parameters influence tendency on chip breakability.
This table shows the parameters influence tendency on chip breakability.

Results

fcr dcr Chip Breakability

Rake Angle

Backwall Height

Land Rake Angle

Land Length

Increase Decrease
32

lizhou:
lizhou:
This pictures shows the comparison between the theoretical results, the experimental
This pictures shows the comparison between the theoretical results, the experimental
Experimental Results - fcr
results, and the semi-empirical model prediction results. ItItis found they matches well.
results, and the semi-empirical model prediction results. is found they matches well.

0.6 0.6
Theoretical Result Theoretical Result
0.5 Experimental Result 0.5 Experimental Result
Empirical Model Result Empirical Model Result
0.4

fcr (mm/rev)
0.4
fcr (mm/rev)

0.3 0.3

0.2 0.2

0.1 0.1

0
0
10 12 14 16 18 20 22 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Rake Angle (deg.) Land Length (mm)

0.5
0.5
Theoretical Result 0.45 Theoretical Result
0.45
Experimental Result 0.4 Experimental Result
0.4
0.35 Empirical Model Result 0.35 Empirical Model Result

fcr (mm/rev)
fcr (mm/rev)

0.3 0.3

0.25 0.25

0.2 0.2

0.15 0.15
0.1 0.1
0.05 0.05
0 0
-20 -15 -10 -5 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Land Rake Angle (deg.) Back-wall height (mm)

33

lizhou:
lizhou:
These pictures are the results of the critical depth of cut.
These pictures are the results of the critical depth of cut.
Experimental Results - dcr
2 2
1.8 Theoretical Result 1.8 Theoretical Result
1.2 1.2

dcr (mm)
dcr (mm)

1 1
0.8 0.8
0.6 0.6
0.4 0.4
0.2 0.2
0 0
10 12 14 16 18 20 22 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Rake Angle (deg) Land Length (mm)

2 2
1.8 Theoretical Result 1.8 Theoretical Result
1.2 1.2
dcr (mm)

1 dcr (mm) 1
0.8 0.8
0.6 0.6
0.4 0.4
0.2 0.2
0 0
-20 -15 -10 -5 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Land Rake Angle (deg) Backwall Height (mm)

34

lizhou:
lizhou:
Although aacomplete 2d model is useful in chip breaking prediction, most commercial
Although complete 2d model is useful in chip breaking prediction, most commercial
inserts in finish cutting are 3d grooved inserts.
inserts in finish cutting are 3d grooved inserts.
When we do the chip control project with ford, we submit aa2d chip breaking system to
When we do the chip control project with ford, we submit 2d chip breaking system to
them at the end of the first year, but they said what they really want in workshop is aa3D
them at the end of the first year, but they said what they really want in workshop is 3D
chip breaking prediction system so that the project has been continued to develop semi-
chip breaking prediction system so that the project has been continued to develop semi-

4. Semi-empirical Chip Breaking
empirical models for 3d grooved inserts.
empirical models for 3d grooved inserts.

Model for 3-D Grooved Inserts

35

3D grooved inserts with non-straight groove are very popular in industry
3D grooved inserts with non-straight groove are very popular in industry
machining application.
machining application.
Chip breaking problem mainly exists in finish-turning cause depth of cut is
Chip breaking problem mainly exists in finish-turning cause depth of cut is
3-D Grooved Inserts
small, while this kind of inserts are the main inserts used in finish-turning
small, while this kind of inserts are the main inserts used in finish-turning
The samples shown here are two typical inserts used in ford powertrain.
The samples shown here are two typical inserts used in ford powertrain.

Important in chip
control research:

Geometry of 3-D grooved inserts • Most chip breaking
problem exists in
finish machining
• More than 70% of
industry insert for
finish machining are
TNMP332K KC850 TNMG332MF 235
3D grooved inserts
Two Samples

36

lizhou:
lizhou:
This figure shows the geometry of the 3d grooved inserts. 77geometric parameters are
This figure shows the geometry of the 3d grooved inserts. geometric parameters are
Geometric Features and Chip Breaking Limits
considered to develop the equations of the chip breaking limits. They are the nose
considered to develop the equations of the chip breaking limits. They are the nose
radius, the land length, the rake angle, the backwall height, the inclination angle, the
radius, the land length, the rake angle, the backwall height, the inclination angle, the
distance of the protrusion and the protrusion angle. The chip breaking limits will be
distance of the protrusion and the protrusion angle. The chip breaking limits will be
described as functions of these parameters through experiments.rε , L, α , bγ 0 , γ n , h, λs )
f cr = F f (
described as functions of these parameters through experiments.
r ε L
d cr = Fd (rε , L,α , bγ 0 , γ n , h, λs )
y

α
l1
B-View
x Wn

Wn bγ0
h
γn

Wn’

A A A‑A
λs

B-View
37

lizhou:
lizhou:
Experiment Design
For the experimental work, we first select 3d grooved commercial inserts as many as
For the experimental work, we first select 3d grooved commercial inserts as many as
possible so that we had aabig sample space to develop our model. Then we do cutting
possible so that we had big sample space to develop our model. Then we do cutting
tests to get the chip breaking charts of the inserts. Then we developed the equations.
tests to get the chip breaking charts of the inserts. Then we developed the equations.
Insert selection
Here is aatypical chip breaking chart.
Here is typical chip breaking chart.
For most inserts used in the cutting tests, they have constant backwall height and
For most inserts used in the cutting tests, they have constant backwall height and
inclination angle, so that we removed these two parameters from the equation.
inclination angle, so that we removed these two parameters from the equation.
Insert geometric
features measurement

Cutting tests –
To get fcr and dcr

Develop
empirical equations

A
22 different commercial inserts were used in cutting test Sample

h and λs are constant 38

lizhou:
lizhou:
For measuring the tool geometric features, we developed aainsert geometric features
For measuring the tool geometric features, we developed insert geometric features
measurement tool and relative software system in cooperation Softwareuniv. of sci.
Insert Geometric Features Measurement with Harbin
measurement tool and relative software system in cooperation with Harbin univ. of sci.
and tech.
and tech.
Here are screen shoot of the software user-interface. ItItis shown how to measure the nose
Here are screen shoot of the software user-interface. is shown how to measure the nose
radius.
radius. A software package has been
developed to process the raw data

A measurement equipment
has been developed to do the
insert geometry measuring

In cooperation with Harbin University of Science &
Technology, Harbin, China, 2001
39

Here is the equations of the chip breaking limits we developed from the experiments.
Here is the equations of the chip breaking limits we developed from the experiments.

Results

 f cr = 0.010 + 0.099rε + 0.0474 L − 0.009α + 0.304bγ 0 − 0.014γ n


d cr = 0.064 + 1.17rε + 0.228 L − 0.06α + 0.753bγ 0 − 0.033γ n


 K fT = 3.45 + 34.13rε + 16.35 L − 3.10α + 104.8bγ 0 − 4.82γ n


 K dT = 2.13 + 39rε + 7.6 L − 2α + 25.1bγ 0 − 1.1γ n


 f 0 = 0.0029in / rev Pre-defined standard cutting condition
 • Work piece material 1010 steel
d 0 = 0.03in
• Cutting speed 523sfpm
• Insert TNMP332K KC850
40

lizhou:
lizhou:
These graphscompare FCR model predictive Fcr results and the experimental results of Results
Fcr - Experimental the
These graphs TNMG33X MF235the model predictive results and the experimental results of the
compare the Model predictive
chip breaking limits. They match well.
chip breaking limits. They match well.
0.0120
TNMP33XK KC850 FCR Model predictive Fcr
0.0100
0.0120
0.0080
fcr (in/rev)

0.0100
0.0060
0.0080

fcr (in/rev)
0.0040 0.0037
0.0035
0.0029 0.0060
0.0020 0.0022 0.0020 0.0054
0.0017 0.0017
0.0011 0.0040 0.0042
0.0000 0.0037
0.0029 0.0029
331 332 333 334 0.0020 0.0021
nose radius 0.0000
331 332 333
nose radius
TNMG33X KC850 FCR Model predictive Fcr

0.0120 TNMG33X QF4025 FCR Model predictive Fcr

0.0100
0.0120
0.0080 0.0082
fcr (in/rev)

0.0071 0.0100
0.0060 0.0065
0.0060 0.0059 0.0080

fcr (in/rev)
0.0072
0.0040 0.0065
0.0063
0.0029 0.0060 0.0056
0.0020 0.0049
0.0040
0.0000 0.0025
0.0020
331 332 333
nose radius 0.0000
331 332 333
nose radius

41

lizhou:
lizhou:
Here shows the critical depth of cut
Here shows the critical depth of cut
TNMG33X MF235 DCR Model predictive Dcr
Dcr - Experimental Results
0.12 TNMG33X KC850 DCR Model predictive Dcr
0.1
0.12
0.08
0.1
dcr (in)

0.070
0.06
0.08

dcr (in)
0.048
0.04 0.04 0.04 0.07
0.033
0.03 0.06 0.06 0.064
0.056
0.02 0.02
0.019 0.05
0.04 0.039
0
0.02
331 332 333 334
331 332 333
nose radius
nose radius

TNMG33X MF235 DCR Model predictive Dcr

TNMP33XK KC850 DCR Model predictive Dcr
0.12

0.1 0.12

0.08 0.1
dcr (in)

0.070
0.06 0.08

dcr (in)
0.048 0.065
0.04 0.04 0.04 0.06
0.033
0.03 0.05
0.04 0.04
0.02 0.02
0.019 0.033 0.034
0.03
0.02
0
331 332 333 334 0
nose radius 331 332 333
nose radius

42

lizhou:
lizhou:
To apply the semi-empirical chip breaking predictive model in real application, we need to
To apply the semi-empirical chip breaking predictive model in real application, we need to
integrate the models to aasystem. A web-based system will be aapowerful tool for online chip
integrate the models to system. A web-based system will be powerful tool for online chip
breaking prediction, and tool geometry and cutting condition design.
breaking prediction, and tool geometry and cutting condition design.

5. Web-based Chip Breaking
Prediction System

 Presently being used by Ford Motor Inc.

43

lizhou:
lizhou:
The system developed in this research has great advantages. The semi-empirical models
The system developed in this research has great advantages. The semi-empirical models
provide aasolid base for the system.
Web-based Chip Breaking Prediction System
provide solid base for the system.
The system is accessible through internet or intranet, so that is very convenient for online
The system is accessible through internet or intranet, so that is very convenient for online
chip breaking prediction and tool / /cutting condition design.
chip breaking prediction and tool cutting condition design.
ItItonly need to do aasmall number of cutting test to establish the necessary databases.
only need to do small number of cutting test to establish the necessary databases.
Also the databases are easy to maintain and expand.
Also the databases are easy to maintain and expand.
• Integrated with the semi-empirical
chip breaking models for chip breaking
prediction
• Available through the Internet.
Powerful online tool for industry usage
• Easy to setup the databases. Easy to
maintain and expand.
44

lizhou:
lizhou:
Web-Based Machining Chip Breaking Prediction System
Here is aascreenshot of the system. User give input to the system, the system returns
Here is screenshot of the system. User give input to the system, the system returns
user aapredictive chip breaking chart.
user predictive chip breaking chart.
User Input
• Insert selection
• Work-piece selection
• Cutting conditions input

Supported by
• Semi-empirical models
• Inserts database
• Material database

45

lizhou:
lizhou:

Web-based Chip Breaking Prediction System
This figure shows the system infrastructure.
This figure shows the system infrastructure.
The system is running on the server side, supported by the models, cutting tools and
The system is running on the server side, supported by the models, cutting tools and
workpiece material databases. Any update of the system will be done in the server side
workpiece material databases. Any update of the system will be done in the server side
without influence the client side.
without influence the client side.
New WP/ Existed
In the client side, user can access the system through web-browser, such as IE or
In the client side, user can access the system through web-browser, such as IE or
inserts Models
Netscape. No installation needed. Username and password are needed to access the
Netscape. No installation needed. Username and password are needed to access the
system.
system.

46

lizhou:
lizhou:
This is the system flow chart.
This is the system flow chart.
System flow chart

Start
Start
Check Search Insert/WP
Check Search Insert/WP Model for 2D
input values in cutting DB Model for 2D
input values in cutting DB grooved tool
grooved tool
Update
Update Model for 3D
parameter list
parameter list
User Input
User Input Decide chip
Decide chip Model for 3D
grooved tool
breaking model grooved tool
breaking model
Update tool
Update tool
information
information Model for other
Retrieve empirical Model for other
Retrieve empirical cutting tools
Predict
Predict equation from DB
equation from DB cutting tools

Chip breaking
Chip breaking
Calculate chip
Calculate chip
breaking limits
breaking limits
Output
Output
Retrieve chip
Retrieve chip
breaking chart
breaking chart
from DB
from DB
En
En
dd
47

lizhou:
lizhou:
How to store chip breaking chart in the database is aaproblem. The chip is classified to 66
How to store chip breaking chart in the database is problem. The chip is classified to
types according to it’s breakability. Rank 11represents the best broken chip, and is
Chip Breaking Chart to Chip Breaking Matrix
types according to it’s breakability. Rank represents the best broken chip, and is
described by aanumber 1. So do other types of chips. Then we can get aachip breaking
described by number 1. So do other types of chips. Then we can get chip breaking
matrix to represent the chip breaking chart and store in the database.
matrix to represent the chip breaking chart and store in the database.

5 3 1 1 1 1 1
5 4 1 1 1 1 1
 
5 4 1 1 1 1 1
 
5 4 1 1 1 1 1
5 5 1 1 1 1 1
 
5 5 1 1 1 1 6
5 5 5 6 6 6 6
 

48

lizhou:
lizhou:
This is the use input interface.
This is the use input interface.
User need to choose inserts, geometric parameters, unit system, cutting conditions.
User need to choose inserts, geometric parameters, unit system, cutting conditions.
The insert picture is shown on the right.
The insert picture is shown on the right.

49

User Input

Insert type selection

Cutting condition selection

Nose radius selection

50

lizhou:
lizhou:
User Input
Also user can get online help simply by click on the hyperlinks. For values out of
Also user can get online help simply by click on the hyperlinks. For values out of
range, system will popup aawarning message and ask user to re-input.
range, system will popup warning message and ask user to re-input.

Metric / inch system selection

Warning message

Online help

51

lizhou:
lizhou:
This is the system output. The chip breaking chart, the chip breaking limits and the
This is the system output. The chip breaking chart, the chip breaking limits and the
insert picture will be given. By clicking the chart, user can get online help.
System
insert picture will be given. By clicking the chart, user can get online help.

output

Prediction Output:
• Overall chip breaking
chart with chip
shapes
• Critical feed rate
• Critical depth of cut
52

lizhou:
lizhou:
The system also has some limitations. It’s only good for the inserts that included by
The system also has some limitations. It’s only good for the inserts that included by
Limitations of the System
the semi-empirical models. It’s not work for inserts with block type chip breaker and
the semi-empirical models. It’s not work for inserts with block type chip breaker and
with complicated geometric features because they are not covered by the model.
with complicated geometric features because they are not covered by the model.
It’s for steel cutting only, not for soft metal cutting.
It’s for steel cutting only, not for soft metal cutting.

• For 2D grooved cutting tools and 3D
grooved cutting tools only. Not work for
cutting tools with block-type chip breaker
and cutting tools with complicated
geometric features.
• For steel cutting only.

53

lizhou:
lizhou:
Here is the summary.
Here is the summary.
6. Summary
In this research, the semi-empirical chip breaking predictive models are developed for
In this research, the semi-empirical chip breaking predictive models are developed for
2D grooved inserts, and for 3D grooved inserts. A web-based system is developed for
2D grooved inserts, and for 3D grooved inserts. A web-based system is developed for
industry application.
industry application.
The semi-empirical chip breaking model has been
extended in 3 aspects:
 Extended semi-empirical chip breaking model
for 2D grooved inserts
 Semi-empirical chip breaking model for 3D
grooved inserts
 Web-based chip breaking prediction system

The technique / system has been used in Ford Powertrain

54

lizhou:
lizhou:
The future work may include developing chip breaking models for inserts with complicated
geometric Future or with block-type chip breaker, and for soft metal cutting.
7. featuresWork - for inserts with
The future work may include developing chip breaking models for inserts with complicated
geometricfeatures or with block-type chip breaker, and for soft metal cutting.
complicated modifications
The reason that the model developed here doesn’t include inserts with complicated
The reason that the model developed here doesn’t include inserts with complicated
geometric features is that general chip breaking limits may not exist for this kind of inserts.
geometric features is that general chip breaking limits may not exist for this kind of inserts.
This chip breaking chart shows aaexample. You can see there are extra chip breaking
This chip breaking chart shows example. You can see there are extra chip breaking
Extra chip breaking region
region when depth of cut and feed rate is small, due to the existence of the bumps on the region
Normal chip breaking
region when depth of cut and feed rate is small, due to the existence of the bumps on the
insert rake face.
insert rake face.

55

lizhou:
lizhou:
Inserts with block-type chip breaker are widely applied in soft metal cutting. We can also
Inserts with block-type chip breaker are widely applied in soft metal cutting. We can also
retrieve aafew geometric features and develop semi-empirical model for this kind of
retrieve few geometric features and develop semi-empirical model for this kind of
inserts. The difficulty is that inserts withget the chip breaking limits from the soft
7. Future Work - is not easy to block-type chip breaker
inserts. The difficulty is that ititis not easy to get the chip breaking limits from the soft
metal cutting.
metal cutting.
h

B

θ
A

ϕ
L γ1

O
B-B Section
B

rε

λs

A A A
ϕ>0 ϕ=0 ϕ<0

Illustration of the geometry of the block-type chip breaker
56

lizhou:
lizhou:
This picture shows aachip breaking chart of the soft metal cutting. Chips of soft metal cutting
This picture shows chip breaking chart of the soft metal cutting. Chips of soft metal cutting
are much more difficult to break than chips from steel cutting. On the other hand, ififthe feed
are much more difficult to break than chips from steel cutting. On the other hand, the feed
rate or depth of cut are too big, the breaking prediction for soft metal cutting
7. Future Work – chip surface quality will be unacceptable. we could find
rate or depth of cut are too big, the surface quality will be unacceptable. IfIfwe could find aa
way to get the chip breaking limits efficiently from the cutting tests, we would be able to
way to get the chip breaking limits efficiently from the cutting tests, we would be able to
develop semi-empirical models for soft metal cutting with inserts with block-type chip
develop semi-empirical models for soft metal cutting with inserts with block-type chip
breaker.
breaker.

57

WPI

Any questions or comments?

58

WPI

THANK YOU!

59

Li zhou-defense

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