Li zhou-defense

1

WPI Worcester Polytechnic InstituteManufacturing Engineering Program

Machining Chip

Breaking Prediction with

Grooved Inserts in

Steel Turning

PhD Dissertation Presentation

PhD Candidate Li Zhou

Advisor Yiming Rong

MFE, WPIDecember 7, 2001

lizhou:

Good morning. My dissertation topic is machining chip formation / breaking prediction

lizhou:

Good morning. My dissertation topic is machining chip formation / breaking prediction

2

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

Table of Contents

lizhou:

Here is the table of contents. In this presentation I’ll first introduce chip control in 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 chip breaking prediction tool development.

The last parts are summary and future work.

lizhou:

Here is the table of contents. In this presentation I’ll first introduce chip control in 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 chip breaking prediction tool development.

The last parts are summary and future work.

3

Introduction

Machining:

material removal (chip-

forming) processChip Flow

Chip Curl

Chip Breaking

lizhou:

Conventionally the concept of machining is removing metal by mechanically forcing a cutting edge through a workpiece, such as turning, milling, they are all chip-forming operations.

For machining chip control study, we need to answer two questions:

1. How chip forms and moves in space?

2. How chip breaks?

To answer the questions, we need to study chip flow, chip curl and chip breaking. Next I’ll talk about it one by one.

lizhou:

Conventionally the concept of machining is removing metal by mechanically forcing a cutting edge through a workpiece, such as turning, milling, they are all chip-forming operations.

For machining chip control study, we need to answer two questions:

1. How chip forms and moves in space?

2. How chip breaks?

To answer the questions, we need to study chip flow, chip curl and chip breaking. Next I’ll talk about it one by one.

4

Introduction - Chip Flowing

Chip side-flow

ηs chip flow angle (actually chip side-flow angle)

Chip back-flow

ηb chip back-flow angle

Johnson, 1962; Jawahir, 1988

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 breaking processes depend very heavily on the nature of chip flow and its direction.

Chip flow has two basic forms:

chip flow on the tool face – which is called as chip side flow (much of the research dealt with the chip side flow, so it is called chip flow)

Chip flow viewed in a 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.

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.

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 breaking processes depend very heavily on the nature of chip flow and its direction.

Chip flow has two basic forms:

chip flow on the tool face – which is called as chip side flow (much of the research dealt with the chip side flow, so it is called chip flow)

Chip flow viewed in a 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.

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.

5

Introduction - Chip Curl

1. Side-curling

2. Up-curling

3. Straight chip

(1, 2, 3: Jawahir 1993)

1,2,3,4: basic chip-curling forms

Real chip-curling is the combination of the basic forms 4. Screwing-curling (Fang, 2000)

After chip flow out, chip will curl, either naturally or forced by obstacles.

Chip curl has 4 basic forms – straight chip, side curl, up curl, and screwing curl

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 it significantly influences the chip breaking.

After chip flow out, chip will curl, either naturally or forced by obstacles.

Chip curl has 4 basic forms – straight chip, side curl, up curl, and screwing curl

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 it significantly influences the chip breaking.

6

Introduction - Chip forms and classificationsC-type and ε-type broken chips

Short helical broken chips

with the length less than 0.5 in

Medium helical broken chips

with the length between 0.5-1 in

Long helical broken chips

with the length between 1 – 2 in

Long helical unbroken chips

with the length larger than 2 in

Long and snarled unbroken chips

Desired

Not Desired

(ISO 3685-1977 gives a comprehensive chip form classification)

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.

According to different chip length, the desired chip can further be classified to 4 types, and the non-desired chip can be classified to 2 types.

(ISO 3685-1977 gives a comprehensive chip form classification)

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.

According to different chip length, the desired chip can further be classified to 4 types, and the non-desired chip can be classified to 2 types.

7

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

Introduction - Importance of chip control

Chip control in machining is an essential problem.

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 machining time, and delays in the delivery of parts.

Efficient chip control will contribute to … … …

Chip control in machining is an essential problem.

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 machining time, and delays in the delivery of parts.

Efficient chip control will contribute to … … …

8

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

Introduction - Objectives

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.

2. Optimize cutting tool design and cutting condition design under chip breaking condition.

Our purpose is for optimizing ………

The objectives in this research are to … and …

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.

2. Optimize cutting tool design and cutting condition design under chip breaking condition.

Our purpose is for optimizing ………

The objectives in this research are to … and …

9

Introduction - Chip Breaking

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

In most cases chips break by contacting with obstacles, which include workpiece, cutting tools, chip breakers.

We have several ways to achieve chip breaking: … … …

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 the practical way to improve chip breakability.

In most cases chips break by contacting with obstacles, which include workpiece, cutting tools, chip breakers.

We have several ways to achieve chip breaking: … … …

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 the practical way to improve chip breakability.

10

Introduction - Cutting Tools Classification

Grooved tool with Complicated modifications: Pimples, dimples, waviness on rake face and cutting edge

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

3D grooved tool

Cutting tools with block type chip breaker

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 classified to 4 types: … … … …

2D …

3D … it has variable groove width along the cutting edge. This is the most popular insert type used in the metal cutting industry.

…

…

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 classified to 4 types: … … … …

2D …

3D … it has variable groove width along the cutting edge. This is the most popular insert type used in the metal cutting industry.

…

…

11

Introduction - Cutting Conditions and Chip Breaking

Chip breakability

Cutting Speed

Depth of Cut

Feed Rate

Decrease

Increase

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

lizhou:

Cutting conditions have essential influence on chip breaking. This table lists their influences. …………

lizhou:

Cutting conditions have essential influence on chip breaking. This table lists their influences. …………

12

Introduction - Chip breaking limits

[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

Chip breaking criterion:

When f > fcr, d > dcr

chip will break;

Otherwise will not break

lizhou:

We can get a chip breaking chart by the feed rate and the depth of cut.

Generally the chip breaking curves are like this. When change cutting speed, the curve will move forward or backward, but keep similar shape.

The chart shows there is a critical feed rate and a critical depth of cut, when …… chip will 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.

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. Therefore our work is greatly simplified.

Based on chip breaking limits theory, Z. Li presented a semi-empirical chip breaking model, which we’ll discuss in detail in the literature review.

lizhou:

We can get a chip breaking chart by the feed rate and the depth of cut.

Generally the chip breaking curves are like this. When change cutting speed, the curve will move forward or backward, but keep similar shape.

The chart shows there is a critical feed rate and a critical depth of cut, when …… chip will 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.

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. Therefore our work is greatly simplified.

Based on chip breaking limits theory, Z. Li presented a semi-empirical chip breaking model, which we’ll discuss in detail in the literature review.

13


2. Literature Review

lizhou:

Next I’ll review previous work on chip control.

lizhou:

Next I’ll review previous work on chip control.

14

Chip Formation Mechanisms – Chip Flow Direction

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.

Model 1: Colwell 1954

• Chip flow perpendicular to the major axis of the projected area of cut

Other Models: Armarego, 1971; Young, 1987; Wang and Mathew, 1988

• Based on above models

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

For chip flow, our main concern is chip flow angle.

Here are the models of chip flow angle.

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

For chip flow, our main concern is chip flow angle.

Here are the models of chip flow angle.

15

Chip Formation Mechanisms – Chip Curl RadiusTo calculate the chip curl radius

• Up-curl

•

• Side-curl

• Nakayama 1990: (only for )

• Huang, 1987

2

2

cos21sin2 n

cn

n

c

n

nC W

l

W

lWR

[Z. Li, 1990]

25.0d

r

chDchch

Dchchch

KhbbhK

bbhKbR

222

222

0

chch hbR

09.075.01

0

For chip curl, our main concern is chip curl radius.

Here are the models of chip curl radius.

For chip curl, our main concern is chip curl radius.

Here are the models of chip curl radius.

16

Chip Breaking Study

1. Material stress analysis – to find the chip breaking strain εB

• Chip curl analysis (Nakayama, 1962; Z. Li, 1990)

• FEA (Kiamecki, 1973; Lajczok, 1980; Strenkowski, 1985)

2. Experimental work

• Database-based prediction (Jawahir, 1990)

• Tool designer – cutting tests

3. Industry application: special devices designed and applied in some cases

lizhou:

Chip breaking have also been studied in detail. The chip breaking study can be classified to 4 methods:

…

…

…

…

Due to the extremely complicated process of chip formation and breaking, the FEA results doesn’t match experimental results very well.

The database system is too time and labor consuming. It is difficult to setup and maintain a big machining database.

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 this dissertation.

lizhou:

Chip breaking have also been studied in detail. The chip breaking study can be classified to 4 methods:

…

…

…

…

Due to the extremely complicated process of chip formation and breaking, the FEA results doesn’t match experimental results very well.

The database system is too time and labor consuming. It is difficult to setup and maintain a big machining database.

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 this dissertation.

17

Literature Review - Common Chip Breaking Criterion

[Nakayama, 1962]

When chip will break and

B )/1/1( LccB RRh

lizhou:

Nakayama presented a chip breaking criterion in 1962. It has become the common chip breaking criterion in research.

In this model, chip flows out with an initial curl radius. After meet obstacles, the chip curl radius becomes bigger and bigger, until it breaks. A new chip is then coming out and repeat this process.

The chip material strain can be described as functions of the curl radius and the chip shape and thickness.

lizhou:

Nakayama presented a chip breaking criterion in 1962. It has become the common chip breaking criterion in research.

In this model, chip flows out with an initial curl radius. After meet obstacles, the chip curl radius becomes bigger and bigger, until it breaks. A new chip is then coming out and repeat this process.

The chip material strain can be described as functions of the curl radius and the chip shape and thickness.

18

Literature Review - The Chip Breaking Limits

[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

Chip breaking criterion:

When f > fcr, d > dcr

chip will break;

Otherwise will not break

lizhou:

We have talked about the chip breaking limits theory. Nakayama’s chip breaking criterion and chip breaking limits theory are the basis of semi-empirical chip breaking model presented by zhengjia li in 1990.

Zhengjia Li developed models of the critical feed rate and the critical depth of cut to predict chip breaking.

lizhou:

We have talked about the chip breaking limits theory. Nakayama’s chip breaking criterion and chip breaking limits theory are the basis of semi-empirical chip breaking model presented by zhengjia li in 1990.

Zhengjia Li developed models of the critical feed rate and the critical depth of cut to predict chip breaking.

19

Literature Review - The Chip Breaking Limits(1) The critical feed rate

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

)cos21(sinsin2 n

n

c

nr

RnhBcr W

lKWCf

Workpiece material property

Cutting ratio: determined by cutting speed and work piece material properties

[Z. Li, 1990]

Here is the theoretical equation of the critical feed rate. It is applied in up-curl dominated chip breaking region.

The function disclose the fact that the critical feed rate is determined by the workpiece material, the cutting tool and chip breaking groove geometry, and the cutting speed.

Here is the theoretical equation of the critical feed rate. It is applied in up-curl dominated chip breaking region.

The function disclose the fact that the critical feed rate is determined by the workpiece material, the cutting tool and chip breaking groove geometry, and the cutting speed.

20

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.

[Z. Li, 1990]

Literature Review - The Chip Breaking Limits(2) The critical depth of cut

Here is the theoretical equation of the critical depth of cut. It is applied in side-curl dominated chip breaking region.

The critical depth of cut is also determined by the workpiece material, the cutting tool and chip 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 is around the value of the nose radius.

Here is the theoretical equation of the critical depth of cut. It is applied in side-curl dominated chip breaking region.

The critical depth of cut is also determined by the workpiece material, the cutting tool and chip 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 is around the value of the nose radius.

21

The Bridge

BigGap

Chip control is important

3D modeling

Bottleneck

• Too many factors involved• low reproducibility

Difficulties

2D modeling

3D modeling

Expand

Academic Research Approaches

Basis of modeling:Mechanics of chip flow

Practical Application Researches

Verytime/money/labor

consuming

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

••• •••

Semi-empiricalmodel

22

Literature Review - Semi-empirical Chip Breaking Model

Critical feed rate

Critical depth of cut

Material Speed Insert

Chip breakability

Material Speed Insert

Chip will break, when:

and crff crdd

fmfvfTcr KKKff 0

mFK

VFK

KKKK

fm

fV

fWnfkfrfT r

dmdvdTcr KKKdd 0

mFK

VFK

KKKK

dm

dV

dWndkdrdT r

[Z. Li, 1990]

• f0 and d0 : the standard chip breaking limits under pre-defined standard condition

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 model for chip breaking prediction.

Here the critical feed rate and the critical depth of cut are presented in this way. The f0 and the d0 are the ……

The kft is the cutting tool modification coefficient. zhengjia li described it as the function of the nose radius, the main cutting edge angle, and the groove width.

the kfv is the cutting speed modification coefficient, it is a function of the cutting speed.

the kfm is the material modification coefficient determined by material properties.

so do the kdt, kdv, and kdm.

Zhengjia li developed the equations of the modification coefficients, so that the chip breaking limits can be predicted under any given conditions without doing cutting test.

Compared with database system, it saves lots of time and labor on experimental work. The semi-empirical model only need a small number of cutting tests to develop the equations of the modification coefficients, then it can predict chip breaking without more experimental work.

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 model for chip breaking prediction.

Here the critical feed rate and the critical depth of cut are presented in this way. The f0 and the d0 are the ……

The kft is the cutting tool modification coefficient. zhengjia li described it as the function of the nose radius, the main cutting edge angle, and the groove width.

the kfv is the cutting speed modification coefficient, it is a function of the cutting speed.

the kfm is the material modification coefficient determined by material properties.

so do the kdt, kdv, and kdm.

Zhengjia li developed the equations of the modification coefficients, so that the chip breaking limits can be predicted under any given conditions without doing cutting test.

Compared with database system, it saves lots of time and labor on experimental work. The semi-empirical model only need a small number of cutting tests to develop the equations of the modification coefficients, then it can predict chip breaking without more experimental work.

23

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

Advantages of the semi-empirical model

1. Need only a small number of cutting tests to develop the empirical equations

2. Bridge the theoretical study and the industry applications

Zhengjia li’s approach has great advantages, but it also has some limitations.

…

…

…

…

In this dissertation li’s model will be extended to include more important geometric features of the 2D grooved inserts. Then semi-empirical model for 3D grooved inserts will also be developed. They are then be integrated to a web-based expert system for online chip breaking prediction.

The system developed in this research is based on a project cooperated with Ford Motor company in the last 3 years, and the system developed in this research is running on Ford powertrain branch.


…

…

…

…



24

My Work1. Extended Zhengjia Li’s 2D

predictive model to include important geometric features that not considered previously;

2. Developed a semi-empirical chip breaking prediction model for 3D-grooved tools

3. Integrated the models into a web-based chip breaking prediction expert system for industry application


…

…

…

…




…

…

…

…



Extended 2DModel

Extended 2DModel

3D Model3D Model

Web-based Chip Breaking Prediction

System

Web-based Chip Breaking Prediction

System

25

3. Extended Chip Breaking Modelfor 2-D Grooved Inserts

lizhou:

In this research the semi-empirical model for 2D grooved inserts are extended to include more geometric features of the cutting tool.

lizhou:

In this research the semi-empirical model for 2D grooved inserts are extended to include more geometric features of the cutting tool.

26

Geometric Featuresof 2-D grooved inserts

0

Wn

h

O

Rc

010

Wn

br1

• Rake angle γ0

• Back-wall height h

• Land length br1

• Land rake angle 01

Tool feed direction

lizhou:

This figure shows the geometric features of 2D grooved inserts.

The rake angle, …, …, and … they are not included in zhengjia li’s model, their influence on chip breaking limits will be studied here.

lizhou:

This figure shows the geometric features of 2D grooved inserts.

The rake angle, …, …, and … they are not included in zhengjia li’s model, their influence on chip breaking limits will be studied here.

27

Theoretical Analysis Result - fcr

)cossin(2

)cos(

)cos()sincos(

)cos(

)cos(

)cossin(2

))cos(

)cos(sincos(2

sin2

00

20

2012

1000

011

00

0

01100

222

hW

bhWb

hW

bhWllhW

kcf

rr

rff

r

rhbcr

lizhou:

Through chip curl analysis, we can get the new theoretical equation of the critical feed rate as below

It 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 backwall height, the land length and the land rake angle into consideration

lizhou:

Through chip curl analysis, we can get the new theoretical equation of the critical feed rate as below

It 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 backwall height, the land length and the land rake angle into consideration

28

Theoretical Analysis Result -dcr

rfrdwhend

f

d

r

rfrdwhenr

f

r

dr

fc

rfrdwhenfr

rfrdwhenfr

a

and

acq

cakpwhere

rfrdwhen

qppf

rrd

rfrdwhen

r

f

r

qpprrd

rcr

r

crrr

rcr

r

rr

rr

B

r

rcr

r

cr

2,cos122

tancotarccot

2,cos12

arcsinarccos2

1

cos

2,cos1sinsin

sin1

2,cos1sincos1

25.0

03.025.0

2,cos1

sin12.006.0

1

4

2,cos1

2arcsin

12.0

12.0arcsin2cos

2

2

2

1

22

1

2

rdcr

lizhou:

We can also get the theoretical equation of the dcr;

These items are close to zero, so that the critical depth of cut is close to the nose radius.

lizhou:

We can also get the theoretical equation of the dcr;

These items are close to zero, so that the critical depth of cut is close to the nose radius.

29

Extended Semi-empirical Chip breaking model for 2-D grooved inserts

Semi-empirical Model

1010 dbdhdddndWdrdT KKKKKKKK

dmdvdTcr KKKdd 0

)(VFK ddV

)(mFK ddm

fmfvfTcr KKKff 0

1010 fbfhfffnfWfrfT KKKKKKKK

)(VFK ffV

)(mFK ffm

lizhou:

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 coefficients are changed to include more geometric features.

To get the new modification coefficients, experimental work are conducted

lizhou:

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 coefficients are changed to include more geometric features.

To get the new modification coefficients, experimental work are conducted

30

Experiment Design

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

lizhou:

In the experiments design, every geometric features were designed as 4 levels. Sixteen customized inserts are made by ourselves to do the cutting tests.

It 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 geometry measurement system and software along with us.

lizhou:

In the experiments design, every geometric features were designed as 4 levels. Sixteen customized inserts are made by ourselves to do the cutting tests.

It 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 geometry measurement system and software along with us.

31

Results

00 0208.032.1 fK

152.1696.01

bK fb

101 fK

hK fh 84.11

10 dK

11

dbK

101 dK

1dhK

lizhou:

From the cutting tests, we got the modification coefficients as shown here.

It 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 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.

lizhou:

From the cutting tests, we got the modification coefficients as shown here.

It 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 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.

rdcr

32

Results

DecreaseIncrease

fcr dcr Chip Breakability

Rake Angle

Backwall Height

Land Rake Angle

Land Length

lizhou:

This table shows the parameters influence tendency on chip breakability.

lizhou:

This table shows the parameters influence tendency on chip breakability.

33

Experimental Results - fcr

0

0.1

0.2

0.3

0.4

0.5

0.6

10 12 14 16 18 20 22

Rake Angle (deg.)

fcr

(mm

/rev

)

Theoretical Result

Experimental Result

Empirical Model Result

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Land Length (mm)

fcr

(mm

/re

v)

Theoretical Result

Experimental Result


0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

-20 -15 -10 -5 0

Land Rake Angle (deg.)

fcr

(mm

/re

v)

Theoretical Result

Experimental Result


0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Back-wall height (mm)

fcr

(mm

/rev)

Theoretical Result

Experimental Result


lizhou:

This pictures shows the comparison between the theoretical results, the experimental results, and the semi-empirical model prediction results. It is found they matches well.

lizhou:

This pictures shows the comparison between the theoretical results, the experimental results, and the semi-empirical model prediction results. It is found they matches well.

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Experimental Results - dcr

00.20.40.60.8

11.21.41.61.8

2

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Backwall Height (mm)

dcr

(m

m)

Theoretical Result

Experimental Result


00.20.40.60.8

11.21.41.61.8

2

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Land Length (mm)

dcr

(m

m)

Theoretical Result

Experimental Result


00.20.40.60.8

11.21.41.61.8

2

-20 -15 -10 -5 0

Land Rake Angle (deg)

dcr

(m

m)

Theoretical Result

Experimental Result


00.20.40.60.8

11.21.41.61.8

2

10 12 14 16 18 20 22

Rake Angle (deg)

dcr

(m

m)

Theoretical Result

Experimental Result


lizhou:

These pictures are the results of the critical depth of cut.

lizhou:

These pictures are the results of the critical depth of cut.

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4. Semi-empirical Chip Breaking Model for 3-D Grooved Inserts

lizhou:

Although a complete 2d model is useful in chip breaking prediction, most commercial inserts in finish cutting are 3d grooved inserts.

When we do the chip control project with ford, we submit a 2d chip breaking system to them at the end of the first year, but they said what they really want in workshop is a 3D chip breaking prediction system so that the project has been continued to develop semi-empirical models for 3d grooved inserts.

lizhou:

Although a complete 2d model is useful in chip breaking prediction, most commercial inserts in finish cutting are 3d grooved inserts.

When we do the chip control project with ford, we submit a 2d chip breaking system to them at the end of the first year, but they said what they really want in workshop is a 3D chip breaking prediction system so that the project has been continued to develop semi-empirical models for 3d grooved inserts.

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3-D Grooved Inserts

TNMP332K KC850 TNMG332MF 235

Geometry of 3-D grooved inserts

Two Samples

Important in chip control research:

• Most chip breaking problem exists in finish machining

• More than 70% of industry insert for finish machining are 3D grooved inserts

3D grooved inserts with non-straight groove are very popular in industry machining application.

Chip breaking problem mainly exists in finish-turning cause depth of cut is 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.

3D grooved inserts with non-straight groove are very popular in industry machining application.

Chip breaking problem mainly exists in finish-turning cause depth of cut is 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.

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rε

),,,,,,(

),,,,,,(

0

0

sndcr

snfcr

hbLrFd

hbLrFf

Geometric Features and Chip Breaking Limits

A

l1

y

x

Wn

α

L

B-View

A

Wn

γn

Wn’

hbγ0

A‑A

λs

B-View

lizhou:

This figure shows the geometry of the 3d grooved inserts. 7 geometric parameters are 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 distance of the protrusion and the protrusion angle. The chip breaking limits will be described as functions of these parameters through experiments.

lizhou:

This figure shows the geometry of the 3d grooved inserts. 7 geometric parameters are 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 distance of the protrusion and the protrusion angle. The chip breaking limits will be described as functions of these parameters through experiments.

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Experiment Design

A Sample22 different commercial inserts were used in cutting test

h and λs are constant

Insert selection

Insert geometricfeatures measurement

Cutting tests – To get fcr and dcr

Develop empirical equations

lizhou:

For the experimental work, we first select 3d grooved commercial inserts as many as possible so that we had a 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.

Here is a typical chip breaking chart.

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.

lizhou:

For the experimental work, we first select 3d grooved commercial inserts as many as possible so that we had a 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.

Here is a typical chip breaking chart.

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.

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Insert Geometric Features Measurement Software

A software package has beendeveloped 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

lizhou:

For measuring the tool geometric features, we developed a insert geometric features measurement tool and relative software system in cooperation with Harbin univ. of sci. and tech.

Here are screen shoot of the software user-interface. It is shown how to measure the nose radius.

lizhou:

For measuring the tool geometric features, we developed a insert geometric features measurement tool and relative software system in cooperation with Harbin univ. of sci. and tech.

Here are screen shoot of the software user-interface. It is shown how to measure the nose radius.

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Results

ncr

ncr

bLrd

bLrf

033.0753.006.0228.017.1064.0

014.0304.0009.00474.0099.0010.0

0

0

ndT

nfT

bLrK

bLrK

1.11.2526.73913.2

82.48.10410.335.1613.3445.3

0

0

ind

revinf

03.0

/0029.0

0

0Pre-defined standard cutting condition

• Work piece material 1010 steel

• Cutting speed 523sfpm

• Insert TNMP332K KC850

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.

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Fcr - Experimental Results

0.0017 0.00200.0029

0.0037

0.0022 0.00170.0011

0.0035

0.0000

0.0020

0.0040

0.0060

0.0080

0.0100

0.0120

331 332 333 334

nose radius

fcr

(in

/rev

)

TNMG33X MF235 FCR Model predictive Fcr

0.0029

0.0065

0.0082

0.00600.0071

0.0059

0.0000

0.0020

0.0040

0.0060

0.0080

0.0100

0.0120

331 332 333

nose radius

fcr

(in

/rev

)

TNMG33X KC850 FCR Model predictive Fcr

0.0029 0.00290.00370.0042

0.0021

0.0054

0.0000

0.0020

0.0040

0.0060

0.0080

0.0100

0.0120

331 332 333

nose radius

fcr

(in

/rev

)

TNMP33XK KC850 FCR Model predictive Fcr

0.0025

0.00560.0065

0.0049

0.00720.0063

0.0000

0.0020

0.0040

0.0060

0.0080

0.0100

0.0120

331 332 333

nose radius

fcr

(in

/rev

)

TNMG33X QF4025 FCR Model predictive Fcr

lizhou:

These graphs compare the model predictive results and the experimental results of the chip breaking limits. They match well.

lizhou:

These graphs compare the model predictive results and the experimental results of the chip breaking limits. They match well.

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Dcr - Experimental Results

0.020.03

0.04 0.04

0.019

0.033

0.048

0.070

0

0.02

0.04

0.06

0.08

0.1

0.12

331 332 333 334

nose radius

dcr

(in

)TNMG33X MF235 DCR Model predictive Dcr

0.020.03

0.04 0.04

0.019

0.033

0.048

0.070

0

0.02

0.04

0.06

0.08

0.1

0.12

331 332 333 334

nose radius

dcr

(in

)

TNMG33X MF235 DCR Model predictive Dcr

0.050.06

0.07

0.039

0.0560.064

0.02

0.04

0.06

0.08

0.1

0.12

331 332 333

nose radius

dcr

(in

)

TNMG33X KC850 DCR Model predictive Dcr

0.040.03

0.05

0.033 0.034

0.065

0

0.02

0.04

0.06

0.08

0.1

0.12

331 332 333

nose radius

dcr

(in

)

TNMP33XK KC850 DCR Model predictive Dcr

lizhou:

Here shows the critical depth of cut

lizhou:

Here shows the critical depth of cut

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5. Web-based Chip Breaking Prediction System

Presently being used by Ford Motor Inc.

lizhou:

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

lizhou:

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

44

• 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.

Web-based Chip Breaking Prediction System

lizhou:

The system developed in this research has great advantages. The semi-empirical models provide a solid base for the system.

The system is accessible through internet or intranet, so that is very convenient for online chip breaking prediction and tool / cutting condition design.

It only need to do a small number of cutting test to establish the necessary databases. Also the databases are easy to maintain and expand.

lizhou:

The system developed in this research has great advantages. The semi-empirical models provide a solid base for the system.

The system is accessible through internet or intranet, so that is very convenient for online chip breaking prediction and tool / cutting condition design.

It only need to do a small number of cutting test to establish the necessary databases. Also the databases are easy to maintain and expand.

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User Input• Insert selection• Work-piece selection• Cutting conditions input

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

Web-Based Machining Chip Breaking Prediction Systemlizhou:

Here is a screenshot of the system. User give input to the system, the system returns user a predictive chip breaking chart.

lizhou:

Here is a screenshot of the system. User give input to the system, the system returns user a predictive chip breaking chart.

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Web-based Chip Breaking Prediction System

ExistedModels

New WP/ inserts

lizhou:

This figure shows the system infrastructure.

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 without influence the client side.

In the client side, user can access the system through web-browser, such as IE or Netscape. No installation needed. Username and password are needed to access the system.

lizhou:

This figure shows the system infrastructure.

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 without influence the client side.

In the client side, user can access the system through web-browser, such as IE or Netscape. No installation needed. Username and password are needed to access the system.

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System flow chart

StartStart

PredictChip breaking

PredictChip breaking

OutputOutput

End

End

Search Insert/WPin cutting DB

Search Insert/WPin cutting DB

Decide chip breaking model

Decide chip breaking model

Retrieve empirical equation from DB

Retrieve empirical equation from DB

Calculate chip breaking limits

Calculate chip breaking limits

Retrieve chip breaking chart

from DB

Retrieve chip breaking chart

from DB

Model for 2D grooved tool




Model for other cutting tools

Model for other cutting tools

Check input values

Check input values

Update parameter list

Update parameter list

Update tool information

Update tool information

User InputUser Input

lizhou:

This is the system flow chart.

lizhou:

This is the system flow chart.

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Chip Breaking Chart to Chip Breaking Matrix

6666555

6111155

1111155

1111145

1111145

1111145

1111135

lizhou:

How to store chip breaking chart in the database is a problem. The chip is classified to 6 types according to it’s breakability. Rank 1 represents the best broken chip, and is described by a number 1. So do other types of chips. Then we can get a chip breaking matrix to represent the chip breaking chart and store in the database.

lizhou:

How to store chip breaking chart in the database is a problem. The chip is classified to 6 types according to it’s breakability. Rank 1 represents the best broken chip, and is described by a number 1. So do other types of chips. Then we can get a chip breaking matrix to represent the chip breaking chart and store in the database.

49

lizhou:

This is the use input interface.

User need to choose inserts, geometric parameters, unit system, cutting conditions. The insert picture is shown on the right.

lizhou:

This is the use input interface.

User need to choose inserts, geometric parameters, unit system, cutting conditions. The insert picture is shown on the right.

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User Input

Insert type selection

Nose radius selection

Cutting condition selection

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User Input

Metric / inch system selection

Warning message

Online help

lizhou:

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

lizhou:

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

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Systemoutput

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

lizhou:

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.

lizhou:

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.

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Limitations of the System

• 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.

lizhou:

The system also has some limitations. It’s only good for the inserts that included by 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.

It’s for steel cutting only, not for soft metal cutting.

lizhou:

The system also has some limitations. It’s only good for the inserts that included by 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.

It’s for steel cutting only, not for soft metal cutting.

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6. Summary

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

lizhou:

Here is the summary.

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 industry application.

lizhou:

Here is the summary.

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 industry application.

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7. Future Work - for inserts with complicated modifications

Extra chip breaking region

Normal chip breaking region

lizhou:

The future work may include developing chip breaking models for inserts with complicated geometric features or with block-type chip breaker, and for soft metal cutting.

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.

This chip breaking chart shows a example. You can see there are extra chip breaking region when depth of cut and feed rate is small, due to the existence of the bumps on the insert rake face.

lizhou:

The future work may include developing chip breaking models for inserts with complicated geometric features or with block-type chip breaker, and for soft metal cutting.

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.

This chip breaking chart shows a example. You can see there are extra chip breaking region when depth of cut and feed rate is small, due to the existence of the bumps on the insert rake face.

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7. Future Work - inserts with block-type chip breaker

O

L

r

s

A

B

B

B-B Section

1

h

A

> 0

A

= 0

A

< 0

Illustration of the geometry of the block-type chip breaker

lizhou:

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

lizhou:

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

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7. Future Work – chip breaking prediction for soft metal cutting

lizhou:

This picture shows a 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, if the feed rate or depth of cut are too big, the surface quality will be unacceptable. If we could find a 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 breaker.

lizhou:

This picture shows a 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, if the feed rate or depth of cut are too big, the surface quality will be unacceptable. If we could find a 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 breaker.

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Any questions or comments?

59


THANK YOU!

Li zhou-defense

Economy & Finance

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