Li zhou-defense

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Li zhou-defense

  1. 1. 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
  2. 2. 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 Contentsmachining, 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 onlinechip 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 2
  3. 3. lizhou: lizhou: IntroductionConventionally 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
  4. 4. 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 indeveloping cutting models for machining, since chip curling and the subsequent chip developing cutting models for machining, since chip curling and the subsequent chipbreaking 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 FlowingChip 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 dealtwith 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 chipback 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
  5. 5. 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 curlReal 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 significantlyinfluences the chip breaking. influences the chip breaking. 1. Side- curling (1, 2, 3: Jawahir 1993) 2. Up-curling 3. Straight chip1,2,3,4: basic chip-curling formsReal chip-curling is the combination of the basic forms 4. Screwing-curling (Fang, 2000) 5
  6. 6. (ISO 3685-1977 gives aacomprehensive chip form classification) (ISO 3685-1977 gives comprehensive chip form classification) Introduction - Chip forms and classificationsBased 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 arebroken 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 helicalAccording 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, andthe 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 6
  7. 7. 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 7
  8. 8. 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 - ObjectivesOur 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 8
  9. 9. 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, chipbreakers. breakers.We have several ways to achieve chip breaking: … … … We have several ways to achieve chip breaking: … … … Introduction - Chip BreakingDue 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 cuttingconditions. 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 arethe 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 9
  10. 10. 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 chipbreakers. 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 beclassified 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 popularinsert 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
  11. 11. 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 Breakinginfluences. ………… 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 11
  12. 12. 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 limitsGenerally the chip breaking curves are like this. When change cutting speed, the curve willGenerally the chip breaking curves are like this. When change cutting speed, the curve willmove 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 willbreak, 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 mostcomplicated 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 breakingmodel, 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 12
  13. 13. lizhou: lizhou: WPINext I’ll review previous work on chip control. Next I’ll review previous work on chip control. Worcester Polytechnic Institute Manufacturing Engineering Program 2. Literature Review 13
  14. 14. People have done lots of work on chip formation mechanisms. And presented People have done lots of work on chip formation mechanisms. And presentedmany models of chip flow and chip curl. many models of chip flow and chip curl. Chip Formation Mechanisms – Chip Flow DirectionFor 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 14
  15. 15. 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 15
  16. 16. 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 tomethods: 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 resultsDue to the extremely complicated process (Nakayama, 1962; Z. Li, 1990) Due to the extremely complicated processof chip formation and breaking, the FEA resultsdoesn’t match experimental results very well. doesn’t match experimental results very well. • FEA too time and labor consuming. is 1980; setup and maintain bigThe database system is (Kiamecki, 1973; Lajczok,difficultto setup and maintain1985) The database system istoo time and labor consuming. ItItis difficult toStrenkowski, aabigmachining database. machining database. 2. Experimental workThe 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 ofthis dissertation. Database-based prediction (Jawahir, 1990) this dissertation. • Tool designer – cutting tests 3. Industry application: special devices designed and applied in some cases 16
  17. 17. 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 Criterionbreaking 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 curlradius 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 andrepeat 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 chipshape and thickness.ε B shape When ε > and thickness. chip will break and ε B = αhc (1 / Rc − 1 / RL ) 17
  18. 18. 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 Limitsand 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 modelpresented 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 topredict 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 18
  19. 19. 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 dominatedchip breaking region. chip breaking region. Literature Review - The Chip Breaking LimitsThe 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 ratematerial, 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
  20. 20. 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 dominatedchip breaking region. chip breaking region. Literature Review - The Chip Breaking LimitsThe 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 cutbreaking 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 hasthe 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 cutis 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. 20
  21. 21. The Bridge Chip control Basis of modeling: is important Mechanics of chip flow 2D modeling Expand Difficulties • Too many factorsPractical 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
  22. 22. 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 bythe 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 thismodel for chip breaking prediction. model for chip breaking prediction. Literature Review - Semi-empirical Chip Breaking ModelHere 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 andthe 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 ≥ thenose 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 dmthe kfm is the material modification coefficient determined by material properties. the kfm is the material modification coefficient determined by material properties. Critical feed rateso 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 fmCompared 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. Thesemi-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 ofthe modification coefficients, then ititcan predict chip breaking without more experimental • f0 and d0 : more experimental the modification coefficients, then can predict chip breaking withoutthe standardwork. work. Critical depth of cut chip breaking limits under pre-defined standard condition Material Speed Insert [Z. Li, 1990] 22
  23. 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.……………… 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 importantgeometricfeatures of the 2D grooved inserts. Then semi-empirical model for 3D grooved features of the 2D grooved inserts. Then semi-empirical model for 3D grooved empirical equationsinserts 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 expertsystem for online chip breaking prediction. system for online chip breaking prediction. 2. Bridge the theoretical study and the industry applicationsThe system developed in this research is based on aaproject cooperated with Ford The system developed in this research is based on project cooperated with FordMotor 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 isrunning on Ford powertrain branch. 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
  24. 24. 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 ModelIn 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 2Dfeatures of the 2D grooved inserts. Then semi-empirical model for 3D grooved features of the 2D grooved inserts. Then semi-empirical model for 3D groovedinserts 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 expertsystem for online chip breaking prediction. system for online chip breaking prediction.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 ModelMotor 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 isrunning on Ford powertrain branch. running on Ford powertrain branch. 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 24
  25. 25. 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 includemore geometric features of the cutting tool. more geometric features of the cutting tool. 3. Extended Chip Breaking Model for 2-D Grooved Inserts 25
  26. 26. lizhou: lizhou: O Geometric FeaturesThis figure shows the geometric features of 2D grooved inserts. This figure shows the geometric features of 2D grooved inserts. RcThe rake angle, …, …, and … they are not included in zhengjia li’s model, their influenceon 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 26
  27. 27. lizhou: lizhou: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 - fcras below as belowItItis 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 geometricfeatures. 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, thebackwall 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 )    27
  28. 28. 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 -dThese 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
  29. 29. 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 toolcoefficients2-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
  30. 30. 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. Sixteencustomized inserts are made by ourselves to do the cutting tests. customized inserts are made by ourselves to do the cutting tests. Experiment DesignItItis difficult to manufacture the designed inserts. We cooperated with the harbin university is difficult to manufacture the designed inserts. We cooperated with the harbin universityof 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 toolgeometry 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
  31. 31. 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 significantinfluence 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 thefcr. 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 resultsshows 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
  32. 32. 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
  33. 33. 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 - fcrresults, 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
  34. 34. 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 1.6 Experimental Result 1.6 Experimental Result 1.4 Empirical Model Result 1.4 Empirical Model 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 1.6 Experimental Result 1.6 Experimental Result 1.4 Empirical Model Result 1.4 Empirical Model 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
  35. 35. 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 commercialinserts 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 tothem 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 3Dchip 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 Breakingempirical models for 3d grooved inserts. empirical models for 3d grooved inserts. Model for 3-D Grooved Inserts 35
  36. 36. 3D grooved inserts with non-straight groove are very popular in industry 3D grooved inserts with non-straight groove are very popular in industrymachining 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 Insertssmall, 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-turningThe 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
  37. 37. 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 Limitsconsidered 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 noseradius, 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, thedistance 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 bedescribed 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
  38. 38. lizhou: lizhou: Experiment DesignFor 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 aspossible 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 cuttingtests 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 selectionHere 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 andinclination 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
  39. 39. 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 Harbinmeasurement 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 noseradius. 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
  40. 40. 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
  41. 41. lizhou: lizhou: These graphscompare FCR model predictive Fcr results and the experimental results of Results Fcr - Experimental theThese graphs TNMG33X MF235the model predictive results and the experimental results of the compare the Model predictivechip 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
  42. 42. 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
  43. 43. 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 tointegrate 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 chipbreaking 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
  44. 44. 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 modelsprovide 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 onlinechip 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
  45. 45. lizhou: lizhou: Web-Based Machining Chip Breaking Prediction SystemHere 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 returnsuser 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
  46. 46. lizhou: lizhou: Web-based Chip Breaking Prediction SystemThis 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 andworkpiece 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 sidewithout influence the client side. without influence the client side. New WP/ ExistedIn 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 ModelsNetscape. No installation needed. Username and password are needed to access the Netscape. No installation needed. Username and password are needed to access thesystem. system. 46
  47. 47. 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
  48. 48. 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 totypes 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 isdescribed 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 breakingmatrix 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
  49. 49. 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
  50. 50. User Input Insert type selection Cutting condition selection Nose radius selection 50
  51. 51. lizhou: lizhou: User InputAlso 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 ofrange, 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
  52. 52. 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 theinsert 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
  53. 53. 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 Systemthe 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 andwith 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
  54. 54. lizhou: lizhou:Here is the summary. Here is the summary. 6. SummaryIn this research, the semi-empirical chip breaking predictive models are developed for In this research, the semi-empirical chip breaking predictive models are developed for2D 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 forindustry 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
  55. 55. lizhou: lizhou:The future work may include developing chip breaking models for inserts with complicatedgeometric 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 modificationsThe reason that the model developed here doesn’t include inserts with complicated The reason that the model developed here doesn’t include inserts with complicatedgeometric 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 regionregion 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 theinsert rake face. insert rake face. 55
  56. 56. 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 alsoretrieve 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 breakerinserts. The difficulty is that ititis not easy to get the chip breaking limits from the softmetal 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
  57. 57. 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 cuttingare 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 findrate or depth of cut are too big, the surface quality will be unacceptable. IfIfwe could find aaway 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 todevelop 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 chipbreaker. breaker. 57
  58. 58. WPIWorcester Polytechnic InstituteManufacturing Engineering Program Any questions or comments? 58
  59. 59. WPIWorcester Polytechnic InstituteManufacturing Engineering Program THANK YOU! 59

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