Important Points in the Chapters
-----------------------------------------6. Forming by Metal Removal
Basic Types of Material Removal Processes
The planner has the classify the shape as per part drawing to:
a. Round symmetrical
b. Prismatic
Above the basic shape there will be special features like holes, threads, slots, and flats.
Processes used for Round symmetrical parts: Turning, Grinding,
Processes used for Prismatic parts: Milling, Grinding
Holes: Drilling, Boring Reaming
Threads: Tapping, Thread Milling
Selection machining technology also is dependent on surface finish.
Turning provides surface finish in the range of 0.8 microns to 25 microns Ra.
Grinding provides surface finish in the range of 0.1 microns to 1.6 microns Ra.
A basic process is selected first. In case of round symmetrical parts, turning is the basic process. If the basic process does not meet the surface roughness specification, an additional machining process is to be added, in addition to the first basic process. Then check the geometric tolerances (for parallelism, perpendicularity, concentricity and angularity). If the last machining process meets the required geometric tolerances the job can be completed. If it does not meet the specification, one machining process has to be added.
When more than one machining process is used, part drawings have to be prepared for each one. The working drawing or operation drawings are needed because the material to be left for the subsequent process has to be clearly indicated. Also the cutting parameters will be different for each operation.
Some guidelines in multiple operations;
1. In the first basic process you can specify the maximum capability value of the process as surface roughness.
2. In case of external dimension, increase the tolerance specified by 10 times to match the surface roughness specified above.
http://www.cnctrainingcentre.com/cnc-turn/cnc-turning-surface-finish/
https://www.kennametal.com/in/en/resources/engineering-calculators/turning-calculators/surface-finish.html
https://www.meadinfo.org/2009/06/surface-finish-roughness-ra.html
Surface roughness/finish obtained in various machining operations from a machine design book
https://books.google.co.in/books?id=hKlfEB8tkcAC&pg=PA121#v=onepage&q&f=false
Machine Design
Jindal U. C.
Pearson Education India, 2010 - Electronic books - 892 pages
Machine Design is a text on the design of machine elements for the engineering undergraduates of mechanical/production/industrial disciplines. The book provides a comprehensive survey of machine elements and their analytical design methods. Besides explaining the fundamentals of the tools and techniques necessary to facilitate design calculations, the text includes extensive data on various aspects of machine elements, manufacturing considerations and materials.
https://books.google.co.in/books?id=hKlfEB8tkcAC
7. Positioning Workpiece and Clamping
After selecting the basic process, the first decision to be examined is the clamping points and the shape of the fixture.
If the body has an irregular shape, the support points have to be indicated by the designer on the drawing.
Jigs and Fixtures are built as an accessory to part processing and their function is to hold the part firmly in the machine. Chucks are covered under fixtures in the book by Halevi.
Chuck related issues
Three jaw chuck: Only cylindrical segments can be placed in the three jaw chuck. Length of contact between the jaws and the length of the chucked segment has to be at least 1.2 times the segment diameter. The minimum length in the chuck has to be at least 5 mm. If for any reason the length is less, the free end has to be checked for concentricity and adjusted. The three jaw chuck holding without any other support can be used upto ratio of length to diameter of 3.5.
Three jaw chuck with support is to be used when length to diameter is greater than 3.5 to 6.
Collet gives more accuracy but the part to be chucked in collet must have smooth surface.
Four jaw chuck: it is used for nonsymmetrical parts that must be adjusted for a centerline on the part.
Face plate: It is actually a fixture plate or plate fixture on which with fixture aid any part can be held.
In the book of Halevi, an algorithm is given to decide the fixture required.
Conclusion
5.1 Group technology methods GT
5.2 Modular Fixturing
The fixture is made up of standard building blocks assembled in a suitable manner. The blocks are disassembled after use and they are used in different fixtures.
5.3 Set up time reduction
Setup time reduction is important. Rotary tables allow machining of the four sides of a cube in one setup. Quick clamping devices, special eccentric cams, slotted bolts and hydraulic or pneumatic clamping etc. are available to design fixtures that reduce setup time.
8. How to Determine the Type of Operation
In this chapter method of determining depth of cut and feed are given. In the next chapter, determination of cutting speed is discussed.1 Boundary Limit Strategy
Technical constraints are set as boundary limits, and then, bearing in mind economic considerations, working point within these limits are determined.
1.1 Definition of technological constraints
Metal cutting theory indicates, minimum and maximum values for depth of cut, feed rate and cutting speed.
If the depth of cut is very less, the metal of the workpiece will only get compressed and will spring back when the took is passed and chip formation will not take place. Similarly, a low feed rate chip forming will not take place and only abrasive forming will take place. Similarly if feed is very high, tool wear process will become crater wear. The required tool wear is flank wear so that there is a definite tool life. Crater wear gives sudden failure. Hence feed rate has to be within a limit for the tool to be within flank wear process.
Similarly in the case of cutting speed also,above a cutting speed, the resulting temperature creates diffusion wear in the tool. At low cutting temperature, the built up edge occurs and proper cutting will not take place. Hence there are lower and higher limits to cutting speed.
Boundary value as per technological constraints
a(tmax) = maximum depth of cut
a(tmin) = minimum depth of cut
f(tmax) = maximum feed
f(tmin) = minimum feed
v(tmax) = maximum cutting speed
v(tmin) = minimum cutting speed
1.2 Part specification constraints
To meet specified surface roughness and tolerances, the feedrate and depth of cut have to be restricted to maximum values.
a(smax) = maximum depth of cut
f(smax) = maximum feed
1.3 Definition of material constraints
The work material also has an effect on allowable maximum depth of cut and cutting speed.
a(hmax) = maximum depth of cut
v(hmax) = cutting speed
1.4 Definition of machine constraints
Vibrations are associated with chip formation and they affect surface finish. These vibrations reduce tool life also.
Experiments indicate that very low depth of cut and feed cause vibrations (chatter). Some authors state 0.06 mm as the lowest limit for depth of cut. Similarly, a feed rate value of 0.04 mm per revolution is specified as the minimum feed rate below which chatter occurs.
There is also a maximum depth of cut and cutting speed above which chatter occurs.
a(vmax) = maximum depth of cut due to chatter (7 mm)
a(vmin) = minimum depth of cut due to chatter (0.15mm)
f(vmin) = minimum feed rate due to chatter (0.04 mm/rev)
v(vmax) = maximum cutting speed due to chatter
1.5 Definition of tool constraints
The tool material also gives boundary conditions to cutting parameters. At high feed rates, plastic deformation of the cutting edge takes place which is not desirable. Recommendations are use a maximum value of feed rate between 0.5 mm per revolution to 0.8 mm per revolution for a cutting speed of 150 meters per minute. There are limits for depth of cut and cutting speed.
a(kmax) = maximum depth of cut related to tool material
f(kmax) = maximum feed related to tool material
v(kmax) = maximum cutting speed due to chatter related to tool material
1.6 User specified constraint
If user provides any limits based on his experience they have to be taken into account by process planners.
a(umax) = maximum depth of cut indicated by user.
f(umax) = maximum feed related indicated by user.
v(umax) = maximum cutting speed indicated by user.
1.7 Boundary limits summary
The above boundary value symbols are listed as per depth of cut, feed rate and cutting speed.
From the list of boundary values for a given situation, the minimum value is selected for maximum values, and the maximum value is selected for minimum values. These selected values are given the symbols.
a(amax) a(amin) f(amax) f(amin) v(amax) v(amin) a indicates acceptable value for various cutting parameters.
2 Analysis of Cutting Conditions vs Part Specifications
The part specification gives the required tolerances and surface roughness. The part has to machined to conform to these specifications
2.1 Effect of cutting speed on surface roughness
A low cutting speeds BUE will occur and it scratches surface giving poor surface finish. As cutting speed increases above a limit, surface burns occur.
Halevi in 2003 book said, tool material and machine rigidity are being improved constantly, and hence recently declared values have to be ascertained and used. In the absence of specific values, Halevi suggested the values of 400 meters per minute as the upper limit and 60 meters per minute as the lower limit on steel parts with tool material being carbide.
2.2 Effect of feed rate on surface roughness
2.2.1 Turning processes
Halevi derived the formulas:
feed rate f rev/minute = 0.1Ra for Ra <= 3.2
feed rate f rev/minute = 0.18 Ra^0.5 for Ra>3.2
The above equations are used for finish cut and it is given the symbol f(smax) maximum feed rate based on surface finish criterion. For rough cuts f(amax) has to be used. A table is provided for maximum feed rate and maximum depth as function of Ra and BHN. Refer Table 1.
2.2.2 Milling processes (Not covered)
2.3 Effect of depth of cut on surface roughness
Maximum depth of cut limit based on surface roughness criterion
a(smax) = 32Ra/(BHN^0.8)
Example: Ra = 1.2 microns; BHN = 160
BHN^0.8 = 57.98
a(smax) = 32(1.2)/57.98 = .66 mm
3 Operational and Dependent Boundary Limits
As process planner makes decisions, these decision create limits for other variables.
3.1 Depth of cut as a function of feed rate
As the feed rate is determined, it puts a limit on the depth of cut. There will be a limit on the cutting force depending on the machine rigidity. The force is related to feed and depth as per the formula
Fx = (Cp)(a^u)(f^v)
Where Cp = specific cutting force (for medium steel it is 220)
a = depth of cut and exponent u = 1.0
f = feed rate and exponent v = 0.75
3.2 Depth of cut as a function of a selected operation
In rough cut operation maximum depth of cut possible as per the boundary conditions is used and any remaining deviations from final specification have to be modified through finish cuts. The amount of material to be removed to correct deviations is given the symbol a(smin) and its value is added to a(amin) and the total has to be less than a(smax) which is the maximum depth of cut allowed for the finishing cut from the boundary limits.
4 The Algorithm for Selecting Cutting Operations
9. How to Select Cutting Speed
1 Introduction
Cutting speed and time taken to do the machining are related as formula for turning machine time = (L/nf) and n is determined by the cutting speed and diameter of the work.
2 Source for Selecting Cutting speed
2.1 Machining data handbooks
2.2 Machinability ratings
2.3 Technical books
2.4 Tool manufacturers
2.5 Machinability computerized systems
3. Cutting Speed Optimization
3.1 Taylor equation
The cost data and Taylor tool life equation are used to find optimal tool life.
3.2 How effective is cutting speed optimization?
In the end, cutting speed decision is economic subject to technological constraint.
3.2.1 Tool life definition
ISO standard 3865 defines the values of tool wear.
3.2.2 Lot size effect
The cutting speed can be modified slightly so that if it is possible the tool life is equal to the batch size.
3.2.3 Economic cutting speed for machining a part
If possible the number of parts after which a tool has to be changed is made the same for all operations.
4 Data for the Extended Taylor Equation
Table 1 in the chapter gives coefficients for various parameters of the extended Taylor equation for 37 groups of materials.
10. How to Select a Machine for the Job
1 Parameters to Consider
Consider the size of the workpiece and its accuracy demands and estimate the required parameters, especially the power.
2 Optimization Strategy Two Phase Method
In the first phase, a theoretical process is generated by considering all technical constraints. For each individual operation, the parameters have been defined; depth of cut, feed rate and cutting speed.
In the second phase, the theoretical operations are transformed from available facilities point of view. Now the operation is specified to comply with the available machine specification.
2.1 Definition of the combinatorial problem
2.2 Mathematical definition of the process planning problem
2.3 Solving the problem by dynamic programming procedure
3 Machine Constraints
3.1 Power and force adjustment
Power is a linear function of cutting speed and cutting forces.
Cutting force is a function of feed and depth of cut.
We can calculate the power required to do the job in minimum time subject to technological constraints. If power of the available machine is less, we have to modify cutting parameters.
It is more profitable to reduce cutting speed.
The power adjustment guideline:
If the power has to be reduced by less than 50%.
1. Reduce the cutting speed to its lowest value.
2. Reduce the feed to lower limit.
3. Reduce the depth of cut, take more passes and adjust feed upward as possible.
3.2 Maximum depth of cut constraint
Each machine has d.o.c. constraint. A d.o.c above this value will result in chatter. So d.o.c has to be reduced below this value and more cuts are to be taken.
3.3 Maximum torque constraints
Torque is obtained by multiplication of cutting force by radius of part or tool. Hence adjustment has to be done appropriately.
3.4 Machine accuracy constraint
Old machines may be used for roughing operations and finish cuts are taken better machines to achieve the required accuracy.
3.5 Spindle bore constraint
If spindle bore is less than the part diameter, the type of holding the work piece will be different from chucking. The allowable bending forces are to be calculated and cutting conditions are to be modified.
3. 6 Time and cost conversion
The optimization criterion can be either maximum production or minimum cost.
4 Preliminary Machine Selection
4.1 First step in machine selection
Selection based on type of machine and its physical dimension.
For round symmetrical work a lathe machine is required. In the first step exclude machines which cannot do the job.
4.2 Second step
Exclude machines who do not have even the minimum power to run a cutting pass on the job.
4.3 Third step in machine selection
In the third step calculate the time require to machine the part of cost incurred in doing the job.
5 Matrix Solution
A matrix is developed with operations as rows and machines that can be used as columns. The time taken is put in each cell.
51 Single machine solution
If the total of operations times on a single machine is less than than the total of the minimum for each machine plus transfer time, single machine solution may be selected.
52 General matrix solution
General matrix solution is required when multiple machines are to be used to complete the job. The dynamic programming method is used for it.
5.2.1 Upward phase
5.2.2 Downward phase
11. How to Select Tools for a Job
This chapter is covered in a separate article.
1 Parameters to Consider
2 Selecting Insert Shape and Toolholder Type
2.1 Selection of insert shape
2.2 Selecting the insert grade
3. Standards for Indexable Inserts
3.1 The first digit
3.2 The second digit
3.3 The third digit
3.4 The fourth digit
3.5 The fifth digit
3.6 The sixth digit
3.7 The seventh digit
4. Standards for Toolholders
4.1 The first digit
4.2 The second digit
4.3 The third digit
4.4 The fourth digit
4.5 The fifth digit
4.6 The sixth seventh eighth and ninth digits
4.7 The tenth digit
5 Review Questions
6 Conclusion
https://nraoiekc.blogspot.com/2020/05/selection-of-tools-and-toolholders-for.html
------------------
Important points are yet to be posted.
12. Hole Making Procedure
1 Introduction 231
2 Basic Technology Concepts 231
21 Process planning optimization strategy 231
2.1.1 First level optimization single hole 232
2.1.2 Second level optimization several holes on one center line 235
3 Tools for Hole Making 237
31 Twist drill TDD from solid 237
32 Insert drill TDD from solid 240
33 Solid carbide drill TDD from solid 241
35 Reamers TDD improve hole 243
36 Boring MDD improve hole 244
37 End milling TDD from solid and disk milling TDD improve hole MDD improve hole 246
371 Computation of machining time 249
41 Computation of a min 250
43 Location tolerance 254
44 Operation diameter final decision 255
5 Example 256
51 A single hole from a solid rough hole 257
52 A single hole from a solid rough hole with location tolerance 259
53 Several holes on one center line 261
6 Review Questions 265
7 Conclusions 268
13. Milling Operations
1 Machining Time 269
11 Tool diameter 271
12 Milling direction face milling
2 Cutting Forces and Power 274
22 Power constraints 277
31 Selecting tool diameter 278
determining the tool path
4 Review Questions
First Edition
Principles of Process Planning: A logical approach
G. Halevi, R. Weill
Springer Science & Business Media, 31-Dec-1994 - Technology & Engineering - 399 pages
Process planning determines how a product is to be manufactured and is therefore a key element in the manufacturing process. It plays a major part in determining the cost of components and affects all factory activities, company competitiveness, production planning, production efficiency and product quality. It is a crucial link between design and manufacturing. There are several levels of process planning activities. Early in product engineering and development, process planning is responsible for determining the general method of production. The selected general method of production affects the design constraints. In the last stages of design, the designer has to consider ease of manufacturing in order for it to be economic. The part design data is transferred from engineering to manufacturing and process planners develop the detailed work package for manufacturing a part. Dimensions and tolerances are determined for each stage of processing of the workpiece. Process planning determines the sequence of operations and utilization of machine tools. Cutting tools, fixtures, gauges and other accessory tooling are also specified. Feeds, speeds and other parameters of the metal cutting and forming processes are determined.
https://books.google.co.in/books/about/Principles_of_Process_Planning.html?id=AK6Y57fKv38C
3rd Edition, Halevi - Chapter 8
https://books.google.co.in/books?id=tcHxCAAAQBAJ&pg=PA148#v=onepage&q&f=false
Process Planning Peter Scallan
https://books.google.co.in/books?id=R7GkqkbZbPIC&printsec=copyright&redir_esc=y#v=onepage&q&f=true
Time Estimation for Machining Activities
Panneer Selvan Book Chapter
Multipass Turning Operation Process Optimization Using Hybrid Genetic Simulated Annealing Algorithm
Abdelouahhab Jabri , Abdellah El Barkany, and Ahmed El Khalfi
Modelling and Simulation in Engineering
Volume 2017 |Article ID 1940635 | 10 pages | https://doi.org/10.1155/2017/1940635
https://www.hindawi.com/journals/mse/2017/1940635/
Precision Product-Process Design and Optimization: Select Papers from AIMTDR 2016
Sanjay S. Pande (IIT Bomba), Uday S. Dixit (IIT Gauhati)
Springer, 18-Apr-2018 - Technology & Engineering - 434 pages
This book introduces readers to various tools and techniques for the design of precision, miniature products, assemblies and associated manufacturing processes. In particular, it focuses on precision mechanisms, robotic devices and their control strategies, together with case studies. In the context of manufacturing process, the book highlights micro/nano machining/forming processes using non-conventional energy sources such as lasers, EDM (electro-discharge machining), ECM (electrochemical machining), etc. Techniques for achieving optimum performance in process modeling, simulation and optimization are presented. The applications of various research tools such as FEM (finite element method), neural networks, genetic algorithms, etc. to product-process design and optimization are illustrated through case studies. The state-of-the-art material presented here provides valuable directions for product development and future research work in this area. The contents of this book will be of use to researchers and industry professionals alike.
https://books.google.co.in/books?id=EEFWDwAAQBAJ
Precision Product-Process Design and Optimization: Select Papers from AIMTDR 2016
Sanjay S. Pande (IIT Bomba), Uday S. Dixit (IIT Gauhati)
Springer, 18-Apr-2018 - Technology & Engineering - 434 pages
This book introduces readers to various tools and techniques for the design of precision, miniature products, assemblies and associated manufacturing processes. In particular, it focuses on precision mechanisms, robotic devices and their control strategies, together with case studies. In the context of manufacturing process, the book highlights micro/nano machining/forming processes using non-conventional energy sources such as lasers, EDM (electro-discharge machining), ECM (electrochemical machining), etc. Techniques for achieving optimum performance in process modeling, simulation and optimization are presented. The applications of various research tools such as FEM (finite element method), neural networks, genetic algorithms, etc. to product-process design and optimization are illustrated through case studies. The state-of-the-art material presented here provides valuable directions for product development and future research work in this area. The contents of this book will be of use to researchers and industry professionals alike.
https://books.google.co.in/books?id=EEFWDwAAQBAJ
Mathematics for Machine Technology
Robert D. Smith, John C. Peterson
Cengage Learning, 24-Dec-2008 - Mathematics - 276 pages
The new edition of this best-selling text has been reviewed and revised to clarify and update an understanding of mathematical concepts necessary for success in the machine trades and manufacturing fields. Mathematics for Machine Technology, Sixth Edition overcomes the often mechanical plug in approach found in many trade-related texts. A complete grasp of mathematical concepts are emphasized in the presentation and application of a wide-range of topics from general arithmetic processes to oblique trigonometry, compound angles, and numerical control. The material covered by this text is accompanied by realistic industry-related examples, illustrations, and actual applications, which progress from the simple to the relatively complex. Mathematics for Machine Technology, Sixth Edition provides readers with practical vocational and technical applications of mathematical concepts necessary to excel in the machine, tool-and-die, and tool design industry.
https://books.google.co.in/books?id=qmJX7hp9_8cC
Other Books
https://books.google.co.in/books?id=_Y-eBQAAQBAJ
https://books.google.co.in/books?id=_Zqwo8b1jKwC
https://books.google.co.in/books?id=ab6iQ-4SG5wC
https://books.google.co.in/books?id=BzYYOgpPRFIC
https://books.google.co.in/books?id=NyFms7nXCY4C Construction Process Planning and Management
https://books.google.co.in/books?id=XkxHtMkvJEgC
https://fac.ksu.edu.sa/sites/default/files/7-manual_process_planning_ams_may06_14_0.pdf
http://www.ejournals.eu/pliki/art/2306/
https://stampingsimulation.com/process-planning-for-beginners-drawing-board-to-production/
Basic study on process planning for Turning-Milling
https://www.jstage.jst.go.jp/article/jamdsm/8/4/8_2014jamdsm0058/_pdf
https://www.bayfor.org/fileadmin/user_upload/forschungsverbuende/forflow/BayFOR-publications-situation-specific-development-processes.pdf
http://www.nitmz.ac.in/uploaded_files/GIAN_Portal-Brochure_-_ADVANCED_SCIENTIFIC_PROCESS_PLANNING.pdf
https://pdfs.semanticscholar.org/7bbb/c214a0b5341723ad2f438be4c5383b029b02.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6164215/
https://purl.fdlp.gov/GPO/gpo100388
Updated on 17 July 2020
14 May 2020
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