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PROSES PRODUKSI I
Dr. Ir. Yanuar Burhanuddin, MT (Staf Pengajar Jurusan Teknik Mesin)
(Universitas Lampung)
Topik Kuliah• Pengantar Proses Manufaktur• Aspek-aspek manufaktur• Pengecoran• Pembentukan Logam Curah (Bulk)• Pembentukan Logam Plat (Sheet)• Pengelasan
BAB 1 PENGANTAR TEKNOLOGI PRODUKSI
PROSES PRODUKSI I
Produksi atau Manufaktur• Produksi: proses pengubahan bahan baku
menjadi produk/komponen.• Manufaktur: diturunkan dari kata Latin yaitu manu
factus yang berarti “dibuat dengan tangan”.• Teknologi produksi memberikan pengetahuan
dasar bahan teknik, penggunaan berbagai perkakas tangan dan mesin-mesin, penerapan berbagai metode produksi yang memfasilitasi pembentukan bahan mentah menjadi bentuk berguna yang diproduksi pada berbagai bengkel produksi.
Definisi Produksi atau Manufaktur• Produksi : 1. proses mengeluarkan hasil;
penghasilan; 2. hasil; 3. pembuatan (KBBI)• Manufaktur: diturunkan dari kata Latin yaitu manu
factus yang berarti “dibuat dengan tangan”.• Definisi:
Pengubahan bahan baku menjadi barang yang berguna dengan tenaga manusia atau mesin-mesin-mesin bertenaga (R. Timings).
• Manufaktur adalah serangkaian aktifitas mengubah bahan baku menjadi produk dengan cara hemat biaya yang paling mungkin. Aktifitas manufaktur termasuk merancang barang/produk, membuat komponen dan merakitnya menjadi produk (subassemblies) menggunakan berbagai metoda dan teknik, menjual produk ke pelanggan, memperbaiki, merawat produk dengan aturan kerja yang baik dan mendaur ulang bahan dan komponen (Springer Handbook of Mechanical Engineering)
TEKNOLOGI PRODUKSI• Teknologi produksi adalah mesin dan sarana
produksi yang membuat/ menciptakan produk fisik nyata yang layak bagi sebuah bisnis. Untuk sebuah usaha kecil, ini berarti setidaknya sebuah bengkel.
MODEL PROSES PRODUKSI
Bahan
PROSESProduk
Energi
Informasi
Mesin
Limbah
Manusia
Manajemen
PDB vs Produksi/Manufaktur
• Hubungan yang sangat dengan antara Produk Domestik Bruto (PDB) dengan produksi/manufaktur
• Kemajuan suatu negara ditopang kemajuan industri manufaktur
Manufaktur Global (Sumber: Timings)
Komponen dan bahan pada mesin mobil
Potongan dari mesin mobil yang menunjukkan berbagai komponen dan bahan yang digunakan. Sumber: Ford Motor Company. Ilustrasi oleh David Kimball.
Komponen pada ProdukProduk Jumlah KomponenSepeda 25Mobil 15.000
Pesawat Angkut Militer
> 4.000.000
Pesawat angkut penumpang Boeing
> 6.000.000
• Beberapa produk hanya mempunyai komponen tunggal (paku, baut, garpu, coat hanger, dll.)
• Beberapa produk adalah rakitan dari beberapa komponen (ball point, pena, mobil, mesin cuci, dll.)
• Semua komponen dibuat atau diproduksi.
•
Pembuatan Lampu Pijar
Komponen-komponen lampu pijar yang umum. Sumber: General Electric Company.
Tahapan-tahapan produksi dalam pembuatan lampu pijar. Sumber: General Electric Company.
Pemilihan Bahan-bahan untuk Klip Kertas
Berbagai contoh bahan dan geometri klip kertas
Pertanyaan:
• Apakah sifat-sifat bahan yang diperlukan?
• Karakteristik pembuatan apa yang diperlukan?
• Kalau jumlah yang akan diproduksi 1 juta/hari apakah strategi produksi sama dengan produksi 10 ribu/hari?
Sejarah ProduksiPeriode Bahan TeknologiSebelum 1 Masehi Emas, tembaga, besi,
perunggu, besi cor, baja cor, kayu
Penempaan, pengecoran, penarikan, penyeteman, potong menggunakan batu/tulang, keling, solder
1 – 1000 M Seng, Baja, Kuningan Bubut kayu, teknologi kaca
1000-1500 M Tungku tiup, penarikan kawat, etsa
1500-1600 M Aluminium Tempa menggunakan kincir air, pengerolan, teknologi kristal
1600-1700 M Pengecoran cetakan permanen, pengerolan
Aktifitas dan Hasil Produksi Manusia Dulu
Sejarah ProduksiPeriode Bahan Teknologi1700 – 1800 M Besi cor, besi krusibel Pengecoran, ekstrusi,
deepdrawing, bor, bubut ulir
1800 – 1900 M Nikel, babbit, baja wolfram, baja galvanis
Pengecoran sentrifugal, Bessemer, teknologi serbuk, frais, bubut copy, mesin gerinda, ekstrusi karet
1900 – 1940 M Plastik, komposit Cor cetakan, cor cetakan lilin, ekstrusi baja, pengelasan pendam, pengelasan busur listrik, pembuatan botol,
1940 - sekarang Plastik, komposit, magnesium, titanium
Proses Produksi• Pengecoran: cor cetakan habis, cor cetakan permanen• Pembentukan Logam Pejal: pengerolan, penempaan,
ekstrusi, penarikan• Pembentukan Logam Plat: pemotongan, penekukan,
penarikan• Pemrosesan Serbuk: pemadatan• Pemrosesan Plastik : injeksi, ekstrusi, kompresi• Pembuangan Logam: pemesinan, non-konvensional• Penyambungan: pengelasan, perekatan, pengelingan• Penyelesaian (Finishing): Pengecatan, Galvanis, Krom,
Sepuh
Jenis-jenis proses produksi
C en tri fugalD ie cas tingInvestm entP erm anen t m o ldS and cas ting
P eng eco ran(P eru bahan Fasa)
E x tru sionF org ingR ollingB ar d ra w ingW ire dra w ing
M as if/C u rah
B end ingB lank ingD raw ingP un ch ingS hear ingS p inn ing
P lat
P em be ntukan(D eform as i)
B low m old ingC as t ingC om press ion m o ld ingE x trus ionIn jection M old ingT herm ofo rm ingT ra nsfe r mo ld ing
P em rosesanP o ly m er
B oringD ri llingF ac ingG rind ingM illingP lan ingT urn ingS aw ingE C M , E D M
P em es ina n(P em buang an G eram)
A no diz ingH on ingP ain tingP la t ingP o l ish ing
P en ye lesa ia n A kh ir(P erm ukaan)
A u to m a tedB ond ingB ra z ingM anu alR ivet ingSo lde r ingW eld ing
P engg ab ung an/P enyam bungan
P rose s Prod uk si
How is the input material changed?
Proses Pengecoran
• Cetakan Pasir (Sand casting)• Cetakan Besi (Die casting)• Cetakan Keramik (Investment casting)• Permanent mold• Centrifugal Casting
Proses Pembekuan
Barang padat Bahan lebur pembekuan
Flow (voids, flash)Cooling time (cycle time)TemperatureMold complexity Warpage Post processing Costs (materials, tooling, processing)
Casting ProcessesSand CastingDie CastingInvestment CastingCentrifugal
Polymer ProcessesInjection MoldingBlow MoldingThermoFormingCompression Molding
Add to your notes
Proses Pembentukan Masif
• Pengerolan (Rolling)• Ekstrusi (Extrusion)• Penarikan (Drawing)• Tempa (Forging)
Rolling
slab
bloom
billet
sheet coil
bar rod
structural
ingot
Extrusion
RamCross
sections
Extrusion die
Billet
Penarikan (Drawing)
Pulling force
Crosssections
Drawing die
Billet
Tempa cetakan tertutup (Closed-die Forging)
Blockedpreform
Gutter
Ram pressure
Flash
Pembentukan Plat (Sheet metal forming)
• Bending• Blanking• Drawing• Punching• Shearing• Spinning
Sheet metal drawing
BlankDrawn part
Clamp force
Blank holder
Die
Punch
Punch ram
Polymer Processes
• Compression molding
• Transfer Molding• Blow molding• Injection molding
Compression molding
Charge
Heated mold
Part
Ram Pressure
Transfer molding
Charge
Ram
Heatedmold Sprue
Part
Ram pressure
Blow molding
Extruderair injector
parison
Part isremoved
Airblown into
parison
Mold halvesclose
Molten parison is extruded
Injection molding
Shear-heating
Cavity halfof mold
Core halfof mold
Ejector pins
Moving
Feed hopper
Sprue
Fixed
Barrel
Pellets
Mold closure direction
Parting plane/surfac
e
Machining processes
E x trus ionF org ingR o llingB ar d raw ingW ire d raw ing
D eform a t ion
C en tri fug alD ie ca s t ingInvestm entP erm a nen t m oldS an d ca st ing
C as ting
B end in gB la nk ingD raw ingP un ch in gS he ar ingS p inn ing
S hee tM e tal
B lo w m o ld ingC ast ingC om press io n m o ld ingE x trus ionIn jec tion M old ingT h erm oform ingT ra nsfe r m old ing
P o lym erP ro cesses
B oringD ri l lingF ac in gG rind ingM ill ingP lan ingT u rn ingS aw ingE C M , E D M
M a ch in ing
A n od iz ingH o ningP ain tingP la t ingP o l ish ing
F in ish ing
A u tom atedB o nd ingB raz ingM a nu alR ive t ingS o lde r ingW eld ing
A ssem bly
M a nu fac tu ringP ro cesses
Machining – removal of material…
Sawing –using a toothed blade.Milling – from a flat surface by a rotating cutter tool. Planing – using a translating cutter as workpiece feeds.Shaping - from a translating workpiece using a stationary cutter. Boring - increasing diameter of existing hole by rotating the workpiece.Drilling- using a rotating bit forming a cylindrical hole.Reaming – to refine the diameter of an existing hole.Turning - from a rotating workpiece. Facing - from turning workpiece using a radially fed tool. Grinding - from a surface using an abrasive spinning wheel.Electric discharge machining - by means of a spark.
Surface roughnessProcess Roughness ( inch)
Machining
Turning 32-250
Boring 16-250
Milling 32-250
Drilling 63-250
Reaming 16-125
Broaching 16-125
Finishing
Precision grinding 2-16
Lapping / honing 2-16
Super finishing 1-8
Machining process considerations
sawing, turning, boring, milling, drilling, grinding, ECM
material removed solid material machining
hardness, strength of materialshear forces = strong jigs & fixtures tool/bit wear, replacementsize of workpiece, fit machine?volume removedrate of removal, hp neededtolerances operator skill, CNCcosts (materials, tooling, processing)Add to your
notes
Aplikasi teknologi informasi untuk membuat cetakan kacamata anti-matahari
Pemesinan rongga cetakan pada pembuatan kacamata anti-
matahari
(a) Model komputer kacamata anti-matahari sebagaiman didesain dan dilihat pada layar monitor
(b) Pemesinan rongga cetakan menggunakan mesin frais yang dikendalikan komputer.
(c) Produk jadi/akhir. Sumber: Mastercam/CNC Software, Inc.
Video
Assembly processes – fastening / joining of 2 or more components
E xtrus ionF o rg ingR ol l ingB ar d raw ingW ire d raw ing
D eform ation
C en tri fug alD ie ca st ingIn vestm entP erm anen t m o ldS and cas t ing
C as ting
B en dingB lan k ingD raw ingPu nch ingSh ea ringSp inn ing
S hee tM etal
B low m old ingC ast ingC om press ion m old ingE x trus ionIn jec tion M o ld ingT h erm o form ingT ran sfe r m o ld ing
P o ly m erP rocesses
B oringD ri llingF ac in gG rind ingM ill ingP lan ingT u rn ingS aw ingE C M , E D M
M achin ing
A nod iz ingH oningP a in tingP la tingP o l ish ing
F in ish ing
A utom atedB o nd in gB raz ingM anu alR iv e tingS o lde ringW eld ing
A ssem bly
M anufac tu r ingP rocesses
permanent?
Pengelasan otomatik mobil
Pengelasan titik (spot welding) bodi mobil pada jalur perakitan mobil. Sumber: Ford Motor Company.
Video
Finishing processes
E xtrus ionFo rg ingR oll ingB ar d raw ingW ire d raw ing
D eform at ion
C e n tri fu galD ie ca s t ingInve stm entPe rm a ne n t m o ldSa nd cas ting
C a st ing
B end ingB lank ingD raw ingPu nch in gSh ear ingSp in n ing
Sh eetM etal
B lo w m o ld ingC as tingC om press io n m old ingE xtru s ionIn je c tio n M old ingT herm o form ingT ra nsfe r m o ld ing
Po lym erProcesses
B o ringD ril lingFa cingG r ind ingM ill ingP lan ingT u rn ingSa w ingE C M , E D M
M ach in ing
A no d iz ingH on ingPa in tingP la t ingPo lish ing
F in ish ing
A utom atedB o nd ingB raz ingM an ualR ive t ingSo ld e r ingW eld ing
A ssem bly
M anu fac tu r ingProcesses
protection?
BAB 1 ASPEK-ASPEK MANUFAKTUR
MANUFACTURING• Manufacturing is not only the making of products• Integration
– Product demand– Product design– Material selection– Manufacturing processing– Product assembly– Management
DESIGN• The Accreditation Board for Engineering and
Technology (ABET) defines engineering design as: ‘‘the process of devising a system, component or process to meet desired needs.’’
• Design is an iterative decision-making process
DESIGN PROCESSIdentifying user needs Concept development
Synthesis
Analysis/Optimization
Evaluation/PrototypingManufacturing ProcessPlanning
CONCURRENT ENGINEERING• 1987: a U.S. Defense Advanced Research Projects
Agency (DARPA) working group • Definition:
‘‘Concurrent Engineering (CE) is a systematic approach to the integrated (concurrent) design of products and their manufacturing and support process.’’
• The need for accelerated product launch in the face of significantly shortened product life cycles
DESIGN FOR MANUFACTURING• Consideration of manufacturing (also termed
as production or fabrication) processes during the design stage of a product is fundamental to successful design.
• Since selection of materials must precede consideration and analysis of manufacturability.
Design for Manufacturing• Design for Casting• Design for Forging• Design for Machining• Design for Injection Molding• Design for Assembly• others
Design for Forging
Design for Machining
Material Selection and Material Processing in Design
New Product Analysis• Everyday we use thousands of different products, from telephones
to bikes and drinks cans to washing machines and microwaves. • But have you ever thought about how they work or the way they
are made?• Every product is designed in a particular way - product
analysis enables us to understand the important materials, processing, economic and aesthetic decisions which are required before any product can be manufactured.
• An understanding of these decisions can help us in designing and making for ourselves.
Getting Started
• The first task in product analysis is to become familiar with the product! What does it do? How does it do it? What does it look like?
• All these questions, and more, need to be asked before a product can be analysed.
• As well as considering the obvious mechanical (and possibly electrical) requirements, it is also important to consider the ergonomics, how the design has been made user-friendly and any marketing issues - these all have an impact on the later design decisions.
Let's take the example of a bike
• What is the function of a bicycle?• How does the function depend on the type of bike (e.g.
racing, or about-town, or child's bike)?• How is it made to be easily maintained?• What should it cost?• What should it look like (colours etc.)?• How has it been made comfortable to ride?• How do the mechanical bits work and interact?
How would we manufacture a bike ?
TopTube
RearDerailleur
Front BrakeRear Brake
SaddleSeatPost
Pedal
Handle Bar
DownTube
Fork
(Courtesy of Trek Bicycle, 2002)
Systems and Components• There are 2 main types of product - those
that only have one component (e.g. a spatula) and those that have lots of components (e.g. a bike).
• Products with lots of components we call systems. For example:
System Components
Product Components
Bike Frame, wheels, pedals, forks, etc.
Drill Case, chuck, drill bit, motor, etc.
Multi-gym Seat, weights, frame, wire, handles, etc.
Product Analysis• In product analysis, we start by considering
the whole system. • But, to understand why various materials
and processes are used, we usually need to 'pull it apart' and think about each component as well.
• We can now analyse the function in more detail and draft a design specification.
Some important design questions
• To build a design specification, consider questions like the following:– What are the requirements on each part (electrical, mechanical,
aesthetic, ergonomic, etc)?– What is the function of each component, and how do they
work?– What is each part made of and why?– How many of each part are going to be made?– What manufacturing methods were used to make each part and
why ?– Are there alternative materials or designs in use and can you
propose improvements?
Design Questions• These are only general questions, to act as a guide - you will need to
think of the appropriate questions for the products and components you have to analyse. For a drinks container, a design specification would look something like:
– provide a leak free environment for storing liquid– comply with food standards and protect the liquid from health hazards– for fizzy drinks, withstand internal pressurisation and prevent escape of bubbles– provide an aesthetically pleasing view or image of the product– if possible create a brand identity– be easy to open– be easy to store and transport– be cheap to produce for volumes of 10,000+
Choosing the Right Materials• Given the specification of the requirements
on each part, we can identify the material properties which will be important - for example:
Choosing the Right Materials
Requirement Material Property
must conduct electricity electrical conductivity
must support loads without breaking strength
cannot be too expensive cost per kg
Material Selection
• One way of selecting the best materials would be to look up values for the important properties in tables. But this is time-consuming, and a designer may miss materials which they simply forgot to consider.
• A better way is to plot 2 material properties on a graph, so that no materials are overlooked - this kind of graph is called a materials selection chart (these are covered in another part of the tutorial).
• Once the materials have been chosen, the next step is normally to think about the processing options.
Choosing the Right Process
• It is all very well to choose the perfect material, but somehow we have to make something out of it as well! An important part of understanding a product is to consider how it was made - in other words what manufacturing processes were used and why.
• There are 2 important stages to selecting a suitable process:– Technical performance: can we make this product with the material
and can we make it well?– Economics: if we can make it, can we make it cheaply enough?
• Process selection can be quite an involved problem - we deal with one way of approaching it in another part of the tutorial.
• So, now we know why the product is designed a particular way, why particular materials are used and why the particular manufacturing processes have been chosen.
• Is there anything else to know?
Wrap Up…
• Product analysis can seem to follow a fixed pattern:– Think about the design from an ergonomic and
functional viewpoint.– Decide on the materials to fulfil the performance
requirements.– Choose a suitable process that is also economic.
• Whilst this approach will often work, design is really holistic - everything matters at once - so be careful to always think of the 'bigger picture'.
Example Analysis• Is the product performance driven or cost driven? • This makes a big difference when we choose materials. • In a performance product, like a tennis racquet, cost is one of the last
factors that needs to be considered. • In a non-performance product, like a drinks bottle, cost is of primary
importance - most materials will provide sufficient performance (e.g. although polymers aren't strong, they are strong enough).
• Although we usually choose the material first, sometimes it is the shape (and hence process) which is more limiting.
• With window frames, for example, we need long thin shaped sections - only extrusion will do and so only soft metals or polymers can be used (or wood as it grows like that!).
Choosing between Different Materials
• There are three main things to think about when choosing materials (in order of importance):– Will they meet the performance requirements?– Will they be easy to process?– Do they have the right 'aesthetic' properties?
• We deal with the processing aspects of materials in a different part of this course.
• For now it is sufficient to note that experienced designers aim to make the decisions for materials and processes separately together to get the best out of selection.
• The choice of materials for only aesthetic reasons is not that common, but it can be important: e.g. for artists.
• However, the kind of information needed is difficult to obtain and we won't deal with this issue further here.
Material Selection• Most products need to satisfy some performance targets, which we
determine by considering the design specification e.g. they must be cheap, or stiff, or strong, or light, or perhaps all of these things...
• Each of these performance requirements will influence which materials we should choose - if our product needs to be light we wouldn't choose lead and if it was to be stiff we wouldn't choose rubber!
• So what approach do we use to select materials?
Using Material Selection Charts• So what we need is data for lots of material
properties and for lots of materials. • This information normally comes as tables of
data and it can be a time-consuming process to sort through them.
• And what if we have 2 requirements - e.g. our material must be light and stiff - how can we trade-off these 2 needs?
• The answer to both these problems is to use material selection charts.
• Here is a materials selection chart for 2 common properties: Young's modulus (which describes how stiff a material is) and density.
Using Material Selection Charts
• On these charts, materials of each class (e.g. metals, polymers) form 'clusters' or 'bubbles' that are marked by the shaded regions.
• We can see immediately that:– metals are the heaviest materials,– foams are the lightest materials,– ceramics are the stiffest materials.
• But we could have found that out from tables given a bit of time, although by covering many materials at a glance, competing materials can be quickly identified.
• Where selection charts are really useful is in showing the trade-off between 2 properties, because the charts plot combinations of properties.
• For instance if we want a light and stiff material we need to choose materials near the top left corner of the chart - so composites look good.
• Note that the chart has logarithmic scales - each division is a multiple of 10; material properties often cover such huge ranges that log scales are essential.
Using Material Selection Charts
• To find the best materials we need to use the Young's modulus - density chart from amongst the available charts. The charts can be annotated to help reveal the 'best' materials, by placing a suitable selection box to show only stiff and light materials.
• What can we conclude?• The values of Young's modulus for polymers are low, so
most polymers are unlikely to be useful for stiffness-limited designs.
• Cambridge Engineering Selector (CES) is the Software used for Material Selection developed by Prof. Ashby.
• Other material property selection charts include:
Wrap Up• By considering 2 (or more) charts, the properties needed to satisfy the
main design requirements can be quickly assessed.• The charts can be used to identify the best classes of materials, and
then to look in more detail within these classes.• There are many other factors still to be considered, particularly
manufacturing methods. The selection made from the charts should be left quite broad to keep enough options open.
• A good way to approach the problem is to use the charts to eliminate materials which will definitely not be good enough, rather than to try and identify the single best material too soon in the design process.
PROCESS-MATERIAL MATRIX
General classification of shape
PROCESS-SHAPE MATRIX
PROCESS-MASS MATRIX
PROCESS-SECTION THICKNESS MATRIX
PROCESS-TOLERANCE LIMIT MATRIX
PROCESS-SURFACE ROUGHNESS MATRIX
CHAPTER 7
86
Manufacturing Process Selection and Design
Overview
• Process Selection– Types of Processes– Process Flow Structures– Product-Process Matrix
• Break-Even Analysis
• Manufacturing Process Flow Design
87
88
Process Selection
89
Process and Process Selection• Process: Any set of activities performed by an
organization that takes inputs and transforms them into outputs ideally of greater value to the organization than the original inputs.
• Process selection refers to the strategic decision of selecting with which kind of production processes to have in the manufacturing plant.
Process SelectionThree primary questions:
• How much variety in products or services will the system need to handle?
• What degree of equipment flexibility will be needed?
• What is the expected volume of output?
90
Types of ProcessesBased on what they do• Conversion process
Iron ore steel sheets, ingredients of toothpaste toothpaste
• Fabrication process: changing raw materials into some specific form Sheet metal car fender, gold a crown for a tooth, cloth
clothes • Assembly process
Assemble parts to components, put toothpaste tubes into a box, fasten a dental crown into someone’s mouth
• Testing process For quality of products
91
Process Types
A process flow structure refers to how a factory organizes material flow using one or more of the process technologies.
• Job shop
• Batch shop
• Assembly Line
• Continuous Flow
92
Job Shop
• Job shop: A process structure suited for low-volume production of a great variety of nonstandard products.– Each job may require a different set or sequence of processing steps
– High flexibility of equipment (General-purpose equipment )
– Skilled workers
– Examples: commercial printing firms, copy center making a single copy of a student term paper, airplane manufacturers, machine tool shops, American Chopper
93
Batch Shop• Batch shop: A process structure that produces a moderate
variety of standard products at relatively low volumes.– A somewhat standardized job shop– Employed when a business has a relatively stable line of products– The products are produced periodically in batches to reduce the impact
of setup time on equipment– The equipment need NOT be as flexible as in a job shop– The skill level of workers need NOT to be as high as in a job shop– Examples:
• Bakeries: make bread, cakes, cookies in batches;• Movie theatre: shows movies to groups (batches) of people;• Airlines: carry batches of people from airport to airport;• Other examples: production of beer, book, magazine, etc
94
Assembly Line
• Assembly line (Repetitive processing): A process structure designed to make discrete parts moving
through a set of specially designed workstations at a controlled rate.– High volume– Standardized products– Slight flexibility of equipment– Skill of workers is usually low– Examples: manual assembly of toys and appliances, automatic
assembly of components on a printed circuit board, production line (automobiles, computers, etc.)
95
Example: Production Line
96
Continuous Flow
• Continuous flow: An often automated process structure that converts raw materials into finished product in one continuous process.– Highly standardized products, no variety– Special-purpose equipment (no need for equipment flexibility)– Skill of workers is low– Examples: petroleum, steel, sugar, flour, and salt
97
Example: Continuous Flow
98
Product-Process Matrix
• Choice of process flow structure is based on two main considerations:– Variety—how much the product changes from customer to customer;– Volume of demand.
• Product-process matrix: Shows the relationship between process structures and product volume and variety characteristics.
• As volume increases and the product line narrows, specialized equipment and standardized material flows become economically feasible. (see next slide)
99
Product-Process Matrix
100
Exhibit 7.1
Volume
Variety
HighLow
High
Low
101
Break-Even Analysis
Break-Even Analysis
• A standard approach to choosing among alternative processes or equipment.
• Most suitable when processes and equipment entail a large initial investment and fixed cost, and when variable costs are reasonably proportional to the number of units produced.
• Break-even Point (BEP)– One option case: determine the point in units (produced and sold) at
which total cost = total revenue. – Multiple options case: determine the points in units at which one
option is indifferent to another.
102
Cost-Volume Relationships (Total Cost)
103
Amou
nt (
$)
0Q (Quantity in units)
Total cost =
VC + FC
Variable cost (
VC)
Fixed cost (FC)
Total cost (TC) = Fixed cost (FC) + Variable cost (VC) = Fixed cost (FC) + Unit cost (v) X Quantity (Q)
Revenue-Volume Relationships (Total Revenue)
104
Am
ount
($)
Q (Quantity in units)0
Total re
venue
Total revenue = Revenue per unit (R) X Quantity (Q)
Cost-Volume Relationships (BEP)
105
Am
ount
($)
Q (volume in units)0 BEP
+ Profit
Total
reve
nue
Total cost
- Loss
Break-even point (BEP): the quantity of output at which total cost and total revenue are equal.
106
Total Revenue (TR) = Total Cost (TC)
Total Revenue = Total Fixed Cost + Total Variable Cost
Unit Revenue* Units = Total Fixed Cost + Unit Cost* Units
R * Q = FC + v * Q
Break Even Quantity: QBEP = FC / (R – v)
One-Option Case
Profit (margin) = Total Revenue – Total Cost
Find out the quantity that makes:
Example -- One-Option Case
Suppose you want to purchase a new computer that will cost $5,000. It will be used to process written orders from customers who will pay $25 each for the service. The cost of labor, electricity and the form used to place the order is $5 per customer.
• How many customers will we need to serve to permit the total revenue to break-even with our costs?
FC = $5,000, R = $25/customer, v = $5/customer Break-even quantity QBEP:
= FC /(R-v) = 5,000/(25-5) = 250 customers
• How many customers should we serve to make a profit of $1,000? Profit = Total Revenue – Total Cost
= R * Q – (FC + v * Q) = (R-v) * Q - FC 1,000 = (25-5) * Q – 5,000
Q = 300 customers
107
Example -- Multiple-Option Case (page 207)
108
Suppose a manufacturer has identified the following options for obtaining a machined part: 1. purchase the part $200/unit, no fixed cost 2. make the part on a semiautomatic lathe $75/unit, fixed cost = $80,000 3. make the part on a machining center $15/unit, fixed cost = $200,000
Which option should the manufacturer choose? TC_buy = 200 * QTC_lathe = 80,000 + 75 * QTC_machine = 200,000 + 15 * Q
Example -- Multiple-Option Case (page 207)
109
0
100000
200000
300000
400000
500000
0 300 600 900 1200 1500 1800 2100 2400
TC_buyTC_LatheTC_Machine
Demand < B BuyB < Demand < A Semiautomatic LatheDemand >A Machine center
B
A
TC_buy
TC_Machine
TC_Lathe
Minimum cost
Example -- Multiple-Option Case (page 207)
• Break-even point B: Total cost of “buy” = Total cost of “Make on lathe” 200 x Demand = 80,000 + 75 x Demand DemandB = 80,000/(200-75) = 640 units
• Break-even point A: Total cost of “Make on lathe” = Total cost of “Make on machine” 80,000 + 75 x Demand = 200,000 + 15 x Demand DemandA= (200,000- 80,000)/(75-15) = 2,000 units
110
111
Manufacturing Process Flow Design
Manufacturing Process Flow Design
• A process flow design can be defined as a mapping of the specific processes that raw materials, parts, and subassemblies follow as they move through a plant.
• The most common tools to conduct a process flow design include assembly drawings, assembly charts, operation and route sheets, and process flowcharts.
112
Assembly Drawing
• An assembly drawing is simply an exploded view of the product showing its component parts.
113
Plug assembly drawing
Assembly Chart
• An assembly chart uses the information presented in the assembly drawing and defines how parts go together, their order of assembly, and often the overall material flow pattern.
114
Assembly chart for plug assembly
Operation and Route Sheet• An operation and route sheet specifies operations and process
routing for a particular part. It conveys such information as the type of equipment, tooling, and operations required to complete the part.
115
Operation and route sheet for plug assembly
Process Flowchart• A process flowchart denotes what happens to the product as it
processes through the productive facility.
116
Process flowchart for plug housing
Recap– Process
– Process selection
– Types of processes
– Process flow structures• Job shop
• Batch shop
• Assembly line
• Continuous flow117
Product-process matrixBreak-even point (BEP)
One-option caseMultiple-option case
Manufacturing process flow design
Manufacturing process decisions• How do we choose the specific manufacturing
processes? • How do the selected materials influence the choice
of manufacturing processes? • Would product function or performance issues
influence our choice of processes?• What criteria should we use to select processes? • Which criteria are more important? • Who will make the final decisions?
Parts undergo sequence of processes• Primary - alter the (“raw”) material’s basic shape or form.
Sand castingRollingForgingSheet metalworking
• Secondary - add or remove geometric features from the basic forms Machining of a brake drum casting (flat surfaces)Drilling/punching of refrigerator housings (sheet metal)Trimming of injection molded part flash
• Tertiary - surface treatments PolishingPaintingHeat-treatingJoining
Part / Mfg. Process Considerations
1. Production Volume2. Part Size (overall)3. Shape Capability (features) boss/depression 1D boss/depression >1D holes undercuts (int./ext.) uniform walls cross sections - uniform/regular rotational symmetry captured cavities
Is process capable of producing part geometry?
ManufacturingProcesses
ProductGeometry
“capable”geometry & processes
Process-first selection approach
Part Information1. Production Volume (run qty)2. Part Size (overall)3. Shape Capability (features)
boss/depression 1Dboss/depression >1Dholesundercuts (int./ext.)uniform walls
uniform cross sectionsregular cross sectionsrotational symmetrycaptured cavities
Axis of rotation (symmetry)
Shape generation capability (of processes)ME 488/588 Design for Manufacture & Assembly Process Capabilitites for Shape Generation Date: 9/2/03Engineer: R. J. E. Design Part Name: no features part For Process
Part Data Input: N N N N N N N N N Assembly Evaluation
Processes Shap
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Dep
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Dep
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>1D
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-Wal
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-Sec
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urfa
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Solidification sand casting Y Y YU Y Y Y Y N N 4 3 1 8 0 0 Ainvestment casting Y Y YU Y Y Y Y N N 5 5 2 12 0 0 Adie casting Y Y YU Y Y Y N N N 4 5 3 12 0 0 Ainjection molding Y Y YU Y Y Y N N N 5 5 5 15 0 0 Astructural foam Y Y YU Y Y Y N N N 4 4 3 11 0 0 Ablow molding - extr Y Y M N Y Y M Y N 3 4 3 0 0 2 Rblow molding - inj Y Y M N Y YU M N N 3 4 3 0 0 2 Rrotational molding Y Y M N Y Y N M N 2 2 1 0 0 2 R
Bulk impact extrusion Y N Y N Y YU N N Y 3 3 1 7 0 0 ADeformation cold heading Y N Y N Y YU N N Y 3 3 1 7 0 0 A
closed die forging Y Y Y Y Y Y N N N 3 2 1 6 0 0 Apowder metal Y N Y YU Y Y N N YU 3 3 1 7 0 0 Ahot extrusion Y N Y M Y Y N N Y 2 2 3 0 0 1 Rrotary swaging N N N N M N N N N 1 1 1 0 0 1 R
Metal machined from stock Y Y Y Y Y Y Y N Y 2 3 2 7 0 0 ARemoval ECM Y Y Y Y Y Y N N N 3 4 1 8 0 0 A
EDM Y Y Y Y Y Y N N N 3 4 1 8 0 0 A
Profile Generation Wire EDM Y N Y Y Y Y N N Y 2 2 3 7 0 0 A
Sheet sheet metal bending Y Y M Y Y Y N N N 4 3 4 0 0 1 RForming thermoforming Y Y M Y Y Y N N N 3 3 3 0 0 1 R
metal spinning N N M N M N Y N N 1 1 1 0 0 2 R© R. J. Eggert, BSU (Based on data from Boothroyd, Dewhurst & Knight) revision 9/02/03
Design & Manufacturing Concerns:Tolerance, Inspection, Quality Control
In terchangeability of Parts
What do the following have in common?- Fuel pump on a car- Printer cartridge- Light bulb
Modern manufacturing depends on interchangeability
Interchangeably depends on size control
For Size Control
Need
Standard unit of length (meter)
Suitable measuring equipment (gageblocks, dial gages, calipers, steel rules,etc.)
Inspection of parts producedQuality Control
Tolerances
Dimensions assigned based onfunctionality requirements and/or designspecifications..Mass-produced parts cannot all beproduced to exact (specified) dimensions.Always variations in dimensions.Due to:Tool and die wear.Changes in processing conditions.Variability in raw material composition andpurity.
Tolerances (TJ- continued
Ta: designer-specified allowed variation in adimension or other geometric characteristic.Every process has standard or commercialtolerances.Tightest Ta are achievable via machining.
In injection molding variations in temperatureand pressure, non-uniform shrinkage,sensitivity of material used, etc affect Ta
In stamping, springback affects Ta
Tolerances (TJ- continued
To achieve functionality designers canlimit range of acceptable dimensionalvariations of parts.The more strict the limitations,the more dimensions subjected to specialtolerance limitations, the more costly thepart.Parts with no Ta tighter than standard areleast costly "Best to consult vendors and industrypublications for""a data.
Internationally Accepted (ISO)Definitions
Limits of s\ze:The two extreme permissiblesizes of a part between which the actual sizemust lie.Example: hole diameter (d)dIT = 50.05 mm (max limit of size);dmir= 49.95 mm (min limit of size)Tolerance (Ta): differencemaximum limit of size and the minimum limitof size.Example: Ta = 50.05-49.95 = 0.10 mm
(ISO) Definitions - continued
Basic Size: The size by reference towhich the limits of size are fixed. Canbe assigned to a hole or shaft.Example:
- Given: Basic size (dia.) of hole = 50mm
_ l
Limits of size: d—
50
(ISO) Definitions - continued+0.10-0.00
- Alternatively: d = 49.95
When parts must fit together (a shaftinside a hole) the tolerances on both partsmust be considered simultaneously.Fit: relationship resulting from thedifference, before assembly, between thesizes of the two parts to be assembled.
Example:dj = hole diameterds = shaft diameterClearance exists if dh>ds
(allows for rotation and sliding of assembled parts)
Interference exists if dh<ds
(allows alignment of parts; provides stiffness)
Fits - continued+0.10 +005
-0.00 -0.05
d, = 50.00 d, = 50.00
Clearance Fit: exists if the min. holediameter > max shaft diameter.Inference I it: exists if the max holediameter < min shaft diameter.
Transitional Fit: exists if sometimes getclearance and sometimes getinterference.
Allowance
" he intentional desired difference between thedimensions of two mating parts.""he difference between the dimensions of thelargest interior-itting part and the smallestexterior-fitting part.
Clearance t: allowance = min clearance.Interference fit: allowance =
Inspection and QC
To ensure that dimensions and tolerancesare being metNeed
Inspection - to determine how well thephysical specifications are being met.
Quality Control - the amount of inspectionnecessary to produce an acceptable part.
Procedure of Measurement andmodeling in your design projects1- Chose the right unit system
2- Chose the right measurement device
3- Nominal dimensions: measure each feature with itscorresponding mating feature at the same time. Thenominal values of two feature should be equal. Roundthe numbers to a value with not many decimal point.4- Tolerances: select the allowance based on the fittingtype. Measure each feature several times and measureseveral features. Estimate the tolerance using theestimated allowance and average of the measurementresults.
Inspection and QC - continued
Inspection of all parts is too $$$$$We want to detect if a process is goingout of control BEFORE defective partsappear.Want to detect assignable causevariations i.e. malfunction of people andmachines, or defective materials, (toolwear, die wear, people wear, etc.)Not normal chance variations due to non-uniformity of materials, equipment, etc.
BAB 2 MATERIAL PROSES PRODUKSI I
BAB 3 PEMBENTUKAN LOGAM
PROSES PRODUKSI I
Module 8 142
Metal Forming
• Metal forming includes a large group of manufacturing processes in which plastic deformation is used to change the shape of metal work pieces
• Plastic deformation: a permanent change of shape, i.e., the stress in materials is larger than its yield strength
• Usually a die is needed to force deformed metal into the shape of the die
Module 8 143
• Metal with low yield strength and high ductility is in favor of metal forming
• One difference between plastic forming and metal forming is
Plastic: solids are heated up to be polymer melt
Metal: solid state remains in the whole process
- (temperature can be either cold, warm or hot)
Metal Forming
Module 8 144
1. General mechanics principle
• The underlying mechanics principle for metal forming is the stress-strain relationship; see Figure 1.
Figure 1
Module 8 145
• True strain: Instantaneous elongation per unit length of the material
0ln
0 LL
LdLL
L
L0: the initial length of a specimen
L: the length of the specimen at time t
the true strain at time t
• True Stress: Applied load divided by instantaneous value of cross-section area
AF /
Module 8 146
• In the forming process we are more interested in the plastic deformation region (Figure 1)
Plastic deformation region
Module 8 147
• The stress-strain relationship in the plastic deformation region is described by
nK Where K= the strength coefficient, (MPa) = the true strain, σ=the true stress n= the strain hardening exponent,
The flow stress (Yf) is used for the above stress (which is the stress beyond yield)
Called FLOW CURVE
Module 8 148
• As deformation occurs, increasing STRESS is required to continue deformation (shown in curve)
• Flow Stress: Instantaneous value of stress required to continue deforming the material (to keep metal “flowing”)
FLOW STRESS
nKfY
Module 8 149
• For many bulk deforming processes, rather than instantaneous stress, average stress is used (extrusion)
• The average flow stress can be obtained by integrating the flow stress along the trajectory of straining, from zero to the final strain value defining the range of interest
nkY
n
f
1
AVERAGE FLOW STRESS
Average flow stress Max. strain during deformation
Strength Coefficient
Strain hardening exponent
Module 8 150
Example 1:Determine the value of the strain-hardening exponent for a metal that will cause the average flow stress to be three-quarters of the final flow stress after deformation.
According to the statement of the problem, we have
4/3fY of fY
333.075.0)1/(1
75.0)1/(
75.0
nn
KnK
YYnn
ff
Module 8 151
• The above analysis is generally applicable to the cold working, where the temperature factor is not considered.
• The metal forming process has three kinds in terms of temperature: (1) cold, (2) warm, (3) hot
• In the case of warm and hot forming, the temperature factor needs to be considered, in particular
Temperature up The (yield) strength down and ductility up
Module 8 152
• Strain rate (related to elevated temperatures)- Rate at which metal is strained in a forming process- In the hot forming or warm forming, the strain rate can affect the
flow stress
hv /h
Speed of deformation (could be equal to velocity of ram)
Instantaneous height of work-piece being deformed
h
mf CY
Flow stress
Strain Rate
Module 8 153
mf CY
whereC strength constantm strain-rate sensitivity exponent
C and m are determined by the following figure which is generated from the experiment
nKfY
Strength coefficient but not the same as K
Module 8 154
Module 8 155
C and m are affected by temperature
Temperature Up
C Down
m Up
Module 8 156
mnf AY
Even in the cold work, the strain rate could affect the flow stress. A more general expression of the flow stress with consideration of the strain rate and strain is presented as follows:
A is a strength coefficient, a combined effect of K, C
All these coefficients, A, n, m, are functions of temperature
Module 8 157
Example 2:A tensile test is carried out to determine the strength constant C and strain-rate sensitivity exponent m for a certain metal at 1000oF. At a strain rate = 10/sec, the stress is measured at 23,000 lb/in2; and at a strain rate = 300/sec, the stress=45,000 lb/in2. Determine C and m
23000=C(10)^m45000=C(300)^m
From these two equations, one can find m=0.1973
Solution:
Temperature in Metal Forming • For any metal, K and n in the flow curve
depend on temperature– Both strength and strain hardening are reduced at
higher temperatures– In addition, ductility is increased at higher
temperatures
HOT AND COLD WORKING
HOT AND COLD WORKING
Cold working is metal forming performed at room temperature. Advantages: better accuracy, better surface finish, high strength and hardness of the part, no heating is required. Disadvantages: higher forces and power, limitations to the amount of forming, additional annealing for some material is required, and some material are not capable of cold working.
Warm working is metal forming at temperatures above the room temperature but bellow the recrystallization one.
Advantages: lower forces and power, more complex part shapes, no annealing is required. Disadvantages: some investment in furnaces is needed. Hot working involves deformation of preheated material at temperatures above the re crystallization
temperature. Advantages: big amount of forming is possible, lower forces and power are required, forming of materials with low ductility, no work hardening and therefore, no additional annealing is required. Disadvantages: lower accuracy and surface finish, higher production cost, and shorter tool life.
Friction in Metal Forming• In most metal forming processes, friction is
undesirable: – Metal flow is retarded – Forces and power are increased– Wears tooling faster
• Friction and tool wear are more severe in hot working
Lubrication in Metal Forming• Metalworking lubricants are applied to tool‑work
interface in many forming operations to reduce harmful effects of friction
• Benefits: – Reduced sticking, forces, power, tool wear– Better surface finish– Removes heat from the tooling
Considerations in Choosing a Lubricant
• Type of forming process (rolling, forging, sheet metal drawing, etc.)
• Hot working or cold working• Work material• Chemical reactivity with tool and work metals • Ease of application• Cost
DefinitionsPlastic Deformation ProcessesOperations that induce shape changes on the work piece by plastic deformation under forces appliedby various tools and dies.
Bulk Deformation Processes These processes involve large amount of plastic deformation. The cross-section of workpiece changes
without volume change. The ratio cross-section area/volume is small. For most operations, hot or warm working conditions are preferred although some operations are carried out at room temperature.
Sheet-Forming Processes In sheet metalworking operations, the cross-section of work piece does not change—the material is only
subjected to shape changes. The ratio cross-section area/volume is very high. Sheet metalworking operations are performed on thin (less than 6 mm) sheets, strips or coils of metal by
means of a set of tools called punch and die on machine tools called stamping presses. They are always performed as cold working operations.
Module 8 165
Metal forming is divided into: (1) bulk and (2) sheet
Metal Forming
Bulk: (1) significant deformation
(2) massive shape change
(3) surface area to volume of the work is small
Sheet: Surface area to volume of the work is large
Module 8 166
Bulk deformation processes
RollingForging
Extrusion Drawing
Traditionally Hot
Module 8 167
Sheet deformation processes (Press working/ Stamping)
BendingDrawing
Shearing
Actually Cutting
BULK DEFORMATION PROCESSES IN METALWORKING
• Rolling• Other Deformation Processes Related to
Rolling• Forging• Other Deformation Processes Related to
Forging• Extrusion• Wire and Bar Drawing
ISE 316 - Manufacturing Processes Engineering
Bulk DeformationMetal forming operations which cause significant
shape change by deformation in metal parts whose initial form is bulk rather than sheet
• Starting forms: cylindrical bars and billets, rectangular billets and slabs, and similar shapes
• These processes work by stressing metal sufficiently to cause plastic flow into desired shape
• Performed as cold, warm, and hot working operations
ISE 316 - Manufacturing Processes Engineering
Why do we use bulk processes?
• Produces common shapes inexpensively• Good mechanical properties
Common shapes
Basic principle
v, F
Reduction in size
• Push or pull• Single shot or
continuous• Hot or cold
• Malleable material• Refine and redirect the
grain• Alters geometry• Alters material
property
Importance of Bulk Deformation
• In hot working, significant shape change can be accomplished
• In cold working, strength can be increased during shape change
• Little or no waste - some operations are near net shape or net shape processes – The parts require little or no subsequent
machining
ISE 316 - Manufacturing Processes Engineering
Four Basic Bulk Deformation Processes
1. Rolling – slab or plate is squeezed between opposing rolls
2. Forging – work is squeezed and shaped between between opposing dies
3. Extrusion – work is squeezed through a die opening, thereby taking the shape of the opening
4. Wire and bar drawing – diameter of wire or bar is reduced by pulling it through a die opening
ISE 316 - Manufacturing Processes Engineering
Deformation process in which work thickness is reduced by compressive forces exerted by two opposing rolls
ISE 316 - Manufacturing Processes Engineering
Figure 19.1 ‑ The rolling process (specifically, flat rolling)
ROLLING
The Rolls The rotating rolls perform two main functions:• Pull the work into the gap between them by
friction between workpart and rolls• Simultaneously squeeze the work to reduce
cross section
ISE 316 - Manufacturing Processes Engineering
Types of Rolling• By geometry of work:
– Flat rolling - used to reduce thickness of a rectangular cross‑section
– Shape rolling - a square cross‑section is formed into a shape such as an I‑beam
• By temperature of work:– Hot Rolling – most common due to the large amount
of deformation required– Cold rolling – produces finished sheet and plate stock
ISE 316 - Manufacturing Processes Engineering
Figure 19.2 ‑ Some of the steel products made in a rolling mill
ISE 316 - Manufacturing Processes Engineering
Figure 19.3 ‑ Side view of flat rolling, indicating before and after thicknesses, work velocities, angle of contact with rolls, and other
features
ISE 316 - Manufacturing Processes Engineering
Flat rolling• A strip of thickness ho enters the roll gap and is
reduced to hf by a pair of rotating• Rolling parameters:
– Initial thickness, ho
– Final thickness, hf
– Roll gap (usually same with hf)– Surface speed of the roll, Vr
– Initial velocity of the strip, Vo
– Final velocity of the strip, Vf
Flat RollingDraft = amount of thickness reduction
ISE 316 - Manufacturing Processes Engineering
fo ttd
where d = draft; to = starting thickness; and tf = final thickness
Reduction = draft expressed as a fraction of starting stock thickness:
otdr
where r = reduction
Flat rolling• Rolling parameters (continued):
– Frictional force, fho – hf = 2R
– Roll force, FF = L w Yavg
– PowerPower = (2 F L N)/60000 ... kW
True Stress-strain Curves
Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.
Figure 2.6 True stress-strain curves in tension at room temperature for various metals. The curves start at a finite level of stress: The elastic regions have too steep a slope to be shown in this figure, and thus each curve starts at the yield stress, Y, of the material
Shape RollingWork is deformed into a contoured cross‑section
rather than flat (rectangular)• Accomplished by passing work through rolls
that have the reverse of desired shape • Products include:
– Construction shapes such as I‑beams, L‑beams, and U‑channels
– Rails for railroad tracks– Round and square bars and rods
ISE 316 - Manufacturing Processes Engineering
Roll Forming (hot):I-beams
Kalpakjian
Lunchtime on a Crossbeam, Unknown, www.buffalogames.com www.civil.ubc.ca
Figure 19.5 ‑ A rolling mill for hot flat rolling; the steel plate is seen as the glowing strip extending diagonally from the lower left corner (photo courtesy of Bethlehem Steel
Company)
ISE 316 - Manufacturing Processes Engineering
Rolling Mills• Equipment is massive and expensive• Rolling mill configurations:
– Two-high – two opposing large diameter rolls– Three-high – work passes through both directions– Four-high – backing rolls support smaller work
rolls– Cluster mill – multiple backing rolls on smaller rolls – Tandem rolling mill – sequence of two-high mills
ISE 316 - Manufacturing Processes Engineering
Slab Production: Hot Rolling
www.labware.com
www.falckacciai.it www.beautifuliron.com
Color & Temp
Figure 19.6 ‑ Various configurations of rolling mills: (a) 2‑high rolling mill
ISE 316 - Manufacturing Processes Engineering
Figure 19.6 ‑ Various configurations of rolling mills:
(b) 3‑high rolling mill ISE 316 - Manufacturing Processes Engineering
Figure 19.6 ‑ Various configurations of rolling mills:
(c) four‑high rolling mill ISE 316 - Manufacturing Processes Engineering
Cluster Mill Multiple backing rolls allow even smaller roll diameters
ISE 316 - Manufacturing Processes Engineering
Figure 19 6 ‑ Various configurations of rolling mills: (d) cluster mill
Tandem Rolling MillA series of rolling stands in sequence
ISE 316 - Manufacturing Processes Engineering
Figure 19.6 ‑ Various configurations of rolling mills:
(e) tandem rolling mill
Thread RollingBulk deformation process used to form threads on
cylindrical parts by rolling them between two dies • Most important commercial process for mass
producing bolts and screws • Performed by cold working in thread rolling machines • Advantages over thread cutting (machining):
– Higher production rates– Better material utilization– Stronger threads due to work hardening– Better fatigue resistance due to compressive stresses
introduced by rolling
ISE 316 - Manufacturing Processes Engineering
Figure 19.7 ‑ Thread rolling with flat dies: (1) start of cycle, and (2) end of cycle
ISE 316 - Manufacturing Processes Engineering
Thread-rolling for bolts: Rolled threads stronger than machined (and less expensive)
Kalpakjian
Ring RollingDeformation process in which a thick‑walled ring of
smaller diameter is rolled into a thin‑walled ring of larger diameter
• As thick‑walled ring is compressed, deformed metal elongates, causing diameter of ring to be enlarged
• Hot working process for large rings and cold working process for smaller rings
• Applications: ball and roller bearing races, steel tires for railroad wheels, and rings for pipes, pressure vessels, and rotating machinery
• Advantages: material savings, ideal grain orientation, strengthening through cold working
ISE 316 - Manufacturing Processes Engineering
Figure 19.8 ‑ Ring rolling used to reduce the wall thickness and increase the diameter of a ring:
(1) start, and (2) completion of process
ISE 316 - Manufacturing Processes Engineering
Rolling problems and defects• Problems:
– Roll deflection– Spreading
• Defects:– Wavy edges– Cracks– Alligatoring– Residual stress
ForgingDeformation process in which work is compressed
between two dies • Oldest of the metal forming operations, dating from
about 5000 B C • Components: engine crankshafts, connecting rods,
gears, aircraft structural components, jet engine turbine parts
• In addition, basic metals industries use forging to establish basic form of large components that are subsequently machined to final shape and size
ISE 316 - Manufacturing Processes Engineering
Forging grain flow
Classification of Forging Operations
• Cold vs. hot forging: – Hot or warm forging – most common, due to the
significant deformation and the need to reduce strength and increase ductility of work metal
– Cold forging - advantage is increased strength that results from strain hardening
• Impact vs. press forging:– Forge hammer - applies an impact load – Forge press - applies gradual pressure
ISE 316 - Manufacturing Processes Engineering
Types of Forging Dies• Open‑die forging - work is compressed between
two flat dies, allowing metal to flow laterally without constraint
• Impression‑die forging - die surfaces contain a cavity or impression that is imparted to workpart, thus constraining metal flow - flash is created
• Flashless forging - workpart is completely constrained in die and no excess flash is produced
ISE 316 - Manufacturing Processes Engineering
Open-die Forging• The simplest forging process.The workpiece is placed
between two flat dies and reduced in height by compressing.
• Used for changing the microstructure from cast structure to a wrought structure
• Forging force:Yf = material flow stress = friction coefficientr = radiush = height
)3
21(2
hrrYF f
Deformation operation reduces height and increases diameter of work (similar to compression test)
Stages in Open-Die Forging
(a) forge hot billet to max diameter
(b) “fuller: tool to mark step-locations
(c) forge right side
(d) reverse part, forge left side
(e) finish (dimension control)
[source:www.scotforge.com]
Open‑Die Forging with No Friction
If no friction occurs between work and die surfaces, then homogeneous deformation occurs, so that radial flow is uniform throughout workpart height and true strain is given by:
where ho= starting height; and h = height at some point during compression
• At h = final value hf, true strain is maximum valueISE 316 - Manufacturing Processes Engineering
hholn
Figure 19.11 ‑ Homogeneous deformation of a cylindrical workpart under ideal conditions in an open‑die forging operation:
(1) start of process with workpiece at its original length and diameter, (2) partial compression, and (3) final size
ISE 316 - Manufacturing Processes Engineering
Open-Die Forging with Friction• Friction between work and die surfaces
constrains lateral flow of work, resulting in barreling effect
• In hot open-die forging, effect is even more pronounced due to heat transfer at and near die surfaces, which cools the metal and increases its resistance to deformation
ISE 316 - Manufacturing Processes Engineering
Figure 19.12 ‑ Actual deformation of a cylindrical workpart in open‑die forging, showing pronounced barreling:
(1) start of process, (2) partial deformation, and (3) final shape
ISE 316 - Manufacturing Processes Engineering
Closed-die forging• The workpiece acquires the shape of the
die cavities, while being forged between two shaped dies.
• Forging force:F = k Yf A
where k = multiplying factor (table 14.1)Yf = flow stressA = projected area
Forging: Heat LossMetal near die surfaces are coolest, flow less
www.lft.uni-
erlangen.de www.freedomalloysusa.com
Range of k values Simple shapes, without flash 3 - 5
Simple shapes, with flash 5 - 8
Complex shapes, with flash 8 - 12
Impression‑Die ForgingCompression of workpart by dies with inverse of
desired part shape • Flash is formed by metal that flows beyond die
cavity into small gap between die plates • Flash must be later trimmed from part, but it serves
an important function during compression:– As flash forms, friction resists continued metal flow into
gap, constraining material to fill die cavity – In hot forging, metal flow is further restricted by cooling
against die plates
ISE 316 - Manufacturing Processes Engineering
Impression‑Die Forging Practice
• Several forming steps often required, with separate die cavities for each step – Beginning steps redistribute metal for more
uniform deformation and desired metallurgical structure in subsequent steps
– Final steps bring the part to its final geometry – Impression-die forging is often performed
manually by skilled operator under adverse conditions
ISE 316 - Manufacturing Processes Engineering
Sequence in impression‑die forging: (1) just prior to initial contact with raw workpiece, (2) partial compression, and (3) final die closure, causing flash to form in gap between die plates.
Impression-Die Forging
Forging die
Stages in Impression-die (Closed-Die) Forging
Impression‑Die Forging Advantages and Limitations
• Advantages compared to machining from solid stock:– Higher production rates– Conservation of metal (less waste)– Greater strength– Favorable grain orientation in the metal
• Limitations:– Not capable of close tolerances– Machining often required to achieve accuracies and
features needed, such as holes, threads, and mating surfaces that fit with other components
ISE 316 - Manufacturing Processes Engineering
Flashless ForgingCompression of work in punch and die tooling
whose cavity does allow for flash• Starting workpart volume must equal die cavity
volume within very close tolerance • Process control more demanding than
impression‑die forging • Best suited to part geometries that are simple and
symmetrical • Often classified as a precision forging processISE 316 - Manufacturing Processes Engineering
Figure 19.10 ‑ Three types of forging (c) flashless forging
ISE 316 - Manufacturing Processes Engineering
Figure 19.18 ‑ Flashless forging: (1)just before initial contact with workpiece, (2)partial compression, and (3)final punch and die closure
ISE 316 - Manufacturing Processes Engineering
Forging Hammers (Drop Hammers)
• Apply an impact load against workpart - two types:– Gravity drop hammers - impact energy from falling
weight of a heavy ram – Power drop hammers - accelerate the ram by
pressurized air or steam • Disadvantage: impact energy transmitted
through anvil into floor of building • Most commonly used for impression-die forging
ISE 316 - Manufacturing Processes Engineering
Figure 19.20 ‑ Drop forging hammer, fed by conveyor and heating units at the right of the scene
(photo courtesy of Chambersburg Engineering Company)
ISE 316 - Manufacturing Processes Engineering
Figure 19.21 ‑ Diagram showing details of a drop hammer for impression‑die forging
ISE 316 - Manufacturing Processes Engineering
Forging Presses• Apply gradual pressure to accomplish
compression operation - types:– Mechanical presses - converts rotation of drive
motor into linear motion of ram – Hydraulic presses - hydraulic piston actuates ram – Screw presses - screw mechanism drives ram
ISE 316 - Manufacturing Processes Engineering
Forging Press
Hydraulic press Mechanical press with an eccentric drive: fasterSlow but high forceand low cost
Forging Presses
Kalpakjian Erie Press
Forging Presses
Knuckle-joint press Screw press Gravity drop hammer:Simplest
Kalpakjian
Upsetting and HeadingForging process used to form heads on nails, bolts, and
similar hardware products • More parts produced by upsetting than any other
forging operation • Performed cold, warm, or hot on machines called
headers or formers • Wire or bar stock is fed into machine, end is headed,
then piece is cut to length • For bolts and screws, thread rolling is then used to
form threads ISE 316 - Manufacturing Processes Engineering
Figure 19.23 ‑ An upset forging operation to form a head on a bolt or similar hardware item The cycle consists of:
(1) wire stock is fed to the stop(2) gripping dies close on the stock and the stop is retracted (3) punch moves forward(4) bottoms to form the head
ISE 316 - Manufacturing Processes Engineering
Figure 19.24 ‑ Examples of heading (upset forging) operations: (a) heading a nail using open dies(b) round head formed by punch (c) and (d) two common head styles for screws formed by die(e) carriage bolt head formed by punch and die
ISE 316 - Manufacturing Processes Engineering
Swaging Accomplished by rotating dies that hammer a
workpiece radially inward to taper it as the piece is fed into the dies
• Used to reduce diameter of tube or solid rod stock
• Mandrel sometimes required to control shape and size of internal diameter of tubular parts
ISE 316 - Manufacturing Processes Engineering
Figure 19.25 ‑ Swaging process to reduce solid rod stock; the dies rotate as they hammer the work In radial forging, the workpiece rotates while the dies remain in a fixed orientation as they hammer the work
ISE 316 - Manufacturing Processes Engineering
TrimmingCutting operation to remove flash from workpart
in impression‑die forging • Usually done while work is still hot, so a
separate trimming press is included at the forging station
• Trimming can also be done by alternative methods, such as grinding or sawing
ISE 316 - Manufacturing Processes Engineering
Figure 19.30 ‑ Trimming operation (shearing process) to remove the flash after impression‑die
forging
ISE 316 - Manufacturing Processes Engineering
ExtrusionCompression forming process in which the work
metal is forced to flow through a die opening to produce a desired cross‑sectional shape
• Process is similar to squeezing toothpaste out of a toothpaste tube
• In general, extrusion is used to produce long parts of uniform cross-sections
• Two basic types of extrusion:– Direct extrusion– Indirect extrusion
ISE 316 - Manufacturing Processes Engineering
ISE 316 - Manufacturing Processes Engineering
Extrusion
Typical use: ductile metals (Cu, Steel, Al, Mg), Plastics, Rubbers
Common products:
Al frames of white-boards, doors, windows, …
Comments on Direct Extrusion • Also called forward extrusion • As ram approaches die opening, a small portion
of billet remains that cannot be forced through die opening
• This extra portion, called the butt, must be separated from extruded product by cutting it just beyond the die exit
• Starting billet cross section usually round, but final shape is determined by die opening
ISE 316 - Manufacturing Processes Engineering
Extrusion:Hollow cross-sections: Use Mandrels
Kalpakjianwww.abra.net.au
Figure 19.32 ‑ (a) Direct extrusion to produce a hollow or semi‑hollow cross‑section; (b) hollow and (c) semi‑hollow cross‑ sections
ISE 316 - Manufacturing Processes Engineering
Figure 19.33 ‑ Indirect extrusion to produce
(a) a solid cross‑section and (b) a hollow cross‑section
ISE 316 - Manufacturing Processes Engineering
Comments on Indirect Extrusion
• Also called backward extrusion and reverse extrusion
• Limitations of indirect extrusion are imposed by the lower rigidity of hollow ram and difficulty in supporting extruded product as it exits die
ISE 316 - Manufacturing Processes Engineering
General Advantages of Extrusion
• Variety of shapes possible, especially in hot extrusion – Limitation: part cross‑section must be uniform
throughout length • Grain structure and strength enhanced in cold
and warm extrusion • Close tolerances possible, especially in cold
extrusion • In some operations, little or no waste of material
ISE 316 - Manufacturing Processes Engineering
Hot vs. Cold Extrusion• Hot extrusion - prior heating of billet to above
its recrystallization temperature – This reduces strength and increases ductility of
the metal, permitting more size reductions and more complex shapes
• Cold extrusion - generally used to produce discrete parts – The term impact extrusion is used to indicate high
speed cold extrusion ISE 316 - Manufacturing Processes Engineering
Extrusion RatioAlso called the reduction ratio, it is defined as
where rx = extrusion ratio; Ao = cross-sectional area of the starting billet; and Af = final cross-sectional area of the extruded section
• Applies to both direct and indirect extrusionISE 316 - Manufacturing Processes Engineering
f
ox A
Ar
Figure 19.36 ‑ (a) Definition of die angle in direct extrusion; (b) effect of die angle on ram force
ISE 316 - Manufacturing Processes Engineering
Comments on Die Angle • Low die angle - surface area is large, leading
to increased friction at die‑billet interface – Higher friction results in larger ram force
• Large die angle - more turbulence in metal flow during reduction– Turbulence increases ram force required
• Optimum angle depends on work material, billet temperature, and lubrication
ISE 316 - Manufacturing Processes Engineering
Comments on Orifice Shape of Extrusion Die
• Simplest cross section shape = circular die orifice
• Shape of die orifice affects ram pressure • As cross‑section becomes more complex,
higher pressure and greater force are required
ISE 316 - Manufacturing Processes Engineering
Figure 19.37 ‑ A complex extruded cross‑section for a heat sink (photo courtesy of Aluminum Company of America)
ISE 316 - Manufacturing Processes Engineering
Extrusion Presses• Either horizontal or vertical
– Horizontal more common • Extrusion presses - usually hydraulically
driven, which is especially suited to semi‑continuous direct extrusion of long sections
• Mechanical drives - often used for cold extrusion of individual parts
ISE 316 - Manufacturing Processes Engineering
Wire and Bar Drawing Cross‑section of a bar, rod, or wire is reduced by
pulling it through a die opening • Similar to extrusion except work is pulled
through die in drawing (it is pushed through in extrusion)
• Although drawing applies tensile stress, compression also plays a significant role since metal is squeezed as it passes through die opening
ISE 316 - Manufacturing Processes Engineering
Figure 19.41 ‑ Drawing of bar, rod, or wire
ISE 316 - Manufacturing Processes Engineering
Area Reduction in DrawingChange in size of work is usually given by area
reduction:
where r = area reduction in drawing; Ao = original area of work; and Ar = final work
ISE 316 - Manufacturing Processes Engineering
o
foA
AAr
Wire Drawing vs. Bar Drawing • Difference between bar drawing and wire
drawing is stock size – Bar drawing - large diameter bar and rod stock– Wire drawing - small diameter stock - wire sizes
down to 0.03 mm (0.001 in.) are possible • Although the mechanics are the same, the
methods, equipment, and even terminology are different
ISE 316 - Manufacturing Processes Engineering
Drawing Practice and Products• Drawing practice:
– Usually performed as cold working– Most frequently used for round cross‑sections
• Products:– Wire: electrical wire; wire stock for fences, coat
hangers, and shopping carts – Rod stock for nails, screws, rivets, and springs – Bar stock: metal bars for machining, forging, and
other processes ISE 316 - Manufacturing Processes Engineering
Bar Drawing • Accomplished as a single‑draft operation ‑ the
stock is pulled through one die opening • Beginning stock has large diameter and is a
straight cylinder • This necessitates a batch type operation
ISE 316 - Manufacturing Processes Engineering
Figure 19.42 ‑ Hydraulically operated draw bench for drawing metal bars
ISE 316 - Manufacturing Processes Engineering
Wire Drawing• Continuous drawing machines consisting of
multiple draw dies (typically 4 to 12) separated by accumulating drums – Each drum (capstan) provides proper force to
draw wire stock through upstream die – Each die provides a small reduction, so desired
total reduction is achieved by the series – Annealing sometimes required between dies
ISE 316 - Manufacturing Processes Engineering
Figure 19.43 ‑ Continuous drawing of wire
ISE 316 - Manufacturing Processes Engineering
DRAWING TOOLS
• The most important tool in the drawing process is without doubt the drawplate.This consist of a plate of high grade steel into which similar shaped holes have been placed whose size in evenly reduced from one hole to another.
• The most common drawplate have round holes and are used to reduce the size of round wire.
Drawing wire with the draw tongs
drawbench
Features of a Draw Die• Entry region - funnels lubricant into the die to
prevent scoring of work and die • Approach - cone‑shaped region where drawing
occurs• Bearing surface - determines final stock size • Back relief - exit zone - provided with a back
relief angle (half‑angle) of about 30 • Die materials: tool steels or cemented carbides
ISE 316 - Manufacturing Processes Engineering
Figure 19.44 ‑ Draw die for drawing of round rod or wire
ISE 316 - Manufacturing Processes Engineering
Preparation of the Work for Wire or Bar Drawing
• Annealing – to increase ductility of stock• Cleaning - to prevent damage to work surface
and draw die• Pointing – to reduce diameter of starting end
to allow insertion through draw die
ISE 316 - Manufacturing Processes Engineering
SHEET METALWORKING• Cutting Operations• Bending Operations• Drawing• Other Sheet Metal Forming Operations• Dies and Presses for Sheet Metal Processes• Sheet Metal Operations Not Performed on
Presses• Bending of Tube Stock
ISE 316 - Manufacturing Processes Engineering
Sheet Metalworking DefinedCutting and forming operations performed on
relatively thin sheets of metal • Thickness of sheet metal = 0.4 mm (1/64 in) to
6 mm (1/4 in)• Thickness of plate stock > 6 mm • Operations usually performed as cold working
ISE 316 - Manufacturing Processes Engineering
Sheet and Plate Metal Products
• Sheet and plate metal parts for consumer and industrial products such as – Automobiles and trucks – Airplanes – Railway cars and locomotives – Farm and construction equipment – Small and large appliances – Office furniture – Computers and office equipment
ISE 316 - Manufacturing Processes Engineering
Advantages of Sheet Metal Parts
• High strength• Good dimensional accuracy• Good surface finish• Relatively low cost • For large quantities, economical mass
production operations are available
ISE 316 - Manufacturing Processes Engineering
Sheet Metalworking Terminology
1. “Punch‑and‑die”– Tooling to perform cutting, bending, and drawing
2. “Stamping press” – Machine tool that performs most sheet metal
operations3. “Stampings”
– Sheet metal products
ISE 316 - Manufacturing Processes Engineering
Three Major Categories of Sheet Metal Processes
1. Cutting – Shearing to separate large sheets; or cut part
perimeters or make holes in sheets2. Bending
– Straining sheet around a straight axis3. Drawing
– Forming of sheet into convex or concave shapes
ISE 316 - Manufacturing Processes Engineering
Figure 20.1 ‑ Shearing of sheet metal between two cutting edges:
(1) just before the punch contacts work
ISE 316 - Manufacturing Processes Engineering
CuttingShearing between two sharp cutting edges
Figure 20.1 ‑ Shearing of sheet metal between two cutting edges:
(2) punch begins to push into work, causing plastic deformation
ISE 316 - Manufacturing Processes Engineering
Figure 20.1 ‑ Shearing of sheet metal between two cutting edges:
(3) punch compresses and penetrates into work causing a smooth cut surface
ISE 316 - Manufacturing Processes Engineering
Figure 20.1 ‑ Shearing of sheet metal between two cutting edges:
(4) fracture is initiated at the opposing cutting edges which separates the sheet
ISE 316 - Manufacturing Processes Engineering
Shearing, Blanking, and Punching
Three principal operations in pressworking that cut sheet metal:
• Shearing• Blanking• Punching
ISE 316 - Manufacturing Processes Engineering
ShearingSheet metal cutting operation along a straight
line between two cutting edges• Typically used to cut large sheets into smaller
sections for subsequent operations
ISE 316 - Manufacturing Processes Engineering
Figure 20.3 ‑ Shearing operation: (a) side view of the shearing operation
(b) front view of power shears equipped with inclined upper cutting blade Symbol v indicates motion
ISE 316 - Manufacturing Processes Engineering
Blanking and PunchingBlanking - sheet metal cutting to separate piece
from surrounding stock• Cut piece is the desired part, called a blank Punching - sheet metal cutting similar to
blanking except cut piece is scrap, called a slug
• Remaining stock is the desired part
ISE 316 - Manufacturing Processes Engineering
Figure 20.4 ‑ (a) Blanking and (b) punching
ISE 316 - Manufacturing Processes Engineering
Clearance in Sheet Metal Cutting
Distance between the punch and die• Typical values range between 4% and 8% of
stock thickness – If too small, fracture lines pass each other,
causing double burnishing and larger force – If too large, metal is pinched between cutting
edges and excessive burr results
ISE 316 - Manufacturing Processes Engineering
Clearance in Sheet Metal Cutting
• Recommended clearance can be calculated by:
c = at where c = clearance; a = allowance; and t = stock
thickness
• Allowance a is determined according to type of metal
ISE 316 - Manufacturing Processes Engineering
Allowance a for Three Sheet Metal Groups
ISE 316 - Manufacturing Processes Engineering
Metal group a
1100S and 5052S aluminum alloys, all tempers 0.045
2024ST and 6061ST aluminum alloys; brass, soft cold rolled steel, soft stainless steel
0.060
Cold rolled steel, half hard; stainless steel, half hard and full hard
0.075
Punch and Die Sizes for Blanking and Punching
For a round blank of diameter Db: Blanking punch diameter = Db ‑ 2c Blanking die diameter = Db where c = clearance
For a round hole of diameter Dh: Hole punch diameter = Dh
Hole die diameter = Dh + 2cwhere c = clearance
ISE 316 - Manufacturing Processes Engineering
Figure 20.6 ‑ Die size determines blank size Db; punch size determines hole size Dh.; c = clearance
ISE 316 - Manufacturing Processes Engineering
Angular ClearancePurpose: allows slug or blank to drop through
die• Typical values: 0.25 to 1.5 on each side
ISE 316 - Manufacturing Processes Engineering
Figure 20.7 ‑ Angular clearance
Cutting ForcesImportant for determining press size (tonnage)
F = S t L
where S = shear strength of metal; t = stock thickness, and L = length of cut edge
ISE 316 - Manufacturing Processes Engineering
Bending Straining sheetmetal around a straight axis to
take a permanent bend
ISE 316 - Manufacturing Processes Engineering
Figure 20.11 ‑ (a) Bending of sheet metal
Metal on inside of neutral plane is compressed, while metal on outside of neutral plane is stretched
ISE 316 - Manufacturing Processes Engineering
Figure 20.11 ‑ (b) both compression and tensile elongation of the metal occur in bending
Types of Sheetmetal Bending• V‑bending - performed with a V‑shaped die• Edge bending - performed with a wiping die
ISE 316 - Manufacturing Processes Engineering
V-Bending • For low production• Performed on a press brake• V-dies are simple and inexpensive
ISE 316 - Manufacturing Processes Engineering
Figure 20.12 ‑ (a) V‑bending
Edge Bending • For high production• Pressure pad required• Dies are more complicated and costly
ISE 316 - Manufacturing Processes Engineering
Figure 20.12 ‑ (b) edge bending
Stretching during Bending• If bend radius is small relative to stock
thickness, metal tends to stretch during bending
• Important to estimate amount of stretching, so that final part length = specified dimension
• Problem: to determine the length of neutral axis of the part before bending
ISE 316 - Manufacturing Processes Engineering
Bend Allowance Formula
where BA = bend allowance; A = bend angle; R= bend radius; t = stock thickness; and Kba is factor to estimate stretching
• If R < 2t, Kba = 0.33 • If R 2t, Kba = 0.50ISE 316 - Manufacturing Processes Engineering
)( tKRABA ba360
2
Springback in BendingSpringback = increase in included angle of bent
part relative to included angle of forming tool after tool is removed
• Reason for springback:– When bending pressure is removed, elastic
energy remains in bent part, causing it to recover partially toward its original shape
ISE 316 - Manufacturing Processes Engineering
Figure 20.13 ‑ Springback in bending shows itself as a decrease in bend angle and an increase in bend radius: (1) during bending, the work is forced to take the radius Rb and included angle Ab' of the bending tool (punch in V‑bending), (2) after punch is removed, the work springs back to radius R and angle A'
ISE 316 - Manufacturing Processes Engineering
Bending Force
Maximum bending force estimated as follows:
ISE 316 - Manufacturing Processes Engineering
where F = bending force; TS = tensile strength of sheet metal; w = part width in direction of bend axis; and t = stock thickness. For V- bending, Kbf = 1.33; for edge bending, Kbf = 0.33
DTSwtKF bf
2
Figure 20.14 ‑ Die opening dimension D: (a) V‑die, (b) wiping die
ISE 316 - Manufacturing Processes Engineering
Drawing Sheet metal forming to make cup‑shaped,
box‑shaped, or other complex‑curved, hollow‑shaped parts
• Sheet metal blank is positioned over die cavity and then punch pushes metal into opening
• Products: beverage cans, ammunition shells, automobile body panels
ISE 316 - Manufacturing Processes Engineering
Figure 20.19 ‑ (a) Drawing of a
cup‑shaped part: (1) start of operation
before punch contacts work
(2) near end of stroke
(b) Corresponding workpart:
(1) starting blank (2) drawn part
ISE 316 - Manufacturing Processes Engineering
Aluminum Beverage Cans
Figure 16.38 (a) Aluminum beverage cans. Note the excellent surface finish. (b) Detail of the can lid showing integral rivet and scored edges for the pop-top.
(a)
Can Manufacture
Figure 16.31 The metal-forming processes involved in manufacturing a two-piece aluminum beverage can.
Clearance in Drawing• Sides of punch and die separated by a
clearance c given by:c = 1.1 t
where t = stock thickness• In other words, clearance = about 10% greater
than stock thickness
ISE 316 - Manufacturing Processes Engineering
Drawing Ratio DR
where Db = blank diameter; and Dp = punch diameter
• Indicates severity of a given drawing operation– Upper limit = 2.0ISE 316 - Manufacturing
Processes Engineering
Most easily defined for cylindrical shape:
p
bDDDR
Reduction r
• Again, defined for cylindrical shape:
ISE 316 - Manufacturing Processes Engineering
b
pb
DDD
r
• Value of r should be less than 0.50
Thickness‑to‑Diameter Ratio
Thickness of starting blank divided by blank diameter
Thickness-to-diameter ratio = t/Db
• Desirable for t/Db ratio to be greater than 1%• As t/Db decreases, tendency for wrinkling
increases
ISE 316 - Manufacturing Processes Engineering
Blank Size Determination• For final dimensions of drawn shape to be
correct, starting blank diameter Db must be right
• Solve for Db by setting starting sheet metal blank volume = final product volume
• To facilitate calculation, assume negligible thinning of part wall
ISE 316 - Manufacturing Processes Engineering
Shapes other than Cylindrical Cups
• Square or rectangular boxes (as in sinks), • Stepped cups, • Cones, • Cups with spherical rather than flat bases, • Irregular curved forms (as in automobile body
panels)
• Each of these shapes presents its own unique technical problems in drawing ISE 316 - Manufacturing
Processes Engineering
Other Sheet Metal Forming on Presses
Other sheet metal forming operations performed on conventional presses
• Operations performed with metal tooling• Operations performed with flexible rubber
tooling
ISE 316 - Manufacturing Processes Engineering
Ironing • Makes wall thickness of cylindrical cup
more uniform• Examples: beverage cans and artillery
shells
ISE 316 - Manufacturing Processes Engineering
Figure 20.25 ‑ Ironing to achieve a more uniform wall thickness in a drawn cup: (1) start of process; (2) during process Note thinning and elongation of walls
Embossing • Used to create indentations in sheet, such
as raised (or indented) lettering or strengthening ribs
ISE 316 - Manufacturing Processes Engineering
Figure 20.26 ‑ Embossing: (a) cross‑section of punch and die configuration during pressing; (b) finished part with embossed ribs
Figure 20.28 ‑ Guerin process: (1) before and (2) afterSymbols v and F indicate motion and applied force respectively
ISE 316 - Manufacturing Processes Engineering
Guerin Process
Advantages of Guerin Process• Low tooling cost• Form block can be made of wood, plastic, or
other materials that are easy to shape• Rubber pad can be used with different form
blocks • Process attractive in small quantity production
ISE 316 - Manufacturing Processes Engineering
Dies for Sheet Metal ProcessesMost pressworking operations performed with
conventional punch‑and‑die tooling• Custom‑designed for particular part • The term stamping die sometimes used for
high production dies
ISE 316 - Manufacturing Processes Engineering
Figure 20.30 ‑ Components of a punch and die for a blanking operation
ISE 316 - Manufacturing Processes Engineering
Figure 20.31 ‑ (a) Progressive die; (b) associated strip
development
ISE 316 - Manufacturing Processes Engineering
Figure 20.32 ‑ Components of a typical mechanical drive stamping press
ISE 316 - Manufacturing Processes Engineering
Types of Stamping Press Frame• Gap frame – configuration of the letter C and
often referred to as a C‑frame• Straight‑sided frame – box-like construction
for higher tonnage
ISE 316 - Manufacturing Processes Engineering
Figure 20.33 ‑ Gap frame press for sheet metalworking
(photo courtesy of E. W. Bliss Company)
Capacity = 1350 kN (150 tons)
ISE 316 - Manufacturing Processes Engineering
Figure 20.34 ‑ Press brake with
bed width of 9.15 m (30 ft) and capacity of 11,200 kN (1250 tons); two workers are positioning plate stock for bending
(photo courtesy of Niagara Machine & Tool Works)
ISE 316 - Manufacturing Processes Engineering
Figure 20.35 ‑ Several sheet metal parts produced on a turret press, showing variety of hole shapes possible
(photo courtesy of Strippet, Inc.)
ISE 316 - Manufacturing Processes Engineering
Figure 20.36 ‑ Computer numerical control turret press (photo courtesy of Strippet, Inc.)
ISE 316 - Manufacturing Processes Engineering
Figure 20.37 ‑Straight‑sided frame press (photo courtesy Greenerd
Press & Machine Company, Inc.)
ISE 316 - Manufacturing Processes Engineering
Power and Drive Systems• Hydraulic presses - use a large piston and
cylinder to drive the ram– Longer ram stroke than mechanical types– Suited to deep drawing– Slower than mechanical drives
• Mechanical presses – convert rotation of motor to linear motion of ram– High forces at bottom of stroke– Suited to blanking and punching
ISE 316 - Manufacturing Processes Engineering
Sheet Metal Operations Not Performed on Presses
• Stretch forming• Roll bending and forming• Spinning• High‑energy‑rate forming processes.
ISE 316 - Manufacturing Processes Engineering
Stretch Forming Sheet metal is stretched and simultaneously
bent to achieve shape change
ISE 316 - Manufacturing Processes Engineering
Figure 20.39 ‑ Stretch forming: (1) start of process; (2) form die is pressed into the work with force Fdie, causing it to be stretched and bent over the form. F =
stretching force
Force Required in Stretch Forming
where F = stretching force; L = length of sheet in direction perpendicular to stretching; t = instantaneous stock thickness; and Yf = flow stress of work metal
• Die force Fdie can be determined by balancing vertical force componentsISE 316 - Manufacturing
Processes Engineering
fLtYF
Roll Bending Large metal sheets and plates are formed
into curved sections using rolls
ISE 316 - Manufacturing Processes Engineering
Figure 20.40 ‑ Roll bending
Roll Forming Continuous bending process in which
opposing rolls produce long sections of formed shapes from coil or strip stock
ISE 316 - Manufacturing Processes Engineering
Figure 20.41 ‑ Roll forming of a continuous channel section:
(1) straight rolls(2) partial form (3) final form
SpinningMetal forming process in which an axially
symmetric part is gradually shaped over a rotating mandrel using a rounded tool or roller
• Three types: 1. Conventional spinning2. Shear spinning3. Tube spinning
ISE 316 - Manufacturing Processes Engineering
Figure 20.42 ‑ Conventional spinning: (1) setup at start of process; (2) during spinning; and (3) completion of process
ISE 316 - Manufacturing Processes Engineering
www.dissco.co.nz
SpinningIdeal for • Lower production volumes• Large parts• Inexpensive tooling
www.traditional-building.com
www.ashfordmetalspinning.co.uk
High‑Energy‑Rate Forming (HERF)
Processes to form metals using large amounts of energy over a very short time
• HERF processes include: – Explosive forming– Electrohydraulic forming– Electromagnetic forming
ISE 316 - Manufacturing Processes Engineering
Explosive FormingUse of explosive charge to form sheet (or plate)
metal into a die cavity • Explosive charge causes a shock wave whose
energy is transmitted to force part into cavity• Applications: large parts, typical of aerospace
industry
ISE 316 - Manufacturing Processes Engineering
Figure 20.45 ‑ Explosive forming: (1) setup, (2) explosive is detonated, and
(3) shock wave forms part and plume escapes water surface
ISE 316 - Manufacturing Processes Engineering
Electromagnetic FormingSheet metal is deformed by mechanical force of
an electromagnetic field induced in workpart by an energized coil
• Presently the most widely used HERF process• Applications: tubular parts
ISE 316 - Manufacturing Processes Engineering
Figure 20.47 ‑ Electromagnetic forming: (1) setup in which coil is inserted
into tubular workpart surrounded by die; (2) formed part
ISE 316 - Manufacturing Processes Engineering
Finite Element SimulationsPredict and minimize tearing and wrinkling locations
nsmwww.eng.ohio-state.edu
www.esi-group.com
tmku209.ctw.utwente.nl
SELESAITERIMA KASIH
Spinning:Makes “cups” from sheet metal,for lower production.(cold)
Roll forming (Hot):Moves bulk metal, makes I-beams
Kalpakjian
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Kalpakjian
Roll forming (Cold):Bends sheetmetal into complex cross-sections
Directional Properties in RollingOriented flowlines:- Less ductility when bent in one direction- More ductility when bent in the other
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Cold Rolling: Sheetmetal production
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www.nzsteel.co.nz finance.pipex.com
Cold Rolling: Sheetmetal production
Cluster rolls support smaller contacting rolls
www.sendzimir.com
www.elgiloy.com
Cold Rolling: Sheetmetal production
Residual Stresses may lead to warping after bar is machined
Large reduction Small reduction
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Roll Forming of Sheetmetal (cold)
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www.cometroll.com www.safeair-dowco.com
Roll Forming of sheetmetal
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Blanking of Sheetmetal: Efficient Nesting of Blanks
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Sheetmetal: Bending
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Springback:
Sheetmetal: Minimum Bend Radius
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Tight radius bends (folds) require metal with ~40% ductility
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Bending of SheetmetalUse notches to avoid tearing and wrinkling in right-angle bends
Press Brakes:For lower production
volumes10-30 foot long50-3000 tons
Bending of Sheetmetal
www.loomismetals.com
Bending:Press-Brake Operations
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Deep Drawing (cold, for sheetmetal)- Punch draws blank into die- Metal is supported on both sides to avoid wrinkling- Hold-down pressure (blankholder force) is primary process variable if too high: tearing if too low: wrinkling
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www.endo-mfg.co.jp
Deep Drawing“Draw beads” may be used to control metal flow
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Cost comparison: manufacturing a round sheet-metal container by spinning and deep drawing. For small quantities, spinning is more economical.
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Progressive Stamping DiesCommon method to handle complex parts
www.nissin-precision.com
Tube-drawingDOM: Drawn Over Mandrel TubingSeamlessThin wall, tight tolerance, strong
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www.twmetals.com
Malicky
“Floating plug”
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