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Traditional Manufacturing Processes

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Traditional Manufacturing Processes Casting Forming Sheet metal processing Powder- and Ceramics Processing Plastics processing Cutting Joining Surface treatment – PowerPoint PPT presentation

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Title: Traditional Manufacturing Processes


1
Traditional Manufacturing Processes
Casting
Forming
Sheet metal processing
Powder- and Ceramics Processing
Plastics processing
Cutting
Joining
Surface treatment
2
Cutting
Processes that involve removal of material from
solid workpiece
Sawing Shaping (or planing), Broaching,
drilling, Grinding, Turning Milling
Important concept PROCESS PLANNING
Fixturing and Location Operations
sequencing Setup planning Operations
planning
3
Sawing
A process to cut components, stock, etc. Process
character Precision very low,, very high
MRR low
4
Sawing
5
Shaping
A process to plane the surface of a workpiece (or
to reduce part thickness Process character High
MRR, medium Surface finish, dimension control
6
Broaching
Precise process for mass-production of complex
geometry parts (complicated hole-shapes) Process
character High MRR, Very good surface, dimension
control, Expensive
7
Drilling, Reaming, Boring
Processes to make holes Process character High
MRR, Cheap, Medium-high surface, dimension control
8
Drilling basics
- softer materials ? small point angle hard,
brittle material larger point angle -
Length/Diameter ratio is large ? gun-drilling
(L/D ratio 300) - Very small diameter holes
(e.g. lt 0.5 mm) cant drill (why?) - F drilled
hole gt F drill vibrations, misalignments, -
Tight dimension control drill ? ream - Spade
drills large, deep holes - Coutersink/counterbor
e drills multiple diameter hole ? screws/bolts
heads
9
Tapping
Processes to make threads in holes Process
character low MRR, Cheap, good surface,
dimension control
Automated tapping
Manual tap and die set
10
Grinding, Abrasive Machining
Processes to finish and smooth surfaces Process
character very low MRR, very high surface,
dimension control
1. To improve the surface finish of a
manufactured part (a) Injection molding die
milling? manual grinding/electro-grinding.
(b) Cylinders of engine turning ? grinding ?
honing ? lapping 2. To improve the dimensional
tolerance of a manufactured part (a)
ball-bearings forging ? grinding control lt 15
mm (b) Knives forged steel ? hardened ?
grinding 3. To cut hard brittle materials
(a) Semiconductor IC chips slicing and
dicing 4. To remove unwanted materials of a
cutting process (a) Deburring parts made by
drilling, milling
11
Abrasive tools and Machines
12
Turning
Processes to cut cylindrical stock into revolved
shapes Process character high MRR, high surface,
dimension control
13
Turning operations
14
Fixturing parts for turning
15
Milling
Versatile process to cut arbitrary 3D
shapes Process character high MRR, high surface,
dimension control
16
Common vertical milling cutters
Flat
Ballnose
Bullnose
17
Up and Down milling
18
Fixtures for Milling Vise
19
Fixtures for Milling Clamps
20
Process Analysis
Fundamental understanding of the process ?
improve, control, optimize
Method Observation ? modeling ? verification
Every process must be analyzed we only look at
orthogonal 1-pt cutting
21
Geometry of the cutting tool
22
Modeling Mechanism of cutting
Old model crack propagation
Current model shear
23
Tool wear observations and models
High stresses, High friction, High temp (1000?C)
? tool damage Adhesion wear fragments of
the workpiece get welded to the tool surface at
high temperatures eventually, they break
off, tearing small parts of the tool with them.
Abrasion hard particles, microscopic
variations on the bottom surface of the chips
rub against the tool surface Diffusion wear
at high temperatures, atoms from tool diffuse
across to the chip the rate of diffusion
increases exponentially with temperature
this reduces the fracture strength of the
crystals.
24
Tool wear, Tool failure, Tool life criteria
  • Catastrophic failure (e.g. tool is broken
    completely)
  • VB 0.3 mm (uniform wear in Zone B), or VBmax
    0.6 mm (non-uniform flank wear)
  • KT 0.06 0.3f, (where f feed in
    mm/revolution).

25
Built-up edge (BUE)
Deposition, work hardening of a thin layer of the
workpiece material on the surface of the tool.
BUE ? poor surface finish Likelihood of BUE
decreases with (i) decrease in depth of
cut, (ii) increase in rake angle, (iii) use of
proper cutting fluid during machining.
26
Process modeling empirical results
Experimental chart showing relation of tool wear
with f and V source Boothroyd
27
Modeling surface finish
Relation of feed and surface finish
28
Analysis Machining Economics
How can we optimize the machining of a part ?
Identify the objective, formulate a model, solve
for optimality
Typical objectives maximum production rate,
and/or minimum cost Are these objectives
compatible (satisfied simultaneously) ?
Formulating model observations ? hypothesis ?
theory ? model
29
Analysis Machining Economics..
Formulating model observations ? hypothesis ?
theory ? model
Observation A given machine, tool, workpiece
combination has finite max MRR
Hypothesis Total volume to cut is minimum ?
Maximum production rate
Model objective Find minimum volume stock for a
given part -- Near-net shape stocks (use
casting, forging, ) -- Minimum enclosing
volumes of 3D shapes
Models - minimum enclosing cylinder for a
rotational part - minimum enclosing rectangular
box for a milled part Solving -- requires
some knowledge of computational geometry
30
Analysis Machining Economics..
Model objective Find optimum operations plan and
tools for a given part
Example
or
?
or
??
Model Process Planning - Machining volume,
tool selection, operations sequencing Solving
- in general, difficult to optimize
31
Analysis process parameters optimization
Model objective Find optimum feed, cutting speed
to maximize MRR/minimize cost/
Feed Higher feed ? higher MRR
Finish cutting surface finish ? feed ? Given
surface finish, we can find maximum allowed feed
rate
32
Process parameters optimization feed
Rough cutting MRR ? cutting speed, V MRR ?
feed, f
? cannot increase V and f arbitrarily
? V ? ? MRR surface finish ? f(V) energy per
unit volume MRR ? f(V)
Tool temperature ? V, f Friction wear ? V
Friction wear ? f
For a given increase in MRR ? V ? lower tool
life than ? f
Optimum feed maximum allowed for tool given
machine power, tool strength
33
Process parameters optimization Speed
Model objective Given optimum feed, what is the
optimum cutting speed
? provided upper limits, but not optimum
Need a relation between tool life and cutting
speed (other parameters being constant)
Taylors model (empirically based) V tn
constant
34
Process parameters optimization Speed
One batch of large number, Nb, of identical
parts Replace tool by a new one whenever it is
worn
Total non-productive time Nbtl tl time to
(load the stock position the tool unload the
part) Nb be the total number of parts in the
batch.
Total machining time Nbtm tm time to machine
the part
Total tool change time Nttc tc time to
replace the worn tool with a new one Nt total
number tools used to machine the entire batch.
Cost of each tool Ct, Cost per unit time for
machine and operator M.
Average cost per item
35
Process parameters optimization Speed
Average cost per item
Let total length of the tool path L
t tool life ? Nt (Nb tm)/t ? Nt / Nb
tm / t
Taylors model Vtn C ? t C 1/n / V1/n
C/V1/n
36
Process parameters optimization Speed
Average cost per item
37
Process parameters optimization Speed
Optimum speed (to minimize costs)
Optimum speed (to minimize time)
Average time to produce part
38
Process parameters optimization Speed
Optimum speed (to minimize costs)
Optimum speed (to minimize time)
Average time to produce part
load/unload time
tool change time
machining time
Substitute, differentiate, solve for V
39
Process Planning
The process plan specifies operations tools,
path plan and operation conditions setups sequen
ces possible machine routings fixtures
40
Process Planning
41
Operation sequencing examples (Milling)
big-hole ? step ? small hole or small hole ? step
? big-hole or
step ? hole or hole ? step
42
Traditional Manufacturing Processes
Casting
Forming
Sheet metal processing
Powder- and Ceramics Processing
Plastics processing
Cutting
Joining
Surface treatment
43
Joining Processes
Types of Joints 1. Joints that allow relative
motion (kinematic joints) 2. Joints that
disallow any relative motion (rigid joints)
Uses of Joints 1. To restrict some degrees of
freedom of motion 2. If complex part shape is
impossible/expensive to manufacture 3. To allow
assembled product be disassembled for
maintenance. 4. Transporting a disassembled
product is sometimes easier/feasible
44
Joining Processes
Fusion welding joining metals by melting ?
solidification Solid state welding joining
metals without melting Brazing joining metals
with a lower mp metal Soldering joining metals
with solder (very low mp) Gluing joining with
glue Mechanical joining screws, rivets etc.
45
Fusion welding
Oxy-acetylene welding
Arc welding
robotic
manual
arc 30,000?C
Gas shielded arc welding
MIG
TIG
Argon
Al
Ti, Mg, Thin sections
46
Fusion welding..
Deep, narrow welds
Aerospace, medical, automobile body panels
Plasma arc welding
Faster than TIW, slower than Laser
NdYAG and CO2 lasers, power 100kW
Laser beam welding
Fast, high quality, deep, narrow welds
deep, narrow welds, expensive
Electron beam welding
47
Solid state welding
Diffusion welds between very clean, smooth pieces
of metal, at 0.30.5Tm
Cold welding (roll bonding)
coins, bimetal strips
48
Solid state welding..
Ultrasonic welding
Medical, Packaging, IC chips, Toys Materials
metal, plastic - clean, fast, cheap
49
Resistance welding
Welding metal strips clamp together, heat by
current
Spot welding
Seam welding
50
Brazing
Tm of Filler material lt Tm of the metals being
joined
Torch brazing
Furnace brazing
Common Filler materials copper-alloys, e.g.
bronze Common applications pipe joint seals,
ship-construction
Soldering
Tin Lead alloy, very low Tm ( 200C) Main
application electronic circuits
51
Gluing
52
Mechanical fasteners
(a) Screws (b) Bolts, nuts and
washers (c) Rivets
(a) pneumatic carton stapler (b) Clips
(c) A circlip in the gear drive of a
kitchen mixer
Plastic wire clips
Plastic snap-fasteners
Wire ?? conductor crimping
53
Traditional Manufacturing Processes
Casting
Forming
Sheet metal processing
Powder- and Ceramics Processing
Plastics processing
Cutting
Joining
Surface treatment
54
Surface treatment, Coating, Painting
Post-production processes Only affect the
surface, not the bulk of the material
  • Improving the hardness
  • Improving the wear resistance
  • Controlling friction, Reduction of adhesion,
    improving the lubrication, etc.
  • Improving corrosion resistance
  • Improving aesthetics

55
Mechanical hardening
Shot peening
Shot peening precision auto gears
source www.vacu-blast.co.uk
Laser peening
source www.uwinint.co.kr
56
Case hardening
57
Vapor deposition
Deposition of thin film (110 mm) of metal
Sputtering important process in IC Chip
manufacture
58
Thermal spraying
High velocity oxy-fuel spraying
Tungsten Carbide / Cobalt Chromium Coating on
roll for Paper Manufacturing Industry
Thermal metal powder spray
Plasma spray
source www.fst.nl/process.htm
59
Electroplating
Deposit metal on cathode, sacrifice from anode
chrome-plated auto parts
copper-plating
Anodizing
Metal part on anode oxidecoloring-dye deposited
using electrolytic process
60
Painting
Type of paints Enamel oil-based smooth,
glossy surface Lacquers resin based dry as
solvent evaporates out e.g. wood varnish
Water-based paints e.g. wall paints,
home-interior paints
Painting methods Dip coating part is dipped
into a container of paint, and pulled out.
Spray coating ? most common industrial painting
method Electrostatic spraying charged paint
particles sprayed to part using voltage
Silk-screening very important method in IC
electronics mfg
61
Painting
Electrostatic Spray Painting
Spray Painting in BMW plant
Silk screening
62
Summary
These notes covered processes cutting, joining
and surface treatment We studied one method of
modeling a process, in order to optimize it We
introduced the importance and difficulties of
process planning.
Further reading Chapters 24, 21, 30-32
Kalpajian Schmid
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