Traditional Manufacturing Processes Casting Forming Sheet metal processing Cutting Joining Powder- and Ceramics Processing Plastics processing Surface treatment
Traditional Manufacturing Processes
Casting
Forming
Sheet metal processing
Cutting
Joining
Powder- and Ceramics Processing
Plastics processing
Surface treatment
Cutting
SawingShaping (or planing),Broaching, drilling,Grinding,TurningMilling
Processes that involve removal of material from solid workpiece
Important concept: PROCESS PLANNING Fixturing and LocationOperations sequencingSetup planningOperations planning
Sawing
A process to cut components, stock, etc.Process character: Precision: [very low,, very high]; MRR: low
Sawing
band saw
hand-held circular saw hand-held hacksaw
band saw
hand-held circular saw hand-held hacksaw
circular saw bladewave teeth (for sheet-metal)
right-left teeth (for soft materials)
band saw blade and blade types
raker teeth (for hard, brittle materials)
circular saw bladewave teeth (for sheet-metal)
right-left teeth (for soft materials)
band saw blade and blade types
raker teeth (for hard, brittle materials)
Shaping
chip
slidetool-post pivotchip
tool-post rotates asslide returns;workpiece shifted;next stroke
(a) (b) (c)
chipchip
slidetool-post pivotslidetool-post pivot
chip
tool-post rotates asslide returns;workpiece shifted;next stroke
chip
tool-post rotates asslide returns;workpiece shifted;next stroke
(a) (b) (c)
A process to plane the surface of a workpiece (or to reduce part thickness
Process character: High MRR, medium Surface finish, dimension control
Broaching
Precise process for mass-production of complex geometry parts(complicated hole-shapes)
Process character: High MRR, Very good surface, dimension control, Expensive
Broaching machine
Broaching tools
Complex hole shapes cut by broaching
Broaching machine
Broaching tools
Complex hole shapes cut by broaching
Drilling, Reaming, Boring
Spade drill: for large, deep holes
Core drilling: to increasediameter of existing holesTwist drill
Step drill: forstepped holes
D
d
Countersink Counterbore Reamer Center drill Gun drill with holes for coolant
Spade drill: for large, deep holes
Core drilling: to increasediameter of existing holesTwist drill
Step drill: forstepped holes
D
d
Countersink Counterbore Reamer Center drill Gun drill with holes for coolant
Processes to make holesProcess character: High MRR, Cheap, Medium-high surface, dimension control
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. < 0.5 mm): can’t drill (why?)
- drilled hole > drill: vibrations, misalignments, …
- Tight dimension control: drill ream
- Spade drills: large, deep holes
- Coutersink/counterbore drills: multiple diameter hole screws/bolts heads
Tapping
Processes to make threads in holesProcess character: low MRR, Cheap, good surface, dimension control
Manual tap and die set Automated tapping
Grinding, Abrasive Machining
Processes to finish and smooth surfacesProcess 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: < 15 m] (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
Abrasive tools and Machines
abrasive wheels, paper, tools diamond grinding wheel for slicing silicon wafers diamond dicing wheel for siliconabrasive wheels, paper, tools diamond grinding wheel for slicing silicon wafers diamond dicing wheel for silicon
Grinding machine
Grinding wheels
Centerless grinding
Grinding machine
Grinding wheels
Centerless grinding
Turning
Processes to cut cylindrical stock into revolved shapesProcess character: high MRR, high surface, dimension control
feed, f
depth of cut, d
feed, f
depth of cut, d
spindle chuck tool-post
carriage
tail-stock
carriage wheel cross-slide wheel
tail-stock wheel
lead-screw
spindle chuck tool-post
carriage
tail-stock
carriage wheel cross-slide wheel
tail-stock wheel
lead-screw
Turning operations
turning taper profile cut groove cut cut-off thread cut
facing face groove boring, internal groove drillingknurling
turning taper profile cut groove cut cut-off thread cut
facing face groove boring, internal groove drillingknurling
feed, f
depth of cut, d
feed, f
depth of cut, d
Fixturing parts for turning
part in a 3-jaw chuck 4-jaw chuck holding a non-rotational part
A collet type work-holder; collets are common inautomatic feeding lathes – the workpiece is a longbar; each short part is machined and then cut-off;the collet is released, enough bar is pushed out tomake the next part, and the collet is pulled back togrip the bar; the next part is machined, and so on.
A long part held between live center (at spindle)and dead center (at tailstock)
steps
part in a 3-jaw chuck 4-jaw chuck holding a non-rotational part
A collet type work-holder; collets are common inautomatic feeding lathes – the workpiece is a longbar; each short part is machined and then cut-off;the collet is released, enough bar is pushed out tomake the next part, and the collet is pulled back togrip the bar; the next part is machined, and so on.
A long part held between live center (at spindle)and dead center (at tailstock)
steps
Milling
Versatile process to cut arbitrary 3D shapesProcess character: high MRR, high surface, dimension control
[source: www.hitachi-tool.com.jp][source: www.phorn.co.uk]
[source: www.hitachi-tool.com.jp][source: www.hitachi-tool.com.jp][source: www.phorn.co.uk][source: www.phorn.co.uk]
[source: Kalpakjian & Schmid]]]
Common vertical milling cutters
Programmed pointon cutterProgrammed pointon cutter
Flat
Ballnose
Bullnose
Up and Down milling
(a) Conventional, or Up milling- chip thickness goes UP;- cutting dynamics: smoother
(b) Climb, or Down milling- chip thickness goes DOWN;- cutting dynamics: bad for forged/castparts with brittle, hard scales on surface
(a) Conventional, or Up milling- chip thickness goes UP;- cutting dynamics: smoother
(b) Climb, or Down milling- chip thickness goes DOWN;- cutting dynamics: bad for forged/castparts with brittle, hard scales on surface
Fixtures for Milling: Vise
Vise fixed to a milling table, holding rectangular part
V-slot vise jaws hold cylindrical parts horizontally/vertically
Vise fixed to a milling table, holding rectangular part
V-slot vise jaws hold cylindrical parts horizontally/vertically
Vise on sine-bar to hold part at an anglerelative to the spindle
Universal angle vise can index parts along any direction
Vise on sine-bar to hold part at an anglerelative to the spindle
Universal angle vise can index parts along any direction
Strap clamp
Clamp support(clamp and support have teeth)
Parallel bars raise the partabove table surface – allowmaking through holes
Bolt (bolt-head is inserted into T-slot in table)
Workpiece
Strap clamp
Clamp support(clamp and support have teeth)
Parallel bars raise the partabove table surface – allowmaking through holes
Bolt (bolt-head is inserted into T-slot in table)
Workpiece
Fixtures for Milling: Clamps
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]
vve
vf
vve
vf
Geometry of the cutting tool
end cutting edge angle
side rake angle
side clearance angle front clearance angle
back rake angle
lead cutting edge angleend cutting edge angle
side rake angle
side clearance angle front clearance angle
back rake angle
lead cutting edge angle
Modeling: Mechanism of cutting
Chip
Tool
Chip forms byshear in this regionde
pth
of c
ut
Friction betweentool, chip in thisregion
Chip
Tool
Chip forms byshear in this regionde
pth
of c
ut
Friction betweentool, chip in thisregion
Old model: crack propagation Current model: shear
Tool wear: observations and models
High stresses, High friction, High temp (1000C) 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.
Tool wear, Tool failure, Tool life criteria
1. Catastrophic failure (e.g. tool is broken completely)2. VB = 0.3 mm (uniform wear in Zone B), or VBmax = 0.6 mm (non-uniform flank wear)3. KT = 0.06 + 0.3f, (where f = feed in mm/revolution).
workpiece
tool
crater wear
flank wear
chip
workpiece
tool
crater wear
flank wear
chip
Built-up edge (BUE)
Deposition, work hardening of a thin layer of the workpiece materialon the surface of the tool.
negative rake angle(for cutting hard, brittle materials)negative rake angle(for cutting hard, brittle materials)negative rake angle(for cutting hard, brittle materials)
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.
Process modeling: empirical results
Experimental chart showing relation of tool wear with f and V[source: Boothroyd]
Modeling: surface finish
Relation of feed and surface finish
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
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
Analysis: Machining Economics..
Model objective:Find optimum operations plan and tools for a given part
Model: Process Planning - Machining volume, tool selection, operations sequencing
Solving: - in general, difficult to optimize
Example:
oror
??
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
Process parameters optimization: feed
Rough cutting:MRR cutting speed, VMRR 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]
Process parameters optimization: Speed
provided upper limits, but not optimum
Need a relation between tool life and cutting speed (other parameters being constant)
Model objective:Given optimum feed, what is the optimum cutting speed
Taylor’s model (empirically based): V tn = constant
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 oneNt = 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: tb
tc
b
tmlpr C
NN
tNN
MMtMtC
Process parameters optimization: Speed
Average cost per item: tb
tc
b
tmlpr C
NN
tNN
MMtMtC
Let: total length of the tool path = L
VLtm 1MLV
VLM
t = tool life Nt = (Nb tm)/t Nt / Nb = tm / t
Taylor’s model Vtn = C’ t = C’ 1/n / V1/n = C/V1/n
CVL
CV
VL
tt
NN nnn
m
b
t/)1(/1
Process parameters optimization: Speed
Average cost per item: tb
tc
b
tmlpr C
NN
tNN
MMtMtC
1MLVVLM
CVL
NN nn
b
t/)1(
nntclpr VCtM
CLMLVMtC /)1(1 )(
Process parameters optimization: Speed
nntclpr VCtM
CLMLVMtC /)1(1 )(
nntc
pr Vn
nCtMCLMLV
dVdC /)21(2 )1()(0
Optimum speed (to minimize costs)
n
tc nn
CtMMCV
)1()(
*
Optimum speed (to minimize time)
cb
tmlpr t
NN
ttt Average time to produce part:
Process parameters optimization: Speed
Optimum speed (to minimize costs)n
tc nn
CtMMCV
)1()(
*
Optimum speed (to minimize time)
cb
tmlpr t
NN
ttt Average time to produce part:
load/unload time
machining timetool change time
VLtm
cb
tmlpr t
NN
ttt
CVL
NN nn
b
t/)1(
Substitute, differentiate, solve for V*
Process PlanningThe process plan specifies:
operationstools, path plan and operation conditionssetupssequencespossible machine routings fixtures
4 x counterbored holes
groove 5mmX5mm
4 x counterbored holes
groove 5mmX5mm
S1
S2
S3
S4
S5 S6
S7
S8
S9
S10
S1
S2
S3
S4
S5 S6
S7
S8
S9
S10
Process Planning
4 x counterbored holes
groove 5mmX5mm
4 x counterbored holes
groove 5mmX5mm
S1
S2
S3
S4
S5 S6
S7
S8
S9
S10
S1
S2
S3
S4
S5 S6
S7
S8
S9
S10
[7.5mm Drill] drill 4 holes 7.5
[HSS 1-pt tool] Face S6
[5mm groove cutter] Groove S9
Setup 3: Clamp part on Drill press,Locate using: S3, S7
[HSS 1-pt tool] turn S5 to 60,face S10, fillet edge on S4
[Center drill] mark, center-drill 4 holes
[HSS 1-pt tool] face S1
[HSS 1-pt tool] face S3
[Drill in tailstock] Center drill
[Drill in tailstock] Drill 32
Setup 2: Chuck part on S4
[10mm counterbore] Counterbore 5mm
[HSS 1-pt tool] turn S2 to 55
[HSS 1-pt tool] turn S4 to 104
Setup 1: Part in chuck
TsTcLdSfVDescription
Fixture: 3-jaw chuck on lathe; Strap clamp + parallel bars on drill-press
Legend:
Batch size= N piecesStock: bar stock diameter: 105Job # :
[7.5mm Drill] drill 4 holes 7.5
[HSS 1-pt tool] Face S6
[5mm groove cutter] Groove S9
Setup 3: Clamp part on Drill press,Locate using: S3, S7
[HSS 1-pt tool] turn S5 to 60,face S10, fillet edge on S4
[Center drill] mark, center-drill 4 holes
[HSS 1-pt tool] face S1
[HSS 1-pt tool] face S3
[Drill in tailstock] Center drill
[Drill in tailstock] Drill 32
Setup 2: Chuck part on S4
[10mm counterbore] Counterbore 5mm
[HSS 1-pt tool] turn S2 to 55
[HSS 1-pt tool] turn S4 to 104
Setup 1: Part in chuck
TsTcLdSfVDescription
Fixture: 3-jaw chuck on lathe; Strap clamp + parallel bars on drill-press
Legend:
Batch size= N piecesStock: bar stock diameter: 105Job # :
V: cutting speed m/minf : feed mm/revS: spindle rpmd: depth of cut mmL: Tool path length, minTc: cutting time, minTs: setup time, min
Operation sequencing examples (Milling)
step holeor
hole step
big-hole step small holeor
small hole step big-holeor…
Traditional Manufacturing Processes
Casting
Forming
Sheet metal processing
Cutting
Joining
Powder- and Ceramics Processing
Plastics processing
Surface treatment
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 motion2. If complex part shape is impossible/expensive to manufacture3. To allow assembled product be disassembled for maintenance.4. Transporting a disassembled product is sometimes easier/feasible
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.
Arc welding
Oxy-acetylene weldingFlame: 3000C
arc: 30,000C
manual
robotic
Gas shielded arc weldingArgon
MIG TIG
Al Ti, Mg,Thin sections
Fusion welding
Plasma arc welding
Electron beam welding
Laser beam welding
Deep, narrow welds
Aerospace, medical, automobile body panels
Faster than TIW, slower than Laser
Nd:YAG and CO2 lasers, power ~ 100kW
Fast, high quality, deep, narrow welds
deep, narrow welds, expensive
Fusion welding..
Solid state welding
Diffusion welds between very clean, smooth pieces of metal, at 0.3~0.5Tm
Cold welding (roll bonding) coins, bimetal strips
Solid state welding..
Ultrasonic welding
25m Al wire on IC Chip
Ultrasonic wire bonder
Medical, Packaging, IC chips, Toys
Materials: metal, plastic
- clean, fast, cheap
Resistance welding
Welding metal strips: clamp together, heat by current
Spot welds on a panSpot welding Robotic Spot welding on auto bodySpot welds on a panSpot welding Robotic Spot welding on auto body
Spot welding
Seam welding
resistance seam weldingresistance welded petrol tank
resistance seam weldingresistance welded petrol tank
Brazing
Torch brazing Furnace brazing
Tm of Filler material < Tm of the metals being joined
Common Filler materials: copper-alloys, e.g. bronze
Common applications: pipe joint seals, ship-construction
SolderingTin + Lead alloy, very low Tm (~ 200C)
Main application: electronic circuits
Gluing
Adhesive type Notes Applications Acrylic two component thermoplastic; quick
setting; impact resistant, strong impact and peel strength
fiberglass, steel, plastics, motor magnets, tennis racquets
Anaerobic thermoset; slow, no-air curing – cures in presence of metal ions
sealing of nut-and-bolts, close-fitting holes and shafts, casting micro-porosities etc.
Epoxy strongest adhesive; thermoset; high tensile strength; low peel strength
metal parts (especially Nickel), ceramic parts, rigid plastics
Cyanoacrylate thermoplastic; high strength; rapid aerobic curing in presence of humidity
[common brand: Crazy glue™] plastics, rubber, ceramics, metals
Hot melt thermoplastic polymers; rigid or flexible; applied in molten state, cure on cooling
footwear, cartons and other packaging boxes, book-binding
Polyacrylate esters (PSA)
Pressure sensitive adhesives all types of tapes, labels, stickers, decals, envelops, etc.
Phenolic thermoset, oven curing, strong but brittle acoustic padding, brake lining, clutch pads, abrasive grain bonding
Silicone thermoset, slow curing, flexible gaskets and sealants Formaldehyde thermoset joining wood, making plywood Urethane thermoset, strong at large thickness fiberglass body parts, concrete gap
filling, mold repairs Water-based cheap, non-toxic, safe wood, paper, fabric, leather
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
Wire conductor: crimping
Plastic snap-fasteners
Traditional Manufacturing Processes
Casting
Forming
Sheet metal processing
Cutting
Joining
Powder- and Ceramics Processing
Plastics processing
Surface treatment
Surface treatment, Coating, Painting
1. Improving the hardness
2. Improving the wear resistance
3. Controlling friction, Reduction of adhesion, improving the lubrication, etc.
4. Improving corrosion resistance
5. Improving aesthetics
Post-production processes
Only affect the surface, not the bulk of the material
Mechanical hardening
Shot peening precision auto gears [source: www.vacu-blast.co.uk]
[source: www.uwinint.co.kr]
Shot peening
Laser peening
Case hardening
Process Dopant Procedure Notes Applications
Carburizing C Low-carbon steel part in oven at 870-950C with excess CO2
0.5 ~ 1.5mm case gets to 65 HRC; poor dimension control
Gears, cams, shafts, bearings
CarboNitriding C and N Low-carbon steel part in oven at 800-900C with excess CO2 and NH3
0.07~0.5mm case, up to 62 HRC, lower distortion
Nuts, bolts, gears
Cyaniding C and N Low-carbon steel part in bath of cyanide salts with 30% NaCN
0.025~0.25mm case, up to 65 HRC
nuts, bolts, gears, screws
Nitriding N Low-carbon steel part in oven at 500-600C with excess NH3
0.1~0.6mm case, up to 1100 HV
tools, gears, shafts
Boronizing B Part heated in oven with Boron containing gas
Very hard, wear resistant case, 0.025~0.075mm
Tool and die steels
Vapor deposition
Deposition of thin film (1~10 m) of metal
Sputtering: important process in IC Chip manufacture
Thermal spraying
High velocity oxy-fuel spraying
Thermal metal powder spray
Plasma spray
Tungsten Carbide / Cobalt Chromium Coatingon roll for Paper Manufacturing Industry
[source: www.fst.nl/process.htm]
ElectroplatingDeposit metal on cathode, sacrifice from anode
Anodizing
chrome-plated auto parts
copper-plating
Metal part on anode: oxide+coloring-dye deposited using electrolytic process
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
Painting Electrostatic Spray Painting
Spray Painting in BMW plant
Silk screening
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.
Summary
Further reading: Chapters 24, 21, 30-32: Kalpajian & Schmid