ppt - ielm

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


chip


(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


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



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



tc

b

tmlpr C

NN

tNN

MMtMtC

1MLVVLM

CVL

NN nn

b

t/)1(

nntclpr VCtM

CLMLVMtC /)1(1 )(


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:


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


groove 5mmX5mm

S1

S2

S3

S4

S5 S6

S7

S8

S9

S10

S1

S2

S3

S4

S5 S6

S7

S8

S9

S10

Process Planning


groove 5mmX5mm


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


[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


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



[Drill in tailstock] Center drill

[Drill in tailstock] Drill 32

Setup 2: Chuck part on S4

[10mm counterbore] Counterbore 5mm



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…


Casting

Forming


Cutting

Joining


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


Casting

Forming


Cutting

Joining


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

ppt - ielm

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