composites manufacturing manufacturing process selection

103
College of Elect. & Mech. Engineering Composites Manufacturing & Manufacturing Process Selection Strategy (the Ashby approach) Dept of Mechanical Engineering, NUST, College of E & ME, Rawalpindi, Pakistan Dr. Rizwan Saeed Choudhry [email protected] Material selection charts in this slide are copyright of Granata Design and should only be used for educational purpose

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Page 1: Composites Manufacturing Manufacturing Process Selection

College of Elect. & Mech. Engineering

Composites Manufacturing &

Manufacturing Process Selection Strategy

(the Ashby approach)

Dept of Mechanical Engineering,

NUST, College of E & ME, Rawalpindi, Pakistan

Dr. Rizwan Saeed Choudhry [email protected]

Material selection charts in this slide are

copyright of Granata Design and should only be used for educational purpose

Page 2: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

COMPOSITES MANUFACTURING

Page 3: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

FULLY AUTOMATED CAR BONNET

MANUFACTURE AT BMW

Page 4: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

MANUAL CAR BONNET MANUFACTURE

USING VARI

Click on image to play video

Page 5: Composites Manufacturing Manufacturing Process Selection

PROCESS SELECTION! - COMPOSITES DRIVING FORCES

Criteria on which composites are selected depend on the industry in

which they will be used same is the case for Processes Selection!

Aerospace: mainly weight reduction with increased stiffness/strength

High scrap levels are (were?) tolerated

There is a preference for high performance materials in order to reach the

weight savings

5

• Fibres need to be continuous and volume

fractions need to be high

– Transportation: Emphasis is on

decreasing cost

• Return on investment, complex

shapes, recycling, etc.

• Need to reduce weight as increased

safety requirements = heavier

vehicles = worse fuel economy

• Manufacturing routes need to be

low-cost and high speed: fibre

volume fractions not so much of an

issue

Aerospace: Strength, stiffness,

weight, quality control

Mechanical Industry: Design, strength, quality

Automotive: Automated fabrication

Perf

orm

an

ce

1/Cost

Page 6: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

6

Prepreg (autoclave) – prepregs were expensive

Capital equipment (Autoclaves, tape layers) are expensive, material

deposition rates and processing are slow

More than 70% of part cost from fabrication!

INEFFICIENT MANUFACTURING PROCESSES

Page 7: Composites Manufacturing Manufacturing Process Selection

COSTS

Car <1

Subway 15

Aircraft 200

Satellite 5,000

$ saved (Fuel) / kg weight reduction per lifetime

Page 8: Composites Manufacturing Manufacturing Process Selection

Materials Design

Manufacturing

SYSTEMS APPROACH TO DESIGNING WITH

COMPOSITES

Page 9: Composites Manufacturing Manufacturing Process Selection

PROCESS SELECTION! - WHY THE FUSS!

Effects of manufacturing

Manufacturing route has to be chosen at part design as

this has a huge influence on the final properties of the

composite

Influences include component geometry, reinforcement

type/format, matrix, quality problems, etc.

9

Knockdown factors

– Main cause of safety margins

introduced are due to

manufacturing problems:

• Up to a 40% reduction in the

composite value is due to

manufacturing issues

• It is essential to know/

understand the different

manufacturing routes in order

to prevent these problems

Page 10: Composites Manufacturing Manufacturing Process Selection

RELATIONSHIP OF MATERIAL PROPERTY WITH PROCESSING

Page 11: Composites Manufacturing Manufacturing Process Selection

PROCESSING FOR PROPERTIES

Page 12: Composites Manufacturing Manufacturing Process Selection

PROCESSING FOR PROPERTIES

Page 13: Composites Manufacturing Manufacturing Process Selection

PROCESS SELECTION

Process

Economics

Page 14: Composites Manufacturing Manufacturing Process Selection

THE PROCESS SELECTION CONSTRAINTS / PROCESS

ATTRIBUTES

Material

1. Type of composite matrix (e.g. Polymeric , Thermoset or thermoplastic, metallic or ceramic)

2. The type of preform (i.e. the form of reinforcement) i.e. yarn, non-crimp fabric, woven fabric, chopped strand, braded etc.

Shape

3. Achievable shapes and geometries

4. The requirement of dimensional control (accuracy and repeatability)

Function & Material

5. Achievable reinforcement volume fraction

6. Achievable control of fibre orientation

7. The dictates of quality control

Process Economics / Environment

8. The requirement of number of parts (production rate)

9. The organizational budget (cost of process)

10. Trade Embargos, Environmental legislation, Local Laws etc.

Page 15: Composites Manufacturing Manufacturing Process Selection

MANUFACTURING PROCESSES (UNDERSTANDING

MATERIAL CONSTRAINT)

Open Mould Techniques

Contact moulding

Hand lay-up, spray

lay-up

Filament winding

15

Closed Mould Techniques

– Liquid composite moulding

– Hot press moulding

– Injection moulding

– Centrifugal casting

Before formally developing the strategies for Process Selection lets revisit

some of the very widely used manufacturing processes and compare then for

the ten constraints/attributes discussed

Manufacturing can be divided into two separate techniques depending on how

the resin is infiltrated into the reinforcement

The techniques can also be classified on the basis of type of preform type.

Preforming may be performed in-house or they may be purchased directly

from an external supplier.

Page 16: Composites Manufacturing Manufacturing Process Selection

MANUFACTURING COMPOSITES

(MATERIAL CONSTRAINT)

Raw

Material

(Fibre & Resin)

Preforms

Wet preforms Dry Preform

1D Preform

(yarn,

roving)

2D Preforming

Technical textiles

incl. woven fabrics,

uni-weave (UD

fabric), Non Crimp

Fabric,

Mats (Chopped &

Continuous)

2D braids

1. Prepregs

(UD and

Woven (2D

and 3D)

2. Moulding

compounds

3D Preforms

(3D Woven

and braided)

Appropriate Product Manufacturing Processes

(Primary shaping, Secondary shaping and joining)

Page 17: Composites Manufacturing Manufacturing Process Selection

MANUFACTURING THERMOSET

COMPOSITES Appropriate Product Manufacturing Processes

(Primary shaping)

Dry Preform 1D Preform

2D Preform 3D Preform 1. Filament

winding

2. Spray up

3. Pultrusion 1. Hand layup

2. VARI/SCRIMP/

Fastrac

3. VARTM

4. TERTM

5. SRIM/RRIM

6. Pultrusion

Wet preforms

Prepreg

1. Vacuum bag moulding

2. Blow moulding

Moulding compounds

1. Compression Moulding for

(SMC and BMC)

2. Injection Moulding (BMC)

Secondary shapping and joining

(water jet cutting, machining, laser

cutting, adhesive bonding and

cocuring, riveting, painting etc…

Page 18: Composites Manufacturing Manufacturing Process Selection

EXAMPLE OF A COMPLETE PRODUCT

MANUFACTURING ROUTE

Prepregging Matrix

Fibres

Lay-up &

Bagging Autoclaving Finishing

Part

Assembling

Continuous Batch Batch Batch

Batch

Adhesive &

Core Materials

Overall process scheme for manufacturing of autoclaved

prepreg based composites

Property testing feedback loop

Page 19: Composites Manufacturing Manufacturing Process Selection

PROCESSES REVISITED A quick review of the more widely used thermoset

composites manufacturing processes

2/2

8/2

014

Page 20: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

HAND AND SPRAY LAY-UP

Resins are impregnated by

hand into fibres which are in

the form of woven, knitted,

stitched or bonded fabrics. This

is usually accomplished by

rollers or brushes, with an

increasing use of nip-roller type

impregnators for forcing resin

into the fabrics by means of

rotating rollers and a bath of

resin. Laminates are left to

cure under standard

atmospheric conditions.

Page 21: Composites Manufacturing Manufacturing Process Selection

21

Coat tool with release agent

Spray gel-coat onto mould tool. • Gel coat produces Class-A surface finish on outer surface

• Gel coat is hardened before laying the fibres

Page 22: Composites Manufacturing Manufacturing Process Selection

22

Select dry reinforcement

form:

Mats, fabrics – but not UD

rovings

Cut and trim to size, and

stipple onto wet/tacky gel

coat layer

Page 23: Composites Manufacturing Manufacturing Process Selection

23

Resin applied using brush rollers

– either manually or through

pumped systems

Product is consolidated by hand using

steel rollers

• Helps remove air bubbles and

achieves desired compaction

• Thick parts are built up in stages

to prevent excessive exotherm

• If necessary a core is bonded and

then lamination continues

Cost: <£500

Size: 1-200m2

Prod. Rate: 1-10kg/hr

Quantity: 1-500/yr

Page 24: Composites Manufacturing Manufacturing Process Selection

24

• Similar to wet lay-up initially

• Resin and reinforcement applied through use of spray gun

– Chops fibre rovings into lengths of 10–70mm (typically 40mm)

– Mixes resin, catalyst and accelerator

– Fibres deposited on surface through action of resin pump

• Part rolled for consolidation

• Resin cured at room temp

Spray-up (or spray lay-up)

Page 25: Composites Manufacturing Manufacturing Process Selection

25

Fibre feed (rovings cheap)

Resin is supplied to

the gun in 2 streams:

Catalyst

Resin

plus accelerator

Typical spray-up gun arrangement

Page 26: Composites Manufacturing Manufacturing Process Selection

26

Big sections very

suitable for spray.

Machine: £5K-10K

Mould: £150-15K

Size: ~10m2

Prod. Rate: 5-50kg/hr

Quantity: 5-2000/yr

Page 27: Composites Manufacturing Manufacturing Process Selection

27

Advantages Similar to wet lay-up but:

• Faster deposition rates

– Suitable for small- to medium-volume parts

– Labour costs lower than for hand laminating

– Allows easy part thickness variation

• Easily automated

Limitations • Reinforcement in chopped format Only

• Concerns about styrene emissions

– Different types of chopper guns produce different styrene emissions due to different mixing methods

• Inconsistent quality

– Product quality dependent on operator skill – dimensional inconsistencies within and between batches

– Difficult to remove trapped air from moulding

• Low volume fraction of fibres – also limited to chopped fibres

• High levels of waste due to overspray

Page 28: Composites Manufacturing Manufacturing Process Selection

28

Easily automated !

• Spray lay-up can be easily

automated using robots (e.g.

Fanuc P200-T modfied paint

robot with AccuChop control

software – Fanuc Robotics)

– Improves product quality

– More consistent products

– Reduced waste – material usage

monitoring

– Feedback on amount of material

applied to a part

Click on image to play video

Page 29: Composites Manufacturing Manufacturing Process Selection

29

Filament winding is one of the first techniques used in mass

production

A carriage unit carrying the fibres moves back and forth while the

mandrel rotates at a specified speed

Controlling the motion of the carriage unit and the mandrel allows the

desired fibre angle to be generated

Fibre tows or rovings are impregnated in bath or resin and wound under

tension over a mandrel in a defined geometric pattern

Process ideal for rotational symmetrical shapes e.g. tubes, pressure

vessels, pipes, rocket motor casings and launch tubes, and storage

tanks

FILAMENT WINDING

Click on image to play

video

Page 30: Composites Manufacturing Manufacturing Process Selection

Polar Winding:

• Mandrel rotates,

feed stays fixed

Chopped fibres dispensed onto

feed section

• Used for making pipes and

tanks

VARIATIONS

Page 31: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering 31

Advantages Filament winding places fibres in exact

orientations for maximum structural efficiency

High volume fractions possible (up to 70%)

For certain applications, e.g. pressure vessels and

fuel tanks it is the only method for manufacturing

cost-effective composite parts

Raw materials and mandrels are low-cost, so parts

are cost-effective

Can be automated for high-volume production

Multi-axis winding allows complex shapes

(examples – connection rods, prostheses, branched pipe work)

Page 32: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering 32

Disadvantages A mandrel is needed therefore only hollow sections are

possible

It is difficult to obtain uniform fibre distribution and resin

content throughout the thickness of the part

High (>1%) void content without use of vacuum, especially at

high winding speeds

Complex programming is required for multi-axial parts

Cannot wind into concave surfaces

Need to follow geodesic paths during winding:

Not all fibre angles are easily produced: 0° to 15° is difficult

Open mould process – therefore there are emissions concerns

The outer surface of the wound component is not smooth

A teflon coated bleeder cloth or shrink tape can be applied over the

surface once winding is complete

Page 33: Composites Manufacturing Manufacturing Process Selection

MSc Composites Science & Engineering 33

Filament winding

Machine: £30k-150k

Tools: £1k-20k

Size: 50×150cm long

Prod. Rate: 3-50m/hr

Quantity: >1500m/yr

Page 34: Composites Manufacturing Manufacturing Process Selection

MSc Composites Science & Engineering 34

Page 35: Composites Manufacturing Manufacturing Process Selection

35

Similar to extrusion but fabric/roving is pulled through a die rather

than pushed

Continuous reinforcements are drawn from a spool and pulled into

pultrusion die

Guides or bushings in front of the die preform the reinforcement

Impregnation with liquid resin is performed either in an open bath (=

cheap) or under pressure in die (= more expensive dies)

Resin is typically filled with calcium carbonate or fire retardants etc

Heated part of die consolidates tool – curing is essentially complete as

part emerges

Sections are cut to desired length

PULTRUSION

Cost: £7k-300k

Size: ~30cm×2m

Cycle time: ~4hr

Quantity: 1-10000/yr Click on image to play video

Page 36: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

PULTRUSION PROCESS ANIMATION

Click on image

to play video

Page 37: Composites Manufacturing Manufacturing Process Selection

37

• Remember the BMW video in start

• RTM is capable of satisfying the low-cost/high-volume 500-50,000 parts per

year of the automotive industry as well as the higher performance/lower

volume 50-5,000 parts per year of the aerospace industry.

• Processing:

– Two-part, matched-metal mould (or tool) is required

– Reinforcement is preformed and placed into the mould

• Cores and inserts are inserted into the preform as required

– Mould is closed under hydraulic/pneumatic pressure or clamped at the edges

– Resin is pumped under low pressure through injection ports into the mould and

follows pre-designed paths through the preform.

• Both the mould and resin can be heated as needed for the application.

Resin Transfer Moulding (RTM)

Click for Video

Page 38: Composites Manufacturing Manufacturing Process Selection

38

VARI • VARI is a liquid moulding processing method popularized by Lotus to

manufacture the Elan, the Esprit, and the Excel automobiles.

• Tooling can be matched or one-sided with a flexible tool

• Vacuum is used to draw the resin through the preform and hold the mould closed

during processing.

• Low volume of parts produced per year:

– The process aims to compete with spray-up and hand lay-up as opposed to RTM

Mould prepared

and gel-coated

Filled with fabrics

and preforms

Page 39: Composites Manufacturing Manufacturing Process Selection

39

Vacuum tight upper tool covers reinforcement • Evacuated to consolidate materials, trap on vacuum line to ensure no

resin drawn into vacuum pump.

Resin supply clamped

to stop resin flow

(gravity assisted!)

VARI (cont…)

Page 40: Composites Manufacturing Manufacturing Process Selection

40

Resin flows and wets out

fabrics to fill cavity

VARI (cont…)

Page 41: Composites Manufacturing Manufacturing Process Selection

41

Final part

Page 42: Composites Manufacturing Manufacturing Process Selection

42

Processing for prepreg

Vacuum bag moulding • Basically an extension of the hand lay-up process where pressure is

applied to the laminate once laid-up:

– Improves consolidation.

Click image for video

Page 43: Composites Manufacturing Manufacturing Process Selection

43

Vacuum bag moulding: processing

• Lamination & Bagging performed at ambient temperature &

pressure

• Vacuum is applied once the resin is of sufficient viscosity to

prevent excess resin bleed (i.e. excessive removal of resin)

– The vacuum is held until the resin has reacted beyond the gel point

– Uniform pressure is needed such that perforated tubes and/or extra

breather cloth may be required to provide a network of air paths

• Vacuum bagging is a useful procedure for bonding core

materials and for forming curved panels where there is a need

for uniform pressure to hold the core in place

– In this case the pressure is held until the adhesive bond is strong

enough to hold the core in place

Page 44: Composites Manufacturing Manufacturing Process Selection

44

Advantages • Higher fibre content and lower void content than with standard hand

lay-up.

– Volume fractions of 58% and void contents below 2% easily achievable

– Improved mechanical properties are achieved as a result

• Better fibre wet-out due to pressure and resin flow

– Heavier fabrics than those commonly used in hand lay-up can be easily wet out

– The additional consolidation pressure helps the reinforcement conform to tight

curvatures

• Health and safety

– The vacuum bag reduces the amount of volatiles emitted

• Pre-preg layup can be Automated for faster production and accurate

control (Click for video)

Page 45: Composites Manufacturing Manufacturing Process Selection

45

Disadvantages • During lamination there are still health & safety issues due to styrene

emissions

– Therefore there are still the cost issues of extracting the VOCs (volatile

organic compounds)

• The extra process adds cost both in labour and in disposable bagging

materials

– Production rates suffer due to extra labour for bagging: bags are only available

in certain widths and it can be difficult to seal adjacent pieces

– Moulds need to be vacuum tight

– Care needs to be taken with resins that emit volatiles: UPE and VE will lose

styrene under vacuum making them porous

• A higher level of skill is required by the operators for the bagging

stage

– There is a need to prevent vacuum leaks while at the same time work needs to

be quick so as to pull vacuum before the resin gels

• Mixing and control of resin content still largely determined by

operator skill

Page 46: Composites Manufacturing Manufacturing Process Selection

Processing for prepreg - Blow Molding

• Being used for

hockey stick

manufacture

• After part layup it

is placed in a two

part heated mould

and high pressure

gas is blown in.

• The layup takes the

shape of mould and

is allowed to cure

and then taken out

Page 47: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

COMPRESSION MOULDING AND THERMO-

FORMING FOR SMC AND BMC

2/2

8/2

014

Page 48: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

SMC – Compression moulding SMC can be cut and handled easily –

weighed for use in moulding process.

Typical part

Charge is cut to shape – but it is NOT a

net shape process. Typically SMC

charge only covers 50-70% of the mould

tool surface.

Page 49: Composites Manufacturing Manufacturing Process Selection

PROCESS SELECTION – PERFORMANCE/VOLUME

CONSTRAINT FOR (FOR POLYMERIC COMPOSITES)

49 (& manufacturing cost)

Page 50: Composites Manufacturing Manufacturing Process Selection

50

?

Performance versus Production

Ideal situation for composite takeup

would be to have high modulus

parts capable of being produced at

over 1000 parts per day

Page 51: Composites Manufacturing Manufacturing Process Selection

2/2

8/2

014

• Low volume production favours RTM

• Large scale production favours SMC

– e.g. Renault Espace: Production had to shift to SMC due

to large demand

PROCESS SELECTION – COST/VOLUME CONSTRAINT

SMC vs. RTM

Page 52: Composites Manufacturing Manufacturing Process Selection

PROCESS SELECTION – COST/VOLUME CONSTRAINT

• Pigmentation adds to value

of final product

• SMC allows modification of

parts allowing easy

production of ‘Special

Editions’

SMC vs. Steel

Page 53: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

PART – 1 SUMMARY

A huge variety of processes can

be used for manufacturing

composites

Each process has certain

advantages and certain

limitations.

Comparing the processes

attribute using a formal

methodology that takes into

account the interaction of

materials, shapes, functions,

process, and economics can

allow us to make a rational

choice

Page 54: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Composites Manufacturing &

Manufacturing Process Selection Strategy

(the Ashby approach)

Part 2 of 2

Dept of Mechanical Engineering,

NUST, College of E & ME, Rawalpindi, Pakistan

Dr. Rizwan Saeed Choudhry [email protected]

Material selection charts in this slide are

copyright of Granata Design and should only be used for educational purpose

Page 55: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

USEFUL REFERENCES

Page 56: Composites Manufacturing Manufacturing Process Selection

PROCESS SELECTION

Process

Economics

Page 57: Composites Manufacturing Manufacturing Process Selection

CLASSIFYING PROCESSES

Page 58: Composites Manufacturing Manufacturing Process Selection

MEMBER ATTRIBUTES - THE BASIS FOR

PROCESS SELECTION

Page 59: Composites Manufacturing Manufacturing Process Selection

MEMBER ATTRIBUTES - THE BASIS FOR PROCESS

SELECTION

Page 60: Composites Manufacturing Manufacturing Process Selection

EXAMPLE – MEMBER ATTRIBUTES FOR COMPOSITES

MANUFACTURING PROCESSES

• Material

• Shape

• Size

• Mass

• Tolerance

• Roughness

• Reinforcement Type and layup

Control on angles during layup Volume Fraction range Void Content achievable

• Batch Size

• Cost Model

• Production rate

• Documentation

Page 61: Composites Manufacturing Manufacturing Process Selection

PROCESS SELECTION

Translation of process

requirements

Function: What must the process do ? (e.g.

moulding? joining? finishing ?)

Constraints What technical limits must be met? (i.e.

Material and shape compatibility)

What quality limits must be met

(Precision, porosity/void content, volume

fraction, fibre orientation control …)

Objectives

What is to be maximized or minimized?

(Cost? Time ? Quality)

Free variables

Choice of process and process-operating

conditions

Page 62: Composites Manufacturing Manufacturing Process Selection

SCREENING USING

CONSTRAINTS

Process - Material

Compatibility

Page 63: Composites Manufacturing Manufacturing Process Selection

SCREENING USING

CONSTRAINTS

Process – Shape

Compatibility

Page 64: Composites Manufacturing Manufacturing Process Selection

SCREENING USING CONSTRAINTS Process – Mass Compatibility

Page 65: Composites Manufacturing Manufacturing Process Selection

SCREENING USING CONSTRAINTS Process – Section thickness Compatibility

Page 66: Composites Manufacturing Manufacturing Process Selection

SCREENING USING CONSTRAINTS Process – Tolerance Compatibility

Page 67: Composites Manufacturing Manufacturing Process Selection

SCREENING USING CONSTRAINTS Process – Surface Roughness Compatibility

Page 68: Composites Manufacturing Manufacturing Process Selection

RANKING – THE COST OBJECTIVE

The Cost function and economic batch size

m= component weight (mass)

f = scrap function

n = number of components

L = load factor

two = write-off time

ń = production rate (units per hour)

Int = integer value function

Page 69: Composites Manufacturing Manufacturing Process Selection

RANKING – THE COST OBJECTIVE Understanding economic batch size

The cost of sharpening a pencil plotted against batch size

Page 70: Composites Manufacturing Manufacturing Process Selection

RANKING – THE COST OBJECTIVE Process-vs-Economic batch size

Page 71: Composites Manufacturing Manufacturing Process Selection

COMPUTER AIDED PROCESS SELECTION

Cambridge Engineering Selector

The cost of sharpening a pencil plotted against batch size

Page 72: Composites Manufacturing Manufacturing Process Selection

CASE STUDY :

FORMING A FAN (FOR VACUUM CLEANERS)

Page 73: Composites Manufacturing Manufacturing Process Selection

CASE STUDY :

FORMING A FAN (FOR VACUUM CLEANERS)

Page 74: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Process - Material

Compatibility

Page 75: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Process – Shape

Compatibility

Page 76: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Process – Mass

Compatibility

Page 77: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Process – Section thickness

Page 78: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Process – Tolerance

Page 79: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Process – Roughness

Page 80: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS) Economic Batch Size

Page 81: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS) Final recommendation

Exploring the cost further

Page 82: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Relative cost of moulding the fan

Page 83: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Traditional and still the most prevalent approach - Trial

and Error based on historic data of usage and availability

Scientific approach: Most Popular theses days

Ashby approach – Cambridge Engineering Selector

Other scientific approaches include Matrix methods such

as Multiple Criteria Ranking Methods, Digital Logic

Method and Analytical Hierarchical Method (AHP)

All scientific approaches to material selection attempt to

ensure that the desired functionality is achieved while

satisfying the constraint(s) and maximizing the desirable

objective(s)

MATERIAL SELECTION PROCESS

Page 84: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Function:

The desirable operation to be performed by the material; e.g. in mechanical design this can be usually translated into quantities that relate directly to material properties; for example a tie-rod resists axial loads and the functional requirement can be expressed in terms of both strength and stiffness.

Objective:

For example minimize mass and cost

Constraints:

E.g. Availability, minimum strength requirements, allergies

Defines the performance (p) for a design problem as functional p = p(F,G,M) where F = functional requirements; G = Geometric parameters; and M = material indices

THE ASHBY APPROACH[1-4]

Page 85: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

If this functional can be written in separable form such as

p = p1(F).p2(G).p3(M) then for a given set of F and G the

problem of Material selection reduces to the one of optimizing

M; i.e. the material indices.

Based on above the Material index is a combination of

materials properties that characterizes the Performance of a

material in a given application [1].

Function, Objective, and Constraint Index

Tie, minimum weight, stiffness E/r

Beam, minimum weight, stiffness E1/2/r

Beam, minimum weight, strength s2/3/r

Beam, minimum cost, stiffness E1/2/Cmr

THE ASHBY APPROACH

Page 86: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Page 87: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Page 88: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Page 89: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Page 90: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Page 91: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

Page 92: Composites Manufacturing Manufacturing Process Selection

College of Electrical and Mechanical Engineering

CASE STUDY: MATERIAL FOR OARS

Page 93: Composites Manufacturing Manufacturing Process Selection

CASE STUDY: MATERIAL FOR OARS

Constraints:

Deflection limits:

Soft = 50 mm, Hard = 30 mm

Weight limit:

As light as possible:

Shape:

Hollow Shaft with variable diameter and flat spoon

Weight hung 2.05 m

from collar

Page 94: Composites Manufacturing Manufacturing Process Selection

CASE STUDY: MATERIAL FOR OARS

Page 95: Composites Manufacturing Manufacturing Process Selection

CASE STUDY: MATERIAL FOR OARS

Page 96: Composites Manufacturing Manufacturing Process Selection

CASE STUDY: MATERIAL FOR OARS

• Wooden oars made of laminated spruce wood

• Requires around 2 weeks to settle down after lamination and gluing

• Weighs between 4 to 4.3 kg

• Quality consistency also depends on availability of same grade of

wood and workers skill.

• CFRP is also better because

1. Possibility of faster production rates

2. More control over stiffness by precisely varying the fibre –

resin content

3. Weight can be easily lowered to 3.9 kg

4. More consistency of part quality

Page 97: Composites Manufacturing Manufacturing Process Selection

CASE STUDY: PROCESS FOR CFRP OARS

Process Requirements:

• Function Moulding (shapping)

• Constraints Material (CFRP)

Shape – Hollow/Solid 3D

Mass – less than 4 kg

Tolerance - ?

Roughness - ?

Control on angles < 2.5o variation ?

Volume fraction > 40% Void Content < 2%

Reinforcement Type –

Continuous (Multidirectional layup)

Batch Size – ? (1000)

Production Time - ? (less than 2 weeks)

Same Process for Spoon and Loom

• Objective Minimize cost

Free variables Choice of Process

Process parameters

Page 98: Composites Manufacturing Manufacturing Process Selection

CASE STUDY : FORMING A FAN (FOR VACUUM CLEANERS)

Process - Material

Compatibility

Oars

Page 99: Composites Manufacturing Manufacturing Process Selection

Process – Shape Compatibility

Process Loom Spoon

1. RTM ++ ++

2. VARI + ++

3. Vacuum

bagging Prep-preg

+++ +++

4. Spray-up +++ +++

5. Filament

Winding

+++ N/A

Process – Mass Compatability

All Five Processes

Process – Fibre Type and Layup

Compatibility

Process Loom Spoon

1. RTM ++ ++

2. VARI ++ ++

3. Vacuum

bagging Prep-preg

+++ +++

4. Spray-up N/A N/A

5. Filament

Winding

+++ N/A

Process – Production Time

Compatability

All Five Processes

CASE STUDY: PROCESS FOR CFRP OARS

Page 100: Composites Manufacturing Manufacturing Process Selection

Process – Batch Size

Compatibility

Process Loom Spoon

1. RTM +++ +++

2. VARI + +

3. Vacuum

bagging Prep-preg

++ +

4. Spray-up +++ +++

5. Filament

Winding

+++ +++

Process – Fibre Orientation

Control Compatibility

Process Loom Spoon

1. RTM + ++

2. VARI + +

3. Vacuum

bagging Prep-preg

+++ +++

4. Spray-up N/A N/A

5. Filament

Winding

+++ N/A

CASE STUDY: PROCESS FOR CFRP OARS

Process – Volume fraction /Void Content Compatibility

Process Loom Spoon

1. RTM ++ ++

2. VARI + +

3. Vacuum bagging Prep-preg +++ +++

4. Spray-up N/A N/A

5. Filament Winding N/A N/A

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Process Shape Layup Vf/Void Orient.. Batc

h

Aggregate

1. RTM 4 4 4 3 6 21

2. VARI 3 4 2 2 2 13

3. Vacuum

bagging

Prep-preg

6 6 6 6 3 27

Cumulative Ranking after elimination of processes which were not applicable on one or more counts

CASE STUDY: PROCESS FOR CFRP OARS

Vacuum bagging with curing is better for the criteria

considered however it may require secondary curing using

oven or autoclave depending on design specifications

On rigorous cost analysis RTM may turn out to be cheaper

in long run especially if part count is increased

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CONCLUSION

Process

Economics

Page 103: Composites Manufacturing Manufacturing Process Selection

USING THE SELECTION CHARTS