plastics welding training - · pdf filetwi was invited to review the internal welding ......

Copyright © TWI Ltd 2015

Plastics Lightweighting Saviour

Best Practice & Assessment of Joint Integrity

of Welded Moulded Plastics Components

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Dr Farshad Salamat-Zadeh

TWI, Cambridge, UK

LIGHTer International Conference Gothenburge, 17-18 November 2015


Introduction

Plastics in Automotive Sector

Assembly of Plastics

Case Studies

Vapour Separator

Standards on Thermoplastics Welding

TWI Services

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Content


Membership based Research and

Technology Organisation since 1946

>4500 company members in 70

countries

1000+ staff

Expertise in manufacturing,

engineering, materials and

joining

£75M turnover

Non profit distributing

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Copyright © TWI Ltd 2015 4

Plastics in Automotive Sector


During the oil crisis of the '70s, automakers realised that plastics could make cars more energy efficient by reducing weight

Advantages: Light weight

Durable

Corrosion resistance

Tough

Resilience

Ease of colouring and finishing

Applications include: Cabin console , door assemblies, headlight and sideview mirror

housings, air intake manifold, fuel tanks, fluid reservoirs such as; windscreen washer, power steering, brake and clutch fluid

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Plastics in Automotive

Oil Prices: http://www.huffingtonpost.com


Engine Coolant Expansion Tank

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Fuel Tank - Internals

Engine Manifold

Throttle Manifold

Steering Fluid Reservoir

Key Fob


Plastics reduced the weight of the average passenger car built in 1988 by 66 kg Saves millions of gallons of petrol each year Will save the energy equivalent of 21 million barrels of oil over

the average lifetime of those cars

By the 1993 model year, over 114 kg of plastics were used in the average vehicle

By 2020 plastic will account for 18% of average vehicle weight

Global trends are pushing automakers to reinvent their product and manufacturing processes

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Automakers face challenging new fuel-economy and greenhouse-gas emissions regulations

In North America passenger cars must meet corporate-average fuel economy (CAFE) standards of 54.5 m/g (4.32 l/100 km) by 2025

In EU, light-duty vehicles will be required to reduce CO2 emissions on new cars to 95 g/km by 2021

Lightweighting in part, requires replacing conventional metals with polymers and hybrid materials

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Replacement of engine components such as the engine manifold requires advanced engineering thermoplastic materials, which need to be moulded into a complex 3D structure

Such structures will often be designed and moulded in two halves

Advanced new-materials with complex designs demand suitable joining solutions

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Assembly of Plastic Components


There are currently 16 different welding techniques available for assembly of plastic parts

Ultrasonic

Spin

Vibration

Orbital

Friction stir

Heated tool

Hot gas

Extrusion

Resistive implant

Heat sealing

Flash-free

Infrared

Laser

Induction

Radio frequency

Microwave

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Assembly of Plastics

Friction Direct Heat Source Electromagnetic


Weld quality of plastics is very much dependent on both the material and the joint design for the specific welding process

Companies have their own internal specifications for Welding of Plastic Parts which dictates both design and welding/joining aspects of plastic components

Verification of weld quality has been a challenging task:

− Visual inspection

− Pressure / burst test

− Microtoming

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The Need


Case Studies


Part

Material

Process

Post process

Issue

Vapour separator

Hostaform® C13031 (POM)

Injection moulding

Linear vibration welding

Leakage at weld

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Vapour Separator


Design Rule

A tongue and groove joint for linear vibration welding (image courtesy of JLR).

A tongue and groove joint showing melt-down region prior to welding (View B), and after welding View-C (image courtesy of JLR).


General quality test

Some components failed within the warranty period whilst in service

Failure at weld is not unique to this component

On average such premature failures are costing automakers between €4M to €7M to investigate and rectify

Visual inspection

Pressure / Burst test

Leak test

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Vapour Separator (POM)


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Failure Investigation Visual Inspection

Uneven weld gaps

General defects witnessed included: Surface detects

Low melt temperature

Inhomogeneous melt

Weld misalignment


General defects witnessed that resulted from the welding process included: Voids

Crack at the edge of the weld-line

Poor weld penetration

Misalignment

Excessive loading

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Failure Investigation Microscopy


(b)

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Failure Investigation

X-ray Radiography & Computed Tomography

HMXCT 225 X-ray Micro-focus machine

CT images of a welded vapour separator: a) complete component with the six critical locations (1-6) marked b) a slice through the part exposing the weld interface and weld-flash

(a)


“Design Rules” for vibration welding dictate critical dimensions which should be adhered to if a good weld is to be expected

In most investigations the unwelded parts of the component are not available to measure and compare against the “Design Rules”

One major advantage of CT is that the joint design dimensions of the welded part under investigation can be measured on the CT images using software which allows live measurement analysis of the weld-lines

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Failure Investigation

Computed Tomography


Computed Tomography


Thermograph Inspection of Tooling & Packaging

On tool core

On tool cavity

Part on conveyer belt

Part in box (packaging)


Standards on Thermoplastics Welding


Many national and international standards on the welding and testing of plastics pipes and geomembranes

Some European standards on manual plastics welding techniques

Hot gas, extrusion, etc.

No international standards on the welding and testing of moulded plastics components

DVS guidelines for heated tool, ultrasonic, vibration and spin welding

Need to determine and promote best practice for the welding and testing of moulded plastics components

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Available Standards


TWI was invited to review the internal welding guides and procedures of a major automotive company

TWI helped to set up a new Working Group within BSI committee WEE/3 “Welding of Thermoplastic Moulded Components”

Aim is to assist Design engineers and Tier-1 suppliers to design correct joints for welding of injection moulded components

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Approach


Overcoming Barriers OEMs

Standard Bodies

TWI and others

Tier-1


Subject: Materials

Sector: Manufacturing & Services

Scope Under the direction of WEE/3 is responsible for the preparation of

British Standards specifically in the welding of thermoplastics materials using the following processes: laser, linear vibration, spin, hot plate, infrared, hot ’convection’ gas and ultrasonic welding. The group also provides the UK input into CEN/TC249/WG16

Who is currently involved

BSI Secretary - PRI/-1

TWI Ltd

Jaguar Cars

Ford Motor Company

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Committee: WEE/3 Welding of thermoplastic moulded components

Rofin-Baasel UK

Mergon International

Telsonic UK Ltd

Cikautxo Group

British Plastics Federation

Emerson

JCB Research

Branson

Dyson

https://standardsdevelopment.bsigroup.com/Home/Page/GetInvolved


Development of a Bespoke Course


Three-day training course and assessment, including practical demonstrations, to improve understanding of material selection,

design and fabrication of moulded plastic components.

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Plastic Welding Training Course

Day – 1 Introduction to plastics & welding principles Heated tool, infrared & hot gas convection welding Vibration welding Demonstrations of heated tool & vibration welding Tour of the facilities

Day – 2 Ultrasonic welding Laser welding Spin welding Ultrasonic & hot air stacking Vibration welding Demonstrations of ultrasonic & laser

welding

Day – 3 Mechanical & non-destructive testing

of plastics welds Design Rules Other welding techniques for plastics Adhesive bonding Multiple-choice examination Feedback & discussion


Joining processes

Vibration welding

Spin welding

Hot plate welding

Ultrasonic welding

Infrared welding

Laser welding

Hot air and ultrasonic staking

Adhesive bonding

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TWI Services - Polymer Division

Services offered

Process selection and optimisation

Mechanical testing

Failure investigation

Joint design

Materials analysis

Training and assessment

Standards development

Non-destructive inspection

Materials selection

Prototype equipment and part development

Pre-production welding

Welding

Mechanical testing

Tensile

Flexural

Flower test

Compressive

Creep

Peel

Fatigue

Impact

Pressure/burst test

Nano-indentation

Inspection techniques

Visual

Microtoming

SEM/EDX

Ultrasonic

X-ray radiography

Thermography

Optical microscopy

Analytical testing

DSC

TGA

DMTA

FTIR

GC-MS

Rheometry

Permeation


All current investigative techniques are valid

X-ray Radiography & CT:

CT has proved to be an impressive tool which provides a non-destructive test of welded parts

Enables direct comparison against “Design Rule”

X-ray, CT highlighted:

Non-uniform weld flash around the perimeter of the weld

The weld step-H (tongue and groove), weld-flash created and the weld-gauge were inconsistent and did not pass the criteria set by automotive company’s Design Rules

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Summary


Enables detection of defects and voids in the parts

Packing pressure

Holding pressure

Gate choice

Tool temperature

Thermography inspection identifies

Heat signature

Uneven cooling

Uneven tool tolerances/pressure

Resulting in unacceptable changes to crystallinity

Recommendation for regular QA checks and components qualification using these technique.

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Summary


Thank you for your attention …

Joining Group

plastics welding training - · pdf filetwi was invited to review the internal welding ......

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