Plastics Lightweighting Saviour Best Practice & Assessment of Joint Integrity of Welded Moulded Plastics Components

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1 Plastics Lightweighting Saviour Best Practice & Assessment of Joint Integrity of Welded Moulded Plastics Components Dr Farshad Salamat-Zadeh TWI, Cambridge, UK LIGHTer International Conference Gothenburge, November

2 Content Introduction Plastics in Automotive Sector Assembly of Plastics Case Studies Vapour Separator Standards on Thermoplastics Welding TWI Services 2

3 Membership based Research and Technology Organisation since 1946 >4500 company members in 70 countries staff Expertise in manufacturing, engineering, materials and joining 75M turnover Non profit distributing 3

4 Plastics in Automotive Sector 4

5 Plastics in Automotive 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 Oil Prices: 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 5

6 Plastics in Automotive Engine Manifold Fuel Tank - Internals Steering Fluid Reservoir Engine Coolant Expansion Tank Key Fob Throttle Manifold 6

7 Plastics in Automotive 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 7

8 Plastics in Automotive 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 CO 2 emissions on new cars to 95 g/km by 2021 Lightweighting in part, requires replacing conventional metals with polymers and hybrid materials 8

9 Plastics in Automotive 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 9

10 Assembly of Plastic Components 10

11 Assembly of Plastics There are currently 16 different welding techniques available for assembly of plastic parts Friction Direct Heat Source Electromagnetic Ultrasonic Spin Vibration Orbital Friction stir Heated tool Hot gas Extrusion Resistive implant Heat sealing Flash-free Infrared Laser Induction Radio frequency Microwave 11

12 The Need 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 12

13 Case Studies 13

14 Vapour Separator Part Material Process Post process Issue Vapour separator Hostaform C13031 (POM) Injection moulding Linear vibration welding Leakage at weld 14

15 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). 15

16 Vapour Separator (POM) General quality test Visual inspection Pressure / Burst test Leak 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 16

17 General defects witnessed included: Surface detects Low melt temperature Inhomogeneous melt Weld misalignment Failure Investigation Visual Inspection Uneven weld gaps 17

18 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 Failure Investigation Microscopy 18

19 Failure Investigation X-ray Radiography & Computed Tomography HMXCT 225 X-ray Micro-focus machine (a) (b) 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 19

20 Failure Investigation Computed Tomography 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 20

21 Computed Tomography 21

22 Computed Tomography 22

23 Computed Tomography 23

24 Thermograph Inspection of Tooling & Packaging On tool core Part on conveyer belt On tool cavity Part in box (packaging)

25 Standards on Thermoplastics Welding 25

26 Available Standards 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 26

27 Approach 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 27

28 OEMs Overcoming Barriers Standard Bodies TWI and others Tier-1 28

29 Subject: Materials Sector: Manufacturing & Services Scope Committee: WEE/3 Welding of thermoplastic moulded components 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 Emerson JCB Research Branson Dyson Rofin-Baasel UK Mergon International Telsonic UK Ltd Cikautxo Group British Plastics Federation 29

30 Development of a Bespoke Course 30

31 Three-day training course and assessment, including practical demonstrations, to improve understanding of material selection, design and fabrication of moulded plastic components. 31

32 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 32

33 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 Joining processes Vibration welding Spin welding Hot plate welding Ultrasonic welding Infrared welding Laser welding Hot air and ultrasonic staking Adhesive bonding Inspection techniques Visual Microtoming SEM/EDX Ultrasonic X-ray radiography Thermography Optical microscopy Mechanical testing Tensile Flexural Flower test Compressive Creep Peel Fatigue Impact Pressure/burst test Nano-indentation Analytical testing DSC TGA DMTA FTIR GC-MS Rheometry Permeation 33

34 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: Summary 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 34

35 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 Summary Recommendation for regular QA checks and components qualification using these technique. 35

36 Thank you for your attention Joining Group 36