Joining process consultancy

Technical appraisal
Welding coordination
Joining process selection
Statistical process optimisation
Litigation
Surface engineering
Cutting
Prototype manufacture

Technical appraisal

TWI's expert staff have a unique blend of technical and practical skills and are ideally equipped, therefore, to review manufacturing practices independently. By carrying out a structured assessment, the experts can identify areas which need management attention. An appraisal can cover any or all aspects of joining technology, engineering materials and design, manufacturing systems and training and education.

Micrograph of plastics butt weld The following subject areas may be considered:

Safety
Design
Selection of materials and consumables
Effective use of joining processes
Layout and materials handling
Skills, training and qualification
Quality systems, documentation and procedures

Welding coordination

EN 729 'Quality requirements for welding - Fusion welding of metallic materials; Part 1. Guidance for Selection and Use states "welding exerts a profound influence on the cost of fabrication and quality of a product. It is important, therefore, to ensure welding is carried out in the most effective way and that appropriate control is exercised over all aspects of the operation". Furthermore, EN 729 calls up EN 719 ' Welding co-ordination. Tasks and responsibilities' which requires the appointment of competent and, in some instances, appropriately qualified welding personnel to perform the tasks that will insure weld quality and reliability in service.

TWI has a team of engineers who hold (EWF) status that includes European Welding Engineer, European Welding Technologist and European Welding Specialist. They are, therefore, able to fulfil the roles defined in EN 719.

Joining process selection

TWI has a team of engineers available to guide your company through a project and advise on the most suitable processes and equipment for a specific job. Long experience, technical expertise, practical skills and access to information databases such as Weldasearch, enable TWI to provide comprehensive advice based on:

Economic considerations
Required joint integrity
Operating conditions and performance
Technical excellence and state-of-the-art technology

Litigation

In cases where inadequacies in the joining process have resulted in loss or damage, TWI can conduct an investigation into the cause and can prepare and provide expert evidence in court if necessary. Areas covered could include disputes involving welding procedure and/or equipment.

TWI has an in-house procedure for conducting such investigations. A principal investigator, who will be a professionally qualified process engineer, will be appointed to lead each investigation and will draw on additional TWI expertise as required.

Joining process investigations are tailored to the objectives of each client, whether these be commercial (breach of contract, insurance, liability), criminal prosecution (health and safety incidents) or technical (understanding what happened and preventing reoccurrence).

Clients may expect a clear report from a TWI joining process investigation, describing the circumstances, identifying the causes, and drawing conclusions. Reports are written and presented in a way that could be used as court evidence should this be necessary.

Where litigation is involved, TWI has standard terms of engagement and gives litigation the priority it requires. The appropriate TWI experts have received training in Expert witness work from the Academy of Experts. A senior manager at TWI reviews projects where litigation is in progress or a prospect to ensure clients receive the best service.

Surface engineering

Virtually all components or finished products manufactured in the UK are subject to some form of surface engineering; from paint, electroplating or heat treatment to welded or sprayed overlays. TWI specialises not only in the thicker coating technologies, such as welding and spraying, but also in thinner coatings, such as power beam surface treatment and sol-gel. TWI has equipment and facilities for providing R&D services, consultancy, demonstrations and training for surface engineering activities which includes:

Arc weld surfacing
Thermal spraying (including high velocity oxyfuel spraying)
Friction surfacing
Laser surfacing and heat treatment
Electron beam
Resistance surfacing
Spark deposition
Sol-gel
Non-destructive testing
Metallography
Wear and corrosion testing
Adhesion testing

TWI has wide experience of the application of surface engineering to meet industry's needs, as demonstrated by a selection of the current collaborative projects:

Application	Industry sector
Dielectric coatings	Electronics
Coatings for press tooling	Automotive
Corrosion resistance	Petrochemical, marine
Soft metal bearings	Automotive
Laser holography for surface treatment	Furniture, electronics, automotive

Cutting

Cutting is an important part of the fabrication process and most fabricated components are subjected to some form of cutting process during their fabrication lifetime. TWI has the experience to provide R&D services, consultancy or demonstrations with the following cutting processes: Laser cutting photo

Plasma
High Tolerance Plasma Arc Cutting (HTPAC)
Abrasive Water Jet (AWJ)
Carbon dioxide laser
Nd:YAG laser
2kW fibre optic laser
CO laser
Oxy-fuel cutting

TWI has a wide experience in cutting to meet industry's needs. Recent projects undertaken by TWI with respect to cutting processes are as follows:

Centres demonstrating best practice cutting
Enhanced cutting process development
Comparison of cutting processes
Investigation into quality of profiled cut edges
Fatigue properties of thermally cut edges
Development of techno-economic software for cutting processes
Oxy-fuel cutting of medium alloyed steels
Comparison of fuel gases for oxy-fuel cutting

Prototype manufacture

TWI has a number of facilities which are almost unique. It is able to use these to assist member companies for prototype or small batch manufacture, where the numbers of components to be made are too few to justify the member company in investing in the necessary equipment itself. These facilities are as follows:

Electron beam welding

One non-vacuum/reduced pressure and three full vacuum electron beam welding facilities are available. The non-vacuum/reduced pressure machine has a 10m (long) x 8m (wide) x 6m (high) chamber, an accelerating voltage of 300kV and a power of 150kW. As an example this can weld 50mm thick steel at atmospheric pressure and at a speed of 1m/minute. The largest of the full vacuum facilities has a chamber 7m (long) x 3.5m (wide) x 3.5m (high), an accelerating voltage of 150kV and a power of 100kW. This can weld 300mm thick steel at 50mm/minute.

Friction welding

A linear friction welding machine is available capable of making joints in rectangular section. Section size depends on material, but, as an example, joints up to 2,000sqm can be made in titanium alloy.

There is a series of continuous drive rotary friction welding machines capable of joining mild steel in diameters up to 125mm.

Other more specialised machines (orbital, friction stir, etc) are also available.

Metal spraying

A number of state of the art high velocity oxy-fuel (HVOF) spraying systems can be coupled to a six axis robot to provide coatings for wear or corrosion resistance or for bio-medical, electronic or thermal barrier purposes.

Laser welding

Resistance welding

Hot Isostatic Pressing (HIP) / Diffusion Bonding (DB)

Three systems available: induction heating under vacuum; radiant heating under vacuum (to 1850°C); radiant heating under inert gas (to 2000°C)

PC driven Hot Isostatic Press (HIP)

Max temperature	2000°C
Max pressure	2000 bar Ar (30,000 psi)
Can be used under vacuum
Workpiece size	75mm diameter 100mm high
or	65mm diameter 150mm high

A cold isostatic pressing facility is also available.

Brazing

Four controlled-atmosphere furnaces available (vacuum or inert gas), heating under radiant or induction conditions up to temperatures of 1850°C. Part sizes of up to 250x250x250mm can be accommodated. If required, components may be pre-metallised in-house via sputter (plasma) deposited coatings.

Microtechnology

Wedge/wedge and ball/wedge wire bonders are available capable of handling wire diameters in the range 7-75 micrometres or ribbon sizes of 25 x 8 up to 75 x 25 micrometres.

Also available are soldering (including lead-free), resistance welding, capacitor discharge welding, resistance seam sealing for hermetic packaging, laser welding and bonding, and ultrasonic welding.

Testing facilities available for components are, shear and wire tensile testers, corrosion tester, humidity chamber, autoclave tester, bubble tester, microfocus, X-ray and fine scale leak testing.

Plastics welding

Wide range of plastics welding techniques, which can be divided into assembly and fabrication.
Assembly includes: ultrasonics, vibration (capable of welding sections up to 8500 sqmm at loads of 1N/sqmm), spin, hot plate (capable of welding sections up to 26,000 sqmm at loads of 0.3N/sqmm), film sealing, RF, implant techniques.
Fabrication includes: hot gas, extrusion.
In addition, experimental welding rigs including: laser, microwave, forced mixed extrusion welding (FMEW), friction stir and infra-red.

Adhesive bonding and composites engineering

TWI offers a unique service for adhesive bonding and composites engineering; a one-stop-shop where all aspects of the structure can be assessed. TWI's multi-disciplinary team agree a brief with you to include: conceptual design; lifetime costs; value for money; joining technology; design for manufacture; appearance; factors important to the manufacturer (timescale, unit cost of production, etc.); testing and finally development costs. This approach has served a variety of clients in successfully introducing change.