Visualising and optimising shield gas flows during high-value manufacture

Many metal manufacturing processes, such as welding and additive manufacture, use shield gas to protect the molten and solidifying metal surfaces from the atmosphere. In carbon steels, nitrogen and oxygen can create non-metallic inclusions that weaken the weld metal. In stainless steels, poor shielding can lead to discolouration of the weld area and increased likelihood of corrosion. The shield gas, typically a mixture of carbon dioxide (CO2) and argon, flows over the heated region to protect it from the atmosphere.

Ultrafast welding of stacked gallium arsenide wafers

Direct laser welding has the capability to ignore the difficulties in bonding of wafer structures in non-linear materials. Rather than growing a series of individual layers to precise dimensions a single wafer of GaAs can be polished to an appropriate, thickness, diced and layered to form an appropriate structure. In this arrangement optical contact (i.e. Van der Waals) holds the layers together. This temporary bonding can then be re-enforced through ps laser welding [3]. Using this process there is little technical restriction on the size of devices which can be constructed.

Surface Engineering with Lasers

High power lasers can be used to produce many different types of surface structures, including optically absorbing nano-structures; controllably oxidised surfaces (markings of different colours); polished surfaces and self-organised nano-gratings.  These different process regimes are dependent on the laser parameters (in particular pulse length, pulse shape, spatial beam shape, intensity). 

Photoelasticity of opaque objects

This project is concerned with measuring the stress-induced birefringence in materials that are opaque at visible wavelengths. We will use THz illumination between 0.3 and 1.5 THz where some fraction is transmitted through a range of non-polar materials including ceramics, plastics and composites. Measuring the stress-induced birefringence will provide information on the internal stress distribution in real components that are opaque at visible wavelengths, removing the need to model it in transparent plastic.

Multi Laser Selective Laser Melting

Additive Manufacturing methodologies are beginning to achieve commercial uptake due to the advantages they bring in terms of part complexity, design freedom and material economy. Selective Laser Melting is one such technology which utilises a scanning galvanometer system to divert a process laser across a metallic powder bed in order to create complex 3D components. In order for the uptake of this technology to continue improvements in build speed and material microstructure coupled with reduction in part defects and process uncertainties must be achieved.

Laser structuring of glass for optical component manufacture

The project is focused around the use of ultra-short picosecond pulsed lasers for the machining and structuring of glass to enable the manufacturing of optical components.  PowerPhotonic currently manufacture freeform and micro-optical components by machining and polishing of fused silica glass using CO2 lasers.  Ultra-short pulse processing at shorter wavelengths offers the prospect of processing a wider range of materials, and generating structures with higher spatial resolution.

Laser micro-sculpting of holographic security markings on high-value metal components

This project will investigate a novel laser marking process based on the laser-micro-sculpting approach, known as ‘YAGboss’.  This process was developed by Renishaw plc and Heriot-Watt University initially for the generation of sinusoidal gratings (scales) on metals for high-accurate positioning encoders and recently for the generation of holographic structures directly embossed onto the surface of 304-grade stainless steel.

Laser hybrid welding of pipeline steels

Laser arc hybrid welding, owing to the complimentary features of the two different heat sources, offers transformational improvement in welding of pipelines.  The main benefits are deep penetration and fast processing speed, owing to the highly focused laser energy and improved gap bridging ability from the arc based power source. This enables significant increase of productivity and reduction of welding distortions, as compared to traditional arc-based welding techniques. In pipeline welding the welding time is a major factor in determining the build rate of pipelines.

Laser finishing - improving the surface finish of powder bed and wire based additive manufacture components

This project will investigate the feasibility of using laser processing for post-machining of parts manufactured by a powder bed and wire based additive manufacturing (AM) processes.  A range of different laser ablation and smoothing approaches will be tested for materials of interest for AM processes, including stainless steel, cobalt-chrome alloy, aluminium and titanium.  Although the project will initially focus on post-processing, in-situ inter-processing approaches will also be explored.

High energy amplifiers for ultrafast lasers

There have been a growing number of manufacturing processes utilising ultra-short-pulse laser beams with pulse durations in the 0.5 to 10 ps range. An important emerging application is the micro-processing of transparent materials, for example glass cutting and surface structuring. Processing of high-value components with ultra-short-pulse lasers has been identified by major industry role players as a key market for which laser technology must be further developed to the kW-level average output power in order to increase production throughput.

Flexible process for the manufacture of diffractive optical elements by laser processing

This project is to develop a laser-direct write technique for the fabrication of optically diffractive surfaces on the surface of stainless steel and other metals, for application in metrology.  The project builds on previous work in which the basic process has been demonstrated; in this project it is being developed into a process where sufficient control can be achieved to make it suitable for medium scale production.


Diagnostics and process improvement of ultrafast ps laser welding applications

Ultra-fast ps welding is in principle a simple procedure. Two materials are brought into close proximity and a laser is focused onto the interface. Absorption at the interface produces a plasma that, when cooled, forms the weld. In practice laser-material interactions and particularly the absorption of the radiation are complex; this leads to a process which is hard to predict and difficult to optimise.  At present we are researching the capability of ps welding to bridge gaps in both similar and dissimilar materials.

Development of high-density interconnect laser material processing techniques for manufacturing printed circuit boards

Mobile electronic devices, such as smartphones & tablet computers, rely heavily on the continued miniaturization of components to allow more functionality in smaller devices. Industry expects Printed Circuit Boards (PCBs) with conductive paths narrower than 10μm to mature within the next three years.

ARMoR - add, remove, measure or repair

Modern manufacturing is seeing migration of mass production out of traditional European strongholds to low cost economies. However, UK manufacturing industry can continue to be globally competitive by focusing on manufacture of high value customised parts providing significant added value. In order to maintain an advantage in this field there is an urgent need to develop processes which underpin manufacture of such specialised parts.

A novel ultrafast laser tool for rapid precision machining of high value materials

Ultrashort pulse laser technology is rapidly evolving as a key enabling technology for many high precision, high value industrial manufacturing applications. However, commercial systems are limited in average power and so are unable to achieve the necessary speeds for some key volume manufacturing applications. This project will develop, demonstrate and optimise a laser system technology which is suitable for many such industrial applications.