3D printing finds its 'sweet spot' through 'nifty shades of grey'

  • Engineers discover new technique to make 3D printing faster and more economical
  • Aerospace and automotive industries will benefit
  • New method could also provide boost to the sports footwear industry

A 'less is more' approach has enabled UK engineers to make 3D printed parts lighter and stronger, using methods that will also make 3D printing faster and more economical.

The technique uses a cutting edge process known as high speed sintering (HSS). Unlike commercial 3D printers that use lasers, HSS marks the shape of the part onto powdered plastic using heat-sensitive ink, which is then activated by an infra-red lamp to melt the powder layer by layer and so build up the 3D part.

Researchers from the University of Sheffield have discovered they can control the density and strength of the final product by printing the ink at different shades of grey and that the best results are achieved by using less ink than is standard.

"All HSS work to date has involved printing 100 per cent black, but this doesn’t get the best results,” explains Professor of Manufacturing Engineering Neil Hopkinson, from the University of Sheffield. “We found that there is a point at which, as the ink levels increase, the mechanical properties start to reduce. This enabled us to identify the ‘sweet spot’ at which you can gain maximum strength with the minimum amount of ink."

The researchers are able to manipulate the density of the material by up to 40 per cent, opening the door to the possibility of 3D printing parts with differing densities at different points. This would enable parts to have greatly reduced weight but equivalent mechanical strength – for example by having a dense outer shell and a lighter inner structure.

"3D printing has focused on optimising the shape of a part in order to reduce its weight and still retain its mechanical properties,” says Professor Hopkinson, who will announce the findings today (5 August 2014) at the Solid Freeform Fabrication Symposium in Austin, Texas. “Printing in greyscale will enable us to optimise the material instead, in a process that would be feasible for commercial manufacture. And by making parts with different densities out of one material, we can also make recycling more straightforward."

The ability to maximise strength while reducing weight means the technique would have obvious applications in the aerospace and automotive industries. But there are other sectors where it could bring benefits – one application envisaged by Professor Hopkinson is in sports footwear, where soles are currently made from dual density foams and could be printed in one material using the new technique.

Although still in development, HSS already holds great promise for industrial use as the process can be scaled to work at comparable speeds to conventional high volume processes, such as injection moulding. The new findings will further reduce the costs of manufacturing using HSS, by reducing the volume of ink energy required to make a product.

Additional information

Solid Freeform Fabrication Symposium
The 25th International Solid Freeform Fabrication Symposium is taking place 4-6 August 2014, at The University of Texas at Austin. Started in 1989 at UT Austin’s Cockrell School of Engineering, the ISFF Symposium is now the leading research-focused additive manufacturing conference in the world. Solid freeform fabrication encompasses technologies, such as 3D printing and selective laser printing, which are capable of producing complex freeform solid objects directly from a computer model of an object.

Engineering in Sheffield

The Faculty of Engineering at the University of Sheffield - the 2011 Times Higher Education’s University of the Year - is one of the biggest and best engineering faculties in the UK. Its seven departments include over 4,000 of the brightest students and 900 staff, and have research-related income worth more than £50M per annum from government, industry and charity sources. Its research income recently overtook the University of Cambridge, confirming its status as one of the best institutions in the world to study engineering. The 2008 Research Assessment Exercise (RAE) confirmed that two thirds of the research carried out was either Internationally Excellent or Internationally Leading.

The Faculty’s expertise is extensive – its academic departments and two interdisciplinary programme areas cover all the engineering disciplines. They are leaders in their fields and outstanding contributors to the development of new knowledge, with world-leading academics linking their research to the teaching of the engineers of tomorrow.

The Faculty has a long tradition of working with industry including Rolls-Royce, Network Rail and Siemens. Its industrial successes are exemplified by the award-winning Advanced Manufacturing Research Centre (AMRC) and the new £25 million Nuclear Advanced Manufacturing Research Centre (NAMRC).

The Faculty of Engineering is committed to ensuring students studying at Sheffield continue to benefit from world-class labs and teaching space through the provision of the University's new Engineering Graduate School. This brand new building, which will become the centre of the faculty´s postgraduate research and postgraduate teaching activities, will form the first stage in a 15 year plan to improve and extend the existing estate in a bid to provide students with the best possible facilities while improving their student experience.

Engineering in Sheffield

The University of Sheffield
With almost 25,000 of the brightest students from around 120 countries, learning alongside over 1,200 of the best academics from across the globe, the University of Sheffield is one of the world’s leading universities.

A member of the UK’s prestigious Russell Group of leading research-led institutions, Sheffield offers world-class teaching and research excellence across a wide range of disciplines.
Unified by the power of discovery and understanding, staff and students at the university are committed to finding new ways to transform the world we live in.

In 2011 it was named University of the Year in the Times Higher Education Awards and in the last decade has won four Queen’s Anniversary Prizes in recognition of the outstanding contribution to the United Kingdom’s intellectual, economic, cultural and social life.

Sheffield has five Nobel Prize winners among former staff and students and its alumni go on to hold positions of great responsibility and influence all over the world, making significant contributions in their chosen fields.


For more information please contact:

Amy Pullan
Media Relations Officer
The University of Sheffield
0114 222 9859