Unlocking Complex Metal Geometries with Additive Manufacturing

A breakthrough in our ability to construct complex metal geometries signals a new dawn in precision components.

Given its remarkable properties, you could be forgiven for questioning how mankind was able to ever start working with tungsten. Its density is around 1.7 times that of lead and it has the highest boiling and melting points of any element in the world.

Even as recently as 100 years ago it was essentially unusable, such are its extraordinary properties. Its extremely high melting point means that it has never been practical to produce complex tungsten components by casting, as can be done with the likes of iron, aluminium and other common metals.

Yet could recent advancements in manufacturing techniques make the leap? 

Our group of experts that have recently begun to create intricate geometrical shapes from tungsten using additive manufacturing techniques think so. The results have been radical.

The Wolfmet tungsten team has developed a highly specialised metallurgy process, essentially fusing successive layers of tungsten powder to build a finished component.

The method is ideal for the manufacture of high-precision components such as collimators and radiation shields in CT, SPECT, MR and X-ray imaging systems. Furthermore, the technique allows components to be produced cost effectively in days and weeks rather than months.

The technique, also called Selective Laser Melting (SLM) or Direct Metal Laser Sintering (DMLS), is an additive manufacturing technique which, for the first time, enables the production of individual metal components with complex geometries without the need for part-specific tooling. The additive manufacturing process uses the high energy laser to shape the layers of metallic powders to form three-dimensional components.

The geometries that can be achieved are not possible using traditional machining, otherwise known as subtractive manufacturing. By removing this design limitation, the possibilities are almost endless. When tungsten’s excellent radiation absorption combined with good thermal resistance is added into the mix, the possibilities become genuinely exciting.  

Improving radiation dose imaging

This was the case for Dosimetry, the measure of radiation during cancer treatment, and the reason why for the last six years universities, labs and hospitals have been working with the team at Wolfmet to carry out extensive research and development activities to test the limits of the new techniques and resulting components.

In molecular radiotherapy treatment of thyroid cancer, it has traditionally not been possible to accurately measure the radiation absorbed by patients during the procedure. As a consequence, only limited information regarding the success of radiotherapy treatment has been available. This presents obvious difficulty for health practitioners and patients alike. Could a complex component manufactured from tungsten hold the answer?  

The University of Liverpool’s Department of Physics, and The Royal Marsden and Royal Liverpool University Hospitals have been working to develop an imaging system (known as DEPICT) to better measure the radiation dose; their aim is to provide a more accurate, personalised treatment of thyroid cancer.

Central to the imaging system’s scanner is a collimator. This is a device which aligns the beams of radiation emitted from the patient so that they are directed onto a detector. The radioactive iodine is ingested by the patient in liquid or capsule form, and then gamma rays are emitted in all directions through the patient, yet only the rays which are aligned with the collimator holes will make it through to the detector. The data received can then be converted into an image on a computer screen.

Previously, lead was the preferred material for collimators. However, tungsten is much more efficient than lead at screening unwanted gamma beams. Additive manufacturing now allows the collimators to be made in tungsten, resulting in much clearer images of the radiation dose received by the patient.

The implications could be significant; the ability to individualise treatments is expected to reduce healthcare costs by providing speedier and more efficient treatments. Importantly, it is hoped that this development will increase rates of successful cancer treatment, leading to improved quality of life and health for those patients. The same principles could mean huge advances in sectors outside healthcare.

A World of Possibilities

Airport and cargo scanners used to examine the contents of transport containers could be upgraded in the same way. The scanners often have tungsten grids which screen out stray X-ray beams to give a more accurate image. These grids are built up manually from many individual tungsten sheets which could soon be replaced by monolithic SLM parts.

The geometrical detail, which can be incorporated into the tungsten, could now mean that increasingly complex components can be created. In future this means it may be possible to provide handheld, lightweight medical scanners which can be used to home in on individual organs whilst producing similarly accurate images.

Tungsten properties are well known, but only now can they be harnessed more fully through this new manufacturing method, allowing us to further drive improvements in the world around us.

For more details contact our team at [email protected]