New High Speed Sintering 3D Printers May Hold The Key to Creating ‘Perfect’ Products

“Nothing is how it should be.”

While this is a very bold statement, when you stop and think about it, it may actually hold some truth, at least when you apply the theory to man-made products. For example, when you purchase a pair of running shoes, they may seem to be just right for your morning jogs around the neighborhood. Are they really though? Probably not. There are so many areas which could be improved upon, if we had just the right technology.

A new 3D printing process, called high speed sintering (HSS), may be just the means of manufacturing that we need in order to allow for the creation of products that are built the way that they “should” be.

Many of you are familiar with one of the more common industrial level 3D printing processes, called selective laser sintering (SLS), which has been being used for the past 30+ years. It works by using a laser which selectively melts (sinters) a powdered material, one layer at a time. After each layer is melted by the highly precise laser, another layer of powder is placed down and the process repeats itself until an object is fully formed.

HSS, works in a very similar manner to SLS, but instead of using a laser to melt the powder into shape, it uses a specialized heat-sensitive ink in its place. An inkjet printer prints carbon black ink onto the powder, one layer at a time, in the exact shape of that object. An infrared lamp is then run over the build bed, and the portion of the powder with the ink receives more energy, thus melting, and then being hardened into a solid object. This is because carbon black is an infrared radiaton absorbing material, which absorbs the energy from the lamp.

A High Speed Sintering Machine

While this method has been being used for quite a while, researchers at the University of Sheffield have found that they can actively control the strength and density of 3D printed objects, simply by printing this ink in different shades of grey. The shades of grey are determined by the amount of carbon black ink used. For example, for an extremely light shade of grey, researchers would print fewer black dots, thus leaving more white powder in between. The lighter the shade of grey (less carbon black), the less infrared energy that is passed through to the powder, thus creating a less dense object.

“All HSS work to date has involved printing 100 per cent black, but this doesn’t get the best results,” said 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. 3D printing has focused on optimising the shape of a part in order to reduce its weight and still retain its mechanical properties. 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.”

What this allows researchers to do, is 3D print parts of objects that use one material but have different densities. It allows for them to create objects that have stiffer, more highly dense sections, as well as light-weight, less dense sections within that same object.  At the same time, it also allows for the creation of parts that use one material, rather than multiple materials. Traditionally, more than one material has been needed when 3D printing parts which need to incorporate multiple characteristics. By changing the density of a single material, researchers are able to create a part out of that single material, just with different densities. This will make the recycling of the parts much simpler, as only one material needs to be recycled.

The team of researchers found that they were able to change the density of the material they used by up to 40 percent, which not only allowed for products of multiple densities and properties, but it also has the potential of saving a ton of money.  These researchers also said that they are working on a more highly advanced HSS machine that will use a true grey-scale, instead of the dot method which the current machine uses. They hope this will allow them to make even stronger, more complex parts in the future.

Without a doubt this technology will allow for more sophisticated parts to be produced for the aerospace and automotive industries. At the same time, it should also make its way to other industries such as shoe manufacturing, as well the creation of sports equipment, such as protective gear, and even apparel. The ability of these machines to create products that have a minimal weight to them, while maximizing strength, will certainly have uses within many industries. What do you think? Will HSS be used more than SLS in the future? Discuss in the High Speed Sintering forum thread on 3DPB.com.  Check out the video below where researchers explain this process in more detail.