3D-Printing Ink in Shades of Gray Maximizes Part Strength While Reducing Weight

Unlike commercial 3D printers that use lasers, high speed sintering (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 UK's 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. The researchers are able to manipulate the density of the material by up to 40 percent, 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. The ability to maximize strength while reducing weight means the technique would have definite applications in the aerospace and automotive industries.

Transcript

00:00:01 [Music] additive manufacturing is essentially the process of joining materials to make objects from 3D model data so computerated design or CAD data uh this is usually done layer upon layer what highs speeded centering does is replaces laser system with an infrared lamp and an inject print head we have a bed of powdered

00:00:27 material and then what we do is input thermal energy into that beds in the form of an infrared lamp the inkject print head prints an ink containing carbon black which is an infrared radiation absorbing material so we print ink in a desired cross-section and then an infrared lamp will pass over the build bed and the cross-section with the ink will receive more thermal energy

00:00:45 than the rest of the build bed due to the carbon black and KN this into the powder and then what we would do is repeat the process so deposit a fresh L powder and repeat the process until we have a completed 3D object what we've done in this research is change the amount of ink in the cross-section what we've done is having various densities of black dots with spaces in between

00:01:03 which changes the amount of carbon black within the cross-section what we found was that at the parameters commonly used for manufacturing Nylon 12 we're actually using an excess of ink by printing in fully black we observe much higher tensil properties so ultimate tensile strength elongation of breaking Young's modulus by printing at lower ink levels

00:01:21 So This research will allow us to produce Parts with much higher mechanical properties and we've seen before allowing it to compete with processes such as injection molding whilst at the same time reducing our ink consumption which saves on relatively expensive ink costs so there are a number of applications for this technology one obvious one is to make

00:01:37 use of the fact that we can start making parts that have different properties throughout different parts of the part so for example we could make things like uh outsoles for running shoes which are quite stiff in certain areas and relatively flexible in other areas and we can do that all with one material so another potential area to take advantage of this technology is the fact that we

00:01:57 can make paths that have different densities so for example we can make parts that are quite stiff and dense on the outside but low weight in the middle so we can start light weighting parts for uh transport applications in automotive and in Aerospace for example from a sustainability perspective this is also very exciting because it allows us to make parts with

00:02:17 a variety of different properties but all using a single material so this means at the end of life uh recycling or reusing of a material is far easier than if we'd had to use lots of different materials in a single part one of the key findings of this technology was how we could use grayscale to change the properties of Parts but the grayscale approach that we

00:02:36 used was one that we call dithering where we make lots of little dots on the part uh our next generation of machine that we're going to make will do what we call True grayscale by printing different sizes of drops and that will allow us to fine-tune this process to optimize our process parameters further and increase part strength we hope um but also to help to uh increase the

00:02:55 quality of parts we make overall