Various manufacturers are already 3D printing metal. This allows creating low-volume parts cheaply and relatively quickly, because they don’t have to develop tooling for these operations. However, scientists say that the process could be improved and the quality of the finished product could be significantly better. One way of achieving that – vibrating the whole thing.
Scientists from the RMIT University’s School of Engineering say that by using ultrasound they can vibrate metal alloy grains into tighter formation during 3D printing. You are actually familiar with the process already. When you are filling a jar with sugar (or any other loose material really) you can fit more of it if you tap the jar. This introduced tiny vibrations to the mix, allowing particles to settle down in empty space. This makes everything more dense.
For you it means that more sugar fits in the jar. For scientists – the metal part ends up being more dense and stronger. Why?
Metals are made from grains – crystals that form during manufacturing of alloys. Conventional 3D printing produced large crystals, which is less than ideal, because the weakest spots are in the lines between those crystals. By shaking the object with ultrasound during the 3D printing process scientists achieve smaller grain formations, which are stronger, because these potentially weaker areas are not lined up. Researchers tested this and found that those parts produced using the vibrating method exhibit a 12% improvement in tensile strength and yield stress.
Scientists can also see the benefit of ultrasonic vibration, because they can turn it on and off during the 3D printing process, which produces an object, which has a layer of stronger metal. Researchers tested this method with the Ti-6Al-4V (titanium alloy commonly used for aircraft parts and medical implants) and the Inconel 625 (nickel-based superalloy often used in marine and petroleum industries). And both worked great.
Ma Qian, supervisor of the project, said: “Although we used a titanium alloy and a nickel-based superalloy, we expect that the method can be applicable to other commercial metals, such as stainless steels, aluminium alloys and cobalt alloys. We anticipate this technique can be scaled up to enable 3D printing of most industrially relevant metal alloys for higher‑performance structural parts or structurally graded alloys”.
Metal 3D printing has a variety of applications. It is already used in niche car manufacturing, but it would be especially useful in making medical implants and replacement parts for industrial machinery. So hopefully ultrasound is an inexpensive solution to make 3D printed objects stronger.