What we do

We manufacture metal 3D printers, which use the newest 3D printing process - Selective Powder Deposition (SPD).

How Selective Powder Deposition works

Overview

Selective Powder Deposition (SPD) is a new 3D printing process, which you can use to print metal, glass, ceramic, and composite materials. There are 2 main variants: infilling and sintering. With infilling you get a 100% solid object, and with sintering you usually get a porous object. The best metal 3D printer video helps visualizing it.

Variant 1 - SPD with infill

First, the 3D printer selectively deposits build and support powders into a crucible. When it finishes filling the whole crucible, you add some infill material, and bake it in a kiln. The temperature in the kiln should be above the melting temperature of the infill, but below the melting temperature of the powders. When the infill melts, it soaks the build powder, but it doesn't soak the support powder, because the support powder is chosen such that it's not wettable by the infill.

To prevent metal oxidation, the atmosphere in the crucible should be reducing. The easiest way to create a reducing atmosphere is to place some carbon (metallurgical coke) or hydro-carbon (plastic) in the crucible. But some metals require a controlled atmosphere furnace with hydrogen and argon.

After the infilling, if you cool down the crucible quickly - you'll get a composite material, because the atoms of the build powder and the infill didn't have enough time to mix. But if you hold it at high temperature for a while - the atoms of the build powder and the infill will diffuse and mix with each other, so you'll get a uniform alloy. The time required for diffusion depends on the metals and temperature. For example, at 790°C, copper+tin can mix uniformly in 2 hours and you'll get bronze. But copper and tungsten, even at 1090°C, won't alloy much even in a day, so you'll get a composite.

When it cools down, remove it from the kiln, and clean it with a wire brush or sand blaster.

Variant 2 - SPD with sintering

The 2nd variant, sintering - is even simpler - you just don't add any infill, and bake it at the temperature sufficient to sinter the build powder. Note that sintering causes shrinkage and warping. By changing the baking temperature, you can influence the amount of shrinkage, warping and porosity. With sintering it's hard to achieve 100% density with pure metals (those that have a single melting point), but it's easy with glass, and some metal alloys, though it requires a vacuum furnace.

Materials

In theory, SPD can be used to 3D print almost any material. Actually, the printer itself is material agnostic, and can pour any powder that flows through a small hole. But when it comes to baking, some materials are easier than others. For the details see Which materials can be 3D printed with SPD

Comparison of metal 3D printing methods (2024)

¹Localized heating and cooling cause internal stress, which can cause warping, so additional support structures are needed for most shapes.

²With sintering, shrinkage and porosity can be traded for one another - reducing the particle size or increasing the temperature or time - results in lower porosity and higher strength, but higher shrinkage. And vice versa.

³With FDM and Binder Jet sintering, the powder particle size must be relatively small, so the shrinkage is usually high, but porosity can be low and strength medium-high. Sintering in argon rather than air - increases the strength, but also increases the price.

⁴With SPD, the powder particle size must be relatively large, so when the powder is non-viscous the shrinkage is usually low, but porosity is high and strength is low.

⁵Glass (and some alloys) become viscous at high temperatures, so sintering them naturally results in low porosity. And when using a vacuum furnace - 0% porosity and full strength can be achieved. This is very useful for glass - it makes it transparent.