How to Use Granular Materials in 3D Printing
Granular materials are used in sintering, melting, and additive applications of binding glues in 3D printing. With them, you can create objects in a wide variety of materials, including glass particles, plastic powders, various metals and alloys — almost any type of material that can be rendered into a fine powder or granular state.
Commercial printers like the multi-color ZPrinter bind together plastic powders by using an ink-jet of liquid glue. To further solidify the resulting objects, post-processing typically includes a dip in cyanoacrylate resin to fill in the gaps between particles.
Without the resin filler, these objects typically lack the structural strength of other forms of additive manufactured products. The use of ink-jet binders allows for color mixing not possible through other forms of fused or sintered production. Other printers, like the VoxelJet system can use materials like granulated plastic and fine sand to create their results.
Sugar and salt
Artistic uses for food-printed items include more than simple extruded chocolate. Granular binding of sugar and salt provides the fine control of details needed to create complex structures like the sugar sculptures. Although sintering and melting of sugar granules is also a way to fabricate objects, the application of heat caramelizes most sugars and creates a color transformation during the process.
Creations for the aerospace, automotive, and medical fields require the use of material much stronger than plastic — typically these are biocompatible metals such as titanium, or materials that can withstand very high temperatures or provide great strength-to-weight ratios for racing cars or aircraft components.
Many materials like titanium and tungsten are difficult to use in traditional manufacturing, where their high melting points and other factors prevent easy integration using traditional manufacturing techniques. Using sintering and melting techniques by laser or electron beam, very high-resolution details can be achieved even when the materials don't alloy well or melt at matching temperatures.
Sand and natural granular materials
Silica and other minerals can be used to create items through additive manufacturing techniques that include granular binding, sintering, and melting of the individual granules into an aggregate natural form of glass.
Researchers like MIT's Markus Kayser are currently exploring the use of naturally occurring sand, fused using only light from the sun, to create sustainable objects and structures in some of the poorest parts of the world where structural materials are costly and difficult to obtain. Kayser’s Solar Sinter creates a rough, solid, natural-glass object from sand taken directly from the Egyptian desert without any further processing.