Compact, inexpensive 3D printers typically utilize a process known as fused filament fabrication (FFF). This involves heating a plastic filament to its melting point, then extruding it through a nozzle. Successive layers of the molten plastic are deposited one on top of the other, forming a single solid object as they cool and fuse together.

According to US Army engineers, though, items printed in this fashion tend to be too structurally weak for rough-and-tough use by soldiers in the field. This is a shame, since if troops were able to carry small, cheap 3D printers with them, they could make parts and tools onsite as needed. And although there are printers that use non-FFF techniques to produce stronger objects, those machines are large and costly, making them impractical for field use.