[NOTE: Please see our update regarding this printer: Finding the best dirt-cheap, field-tough 3D printer for science and conservation work: six months later.]
Somewhere between the Prusa printers with their paired z-axis motors and the cantilever systems with a gantry arm spanning the x- or y-axis with only a single point of support, lies printers like the Creality Ender-3. Where a more conventional 3D printer uses rails and linear bearings to drive the axes, these printers forgo the standard model.
You won’t find a single linear bearing on the Creality Ender-3 or it’s clones. Instead, rubber rollers pass through v-slot grooves in extruded aluminum, removing the need for complex gantry systems.
This is an incredibly robust method for cutting costs, but it is not a compromise. Roller and v-slot printers can be just as precise as their rail and bearing counterparts, and the mandated all aluminum construction makes them strong and durable.
For a general-use field-ready 3D printer, you could not do much better than the Creality Ender-3.