10 Options for RepRap 3D Printers' Electronics and Extruders
RepRap 3D printers use the popular open-source Arduino microcontrollers along with stepper motor controllers and motors and sensors for movement control. Some custom 3D printer boards integrate the Arduino's functions with the related items typically found on a 3D printing "shield" that attaches to the basic format. The best of these boards are:
RAMPS (RepRap Arduino Mega Pololu Shield): This is the original Arduino shield designed for multiple stepper motor control and for management of the extruder and built plate heaters. It includes all the electronics needed for a RepRap in one small package for low cost. The design is modular and offers plug-in stepper drivers and extruder control electronics.
RAMBo (RepRap Arduino-compatible Mother Board): The RAMBo is a modular all-in-one combination of the Arduino board and RAMPS shield. It offers convenience, reliability, and performance.
Sanguinololu: A popular build-it-yourself all-in-one board combining both microcontroller and stepper motor controllers. The board features flexible expansion ports and supports a variety of power sources.
RUMBA (RepRap Universal Mega Board with Allegro driver): A modular integrated board with six motor outputs and support for a variety of power sources. Its modules support LCD panels, external memory cards, and other add-on capabilities.
ELEFU-RA: RA is a 3D printer controller board and Elefu is a control panel; these two technologies work well together. As a developer-integrated electronics set the combination can plug in standard ATX computer power supplies.
RepRap extruders are important elements — they slide plastic filament incrementally into the heated hot-end, where a small amount of molten plastic is pushed out with each step. There are a number of approaches for making an extruder. The best include the following:
Geared: Some extruders include gears to slow the advance of filament and to gain greater control. If necessary, gears can also increase the force used to advance the filament into the hot-end.
Hobbed: A hobbed bolt (a bolt with teeth cut into its circumference) can be used like gears to slow the advance of the filament and to gain control. The hobbed bolt holds the filament against an idler wheel so its advance and retraction can be carefully controlled.
Bowden: Instead of forcing filament directly into the hot-end, like other extruders, a Bowden extruder forces the filament through a tube that connects the extruder and the hot-end. This approach keeps the extruder (and for non-Cartesian formats, the directly attached extruder motor) distant from the hot-end, which allows the hot-end to be lighter and more agile.
Syringe: A syringe can be used with a constrained strap to incrementally extrude paste or gel materials instead of the usual melted plastic.
Multi-color and dual: Multiple gearboxes and motors allow these extruders to advance multiple filaments into the hot-end at the same time. By using a variety of colored filament, and by varying the rate of extrusion for each color, you can use these extruders to create multi-colored prints.
Dual extruders, which simply combine two extruders side by side, are a common variation, useful for combining PVA (polyvinyl alcohol) or other soluble support materials with object filament material.