The RepRap project is an initiative to develop a 3D printer (RepRap, short for "replicating rapid prototyper") that can print most of its own components. As an open design, all of the designs produced by the project are released under a free software license, the GNU General Public License.
RepRap uses a variant of fused deposition modeling, an additive manufacturing technique. The project calls it Fused Filament Fabrication (FFF) to avoid trademark issues around the "fused deposition modeling" term.
To date, the RepRap project has released four 3D printing machines: "Darwin", released in March 2007, "Mendel", released in October 2009, "Prusa Mendel" and "Huxley" released in 2010. Developers have named each after famous biologists, as "the point of RepRap is replication and evolution".[1]
Due to the self-replicating ability of the machine, authors envision the possibility to cheaply distribute RepRap units to people and communities, enabling them to create (or download from the internet) complex products without the need for expensive industrial infrastructure.[2] They intend for the RepRap to demonstrate evolution in this process as well as for it to increase in number exponentially.[3][4]
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RepRap was founded in 2005 by Dr Adrian Bowyer, a Senior Lecturer in mechanical engineering at the University of Bath in the United Kingdom.
As an open-source project designed to encourage evolution, many variations exist, and the designer is free to make modifications and substitutions as they see fit. However, RepRap 3D printers generally consist of a thermoplastic extruder mounted on a computer-controlled Cartesian XYZ platform. The platform is built from steel rods and studding connected by printed plastic parts. All three axes are driven by stepper motors, in X and Y via a timing belt and in Z by a leadscrew.
At the heart of the RepRap is the thermoplastic extruder. Early extruders for the RepRap used a geared DC motor driving a screw pressed tightly against plastic filament, forcing it past a heated melting chamber and through a narrow extrusion nozzle. However, due to their large inertia, DC motors cannot quickly start or stop, and are therefore difficult to control with precision. Therefore, more recent extruders use stepper motors (sometimes geared) to drive the filament, pressing the filament between a splined or knurled shaft and a ball bearing.
RepRap's electronics are based on the popular open-source Arduino platform, with additional boards for controlling stepper motors. The current version electronics uses an Arduino-derived Sanguino motherboard, and an additional, customized Arduino board for the extruder controller. This architecture allows expansion to additional extruders, each with their own extruder controller.
The first publicly-released RepRap, Darwin, has an XY gantry mounted above a moving Z-axis print bed. Darwin's Z axis is constrained by a leadscrew at each corner, all linked together by timing belts to turn in unison. Electronics are mounted on the steel supports of its cuboid exterior, and on a second platform at the base. In an effort to minimize the number of non-printed components (or "vitamins"), Darwin uses printed sliding contact bearings on all of its axes.
Mendel replaced Darwin's sliding bearings with ball bearings, using an exactly constrained design that minimizes friction and tolerates misalignment. It also rearranged the axes, so that the bed slides in the horizontal Y direction, while the extruder moves up and down and in the X direction. This makes Mendel less top-heavy and more compact than Darwin, while also removing the overconstraint of Darwin's four Z axis leadscrews. The build envelope for Mendel is 200 mm (W) × 200 mm (D) × 140 mm (H) or 8" (W) × 8" (D) × 5.5" (H).[12]
RepRap has been conceived as a complete replication system rather than simply a piece of hardware. To this end the system includes computer-aided design (CAD) in the form of a 3D modeling system and computer-aided manufacturing (CAM) software and drivers that convert RepRap users' designs into a set of instructions to the RepRap hardware that turns them into physical objects.
Two different CAM toolchains have been developed for the RepRap. The first, simply titled "RepRap Host", was written in Java by lead RepRap developer Adrian Bowyer. The second, "Skeinforge", was written independently by Enrique Perez. Both are complete systems for translating 3D computer models into G-code, the machine language that commands the printer.
Virtually any CAD or 3D modeling program can be used with the RepRap, as long as it is capable of producing STL files. Content creators make use of any tools they are familiar with, whether they are commercial CAD programs, such as SolidWorks, or open-source 3D modelling programs like Blender.
RepRaps print objects from ABS, Polylactic acid, and similar thermopolymers.
Polylactic acid has the engineering advantages of high stiffness, minimal warping, and an attractive translucent colour. It is also biodegradable and plant-derived.
Unlike in most commercial machines, RepRap users are encouraged to experiment with printing new materials and methods, and to publish their results. Methods for printing novel materials (such as ceramics) have been developed this way.[13]
The RepRap project has not yet identified a suitable support material to complement its printing process.
Printing electronics is a major goal of the RepRap project so that it can print its own circuit boards. Several methods have been proposed:
Other 3D printer designs (such as the commercial Makerbot) and parts constructed by other means (such as Meccano) may be used to bootstrap the RepRap process by building RepRap parts. Many such machines are based around RepRap designs and use RepRap electronics. These are generally known by the name "RepStrap" (for "bootstrap RepRap") by the RepRap community. A RepStrap is any open-hardware rapid prototyping machine that makes RepRap parts and is itself made by fabrication processes which aren't under the RepRap umbrella yet.[16] Some RepStrap designs are similar to Darwin or Mendel, but have been modified to be made from laser cut sheets or milled parts.[17][18] Others, such as the Makerbot, share some design elements with the RepRap (especially electronics) but with a completely reconfigured mechanical structure.
Although the aim of the project is for RepRap to be able to autonomously construct much of its mechanical components in the near future using fairly low-level resources, several components such as sensors, stepper motors or microcontrollers are currently non-replicable using the RepRap's 3D printing technology and therefore have to be produced independently of the RepRap self-replicating process. The goal is to asymptotically approach a 100% replication over a series of evolutionary generations. As one example, from the onset of the project the RepRap team has explored a variety of approaches to integrating electrically conductive media into the product. Success on this initiative should open the door to the inclusion of connective wiring, printed circuit boards and possibly even motors in RepRapped products.[19] Variations in the nature of the extruded, electrically conductive media could produce electrical components with different functions from pure conductive traces, not unlike what was done in John Sargrove's sprayed-circuit process of the 1940s (also known as Electronic Circuit Making Equipment or ECME). Printed electronics is a related approach. Another non-replicable component is the threaded rods for the linear motions. A current research area is in using replicated Sarrus linkages to replace them.[20]
Project sponsors include:
The stated goal of the RepRap project is to produce a pure self-replicating device not for its own sake, but rather to put in the hands of individuals anywhere on the planet, for a minimal outlay of capital, a desktop manufacturing system that would enable the individual to manufacture many of the artifacts used in everyday life. From a theoretical viewpoint, the project is attempting to prove the hypothesis that "Rapid prototyping and direct writing technologies are sufficiently versatile to allow them to be used to make a von Neumann Universal Constructor".[21]
The self-replicating nature of RepRap could also facilitate its viral dissemination and may well facilitate a major paradigm shift in the design and manufacture of consumer products from one of factory production of patented products to one of personal production of un-patented products with open specifications. Opening up product design and manufacturing capabilities to the individual should greatly reduce the cycle time for improvements to products and support a far larger diversity of niche products than the factory production run size can support.[22]