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Unfortunately, this submission was rejected on the grounds that an entry already exists on Wikipedia. The authors have been invited to merge their draft replacement into the existing article instead.

Because this article represents a complete history and timeline of the RepRap project, written by the people who were directly involved with the project, we think there is great value in sharing this draft replacement with our readers.

Our thanks to Dr. Adrian Bowyer for his permission to reproduce the text and images.

Entry Start

The RepRap project started as a British university initiative to develop a 3D printer that can print many of its own components and be low-cost, but it is now made up of hundreds of collaborators world wide.^[1] RepRap (short for replicating rapid prototyper) uses an additive manufacturing technique called fused filament fabrication (FFF) to lay down material in layers: a plastic filament is unwound from a coil, melted and fused to manufacture a part. This process was originated and is exploited commercially by Stratasys, starting in the early 1990s.

RepRap is an open design, so all of the intellectual property produced by the project is released under a free software license, the GNU General Public License.^[2]

Owing to the partially self-replicating ability of the machine, some people envision the possibility of cheaply distributing RepRap 3D printers to people and communities, enabling them to create (or to download from the Internet) products without the need for expensive industrial infrastructure (this is known as distributed manufacturing)^[3]^[4]^[5]. The originators of RepRap intend for it to demonstrate evolution by a process analogous to selective breeding (people design improvements to the machine and distribute them on-line for others to reproduce) as well as for it to increase in number exponentially.^[1]^[6] A study has shown that using RepRaps to print common products results in economic savings, which, according to its authors, justifies the investment in a RepRap 3D printer.^[7]

Reprap_Darwin — RepRap version 1.0 (Darwin)

History

RepRap was invented on 2 February 2004 by Adrian Bowyer, then a Senior Lecturer in mechanical engineering at the University of Bath in the United Kingdom. Work started on the project in 2005.

The design of the project’s initial 3D printer “Darwin” was released in March 2007. This was followed by “Mendel”, released in October 2009, and “Prusa Mendel” and “Huxley” released in 2010, although hundreds of variations exist^[8]. The core developers have named each after famous evolutionary biologists, as “the point of RepRap is replication and evolution”, however, other variants are often named after individual designers or given names they prefer.^[9]

2 February 2004: RepRap invented.
23 March 2005: The RepRap blog is started and research begins.^[10]
Summer 2005: Funding for initial development at the University of Bath of £20,000 is obtained from the UK’s Engineering and Physical Sciences Research Council.^[11]
13 September 2006: The RepRap 0.2 prototype successfully prints the first part of itself, which is subsequently used to replace an identical part originally created by a commercial 3D printer.
9 February 2008: RepRap 1.0 “Darwin” successfully makes at least one instance of over half its total rapid-prototyped parts.
14 April 2008: Possibly the first end-user item is made by a RepRap: a clamp to hold an iPod securely to the dashboard of a Ford Fiesta.^[12]^[13]
29 May 2008: Within a few minutes of being assembled, the first completed “child” machine makes the first part for a “grandchild” at the University of Bath, UK.
23 September 2008: It is reported that at least 100 copies have been produced in various countries. The exact number of RepRaps in circulation at that time is unknown.^[14]
30 November 2008: First documented “in the wild” replication occurs. Replication is completed by Wade Bortz, the first user outside of the developers’ team to produce a complete set for another person.
2 October 2009: The second generation design, called “Mendel”, prints its first part. The Mendel’s shape resembles a triangular prism rather than a cube.
January 2009: MakerBot Industries is founded by RepRap volunteers and others to sell 3D printers based on RepRap that are open-source, but are not self-replicating. MakerBot was the first company based on RepRap.
13 October 2009: RepRap 2.0 “Mendel” is completed.
27 January 2010: The Foresight Institute announces the “Kartik M. Gada Humanitarian Innovation Prize” for the design and construction of an improved RepRap. The administration of the prize is later transferred to Humanity+.^[15]
31 August 2010: The third generation design, “Huxley”, is officially named. Development is based on a miniaturized version of the Mendel hardware with 30% of the original print volume.
January 2011: Aleph Objects founded to produce open-source LulzBot 3D printers based on RepRap^[16]. The number of RepRap-based companies making 3D-printers grows.
2011/2012: RepRap and RepStrap building and usage are increasing within the technology, gadget, and engineering communities. RepRaps or commercial derivatives have been featured in many mainstream media sources, and are on the permanent watch lists of such technology media as Wired and some influential engineering-professionals’ news media.^[17]^[18]^[19]^[20]^[21]
Late 2012: The first Delta RepRap design, Rostock, is in development. Delta machines use a non-Cartesian axis design.
July 2013: The Gada Prize is awarded to RepRap Morgan, designed by Quentin Harley.^[22]
12 May 2015: The Dollo self-replicating 3D printer with a very high proportion of self-replicated parts is introduced by Ben and Benjamin Engel.^[23].
8 September 2015: RepRap Snappy is introduced by Revar Desmera of the Bay Area RepRap User Group. Like the Dollo it has a very high proportion of self-printed parts (73%) and assembly is achieved by clipping those parts together as opposed to using nuts and bolts.^[24]
January 2016: RepRapPro (one of many commercial RepRap companies, but one founded by Adrian Bowyer and others) announced on their website that they were to cease trading. The reason given was congestion of the market for low-cost 3D printers derived from the RepRap Project and the inability to expand in that market.

Goals

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 comparatively small outlay of capital, a desktop manufacturing system that would enable the individual to manufacture many of the artefacts used in everyday life.^[1] 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“.^[25]

The project’s goal is to asymptotically approach 100% replication over a series of evolutionary generations.

The self-replicating nature of RepRap could also facilitate its viral dissemination and may 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 may greatly reduce the cycle time for improvements to products and support a far larger diversity of niche products than factory production run sizes can support.

First_replication — All of the plastic parts for the machine on the right were produced by the machine on the left. Adrian Bowyer (left) and Vik Olliver (right) are members of the RepRap project.

Hardware

As the project was designed to encourage evolution, many variations have been created.^[8]^[26] As an open source project designers are free to make modifications and substitutions, but they are obliged by the GNU General Public Licence to re-share their improvements.

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 RepRap used a geared DC motor driving a screw pressed tightly against plastic filament feedstock, forcing it past a heated melting chamber and through a narrow extrusion nozzle. However DC motors cannot precisely start or stop without feedback, and are therefore difficult to control with precision. Therefore, more recent extruders use stepper motors (sometimes geared) to drive the filament, pinching the filament between a splined or knurled shaft and a ball bearing.

Most designs for RepRap’s electronics are based on the open-source Arduino platform, with additional circuitry for controlling stepper motors and heaters.

Software

Initially two different CAM toolchains were developed for RepRap. The first, called “RepRap Host”, was written in Java by Adrian Bowyer and others. The second, “Skeinforge“, was written independently by Enrique Perez. Both were complete systems for slicing 3D computer models into laminae, each of which was then output as G-code instructions to move the machine and to drive the plastic extrusion.

Later, other slicing programs such as slic3r and Cura^[27], were created.

Separately, the Pronterface^[28] program has been written to control RepRaps interactively and to start them running files of G-Code instructions generated by slicing programs. Some RepRaps support a web interface, allowing them to act as a webserver on a network and to be controlled from a web browser.

The closed source KISSlicer^[29] and Repetier Host^[30] are also used.

The RepRap community prefers free and open-source 3-D design programs like Blender, OpenSCAD, and FreeCAD for generating designs of parts to be printed, but virtually any CAD or 3D modeling program can be used with the RepRap, as long as it is capable of producing STL files (slic3r also supports .obj and .amf files). Thus, content creators make use of any tools they are familiar with, whether they are commercial CAD programs, such as SolidWorks and Autodesk AutoCAD, Autodesk Inventor, Autodesk 123D Design, Tinkercad, or Google Sketchup along with the libre software.

Replication materials

RepRaps print objects from ABS, Polylactic acid (PLA), Nylon, HDPE, TPE and similar thermoplastics. Different machine designs support different plastics.

Polylactic acid was introduced as a material for 3D printing by Vik Olliver of the RepRap Project in May 2007 and is the most widely used material. It has the engineering advantages of high stiffness, good resistance to wear and low warping on cooling. It is also biodegradable and plant-derived.

The mechanical properties of RepRap-printed PLA and ABS have been tested and have been shown to be equivalent in tensile strength to prints from proprietary 3D printers.^[31]

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. In addition, several RecycleBots have been designed and fabricated to convert waste plastic, such as shampoo containers and milk jugs, into inexpensive RepRap filament.^[32] There is some evidence that using this approach of distributed recycling is better for the environment ^[33]^[34] and would be useful for creating “fair trade filament”.^[35]

In addition, 3D printing products themselves at the point of consumption by the consumer has also been shown to be better for the environment.^[36]

Printing electronics is a major goal of the RepRap project so that it can print its own circuitry. Several methods have been proposed:

Wood’s metal or Field’s metal: low-melting point metal alloys to incorporate electrical circuits into the part as it is being formed.
Silver/carbon-filled polymers: commonly used for repairs to circuit boards and are being contemplated for use for electrically conductive traces.^[37]
Direct extrusion of solder^[38]
Conductive wires: can be laid into a part from a spool during the printing process.

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 the sprayed-circuit process of the 1940s named Electronic Circuit Making Equipment (ECME), described in the article on its designer, John Sargrove.

Using a MIG welder as a print head a RepRap deltabot stage can be used to print metals like steel.^[39]^[40]

RepRaps have been used as bioprinters for tissue engineering.^[41]

The RepRap concept can also be applied to a milling machine.^[42]

Construction

Other 3D printer designs (such as the commercial MakerBot) and parts constructed by other means (such as Meccano or wood) may be used to “bootstrap” the RepRap process by building RepRap parts. Many such machines are based on 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. Some RepStrap designs are similar to Darwin or Mendel, but they have been modified to be made from laser cut sheets or milled parts.

Although the aim of the project is for RepRap to be able to autonomously construct many of its own mechanical components 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.

RepRap_v2_Mendel — Version 2 ‘Mendel’ holding recently printed physical object next to the driving PC showing a model of the object on-screen

Criticisms

RepRap (and other systems for manufacturing by individuals) may allow people to bypass patents by making patented technology for themselves, giving rise to the same problems for patent holders that copyright holders in music and other media are already subject to because of the ease of distributing digital recordings. This may be more of a problem in countries such as the USA, where personal use of unpaid-for patented technology is an infringement, rather than, for example, the EU, where personal use of patented technology not-for-profit is permitted.^[43]

Educational applications

RepRap technology has potential in educational applications.^[44]^[45]^[46] RepRaps have already been used for an educational mobile robotics platform.^[47] Some authors have claimed that RepRaps offer an unprecedented “revolution” in STEM education.^[48] The evidence for such claims comes from both the low cost ability for rapid prototyping in the classroom by students, but also the fabrication of low-cost high-quality scientific equipment from open hardware designs forming open-source labs.^[4]^[5]

Commercial applications

When the RepRap Project started 3D printers were retailing in excess of US$100,000, dropping to around $15,000 by 2012. By then kits using RepRap technology were available for $500^[49]. That figure is now approximately $300^[50]. Almost all the low-cost 3D printers now available are based on technology derived from, and sometimes created by, the RepRap Project and many companies worldwide have formed (mainly in the period from 2010 to the present) to sell RepRaps and non-replicating 3D printers based on RepRap.^[51]