RepRap Project

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RepRap 0.1 prototype being demonstrated at Paraflows 2006 in Vienna by its designer, Vik Olliver {09/06}

The RepRap Project is a project aimed at creating a self-replicating machine which can be used for rapid prototyping. A rapid prototyper is a 3D printer that is able to fabricate three dimensional artifacts from a computer-based model. RepRap is described as 'self-replicating' because it is being designed with the ability to reproduce the components necessary to build another version of itself.

Due to the replicating ability of the machine it should be possible to cheaply distribute them to people and communities enabling them to create (or download from the internet) complex products and artifacts without the need for expensive industrial infrastructure. It is speculated that the RepRap will eventually demonstrate evolution in this process as well as being able to increase in number exponentially. This gives RepRap the potential to become a powerful disruptive technology by enabling low-cost personal fabrication.

The goal of the RepRap project is not to produce a pure self-replicating device for it 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 will enable the individual to manufacture many of the artifacts used in everyday life. The self-replicating nature of RepRap will also facilitate its viral dissemination and may well facilitate a major paradigm shift in the design in manufacture of consumer products from one of patented, factory production to open-source, personal production. Opening up product design and manufacturing capabilities to the individual should greatly reduce the cycle time for kaizen improvements to products and support a far larger diversity of niche products than the factory production run size can support^[1].

From a theoretical viewpoint, the project is attempting to prove the following hypothesis:

Rapid prototyping and direct writing technologies are sufficiently versatile to allow them to be used to make a von Neumann Universal Constructor. ^[2]

[edit] Background

Threaded rod gripper fabricated by the RepRap 0.2 and subsequently used to replace an identical part from the same machine, Vik Olliver {13/09/06}

Dr. Adrian Bowyer, a Senior Lecturer in mechanical engineering at the University of Bath in the United Kingdom, invented and initiated RepRap, and leads the project team.^[3] The project itself uses rapid prototyping (specifically fused deposition modeling), and will make the results available under the GNU General Public License at no cost, allowing other investigators to work on the same idea and evolve it as well.

Currently, low-end commercial 3D prototypers cost about US$30K (Z-Corp). Prototypes made by these low-end commercial machines costing around US$2 per cubic centimetre to fabricate. The Reprap Project is on track to produce an open source 3D prototyping machine and accompanying software that costs about US$400 to build and which can fabricate objects at a cost of about US$0.02 per cubic centimeter.

[edit] Current status

On 13 September 2006 the RepRap 0.2 prototype successfully printed the first part of itself which was subsequently used to replace an identical part originally created by a commercial 3D printer.

A short production run (~1 km) of 3 mm polycaprolactone filament suitable for use in the Mk II extruders used in several operational and near-operational reprap prototypes has been produced for the project. With 1km of polycaprolactone filament, the project has been able to produce larger artifacts and also test the candidate systems for days instead of for hours, as was the case with hand-produced filament.

Vik Olivier's Zaphod prototype has replicated a parts set for the Mk II extruder. Vik assembled the parts into a working Mk II and has successfully employed it as a second extruder on Zaphod. The use of polycaprolactone for the parts set instead of ABS required that several minor changes be made when assembling them into a working Mk II.

[edit] Hardware development

Mk II fused deposition extruder (created by Dr. Adrian Bowyer).

While the RepRap project was formally launched in March of 2005, the rate of hardware development exploded after the development of the Mk II fused deposition extruder by Dr. Bowyer in November 2005.^[4] The Mk II represents a major advance in the state-of-the-art in that it can operate in a room temperature environment rather than a closed box heated to a temperature just short of the melting point of the polymer being extruded. This greatly reduces both the cost of producing a system and makes specifying materials used in such systems much less critical.

[edit] Full RepRap prototypes

Originally assembled in February 2006, as of 10 May 2006 the first full prototype replicator, RepRap 0.1, designed by Vik Olliver in New Zealand, soon began to extrude forms. By mid-July objects of up to 15 layers in depth and 50 mm in diameter were extruded by Da Witch, Vik Olliver's prototype RepRap machine.

The polymer components of the 3D positioning system and polymer extrusion head were created using a commercial FDM machine. The system was subjected to intensive shakedown exercises by Vik Olliver and Simon McAuliffe to integrate the software, firmware and hardware components.

As of September 2006 Da Witch has been rebuilt to make it portable and a second extruder head has been added. The modified RepRap 0.2 has been dubbed Zaphod. Vik Olivier has delivered a lecture about and demonstration of Zaphod and the RepRap research programme in Vienna at the Paraflows 2006 digital arts congress there during 9 September 2006 - 16 September 2006.

RepRap's prototype self-replicating FDM 3D printer, Zaphod, has recently created a full set of the plastic parts needed to make its own FDM extruder.^[5]

In February, another RepRap prototype, Tommelise^[6] was rolled out and went into testing. Tommelise recently demonstrated that a modified version of the Mk 2 with a different extruder barrel could successfully extrude Acrylonitrile butadiene styrene (ABS), high density polyethylene (HDPE) and homopolypropylene (HPP), all engineering plastics with much higher melting points, at production rates.^[7]

[edit] Other prototypes

Other full prototypes at various stages of development are presently being built by Sells and Bellmore.

To date virtually all RepRap prototypes have been repstrapped. Vik Olliver's prototype, which has evolved into RepRap 0.2, began largely as an assembly of Meccano parts, and to give a notion of the range of materials that can be utilized the bootstrapped prototype, Tommelise^[8], is almost entirely built of milled poplar.^[9]

The materials chosen reflect local conditions and the skillset that the individual team member brings to the project.

[edit] Software development

RepRap 0.1 prototype (created by Vik Olliver).

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.

The RepRap team has, for now, identified the open source Art of Illusion (AoI) 3D modeling system as the front end for the RepRap system. AoI is well-suited for this role both because of its power to model 3D objects and because it is written in the ubiquitous multiplatform Java programming language. The basic AoI modeling platform is being tailored to the special needs of the RepRap project via scripts.

Work on RepRap's CAM system also being written in Java is currently in an advanced state of development. That work is being is being pursued by both Simon McAuliffe and Adrian Bowyer and is being tested as part of the RepRap 0.1 shakedown exercises.

[edit] Materials

RepRap 0.1 building an object

RepRap will have multiple extruders for applying various materials in the creation of parts.

Potential structural materials include:

• Thermoplastic polymer - which is what is being concentrated on currently. This is generally used to create structure. Polycaprolactone is currently the target material though tests with polylactic acid will be undertaken in the next several months.
• Ceramic slurries - to create very hard and strong ceramic structure. Silicon nitride is currently being contemplated in this role, though several similar refractories are being considered.

Potential support structure materials include:

• Plaster/cellulose mixes - can be washed away from the finished product with lukewarm water.
• Icing sugar - can be washed away from the finished product with lukewarm water.
• polycaprolactone/marble dust mixes - can be peeled away from the finished product.

Silicone polymer has been proposed for gaskets, seals and flexible parts.

Electroconductive materials include:

• Wood's metal or Field's metal - low-melting point metal alloys (lower than the melting point of the plastic) to incorporate electrical circuits into the part as it is being formed.
• Silver-filled polymers - are commonly used for repairs to circuit boards and are being contemplated for use for electrically conductive traces.

Chocolate has been proposed as a whimsical extruded material. This could allow the manufacture of complex 3D Easter eggs and other such items.

[edit] Limitations of self-replication

Although it appears likely that RepRap will be able to autonomously construct much of its mechanical components in the near future using fairly low-level resources, it would still require an external supply of several currently non-replicable components such as sensors, stepper motors, cameras, or microcontrollers. A certain percentage of such devices will have to be produced independently of the RepRap self-replicating process. The goal is, however, 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 will open the door to the inclusion of connective wiring, printed circuit boards and possibly even motors in RepRapped products^[10]. Variations in the nature of the extruded, electrically conductive media could produce electrical components with different functions than pure conductive traces not unlike what was done in John Sargrove's sprayed-circuit process of the 1940s.

[edit] Project members

Meccano repstrap of RepRap 0.1 prototype (created by Vik Olliver).

• Sebastien Bailard, in Ontario.
• Brett Bellmore in Michigan.
• Dr. Adrian Bowyer, Senior Lecturer in the Mechanical Engineering Department University of Bath.^[3]
• Michael S. Hart, creator of Project Gutenberg, in Illinois.
• Dr. Forrest Higgs, Brosis Innovations, Inc. in California.
• James Low, undergraduate in the Mechanical Engineering Department at the University at Bath.
• Simon McAuliffe in New Zealand.
• Vik Olliver, Diamond Age Solutions, Ltd. in New Zealand.^[11]
• Ed Sells, postgraduate in the Mechanical Engineering Department at the University at Bath.
• Zach Smith, in the United States.

[edit] Sponsors

• Reece Arnott
• The Bath University Innovative Manufacturing Research Centre^[12]
• The Engineering and Physical Sciences Research Council^[13]
• The Fluorocarbon Co. Ltd.^[14]
• Michael Ingram
• Lukasz Kaiser
• The Nuffield Foundation
• Carl Witty

[edit] References

[edit] See also

• Fabber
• Rapid prototyping
• Self-replicating
• Open design
• Robot
• John von Neumann
• Von Neumann machine
• Fab lab
• Desktop manufacturing

[edit] External links

• Official RepRap site.
• RepRap object repository
• The RepRap Project, Reports and Documentation
  • Construction of Rapid Prototyping Testbeds Using Meccano, Final Report, 27-April-2005, PDF, 2471 KB
• RepRap Official Blog. - Official Developers Blog
• RepRap Bootstrap Blog. - Building a bootstrap RepRap
• 'Replication revolutionary', New Electronics, 12 December 2006
• '3D printer to churn out copies of itself', Celeste Biever, NewScientist.com news service 18 March 2005
• 'The machine that can copy anything', Simon Hooper, CNN, Thursday, June 2, 2005
• Self Replicating Robots And The Developing World., KnowProSE.com, Sunday June 5, 2005.