Illustration: Rob Nance

Illustration: Rob Nance

RepRap is short for Replicating Rapid Prototypers, the original open source desktop 3D printers. Initially conceived in 2005 by Adrian Bowyer, at the time a senior mechanical engineering lecturer at the University of Bath in England, RepRaps were designed to reproduce many of their own components — printers printing printers. The rest of the hardware needed is easily acquired at a low cost, allowing everyone equal access to the necessary technology to produce their own goods.

Bowyer went on to design the first well-known RepRap, the Darwin. Now a director at RepRapPro, he describes the RepRap project as a symbiotic relationship: These machines would produce our goods at a low cost while we would provide the assistance they needed to reproduce themselves, like the relationship between insects and the plants they pollinate. RepRaps would undergo a process of selection similar to biological organisms. They would evolve as they spread and as new technology became available.

And that is exactly what has happened. From that concept grew — and continues to grow — a great family of printers bearing a great many innovations that appear not only throughout the RepRap tree but in commercial printers. Many of the printers reviewed in this issue owe parts of their design to the RepRap movement.


Darwin line (top)

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1. Darwin, Adrian Bowyer, 2007

The cube-shaped Darwin is considered the first RepRap printer. A Cartesian machine constructed largely of steel rods and plastic 3D printed junctions, it used a descending build platform that tended to bind due to four lead screws that raised and lowered each corner of the platform. This axial orientation was used in at least nine of this year’s tested printers.

Prusa line (center)

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2. Mendel, Ed Sells, 2009

The RepRap line took a big design shift with the Mendel. In addition to being easier to assemble, the cube was traded in for a prism shape, which moved most of the weight to the base, making it more stable. Furthermore, it enabled the four lead screws to be replaced by just two, greatly reducing the binding and leveling issues that caused so many jams.

3. Prusa Simplified Mendel, Josef Prusa, 2010

Josef Prusa, a young “proud dropout” from the University of Economics in Prague, simplified the Mendel so much that assembly time was dramatically reduced. At this stage, an experienced builder could construct one in a weekend. Fewer parts and the streamlined design meant you could print the necessary joiners in half the time.

4. Prusa Mendel 2, Josef Prusa, 2011

With a few more tweaks, the second iteration of the Prusa Mendel introduced more complexity to the machine, while streamlining the hardware used to build it. A heated build plate helps prints adhere and avoid warping, and the X carriage was redesigned to accommodate linear bearings and bushings. By this point, the community was gaining traction, and this model became extremely popular, attracting many new participants and hobbyists.

5. Prusa Mendel i3, Josef Prusa, 2012

The i3 became still more popular, a flagship for the RepRap movement. A whole tree sprouts off from here — if you’re looking at getting a RepRap, it’s probably an i3. Primary improvements include an open design to maximize build volume, a stable, rigid frame, and an overall reduction in parts.

MendelMax line (left)

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6.  MendelMax, Maker’s Tool Works, 2011 The folks at Maker’s Tool Works took the Mendel concept and designed a new frame, constructing it with aluminum extrusions as opposed to rods. This made the frame very rigid and durable while retaining the original RepRap construction ideal of using printed joinery.

7. MendelMax 2.0, Maker’s Tool Works, 2013

There’s a bit of crossover here; the 2.0 was clearly influenced by the Prusa i3 in its open framework, again built with rigid aluminum extrusions. This MendelMax is actually sort of a Mendel/i3 hybrid because it still has the top-mounted Z-axis motors. It features a larger print volume and a simplified construction, requiring fewer parts.

Rostock line (right)

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8. Rostock, Johann C. Rocholl, 2012

The Rostock is a prototype delta-style RepRap and is progenitor to a far-reaching branch of the RepRap tree. Delta robots (of the non-printing variety) have a long-standing reputation for speed in various manufacturing applications, so it made perfect sense to adopt this style of bot in 3D printing. It’s not unreasonable to expect print speeds of around 350mm/s from a delta printer (see SeeMeCNC’s Rostock Max v2 kit, page 41).

9. Kossel, Johann C. Rocholl, 2012

Later in 2012, Rocholl released the Kossel, another member of the RepRap family with the namesake of another famous biochemist/geneticist. (Notice the evolutionary trend?) Today, Rocholl still has the design classified as “experimental.” This machine took advantage of aluminum extrusions in its frame construction, just like the MendelMax, which allowed an exceptional build height of about 400mm (16″).

10. Rostock Mini, Brian Evans, (2012)

The Rostock Mini is a shorter and more structurally stable version of the original Rostock. The other main improvement is the attractive frame components, which were designed to be CNC cut from wood or acrylic. This iteration has proven to be reliable and is very popular in the RepRap community.

Branches on Branches

The RepRap family tree is much greater than the three branches you see here. There are dozens of branches, each representing an open source machine, and tracing its lineage in some form to the original Darwin. And there’s plenty more that aren’t directly related, but still tie into the Darwin, at least in ideology.

Open Source

A passionate and robust community, freely exchanging ideas, is pushing the evolution of this symbiosis forward. Cross-pollination of designs is leading to variation that is already pretty complex.

At the heart of RepRap is its open source GNU General Public License. Originally created for software, GPL is applicable here because RepRap designs and files are considered the “source code” for future iterations. Not only can you build your own, you can sell them as kits or completed machines. Just don’t try to use it in a proprietary system.

A RepRap for Everyone

With the i3’s popularity many companies have created their own version of this capable printer that you can buy today. BQ, BeeVeryCreative, MakerFarm, MakeBlock, and Prusa3D, to name a few, all produce i3 variants as kits or fully assembled packages. With so many options, there may be an i3 to fit everyone.

Midwest RepRap Fest

The biggest RepRap event in the world takes place each year in Goshen, Indiana, home of printer company SeeMeCNC. Over the weekend, attendees check out custom and rare machines, and attend talks by RepRap luminaries. It’s one of the best places to see how large, diverse, and creative the RepRap community is.

The Future of RepRap

RepRap is still going strong. It has become the basis for many printers, some directly available to purchase or as kits to build. The RepRap wiki hosts a thriving, global community. Meanwhile, Josef Prusa, who has become a core developer for RepRap, is working on i4, though there’s very little information on its design.

Among RepRaps in general, constraints like build volume and print material will continue to fall away. Considering that RepRap is, at its core, biomimetic, we can anticipate the same sort of vicious selection that any organism undergoes in its journey toward optimization.