Getting it Right by Getting it Wrong: RepRap and the Evolution of 3D Printing

The beginning of the DIY 3D printing movement was a heady time. There was a vision of a post-scarcity world in which everything could and would be made at home, for free. Printers printing other printers would ensure the exponential growth that would put a 3D printer in every home. As it says on the front page: “RepRap is humanity’s first general-purpose self-replicating manufacturing machine.” Well, kinda.


Original Darwin. Photo: Adrian Bowyer, founder of RepRap.

Just to set the record straight, I love the RepRap project. My hackerspace put our funds together to build one of the first few Darwins in the US: Zach “Hoeken” came down and delivered the cut-acrylic pieces in person. I have, sitting on my desk, a Prusa Mendel with 3D parts printed by Joseph Prusa himself, and I spent a fantastic weekend with him and Kliment Yanev (author of Pronterface) putting it together. Most everyone I’ve met in the RepRap community has been awesome, giving, and talented. The overarching goal of RepRap — getting 3D printers in as many peoples’ hands as possible — is worthy.

But one foundational RepRap idea(l) is wrong, and unfortunately it’s in the name: replication. The original plan was that RepRap printers would print other printers and soon everyone on Earth would have one. In reality, an infinitesimal percentage of RepRap owners print other printers, and the cost of a mass-produced, commercial RepRap spinoff is much less than it would cost me to print you one and source the parts. Because of economies of scale, replicating 3D printers one at a time is just wasteful. Five years ago, this was a controversial stance in the community.

On the other hand, the openness of the RepRap community has fostered great advances in the state of the DIY 3D printing art. Printers haven’t reproduced like wildfire, but ideas and designs have. It’s time to look back on the ideal of literal replication and realize that the replication of designs, building methods, and the software that drives the RepRap project is its great success. It’s the Open Hardware, smarty! A corollary of this shift in thought is to use whatever materials are at hand that make experimentation with new designs as easy as possible, including embracing cheap mass-produced machines as a first step. The number of RepRaps may never grow exponentially, but the quality and number of RepRap designs can.


One of the key early design goals for the RepRap was to be able to replicate quickly, which would lead to the exponential growth of RepRaps around the globe. Adrian Bowyer, the founder of the RepRap project, gave a keynote address at the Seventh National Conference on Rapid Design, Prototyping & Manufacturing

All current engineering production generates goods in an arithmetic progression. Sometimes this is very fast − suppose an injection moulding machine makes plastic combs at the rate of 10,000 an hour. Suppose further that a RepRap machine can make one copy of itself a day, and also just one comb. After merely 18 days, the RepRap machines will be making more combs than the injection moulder, assuming people give them house-room.

Ten years later, the RepRap project is a phenomenal success — there are RepRap printers in the hands of hobbyists everywhere and the advances in the later models have come entirely from that community. But RepRap is by no means an exponentialsuccess. At any of Adrian’s proposed rates of replication, there would be a bazillion times more RepRaps by now than there are atoms in the known universe. I bet you even know some people who don’t own one. Proof by contradiction.

The bot does all the work. Simon Kühling just chills.

The bot does all the work. Simon Kühling just chills.

What happened? Almost nobody is replicating. The missing ingredient in the exponential-growth formulation is the number of people driving the machines (never mind the fact that you’re looking at a non-negotiable one-time outlay of a few hundred dollars for motors and electronics). Running a 3D printer of any design or make, as anyone who shepherds one knows, requires a deal of maintenance.

Almost nobody is printing RepRap parts because they are, like I am, trying to keep the machine working while printing the cool stuff that they wanted in the first place. Or they’re printing new and improved parts for their current machine. Or they’re printing the parts for their next, improved, machine. But they’re not wasting their time simply replicating.

Ironically, in that same keynote speech, Prof. Bowyer gets this part of the argument right but doesn’t follow its logical conclusion. He mentions that, as more people started printing parts for RepRaps, the price of these parts would drop to the material cost, which is nearly zero. This means free RepRap parts for everyone, right? Nope, it means that as long as anyone has anything else to do with their time that they value more than printing RepRap parts, they’ll do that because there’s just no money in printing RepRap parts.


A very nice set of parts from RepRapParts, Germany

And this is exactly what happened. Four years ago, when the Prusa Mendel design was busting out onto the scene, a set of printed plastic parts cost around $120. Two years later, it was more like $40 or $60. Now, even cheaper parts can be obtained for something like $10-$20, but those sets that are imported from overseas where the cost of one’s time, as measured in the average hourly wage, is a lot lower than it is here. At that price, for a few hours of running my machine, including the cost of plastic and maintenance, I’m not replicating.

The biggest misunderstanding of the RepRap project is that people’s time isn’t free and unbounded. A large number of folks just want to print something with their 3D printer, and they want it to print nicely without significant tuning. That’s why we see a wide variety of machines that will never be able to replicate themselves for sale in the $1200 – $2500 range, when anyone can build a RepRap themselves for around $500 or less. The expensive machines are being built for out-of-the-box usability, and the purchasers of these machines are trading money upfront for the time that they would otherwise have to spend tweaking and maintaining the machine.

At the same time, inexpensive mass-produced machines based on the RepRap design compete with replicated machines at the lower end of the market. Simply put, economies of scale make the average cost of producing a RepRap lower as the quantity produced goes up. It makes absolutely no sense for me to replicate plastic printer parts when my potential buyer can get everything for the entire build cheaper from overseas. And I’m not complaining. This is a good thing because it means more machines, faster, in the hands of the DIY experimenters who will make the next breakthroughs.



The original Mendel: Threaded rods and printed vertexes. Photo: Adrian Bowyer

Another part of the RepRap’s founding inspiration was biological, and this was implicated in the view the RepRaps had to replicate. After all, all biological life on the Earth perpetuates itself by reproduction. (Deep thought: reproduction is what life is.) So the RepRap in Bowyer’s ideal vision should be made out of parts that it would be able to make. This lead to early design choices including the use of the dreaded, threaded-rod frame, and an emphasis on simplicity and fab-ability over precision. The reliance on non-printable parts, “vitamins” in the biological metaphor, was to be minimized even if that meant making a less robust machine that was fiddly to calibrate.

In insisting on self-reliance, Bowyer misunderstood the ecology of the RepRap. Do bees produce everything they need to survive? No, the flowers help them out a lot. Flowers don’t exist in a self-reproducing vacuum either — they rely on bees and other insects to reproduce. The point is that nothing in nature is self-reliant, even for reproduction. Everything relies on something else. Why shouldn’t a RepRap evolve to be the cheapest and best possible device given the parts available, printed or otherwise? (A factory turning out inexpensive aluminum extrusions and shipping them across the globe is the flower in this twisted metaphor.)


MendelMax: A Mendel made of aluminum extrusion. Slightly more expensive, significantly more rigid. Photo: Kludgineer

Our DIY ecosystem has become rich in “vitamins” since the founding of the RepRap project. It’s now easy and cheap to get even relatively sophisticated parts like aluminum extrusions and linear motion slides direct from factories in China. One-off PCBs used to be prohibitively expensive to produce, but that’s no longer the case. Motor driver circuits, motors, and even niche parts have become cheaper. In a nutrient-rich environment, it makes sense biologically to evolve to take advantage of them.

Fortunately, insisting on building a frame yourself entirely out of threaded rod has become an anachronism — all of the new printer designs since the Mendel 90 to the Prusa i3 use an easy-to-calibrate design that’s based on large cutouts of metal or plastic for parts of the structure that require stiffness. One of the first salvos in this revolution was fired by the MendelMax, which is essentially a Mendel made out of extrusions. Then came the various delta bots, epitomized by the Rostock and its brother, the Kossel, that left replicability entirely behind.

I’m enthusiastic to see the directions that the community has taken over the last five years or so — relying as they do on more “vitamins” and resulting in higher quality and less time wasted in calibration, tuning, and maintenance. It’s to the point now that the use of aluminum extrusions isn’t even given a second though.


One of the important early ideals of the RepRap movement — universal replication and free printers for everyone — was pretty much a failure.  Still, to quote again from the website: “RepRap was the first of the low-cost 3D printers, and the RepRap Project started the open-source 3D printer revolution. It has become the most widely-used 3D printer among the global members of the Maker Community.” This is all true, and then some. RepRap has spawned a truly global community of enthusiasts all working on advancing the state of the art in DIY 3D printing. The number and quality of people working on the project is really amazing.

Rostock printer. Photo: Johann C. Rocholl -- its inventor.

Rostock printer. Photo: Johann C. Rocholl — its inventor.

But in my mind the biggest advances have been in the designs of the machines themselves. A decent 90-degree-frame RepRap-style bot today is significantly better than a Prusa of only four years ago, and infinitely better than the original Darwin of ten years ago. And it costs around half the price to assemble one. In addition, the ecosystem has grown to include out-there designs like the delta bots. All of these machines are awesome, but none of them are replicating to any serious degree, even the ones that could in principle. But who cares?

What’s awesome about RepRap is that, even though the founding replication idea behind RepRap has been a failure, the community and the machines that they’ve made have adapted to our “vitamin”-rich environment. Perhaps the utopian story of the replication-driven end to scarcity was useful or necessary in attracting people to the project in its early days. But ten years out, the community has already proved its value, and that’s not in making infinite numbers of printers, but in making shared, DIY design innovations: the nature of RepRap evolution has itself evolved.

Headline image courtesy [ccecil], design by [loubie]. And thanks to Freenode’s #reprap channel for the good discussion.


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The Next Generation of Boston Dynamics’ ATLAS Robot Is Quiet, Robust, and Tether Free 

Image: Boston Dynamics via YouTube

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Continue reading The Next Generation of Boston Dynamics’ ATLAS Robot Is Quiet, Robust, and Tether Free