Why aren't 3d printers and robotic arms already used to create the first versions of self-replicating machines?

Question

The ability to create self-replicating machines can give some very useful benefits. So what is the problem with creating this type of stuff?

Let's say we have two pieces of equipment - 3d printers and robotic arms. These items are already available and are easy to create.

It looks like they are enough to create self-replicating machines. 3d printers are able to print any details for arms and printers. Robotic arms are able to assemble other arms and printers. Both equipment items are able to create almost any other kind of stuff.

So we need only one set of 3d printers and arms with a basic program to start the process. The more sophisticated programs can be added later to create almost any type of equipment from design. If there are enough rough materials, this process can be scaled indefinitely and allow to construct, gather resources, etc.

So, what is the problem with that scheme? Why is is not used already yet everywhere?

Answer 1

We also discussed this topic at physics.stackexchange, take a look at physics related issues there. To summarize all the comments there, here is my answer to this topic as a complilation of all issues in discussions (feel free to propose your explanations).

It looks like there are no special technical problems with that. Basically, both arms (i.e. manipulators) and 3d printers consist of servomotors, wires, chips and structural mechanical elements. They all can be easily 3d printed, that's no doubt I guess.

As often seen in modern science/research/development, the only problem is with funding. The problems with this scale require some solid funds for a large amount of time. That is not compatible with modern financial world, that is aiming at low term profits in simple stuff. Both states and commercial sectors (venture firms) are not currently able or willing to fund it due to uncertainties.

The solution might be in centralized fundings using tax from states via UN or something. It may be like a cross-state global research and development fund (with let's say 1% of GDP per state shares). The results (products and tech blueprints) may be shared to participants due to their share part. But that require a lot of changes/efforts and currently is not available in the nearest future unfortunately.

Answer 2

The problem is accuracy degrades exponentially and no 3d printed part today can accurately fix the accuracy issue.

The other issue is, to make modern things requires a ridiculous amount of specialized industry.

What your proposing will only work if we can 3d print at a tiny, tiny scale. If you can reliably print semiconductors, then this will be viable.

Answer 3

This is a high-level answer.

• Much of the focus has been on nanotech as opposed to self-replication on the macro scale

Search of Google Scholar with keywords "self replicating machines molecular nano" reveals a slew of papers, especially in the early 2000's, with diminishment in activity subsequently. (My recollection is it turned out to be harder than initially hoped, but CRISPR has gotten a lot of attention in regard to molecular scale machines.)

There may be a weakening distinction between what constitutes a machine at this scale subsequent to CRISPR, i.e. organic machines vs. inorganic machines.

Biology provides numerous examples of self-replicating machines, but artificially engineering such complex systems remains a formidable challenge. In particular, although simple artificial self-replicating systems including wooden blocks magnetic systems modular robots5,6 and synthetic molecular systems have been devised, such kinematic self-replicators are rare compared with examples of theoretical cellular self-replication. One of the principal reasons for this is the amount of complexity that arises when you try to incorporate self-replication into a physical medium

_{Kim, J., Lee, J., Hamada, S. et al. Self-replication of DNA rings. Nature Nanotech 10, 528–533 (2015)}

Programmable manufacturing systems capable of self-replication closely coupled with (and likewise capable of producing) energy conversion subsystems and environmental raw materials collection and processing subsystems (e.g. robotics) promise to revolutionize many aspects of technology and economy, particularly in conjunction with molecular manufacturing. The inherent ability of these technologies to self-amplify and scale offers vast advantages over conventional manufacturing paradigms, but if poorly designed or operated could pose unacceptable risks.

_{Rabani E.M., Perg L.A. (2019) Demonstrably Safe Self-replicating Manufacturing Systems. In: Schmorrow D., Fidopiastis C. (eds) Augmented Cognition. HCII 2019. Lecture Notes in Computer Science, vol 11580. Springer, Cham.}

However, search using the terms "self replicating machines macro scale" does return many results, some recent.

This may be more what you're looking for:

This paper introduces the concept of a physical self-replicating machine for deployment on the Moon utilizing raw material available on the Moon. A detailed but selective review is given in order to highlight clearly the novel aspects of this concept. In particular, it is hypothesized that if electric motors and vacuum tubes can be 3D printed from the limited repertoire of lunar materials, 3D printing constitutes a universal construction mechanism. This follows from the observation that mechatronic components are the constituent parts of all robotic mechanisms. In particular, we examine the use of 3D printing of electronics as a physical instantiation of a Turing machine. Several general implications of such a self-replicator are considered including whether it constitutes artificial life and mitigation against runaway replication.

_{Alex Ellery; September 4–8, 2017. Building physical self-replicating machines. Proceedings of the ECAL 2017, the Fourteenth European Conference on Artificial Life. ECAL 2017, the Fourteenth European Conference on Artificial Life. Lyon, France. (pp. pp. 146-153).}

Possibly this type of endeavor has more chance of serious funding, since the long-term rewards are so potentially great, and cost of using humans in those environments is presumed to be even greater.

(At least one super-power seems interested in a moon-base, and Elon wants to die on Mars;)

• Runaway self-replication seems to be a concern in all areas

This could be why there is some reticence (see gray goo—only needs to be "intelligent" at one thing;) but it would seem to be less of a concern at the macro-scale in a terrestrial setting at current level of AI. In this domain, it's almost certainly a question of cost vs. cost of human labor.

Answer 4

You are glossing over the difficulty of building chips and electronics. That is very hard, and requires customised machines. So now you need to build also those machines. And to build those machines you will need other machines. And so on.

You quickly realise that it is very hard to build a realistic closed cycle. Moreover, metal 3d printing is still immature and the most complex fully automated systems are relatively simple and still require constant human mainteinance.

Given the current state of the art, it would be possible in principle, but not in practice. De facto, your own answer about economics is correct, but this answer explains why is that expensive.

At the moment we don't even have 3d printers able to fully 3d print themselves (no autonomous assembly, just building the parts). See the reprap project.