The term clanking replicator refers to an artificial self-replicating system that relies on conventional large-scale technology and automation. They are also sometimes called "Auxons," from the Greek word auxein which means "to grow.". The term evolved to distinguish such systems from the microscopic "assemblers" that nanotechnology may make possible.
It is unlikely that this would all be contained within an single monolithic machine, but would rather be an automated factory that is capable of manufacturing all of the components that make it up and assembling them at a remote site. The factory could produce mining robots to collect raw materials, construction robots to put new machines together, and repair robots to maintain itself against wear and tear, all without human intervention or direction. The advantage of such a system lies in its ability to expand its own capacity rapidly and without additional human effort.
The idea of non-biological self-replicating systems was first seriously suggested by mathematician John von Neumann in the late 1940s when he proposed a kinematic self-reproducing automaton model as a thought experiment. See von Neumann, J., 1966, The Theory of Self-reproducing Automata, A. Burks, ed., Univ. of Illinois Press, Urbana, IL.
In 1980, NASA conducted a summer study entitled Advanced Automation for Space Missions, edited by Robert Freitas, to produce a detailed proposal for the use of self-replicating factories to develop lunar resources without requiring additional launches or the support of human workers on-site. This study inspired the science fiction novel Code of the Lifemaker (ISBN 0-345-30549-3) by author James P. Hogan. An early fictional treatment was the short story Autofac by Philip K. Dick, published in 1955, which actually seems to precede von Neumann's original paper about self-reproducing machines. Another example can be found in the 1962 short story Epilogue by Poul Anderson, in which self-replicating factory barges were proposed that used minerals extracted from ocean water as raw materials. Clanking replicators are mentioned briefly in the fourth chapter of K. Eric Drexler's book Engines of creation.
As the use of industrial automation has expanded over time, some factories have begun to approach a semblance of self-sufficiency that is suggestive of clanking replicators. However, it is unlikely that such factories will achieve "full closure" in the near future so long as human labour and external spare part supplies remain conveniently available to them. Fully-capable machine replicators are most useful for developing resources in dangerous environments which are not easily reached by existing transporation systems.