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“ Although most modern computer-controlled machining systems have "a finite number of tool-storage locations - 24, 48, or 60 tools, for example - the number that could be built into a system runs into the thousands" (Gettleman, 1979) . If the seed is comprised of about 1000 different kinds of parts, each requiring a template pattern for the casting robot, Gettleman's estimate for N/C machine tooling makes plausible the satisfaction of this requirement by extensions of current technology. ”

“ However, it is often asserted that machining the laser end mirrors to high accuracy may be a major roadblock to automated manufacture of lasing devices. Nazemetz (personal communication, 1980) has pointed out that a laser is accurate enough to surface a rough-hewn mirror to the accuracy required for its own construction. In a pinch, concave mirrors could be hewn from solid metal or basalt blanks simply by sweeping the laser beam radially across the disks, applying higher power nearer the center so more material volatizes there, thus creating a perfect spherical or parabolic surface gradient. ”

“ The purpose of describing the above nonlaser welding and machining systems is to suggest that laser machining should be equally automatable because the laser may be viewed as another modality for delivering heat or cutting action to a workpiece. Any nonlaser automated welding/machining technology in principle may be modified to accept a laser as its active machining element. ”

“ A skilled technician can preprogram the complete machining cycle for any given part. The Lockheed CAD/CAM system (see below) permits still more sophisticated computerized design and parts fabrication. It seen but a few conceptually simple steps from this level of technology to that required for a "universal" contour-carving device like the casting robot. Such a system will require vision system, excellent tactile sensing, an automatic tool-changing and pattern-changing capability, and development of an automatic feedstock handling system for metal, gases, and refractories. ”

“ Machining cells, based on the principle of group technology, will be controlled by a hierarchy of minicomputers and microcomputers, and will receive workpieces via an automated transfer system. Each machine cell will be equipped with inspection and diagnostic systems to monitor such useful parameters as tool wear, product quality, and the conditions of machine operation. ”

“ The major advantages of basalt are its easy availability, its tolerance of machining, good compressive strength, and high density in some uses. Anticipated applications include machine support bases, furnace support walls, robot manipulator tools (to avoid vacuum welding) , and other special parts where weight is not a problem. Because plaster fuses at 1720 K - very near the melting point of basalt - and loses its water of crystallization around 475 K, it cannot be used to make basalt castings. ”

“ Precision machining of liquid- and air-tight valves, laser mirror surfaces, and various other small intricate parts will demand the closest scrutiny of the rate at which energy is delivered to the workpiece. Lasers may also be used for super-accurate ranging and sizing measurements, which require an ultralow power capability as well as sophisticated optics, timing, and data processing systems. Automation of the LMF Laser Machining System will require close computer/mechanical control to perform each of the seven basic machining steps described earlier in section 5F.5. ”

“ According to Ansley (1968) , small castings using nonferrous metals (aluminum, magnesium, or copper alloys) may be produced using plaster molds with a surface finish as fine as 2-3 μm and an accuracy of +/-0.1 mm over small dimensions and +/-0.02 mm/cm across larger surfaces (a drift of 2 mm over a 1 m2 area) .
Traditionally, the plaster casting technique requires a split metal pattern in the shape of the object to be cast. This pattern is used to make a hollow mold into which molten metal is poured, eventually solidifying to make the desired part. ”

“ Mixing is accomplished by physical agitation, after which the contents are fed into a solar furnace to be melted. If net solar efficiencies are roughly the same as for the 5 kg capacity induction furnace (output 30 kg/hr) described in the MIT space manufacturing study (Miller and Smith, 1979) , then about 30 kW of power are required which may be drawn most efficiently from a large collector dish roughly 6 m diam. There are at least three hopper/furnace subsystems required - a minimum of one each for iron, basalt, and aluminum alloys. ”

“ Laser beam machining is "especially adaptable and principally used for relatively small materials processing applications such as cutting, trimming, scribing, piercing, drilling, or other delicate material removal operations similar to milling or shaping" (Yankee, 1979) .
Dunning (unpublished Summer Study document, 1980) has suggested a variety of space and lunar applications for laser machining, including flash trimming of cast basalt parts; engraving bar codes on parts to enable quick and accurate recognition by robot vision systems; drilling holes in workpieces an inch thick or less ”

“ Nonlaser machining is also highly automated. The generalized machining center can perform a number of functions in typical operation including milling, drilling, boring, facing, spotting, counterboring, threading, and tapping, all in a single workpiece setup and on many different surfaces of the workpiece (Gettleman, 1979) . A numerical-control machine operated by the Giddings and Lewis Machine Tool Company has an automatic tool changer with 40 tools. It machines all sides of a workpiece with one setup. ”

“ Design all functional and physical characteristics for greatest simplicity. As a general principle, service life of a part is greatly increased when design of that part is both simple and sturdy ("robust") . Performance is more predictable and costs (money, build time, repair time) are lower for simpler parts. Design for the most economical production method. ”

“ Specify finish and accuracy no greater than are actually needed. If a part will adequately serve its intended purpose at some lower level of accuracy of machining than is technologically possible, then cheaper, simpler production processes may be used which make closure easier to attain. ”

“ The original forecast was that MUM technology would go into operation sometime during the 1980s. At a conference in Tokyo in September of last year, Fujitsu FANUC Ltd., a leading international manufacturer of numerical control (NIC) machining equipment, announced its plans to open a historic robot-making factory near Lake Yamanaka in Yamanashi Prefecture in late November. At the plant, then still under construction, industrial robots controlled by minicomputers would produce other industrial robots without major human intervention save minor machine operation and administrative tasks. ”

“ After the casting robot makes molds for the parts, the molds are filled with molten aluminum alloy. The metal hardens, the mold is broken, and the pieces are recycled back into plaster of Paris; the aluminum parts formed in the mold are conveyed to the laser machining and finishing station. ”

“ At any given time about 200 tools are in automatic toolchanging carousels, available for selection by the computer, although about 500 are generally available in the system. The computer can simultaneously direct the fabrication of as many as 16 different kinds of parts of totally different design which are either being machined, waiting in queue to be machined, or are in the transfer loop. The entire system is capable of manufacturing about 500 completely different parts. During each 12-hr shift the system is run by three human operators and one supervisor. ”

“ Although machines designed for construction and use in space may employ radically different components than their terrestrial counterparts, to a first approximation it may be assumed that they will be comprised generally of the same kinds of parts found in commonplace machines on Earth such as bolt, nut, screw, rivet, pulley, wheel, clutch, shaft, crank, rod, beam, wire, plate, disk, bushing, cable, wedge, key, spring, gasket, seal, pipe, tube, and hose. ”

“ Various aluminum alloys may be selected for parts, whereas pure metal is required for vapor deposition processes. Castable basalt may require fluxing but otherwise is a fairly straightforward melt.
Metallurgical duties are performed at the input terminus of the fabrication sector. Mobile chemical processing sector robot carriers dump measured quantities of metals and other substances into cold fabrication sector input hoppers (made of cast basalt and perhaps stored under a thin oxygen atmosphere to preclude vacuum welding) . ”

“ Vapor deposition is the least complicated, most versatile method of producing metal film sheets to be used as the manufacturing substrate for microelectronics components, mirrors or solar cells, or to be sliced into narrow strips by the laser for use as wire. The extruder is used to produce thread fibers of insulating material, presumably spun basalt drawn from a lunar soil melt as described in section 4.2.2.
5F.3 Casting Robot
The casting robot is the heart of the proposed automated fabrication system. ”

“ Refractory bodies are fabricated from pure oxides by powder pressing, ramming, extruding, or slip casting. The last of these is the simplest, but requires a very fine powder. This powder is normally prepared by ball milling. Steel mills and balls are used, and the iron is later separated by chemical means. For simplicity in LMF design, the iron alloy powder inevitably mixed with the milled product can be removed by magnetic separation.
High-alumina cements and refractories may be the best option for lunar manufacturing applications. ”

“ Laser cutting speeds typically are as much as 30 times faster than friction sawing (Yankee, 1979) . Cutting accuracy is about 0.01 mm/cm under closely controlled conditions. All metals - including high-strength, exotic, and refractory alloys such as Inconel and titanium, as well as aluminum, stainless steel, and brass - and nonmetals such as diamond, ceramics, and plastics may be vaporized by laser beams. Hence, parts of these materials may be easily machined. Burr-free laser holes may be drilled as small as 10-100 μm. ”

“ Clearly, the Dynell automated sculpting system is not too distant from the casting robot, conceptually or technologically. If treated as a serious item for further development, it is likely that casting robot technology could be ready in a decade or less starting from the current state-of-the-art.
Laser Machining System Automation
Nonlaser spot welding has been a standard automated industrial technique for many years. ”

“ Ultimately, the LMF factory in production phase may be called upon to perform many if not all of these functions. However, most may be unnecessary for initial system growth or replication. indeed, optimum seed design should permit maturation to adulthood in the minimum time with the fewest parts using the fewest machine operations possible.
The team concluded that four basic processes - plaster casting, vapor deposition, extrusion, and laser machining are probably sufficiently versatile to permit self-replication and growth. ”

“ This list would be a total inventory of every distinct part which would result if factory machines were all torn down to their most basic components - screws, nuts, washers, rods, springs, etc. To show 100% closure, it would then be necessary to demonstrate the ability of the proposed automated parts fabrication sector to produce every part listed, and in the quantities specified, within a replication time of T = 1 year, starting from raw elemental or alloy feedstocks provided from the chemical processing sectors. ”

“ The major problems with the process in terrestrial applications are maintenance of the vacuum and high energy consumption, neither of which are factors on the lunar surface or in an orbital environment. ”

“ Move the proper workpiece to the machine, Load the workpiece onto the machine and affix it rigidly and accurately, Select the proper tool and insert it into the machine, Establish and set machine operating speeds and other conditions of operation, Control machine motion, enabling the tool to execute the desired function, Sequence different tools, conditions, and motions until all operations possible on that machine are complete, and Unload the part from the machine. ”

“ A number of different metal alloys will be required for casting various parts and molds. Different alloys of iron may be chosen for the steel balls for ball milling, the basalt casting molds, and the individual part that might be comprised of steel or iron. ”

“ The plant is the first "unmanned" factory in the world machinery industry. producing robots and other equipment worth about $70 million in the first year of operation with only 100 supervisory personnel. In 5 years the plant is expected to expand, perhaps with some of the robots it itself manufactures, to a $300 million annual output with a workforce of only 200 people, less than a tenth the number required in ordinary machine factories of equivalent output. ”

“ However, it is estimated that up to 80% of the laser cutting energy comes from the exothermic oxidation reaction, so in this latter case laser energies would have to be on the order of five times the value for the equivalent O2-atmosphere machining.
The problem of closure is even more critical in a replicating autonomous remote factory. The materials closure problem is solved in large measure by resorting to CO2 gas laser technology. ”

“ All types of costs are lower when fewer operations are required to produce a part according to specifications. The greatest savings result when the number of separate processing operations necessary to complete a part is reduced. Multiple operations which can be combined into fewer operations, or functionally similar parts requiring fewer production steps, should be changed in a design. ”

“ Castings of less than 0.45 kg and as massive as 11,350 kg have been made on Earth. Commercially, when compared to aluminum die casting, plaster mold casting is considered economical if 1000 parts or less are produced, although production runs up to 2000 parts may also be considered economical if the parts are especially complex. ”