Page:Advanced Automation for Space Missions.djvu/181

1. Unimate sensors scan electric furnace temperature. Adjusts temperature for optimum viscosity.
2. Unimate introduces 100 kg of raw basalt into furnace through hopper feed gate.
3. Unimate raises furnace temperature to above liquidus with serial decrease to optimum temperature as melting proceeds.
4. Unimate causes discharge of set volume of melt into crucible resting on detent plugging mm-sized hole in crucible base.
5. Unimate sensors monitor crucible temperature fall-off until viscosity increase prevents leakage of charge.
6. Unimate positions crucible within induction coil above drum reel in raised position.
7. Unimate system activates induction furnace to lower viscosity of charge using programmed weight/temperature program to produce temperature (viscosity) plateau until first molten basalt droplet draining from crucible is grasped by clip on reel drum.
8. Unimate controller triggers drum release and turn operation begins, which results in the drawing of fiber.
9. Unimate sensors observe basalt fiber thread output using fiber optic techniques. Fiber diameter controls reel rate and furnace temperature. If no fiber is present, drum is raised and operation repeated.
10. Crucible weight-sensitive switch cuts off induction furnace as melt is consumed. Fiber breaks, filled reel drum is removed by Unimate and is replaced by an empty.
11. Reel drum is raised and empty crucible moved by Unimate onto detent below furnace. Procedure begins again.

formation, burning or melting (DeCarmo, 1979). If the shearing blades have curved edges like punches or dies the process is given another name (e.g., blanking, piercing, notching, shaving, trimming, dinking, and so on as noted in table 4.17.)

Shearing already has been automated in many industries. For instance, the Chambersburg Engineering Company has incorporated a 2000B Unimate into a trimming operation performed on the output of an impact forging system. The robot moves 1400 K platters from the forge to hot trimmers, sensing, via hand tooling interlocks, that it has properly grasped the platter. An infrared detector checks parts for correct working temperatures, and the robot rejects all platters for which either grasp or temperature requirements are not met (Unimation, 1979).

Despite its tremendous utility on Earth, shearing appears less desirable than other options for space manufacturing because of the problems of cold welding and shearing tool wear. Also, ceramic and silicate forms cannot be processed by conventional shearing techniques. The most attractive alternative may be laser-beam cutting, piercing, punching, notching, and lancing. Yankee (1979) has reviewed laser-beam machining (LBM) generally, and additional data are provided in section 4.3.1. The application of LBM techniques to metals for shearing operations is an established technology, whereas laser beam cutting of basalt and basalt products is not well-documented.

4D.2 Deformation Criteria and Research Options for Space Manufacturing

In general, deformation processes that do not require gas or liquid drives but emphasize electrical or electromagnetic mechanical power sources appear more practical for space manufacturing applications. Processes yielding thin-walled or ribbon forms such as reversible rolling or electroforming appear favorable. The mass/production ratio argues against heavy forges and in favor of roller technology, an approach which also should improve the quality of output in high-vacuum manufacturing environments. Deformation processes involving forming or shearing typically consume little material (except for fluid-driven devices). On the Moon, the optimum near-term design philosophy is to develop automated systems powered exclusively by electric and magnetic forces.

In order to make tool products, versatile semiautomated machines are initially required for the terrestrial demonstration program Tool life and machining time must be assessed in view of the extraterrestrial conditions anticipated. For example, Ostwald (1974) has reviewed these