Manufacturing & Prototyping

Venting Closed-Cell Foam Panels

Stresses caused by differential gas pressures are reduced. A technique for reducing in-flight loss of closed-cell foam insulation has been devised. In the original application, foam is used for thermal insulation on the external tank of the space shuttle. As the space shuttle ascends, aerodynamic effects cause an increase in surface temperature of the foam. This heating increases the internal cell gas pressure and reduces cell wall strength. The difference between the increasing pressure of the gases trapped in the foam cells and the decreasing pressure of the ambient air contribute to stresses that can break off pieces of foam during flight. Perforating the foam with small holes makes it possible for some trapped gases to escape, reducing the stresses sufficiently to keep the foam intact during ascent. This technique reduced in-flight foam loss by more than 95 percent. The vent holes could offer similar benefits in other applications where materials are subjected to thermal and pressure gradients.

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Digital Preassembly Process

Assembly of major elements of large structures is simulated in a CAD environment. Because the International Space Station is being assembled in orbit, there was a need to verify in advance that it could, indeed, be assembled there and that the various assembled parts would function as intended. A digital preassembly process was devised to satisfy this need for verification, without having to perform assembly on Earth. The process enables designers to simulate the assembly of major elements of large structures by use of a computer-aided design (CAD) system. The process could also be applied in any type of manufacturing and in many types of construction.

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Punches and Dies for Rounding Corners of Metal Sheets

Corners can be formed to desired radii without sawing, snipping, or filing. Punch-and-die sets have been designed for use in rounding corners of rectangular metal sheets to specified radii. One of the traditional procedures for rounding a corner on a rectangular metal sheet is to first make a rough cut with a band saw and/or hand metal snips, then to file the roughly cut edge; this procedure is time-consuming and does not result in an accurate radius. The use of a punch-and-die set of the present type takes less time and results in a corner with an accurate radius.

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Expendable Composite-Layup Dies From Rapid-Prototype Masters

Small production runs of intricate parts can be accomplished at relatively low cost. A method that exploits rapid prototyping has been conceived to reduce the time and cost associated with the production of small quantities of composite-material parts that have complex shapes. In this method, mandrels and dies used in forming composite layups are sized and shaped by molding them on rapid-prototype masters and are made of disintegrating mold material (DMM). The method is particularly suitable for manufacturing ventilating air ducts and water ducts for the International Space Station and manifolds and ducts for low-temperature [

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Hermetic Wafer Bonding by Use of Microwave Heating

Clamping is unnecessary, and the only appreciable heating occurs in the metal bond. Microwave heating is the basis of a simple technique for quickly and gently bonding two metallized dielectric or semiconductor wafers to each other. The technique can be used, for example, to bond a flat, gold-coated silicon wafer to another gold-coated silicon wafer that is flat except for a cavity, in order to hermetically seal the cavity (see figure). The technique has the potential to become a standard one for bonding in the fabrication of microelectromechanical systems (MEMS).

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Chemical Machining of Microscopic Holes and Grooves in Glass

This technique overcomes disadvantages of conventional macro- and micromachining. A technique for making precise, microscopic holes and grooves in glass workpieces has been invented. The technique differs from both (1) traditional macroscopic mechanical drilling and milling and (2) conventional micromachining that involves etching through photolithographically patterned masks. The technique can be used, for example, to make holes between 20 µm and 1 mm in diameter.

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Tool for Installing a Seal Ring Between Pipe Flanges

Sealing surfaces are kept clean and injuries to fingertips are prevented. A tool has been devised to facilitate the accurate placement of a seal ring between the hubs of two pipe flanges that are to be clamped together. Heretofore, technicians have resorted to impro- visations that have included, variously, insertion of a ring with fingertips, lowering a ring into place by use of string or tape, sticking a ring to one hub by use of grease while the other hub is brought into alignment, and/or positioning a ring by use of a screwdriver or knife. All of these improvisations entail susceptibility to incorrect placement of the ring and contamination of sealing surfaces. Moreover, by inserting fingertips in the narrow pinch gap between the hubs, a technician risks injury.

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