Manufacturing & Prototyping

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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Weld Repair of a Directionally Solidified Superalloy Article

The weld is also directionally solidified to preserve the desired grain structure. An arc-welding technique for repair of a directionally solidified (DS) nickel-base superalloy article (e.g., a turbine blade or vane) has been devised. The technique equally is applicable to a part as cast or a part that has been damaged in use. Unlike ordinary gas tungsten arc (GTA) welding, this technique results in a predominantly DS microstructure in the repaired region, similar to the microstructure of the DS casting. In addition, whereas ordinary GTA welding often involves the use of a filler material different from that of the workpiece, the weld filler material used in the present technique is of the same composition as that of the DS casting, so that undesired localized chemical differences are not introduced into in the repair region.

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Low-Temperature Thermocompressive Au-to-Au Diffusion Bonding

This technique is suitable for fabrication of microelectro- mechanical structures. A technique of thermocompressive gold-to-gold diffusion bonding at relatively low temperature has been devised to provide stable, uniform, strong bonds between struc- tural components of microelectromechanical systems. The technique can also be used for vacuum sealing of microscopic cavities. Unlike some other metal-to-metal diffusion bonding techniques, this technique does not entail significant outgassing or the formation of intermetallic compounds. The technique is suitable for bonding of parts made of silicon, quartz, low-thermal-expansion glass, and other materials that can withstand the relatively mild rigors of a low-temperature thermocompressive-bonding process. Two parts to be joined by this technique must have faying surfaces that are either flat or shaped to fit each other. In preparation for bonding, each of the faying surfaces is coated with a layer of chromium, then with a layer of gold (see figure). The coating is done by electron-beam evaporation. The coated substrates are cleaned, then clamped together with their gold layers touching in the desired final configuration in a press in a vacuum chamber.

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Process for Rapid Prototyping in Ceramic-Matrix Composites

Precursors of continuous-fiber-reinforced CMCs are deposited in patterned layers. The ceramic-composite advanced tow- placement (CCATP) process is a means of laying down continuous-fiber-reinforced, ceramic-matrix composite (CMC) materials in patterned layers to form objects that could have complex three-dimensional shapes. The CCATP process is a member of the growing family of solid-freeform processes in art of rapid prototyping.

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