Manufacturing & Prototyping

Heat Transfer Analysis for Optimizing Solar Cell Casting Equipment

Finite element analysis was used to develop a miniature furnace to cast the solar cell wafers. Solar Power Industries’ (SPI) current annual production capacity for processing polycrystalline silicon feedstock into completed solar cells has grown to 40 megawatts, with plans to increase capacity to 250 megawatts over the next several years. SPI’s solar cell manufacturing process consists of three main steps:   Ingot and Wafer Production—High-quality silicon feedstock (containing specific quantities of dopants such as boron in order to alter electrical properties) is melted and solidified inside a directional solidification furnace to cast polycrystalline silicon ingots. The ingots are cut into rectangular blocks with a square cross-section, and then the blocks are sawed into thin multicrystalline wafers. Cell Production — The wafers are etched to remove surface damage caused by sawing. The wafers are then processed in a series of steps to produce photovoltaic cells. Module Assembly — Individual cells are connected by soldering to flat wires. Strings of cells are then joined to parallel connector wires and laminated to produce a solar module.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Improved Sand-Compaction Method for Lost-Foam Metal Casting

The flow of sand is redirected for better filling and compaction. An improved method of filling a molding flask with sand and compacting the sand around a refractory- coated foam mold pattern has been developed for incorporation into the lost-foam metal-casting process. In comparison with the conventional method of sand filling and compaction, this method affords more nearly complete filling of the space around the refractory-coated foam mold pattern and more thorough compaction of the sand. In so doing, this method enables the sand to better support the refractory coat under metallostatic pressure during filling of the mold with molten metal.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Improved Probe for Evaluating Compaction of Mold Sand

Sand is not perturbed during switching among different measurement positions. A nominally stationary tubular probe denoted a telescopic probe has been developed as an improved alternative to a prior movable probe used to evaluate the local degree of compaction of mold sand. The prior movable probe consists mainly of a vertically oriented tube with screen vents at its lower end. The upper end is connected to a source of constant airflow equipped with a pressure gauge. The probe is inserted vertically to a desired depth in a sand-filled molding flask and the back pressure at the given rate of flow of air is recorded as a measure of the degree of partial impermeability and, hence, of the degree of compaction of sand in the vicinity of the probe tip.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Micromachined Slits for Imaging Spectrometers

Slits can now be made about 100× the precision previously attainable. Slits for imaging spectrometers can now be fabricated to a precision much greater than previously attainable. What makes this possible is a micromachining process that involves the use of microlithographic techniques. This micromachining process supplants a prior machine-shop process.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Fabricating Nanodots Using Lift-Off of a Nanopore Template

Applications include nano-scale electronic and magnetic devices. A process for fabricating a planar array of dots having characteristic dimensions of the order of several nanometers to several hundred nanometers involves the formation and use of a thin alumina nanopore template on a semiconductor substrate. The dot material is deposited in the nanopores, then the template is lifted off the substrate after the dots have been formed. This process is expected to be a basis for development of other, similar nanofabrication processes for relatively inexpensive mass production of nanometer- scale optical, optoelectronic, electronic, and magnetic devices.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Making Complex Electrically Conductive Patterns on Cloth

Circuit patterns are implemented in tightly woven cloth instead of stitched conductive thread. A method for automated fabrication of flexible, electrically conductive patterns on cloth substrates has been demonstrated. Products developed using this method, or related prior methods, are instances of a technology known as “e-textiles,” in which electrically conductive patterns are formed in, and on, textiles. For many applications, including high-speed digital circuits, antennas, and radio frequency (RF) circuits, an e-textile method should be capable of providing high surface conductivity, tight tolerances for control of characteristic impedances, and geometrically complex conductive patterns. Unlike prior methods, the present method satisfies all three of these criteria. Typical patterns can include such circuit structures as RF transmission lines, antennas, filters, and other conductive patterns equivalent to those of conventional printed circuits.

Posted in: Briefs, TSP, Manufacturing & Prototyping

Read More >>

Direct Metal Laser-Sintering of Titanium

DMLS titanium parts can be used in aerospace and medical applications. During the first decade of direct metal laser-sintering (DMLS), the metals employed were generally ones developed specifically for DMLS, rather than those used in traditional metalforming methods. But in recent years, the range of available powder metals and the production quality of DMLS parts have advanced considerably, driving new interest in rapid manufacturing.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.