Fabricating time

The sol-gel technique offers excellent composition control, low-temperature processing and short fabrication times at comparatively low cost. One of its disadvantages consists of the fact that only a small thickness (up to 200 nm) of high-quality film can be achieved in one coating cycle, so several... 

There is a continuous stream of improvements in PC. Control of machines continually enters new eras that dramatically improve ease of machine setup, allow ease of ensuring to meet fabricated product requirements, more uninterrupted operation, simplify remote handling, reduce fabricating times, cut energy costs, boast part quality, and so on. 

In order to produce surface-relief electro-optic gratings, Munakata et compared two fabrication methods of SRG inscription. In the first, the SRG was produced with an interference pattern of cw laser, with relatively modest intensities. The gratings so recorded were photo- and thermally erasable, and efficient writing was polarization dependent. In the second method, a phase mask was employed to provide the periodic intensity modulation of a pulsed laser, the 3rd-order harmonic (at 355 nm) of a Nd YAG laser. The SRG was produced with a single laser pulse, allowing a very short fabrication time (less than Is). The direshold for ablation was 500 mj/(em pulse), and the amplitude of the SRG increased with pulse energy. A depth of up to 300 rim could be achieved, leading to a smooth but not sinusoidal surface modulation. 

The heat released by the electrochemical discharges is only partially transferred to the workpiece. Part of it is evacuated through the electrolyte and the tool-electrode. The greater the heat removed from the machining zone, the better is the machining in terms of quality. As expected, the major drawback is the decreased material removal rate. In general, a trade-off has to be reached between quality and fabrication time. 

These techniques are able to process both metals and non metals. As a result of intensive research, disadvantages of these techniques, such as high fabrication time, insufficient accuracy, and high cost, have been widely eliminated. Today, maximum part dimension is limited to less than 1000 mm. 

A typical dielectric welding tool consists of two platens that are electrically connected to a generator that imposes an alternating electric field. The platens are used both as electrodes and apply pressure to the joint area. Various parameters will affect the quality of the dielectric weld. These include the type of fibre in the fabric, its propensity to heat in a dielectric field (called the material s dielectric loss), the thickness of the fabric, and the melt temperature of the fabric. Time, pressure, and field frequency (directly related to temperamre) will also affect the quality of the joint. The frequency of the field being generated can be from the radiofrequency range (13—100 MHz) up to microwave frequency (2—20 GHz). 

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