LD process

A biochemically important pair of compounds, namely, NAD-NADH, together with a series of model nucleotides, have been investigated by LD and PD. °,Two laser beams were used in that experiment (266 and 347 nm), and the results were compared to those obtained by Cf PD. For simple nucleotides the major ions produced during LD processes are not dependent on the wavelength used. However, the results obtained for NAD-NADH (positive and negative mode) do not follow that trend. Although the exact reason for these differences is still unknown, it can be speculated that an interaction between wavelength and the resonance forms of the aromatic base can account, in part, for this deviation in pattern. 

Several variations of the oxygen steelmaking process have been developed. They include bottom-blown converters (e.g., the OBM process, the Q-BOP process and the LSW process) and the top-blown converters (e.g., the LD process, its variant the LD-AC process, the Kaldo process and the Oberhausen process) [27.3,27.8]. 

Oxygen-Furnace Process Method of steelmaking in which an oxygen stream is directed downward onto a melted mass of pig iron and scrap, thereby producing high-quality carbon steels also known as LD process, after the Austrian towns of Linz and Donawitz, where it was developed. 

Gohel MC, Patel LD. Processing of nimesulide-PEG 400-PG-PVP solid dispersions preparation, characterization, and in vitro dissolution. Drug Dev Ind Pharm 2003 29(3) 299-310. 

Laser direct structuring is based on the notion of laser activation of specially additivated plastics. The additives that enable the LDS process and that are finely distributed in the MID basic body are transformed into catalytically effective species during laser structuring and must satisfy different requirements [6] ... 

FIGURE 2.17 Current portfolio of materials compatible with the LPKF-LDS process (graphics courtesy of LPKF)... 

This metallization bath is widely used in prototyping, particularly for testing different structuring parameters of the LPKF-LDS process. It has a footprint of 50 x 40 cm and plugs into a standard socket outlet. The fact that it works only with copper is a drawback, as is the short life cycle [106]. 

Beaker metallization is limited to about 10 ijm of copper per bath pass, because the bath has to be analyzed and rebalanced as soon as a defined time has elapsed. A ballpark figure for growth rate is approximately 1 pm every ten minutes. Hypothetically speaking, copper can be plated in thicker layers even by beaker deposition. Repassing the copper-plated plastic part in the analyzed and rebalanced copper bath makes it possible to build copper layers thicker than 10 pm. The cost effectiveness of the process should not be the primary variable. The thickness of the copper buildup with the ProtoPlate LDS process is limited by the life of the bath. The maximum plating thickness is 8 to 15 pm. 

Table 3.3 clearly shows that the values for the galvanically assisted and hot-emboss metallization processes are very good. The literature gives a value of 58.8 [m/Qmm j for bulk copper at 20 °C [54]. The conductivity of chemically reductive metallization on LDS-activated surfaces is about 60%, which is a consequence of the lower crystallite density in chemical plating. The wide scatter is due to the roughness discussed in Section 3.2.3 and produced by the LDS process. The poor conductivity for Flamecon is due to the process as such. Molten metal particles are sprayed on to the surface, and the plating forms as individual particles intermesh. The outside layer of the individual particles of copper hampers electron flow, and electric conductivity diminishes accordingly [54]. 

Sintered models are porous, so infiltrating surface-sealing processes can be used. Sintered parts are not as detailed and are rougher than stereolithographic parts, but mechanically they are stronger and can sustain higher loads [61,186]. Plastics compatible with the LPKF-LDS process for surface structuring (see Section 7.3) are not available for either of these processes. 

Before it can be structured in the LDS process, each plastic body has to be thoroughly cleaned in a wet-chemical process and then dipped, in order to remove metallic residues of the machining tools. Dipping is a process in which the parts are immersed first in a strong alkaline and then a strong acidic solution at elevated temperature. 

LDS Process with Moldings from Rapid Tooling Injection-Molding Tools... 

The alternative is to use the laser-sintering process to manufacture form inserts from steel (Section 7.2.6). LDS parts injection-molded with these form inserts can be readied for the LDS process without wet-chemical dipping. On account of the process-related surface roughness of form inserts manufactured by DMLS, there is a slight tendency toward more overmetallization, but this is not generally considered a critical issue. 

LDS Process with Moldings from Steel Tools with Nonhardened Inserts... 

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