Additive manufacturing, also known as 3D-printing, describes all production processes where the component produced is built up layer by layer from raw material (which can be a melt, a powder, a string or a wire). It is contrary to conventional production methods, where a cast or forged blank material is removed to get the desired component. The best known technique for additive manufacturing with metals is the selective laser melting (SLM), where metal powder is laid on in layers of typically 20-100 µm and is then melted by laser beams on those areas designed to become the product. Those areas will solidify to a compact mass with the properties of the base metal. Because production costs are about 70 times higher with this method than with conventional production methods, the additive manufacturing of larger components, as e.g. valve bodies, is still a dream of the future. The high specific costs limit use to relatively small components, where additive production can generate a measurable customer benefit. Especially the potential to produce inner contours with any shape and the direct production from CAD-data allowing individual solutions for applications where conventional constructions have reached their limits. Using the example of a multistage valve trim to prevent cavitation one recognizes easily that especially for these applications an additive produced throttling cartridge has several advantages as: a) The possibility of an individual sizing without significant extra costs, because the production can directly be transferred from the CAD-data b) The feature of building up inner contours allow a compact (one-piece) throttling cartridge c) The free arrangement of flow channels over the valve stroke which results in a more regular characteristic curve and better control d) The use of standard valve bodies even with more than six throttle stages; which results in comparable production costs for the complete valve.
Arca sees the next development step in throttling cartridges that are optimized for control valves with strong dependency of the differential pressure to the flow (and therewith the valve stroke). Such process conditions are typical for the control of feed water at spray-nozzles and steam conditioning. With smaller flow rate the entire pressure difference of the system lies at the control valve (with corresponding potential of cavitation), with huge flow rate at the nozzle. At the valve with full opening only a very small differential pressure and therewith no cavitation appears, however a rather large Kv -value is required. What could suggest itself more than to develop a throttling cartridge that holds in “lower” areas a high number of throttle levels and is in the higher area only single stage sized – optimized for a cavitation free control over the entire controlling range? Additive production makes (almost) everything possible!