AS ISO ASTM 52910-2020 pdf download.Additive manufacturing一Design 一Requirements, guidelines and recommendations.
5.2 Design opportunities
5.2.1 Background — AM fabricates parts by adding material in a layer-by-layer manner. Due to the nature of AM processes, AM has many more degrees of freedom than other manufacturing processes. For example, a part can be composed of millions of droplets if fabricated in a material jetting process. Discrete control over millions of operations at micro to nano scales is both an opportunity and a challenge. Unprecedented levels of interdependence are evident among considerations and manufacturing process variables, which distinguishes AM from conventional manufacturing processes. Capabilities to take advantage of design opportunities can be limited by the complexities of process planning.
5.2.2 Overview — The layer-based, additive nature means that virtually any part shapes can be fabricated without hard tooling, such as moulds, dies or fixtures. Geometries that are customized to individuals (customers or patients) can be economically fabricated. Very sophisticated geometric constructions are possible using cellular structures (honeycombs, lattices, foams) or more general structures. Often, multiple parts that were conventionally manufactured can be replaced with a single part, or smaller number of parts, that is geometrically more complex than the parts being replaced. This can lead to the development of parts that are lighter and perform better than the assemblies they replace. Furthermore, such part count reduction (called part consolidation) has numerous benefits for downstream activities. Assembly time, repair time, shop floor complexity, replacement part inventory and tooling can be reduced, leading to cost savings throughout the life of the product. An additional consideration is that geometrically complex medical models can be fabricated easily from medical image data.
5.2.3 In many AM processes, material compositions or properties can be varied throughout a part. This capability leads to functionally graded parts, in which desired mechanical property distributions can be fabricated by varying either material composition or material microstructure. If effective mechanical properties are desired to vary throughout a part, the designer can achieve this by taking advantage of the geometric complexity capability of AM processes. If varying material composition or microstructure is desired, then such variations can often be achieved, but with limits dependent on the specific process and machine. Across the range of AM processes, some processes enable point-by-point material variation control, some provide discrete control within a layer, and almost all processes enable discrete control between layers (vat photopolymerization is the exception). In the material jetting and binder jetting processes, material composition can be varied in virtually a continuous manner, droplet-to-droplet or even by mixing droplets. Similarly, the directed energy deposition process can produce variable material compositions by varying the powder composition that is injected into the melt pool. Discrete control of material composition can be achieved in material extrusion processes by using multiple deposition heads, as one example. Powder bed fusion (PBF) processes can have limitations since difficulties can arise in separating unmelted mixed powders. It is important to note that specific machine capabilities will change and evolve over time, but the trend is toward increasing material composition flexibility and property control capability.
5.2.4 A significant opportunity exists to optimize the design of parts to yield unprecedented structural properties. The concept of design for functionality can be realized, meaning that if a part’s functions can be defined mathematically, the part can be optimized to achieve those functions. Novel topology and shape optimization methods have been developed in this regard. Resulting designs can have very complex geometric constructions, utilizing honeycomb, lattice or foam internal structures, can have complex material compositions and variations, or can have a combination of both. Research is needed in this area, but some examples of this are emerging.
5.2.5 Other opportunities involve some business considerations. Since no tooling is required for part fabrication using AM, lead times can be very short. Little investment in part-specific infrastructure is needed, which enables mass customization and responsiveness to market changes. In the case of repair, remanufacturing of components could be highly advantageous both from cost as well as lead time perspectives.AS ISO ASTM 52910 pdf download.