ISO ASTM 52950-2021 pdf free download

ISO ASTM 52950-2021 pdf free download.Additive manufacturing — General principles — Overview of data processing
4.1.1 General
A complete 3D data set of the part forms the basis of additive manufacturing. Most commonly, this is created by direct 3D CAD modelling. The data sets can also be generated by 3D scanned data if the parts exist in a physical form (see Figure 1). A representation based on facets is then generated from the volume or area model through polygonization or triangulation (see 4.1.2.4) and transferred to the additive manufacturing process in a suitable data transfer format. This software-assisted process runs automatically as far as possible.
4.1.2 Explanation of the key terms used in Figure 1
4.1.2.1
3D CAD modelling (solid modelling) 3D CAD modelling is the process most commonly used during design to produce a digital 3D model. The starting point can be an idea for a product, which takes shape and becomes increasingly defined directly on the computer screen during the process, or a previously generated image of the object in the form of sketches, drawings, etc. which can be converted to 3D data through a modelling process in CAD systems. Volume can be described using two different techniques, or a combination of both. The object is either composed of basic volumes (shapes) (e.g. cuboid, wedge, cylinder, cone, sphere, and toroid) which generate the actual object via a sequence of Boolean operations, or the volume is described by its surrounding boundary surfaces and the location of the material relative to the boundary surfaces.
4.1.2.2
3D digitalization 3D digitalization is the process in which the surface geometry of a physical object is measured using appropriate hardware and software and recorded in a digital point cloud model. The objects can be manually produced or finished models which need to be copied in digital form. The use of 3D digitalization is particularly efficient if the model has empirically drafted, freeform surface areas, since these are difficult to reproduce through direct 3D CAD modelling.
4.1.2.3 Surface reconstruction
Surface reconstruction is a means of processing data generated through 3D digitalization. Starting from the computer-generated point cloud, mathematically described curves and surfaces are generated with sufficient topological information to adequately recreate the object surface. These data can then be stored separately or integrated into an existing CAD volume model. Surface reconstruction thus creates a bridge between 3D digitalization and CAD modelling.
4.1.2.4 Polygonization/triangulation
This software-assisted process is used to generate a volume-based facet model either from the point cloud following 3D digitalization or from the volume model after 3D CAD modelling. The object surface is represented by a multiplicity of tiny, planar facets, or polygons, which are stretched between the points. The number and size of the facets are one aspect which determines how accurately the actual surface geometry is reproduced. This process creates a data set.
4.2.1 General
The most common interface formats used within the dataflow are explained in 4.2.2 to 4.2.8 . The STL format is the most commonly used data format for data transfer. If the STL format cannot be exported due to the absence of the interface module (not supplied as standard with all CAD software programs), the data can be transferred to other CAD programs via interface formats (e.g. STEP or IGES), which shall then enable an STL output. NOTE Conversion problems can arise when transferring data through system-neutral interfaces, since interfaces capabilities (despite established standards) vary greatly and programs operate with varying degrees of accuracy (e.g. in the acceptance of the joining of two adjacent surfaces).