Abstract
Soon after the first computers were available in industry, the use of computers in product development and manufacturing started. Manual design and manufacturing steps were replaced by computer assisted steps. Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) emerged. In the start of this evolution most of the process pipeline for design and manufacturing was paper-based. Computers were used for calculation at single steps. Manual input was provided (e.g., paper tape or punched cards) and the output printed on paper or drawn by plotters on paper or mylar. The first CAD-systems were addressing 2D construction drawings. Gradually, CAD tools began to support objects represented by 3D wireframes of curves, and then moved on to mathematical surfaces representing the outer surfaces of the object. Consistent representation of the outer hull of an object was formalized with the introduction of BREP solid models in Ian Braids PhD thesis in 1973. Then followed the introduction of sculptured surfaces into BREP-models, an approach standardized in the ISO 10303 standard (STEP) in the early 1990s. As the STEP-standard got a foothold and BREP based solid modelling matured, exchange of CAD-models between CAD-systems from different vendors was facilitated, and more and more steps in the design and manufacturing process could be computerized. Around the year 2000, CAD-seemed to solve most of the industrial needs for subtractive manufacturing processes,. However, the CAD-models represented the nominal objects to be produced, not a model of the as-built object, so it was not a digital twin.
In the late 1980s 3D Systems introduced Stereolithography or "SLA" printing, the first digital driven additive manufacturing process. Additive manufacturing has gone through many evolutionary steps since then, and many alternative additive manufacturing technologies are now available, tailored for different polymers and alloys. The interest from industry in additive manufacturing processes has in the last decade been growing fast. While subtractive manufacturing assumed that the material used is isotropic, additive manufacturing processes result in objects with significant anisotropies (big variations in material properties including directional dependence). Consequently, there is a need to also to represent the interior material of an object mathematically. Both for the purpose of controlling the anisotropies already during design, as well as to know what they are after production. A digital twin of the complete object is needed. This must represent both the outside surfaces and interior structure, e.g., lattice structures that reduce the amount of material used as well as variations in the material. In powder bed metal manufacturing, the metal powder is heated by, e.g., lasers. Locally the transition from metal powder though melted metal to solidification is in nanoseconds, but a printing process can last many hours. Thermal stresses usually build during the additive manufacturing process and there is a need to control this to avoid thermal distortions of the shape, as well as interior cracks. Thus, simulation plays an integral part of controlling additive manufacturing process. However, simulation is just a prediction, so currently additive manufacturing machines are equipped with sensors (images, thermal, etc.) that record enormous amounts of data that needs to be analysed.
In this presentation I will give an overview of the evolution of CAD to the current needs for novel solutions and approaches triggered by additive manufacturing. I will also present what is addressed in the two Horizon 2020 Innovation Actions www.change2twin.eu (2020-2024) and www.pulsate.eu (2020-2024). These two projects respectively address digital twins in manufacturing, and advanced laser based and additive manufacturing.
In the late 1980s 3D Systems introduced Stereolithography or "SLA" printing, the first digital driven additive manufacturing process. Additive manufacturing has gone through many evolutionary steps since then, and many alternative additive manufacturing technologies are now available, tailored for different polymers and alloys. The interest from industry in additive manufacturing processes has in the last decade been growing fast. While subtractive manufacturing assumed that the material used is isotropic, additive manufacturing processes result in objects with significant anisotropies (big variations in material properties including directional dependence). Consequently, there is a need to also to represent the interior material of an object mathematically. Both for the purpose of controlling the anisotropies already during design, as well as to know what they are after production. A digital twin of the complete object is needed. This must represent both the outside surfaces and interior structure, e.g., lattice structures that reduce the amount of material used as well as variations in the material. In powder bed metal manufacturing, the metal powder is heated by, e.g., lasers. Locally the transition from metal powder though melted metal to solidification is in nanoseconds, but a printing process can last many hours. Thermal stresses usually build during the additive manufacturing process and there is a need to control this to avoid thermal distortions of the shape, as well as interior cracks. Thus, simulation plays an integral part of controlling additive manufacturing process. However, simulation is just a prediction, so currently additive manufacturing machines are equipped with sensors (images, thermal, etc.) that record enormous amounts of data that needs to be analysed.
In this presentation I will give an overview of the evolution of CAD to the current needs for novel solutions and approaches triggered by additive manufacturing. I will also present what is addressed in the two Horizon 2020 Innovation Actions www.change2twin.eu (2020-2024) and www.pulsate.eu (2020-2024). These two projects respectively address digital twins in manufacturing, and advanced laser based and additive manufacturing.
