Periodic Reporting for period 2 - CAxMan (Computer Aided Technologies for Additive Manufacturing)
Reporting period: 2017-03-01 to 2018-08-31
The objectives of CAxMan were to establish cloud-based toolboxes, workflows and a one stop-shop for interoperable CAx-technologies supporting AM with respect to design, simulation, process planning and quality control. More specifically, to establish analysis-based design approaches that reduce material usage, increase weight savings through internal cavities and voids, and enhance process planning by exploiting thermal and stress analyses. All objectives were achieved expect for the one-stop-shop, where the efforts on the legal framework are continued in H2020 project CloudiFacturing.
Analysis-based design has been built on trivariate splines to represent the interior of objects mathematically. Trivariate splines are the foundation the new volumetric CAD-representation (V-rep) now being introduced in ISO 10303. The geometric concepts of V-rep were published as part of STEP part 42 in 2018, and a corresponding STEP Application Reference Module denoted ""Extended B-spline geometry"" was developed in CAxMan.
V-rep is well suited for the representation of variable/graded materials and anisotropic material, and is fundamentally different from B-rep CA. The trivariate splines are the basis for Isogeometric Analysis (IgA). In CAxMan we realised that block structured splines used in IgA were not sufficient for the interoperability of CAD and IgA. It was decided it to use trimmed trivariate splines. This in principle solves the interoperability issue between B-rep CAD and V-rep CAD/ IgA. However, it poses challenges to the numerical quadrature used in IgA. While quadrature over untrimmed elements is well understood, quadrature over trimmed elements is not. Untrimming, has been developed to address the challenge.
Novel technology for volumetric subdivision for designing voids and cavities has been developed. It has been observed for the mould use case that the voids reduce the thermal strains compared to a similar object without voids. Further, the metric quality control has shown that thermal distortions are smaller for the mould with voids than the without voids. This both reduce the amount of material used and the time needed for subtractive processes. The measured distortions are well aligned with the distortions predicted by thermal simulations developed in CAxMan for the AM-process used.
Using data exchange standards such as STEP and QIF, and cloud workflows for process planning, thermal-stress simulation and metrology-based quality control workflows are mutually interoperable. Interoperability is also established with Missler's TopSolid. Process planning supports thermal stress and distortion simulation, by replacing support structures with spring-like elements acting as boundary conditions. This makes the thermal simulation faster and enables efficient use simulation to predict thermal distortions for different model orientations, temperature ranges, and support structure configurations. Orientation can be optimized according to different criteria, e.g. surface quality, build time and the need for support structures.
Thermal analysis and residual stress simulation target material deposition methods and is complemented by a module for heat treatment. The ambition has been to provide very fast solutions (e.g. minutes, hours), which are suitable for optimisation loops running in the cloud and exploiting HPC resources. The approach is based on a strategy for simplified analysis using inherent strain methods that are suitable for powder-bed AM technologies. The solution has been calibrated through validation benchmarks and integrated into TopSolid.
The quality analysis workflow use 3D scanning to measure the deviation between the nominal CAD-model and the object produced by AM. It provides a deviation map that in CAxMan has been transferred to the CAD-system TopSolid, using the latest version of the QIF-standard.
The main effort in interfacing AM and subtractive manufacturing (SM) has been related to the development of new technology for offset calculations. New technology for simplifying patch networks of surfaces, by replacing them with large functional surfaces better suited for efficient and high-quality NC has also been developed and integrated into Top Solid.
For the injection mould use case, weight saving of 50% are achieved by creating a dedicated “structural mesh”, outside of which material is not necessary. The cycle time when moulding is improved by 10% due to reduction of cooling time by 35%: this turns into a reduction by 10% of the energy used during the injection moulding process. For the Nugear use case, manufacturing costs are reduced by 10%, machining time reduced by 25%, part weight reduced by up to 60% and waste material by up to 95%. AM has also allowed for a perfect balance of the “double face” configuration never achieved before.
CAxMan has identified 4 key exploitable results that involves innovation items from multiple partners. In addition, three joint exploitations involving multiple partners are identified. In addition 23 innovation items are described in the CAxMan Innovation shop with links to more detailed information (https://caxman.boc-group.eu/innovation-shop). Three videos are published on YouTube."
CAxMan has had a driving role with respect to anchoring V-rep and IgA in ISO 10303 STEP. This is expected to have a long-term influence on the deployment of V-rep and IgA in industry. CAxMan has also been among the first to use the newest version of the QIF-standard for establishing interoperability between metrology (M3 from TRIMEK) and CAD/CAM (TopSolid from Missler).
Interoperability between V-rep and IGA also opens for further progress on design optimisation loops for IGA that integrate process planning and thermal-stress simulation. Here, the novel fast and accurate prediction of thermal distortion used on the mould use case played a central role. To the best of our knowledge, the efficient design of internal voids using parameterized subdivision methods is novel.
The focus on interoperability in CAxMan has resulted in interoperability between the open source libraries GoTools, IGATools and CAxLib. The combination of these will have a much higher impact than the standalone use of the libraries.
CAxMan successfully built synergies with the EU project CloudiFacturing, which combines the results of CloudFlow and CloudSME and to which CAxMan is commercially aligned, in order to join forces with other stakeholders and to reach a higher volume of potential customers, while offering dedicated services for Additive Manufacturing.
In general, CAxMan tools allow users to reduce cost of parts produced by AM, reducing the number of trials to get a compliant part, reducing weight and waste material as well as increasing dimensional precision of components.