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A mold insert case study on Topology Optimized design for Additive Manufacturing

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The additive manufacturing (AM) of injection molding inserts has gained popularity during recent years primarily due to the reduced design-to-production time and form freedom offered by AM. In this paper, topology optimization (TO) is performed on a metallic mold insert which is to be produced by the Laser Powder Bed Fusion (LPBF) technique. First, a commercially available TO software is used, to minimize the mass of the component while ensuring adequate mechanical response under a prescribed loading condition. The commercial TO tool adopts geometry-based AM constraints and achieves a mass reduction of ~50 %. Furthermore, an in-house TO method has been developed which integrates a simplified AM process model within the standard TO algorithm for addressing the issue of local overheating during manufacturing. The two topology optimized designs are briefly compared, and the advantages of implementing manufacturing constraints into the TO algorithm are discussed.
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... The conducted studies confirm the importance of using the system, part, and process design approach and having efficient design as the selection criterion. The objective of efficient design is to improve the efficiency and performance of the tool in operation, i.e. shorter cycle time, avoidance of stops, minimization (or elimination) of the rejections, improved quality, maximization of the production efficiency etc. [11,25,[30][31][32][33][34][35][36]. ...
... Efficient design is of particular significance for the production tools in hot working and injection molding. The importance of process design and its close relationship to part and system design is illustrated in [36]. ...
... The conducted studies have shown that efficient operational performance as the target yields the best results as the tool, die, or mold is designed for and made by L-PBF [1,11,25,[30][31][32][33][34][35][36]. This review shows that it is possible to improve this operational performance by adding LMPp (DED-p, LC) for surface functionalization [41][42][43][44][45][46][47][48][49][50][51] and tool, die, or mold remanufacture [52,[56][57][58][59][60][61][62][63][64]. ...
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This paper explores the possibilities to use laser-based additive processes to make, surface treat and repair/remanufacture tools, dies and molds for cold working, hot working, and injection molding. The failures encountered in these applications are described. The materials used conventionally and in the laser additive processes are accounted for. The properties of the tools, dies and molds made by Laser-based Powder Bed Fusion (L-PBF) are as good as and in some cases better than the properties of those made in wrought materials. Shorter cycle time, reduced friction, smaller abrasive wear, and longer life cycle are some of the benefits of L‑PBF and Directed Energy Deposition with powder (DED-p) (or Laser Metal Deposition with powder, LMD‑p, or Laser Cladding, LC). L‑PBF leads to higher toolmaking costs and shorter toolmaking lead time. Based on a review of conducted investigations, this paper shows that it is possible to design and make tools, dies and molds for and by L‑PBF, surface functionalize them by DED-p (LMD‑p, LC), and repair/remanufacture them by DED-p (LMD‑p, LC). With efficient operational performance as the target for the whole tool life cycle, this combination of L‑PBF and DED-p (LMD‑p, LC) has the greatest potential for hot working and injection molding tools and the smallest for cold working tools (due to the current high L‑PBF and DED-p (LMD‑p, LC) costs).
... An L-PBF inclusive manufacturing of the tooling for injection molding has been addressed in many studies. The possibility to design, manufacture and use conformal cooling channels has been subject to investigation from different perspectives in the many of these studies [59,[141][142][143][144][145] Figure 29. ...
... The height = the outer diameter = 200 mm, the outer skin thickness = 6 mm, and the lattice diameter = 0.5 mm in Figure 30 As mentioned above, the implementation of conformal cooling channels to enhance the cooling efficiency has been the most common example of L-PBF design freedom in the injection molding sector and corresponding academic research. To benefit further from the L-PBF potential, the removal of excessive non-contributing material, topology optimization, should also be considered [145]. ...
... In this study, two topology optimization methods were considered and used [145]: ...
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The journey of production tools in cold working, hot working, and injection molding from rapid tooling to additive manufacturing (AM) by laser-based powder bed fusion (L-PBF) is described. The current machines and their configurations, tool steel powder materials and their properties, and the L-PBF process parameters for these materials are specified. Examples of production tools designed for and made by L-PBF are described. Efficient design, i.e., high tooling efficiency and performance in operation, should be the primary target in tool design. Topology and lattice structure optimization provide additional benefits. Using efficient design, L-PBF exhibits the greatest potential for tooling in hot working and injection molding. L-PBF yields high tooling costs, but competitive total costs in hot working and injection molding. Larger object sizes that can be made by L-PBF, a larger number of powder metals that are designed for different tooling applications, lower feedstock and L-PBF processing costs, further L-PBF productivity improvement, improved surface roughness through L-PBF, and secured quality are some of the targets for the research and development in the future. A system view, e.g., plants with a high degree of automation and eventually with cyber-physically controlled smart L-PBF inclusive manufacturing systems, is also of great significance.
... Therefore, a significant portion of current AM research is focussed on investigating these different aspects of precision, namely the repeatability, predictability, and robustness of the process. Various approaches have been employed for this purpose, including investigating the design for precision AM using topology optimization [11], computational modeling of the L-PBF process [12], and statistical process optimization studies [13]. These methods are also complemented by studies on improving methods for the finishing of parts [14], as well as for metrology [15]. ...
... In particular, Sinico et al. compared two topology optimization (TO) techniques-one based on commercial software and another based on an in-house developed TO method that also compensates for localized overheating caused during part manufacturing. This work discusses the precision benefits that are achieved when manufacturing constraints are included within topology optimization, rather than just purely geometric constraints [11]. Bayat et al. developed a multi-physic numerical model of the L-PBF process, which was then used to track the formation of porosities that cause imprecision while printing. ...
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The rise in popularity of Additive Manufacturing technologies and their increased adoption for manufacturing have created a requirement for their fast development and maturity. However, there is still room for improvement when compared with conventional manufacturing in terms of the predictability, quality, and robustness. Statistical analysis has proven to be an excellent tool for developing process knowledge and optimizing different processes efficiently and effectively. This paper uses a novel method for printing overhanging features in Ti-6Al-4V metal parts, by varying process parameters only within the down-facing area, and establishes a methodology for predicting dimensional errors in flat 45° down-facing surfaces. Using the process parameters laser power, scan speed, scan spacing, scan pattern, and layer thickness, a quadratic regression equation is developed and tested. An Analysis of variance (ANOVA) analysis concluded that, within the down-facing area, the laser power is the most significant process parameter, followed by the layer thickness and scan speed. Comparatively, the scanning pattern is determined to be insignificant, which is explained by the small down-facing area where the various scanning patterns play no role. This paper also discusses the interaction effects between parameters. Some thoughts on the next steps to be taken for further validation are discussed.
... Lastly, it was shown here that extension of the hotspot constraint to a 3D setting is straightforward. This is also exemplified by Sinico et al. (2019) where the method was applied for TO of an industrial injection mold design. Experimental validation of 3D designs using optical tomography-based in situ monitoring technique is currently under investigation. ...
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A novel constraint to prevent local overheating is presented for use in topology optimization (TO). The very basis for the constraint is the Additive Manufacturing (AM) process physics. AM enables fabrication of highly complex topologically optimized designs. However, local overheating is a major concern especially in metal AM processes leading to part failure, poor surface finish, lack of dimensional precision, and inferior mechanical properties. It should therefore be taken into account at the design optimization stage. However, including a detailed process simulation in the optimization would make the optimization intractable. Hence, a computationally inexpensive thermal process model, recently presented in the literature, is used to detect zones prone to local overheating in a given part geometry. The process model is integrated into density-based TO in combination with a robust formulation, and applied in various numerical test examples. It is found that existing AM-oriented TO methods which rely purely on overhang control do not ensure overheating avoidance. Instead, the proposed physics-based constraint is able to suppress geometric features causing local overheating and delivers optimized results in a computationally efficient manner.
... A comparison between two designs was presented in a paper by Sinico et al. one design created using a commercial software, Siemens NX, and the other using an in-house method developed to integrate an algorithm to address the issue of local overheating during the LPBF process. Promising results were achieved in both cases [128,204]. ...
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