Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

Ranjan, Rajit; Ayas, Can; Langelaar, Matthijs; Keulen, Fred van

doi:10.3390/ma13204576

Cited by 28 publications

(37 citation statements)

References 40 publications

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“…However, an important AM limitation, which is not yet explicitly addressed in the context of TO, is that of local overheating or heat accumulation during the manufacturing process. Recent experimental observations and better understanding of AM process physics reveal that overheating is not uniquely associated to overhangs, and dedicated analysis of the local thermal history is needed to characterize overheating (Adam and Zimmer 2014;Ranjan et al 2020). The effect is observed in both polymer and metal manufacturing.…”

Section: Introductionmentioning

confidence: 99%

“…A similar observation was presented by Patel et al (2019), showing dross formation even when acute overhangs were avoided. Finally, Ranjan et al (2020) presented LPBF thermal models and showed that the same degree of overhang can result in different thermal behaviour, depending on the heat evacuation capacity of other features in the vicinity. Hence, the geometrical approach of using a unique critical overhang angle throughout the domain could be insufficient for preventing overheating in some regions.…”

Section: Introductionmentioning

confidence: 99%

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Controlling local overheating in topology optimization for additive manufacturing

Ranjan

Ayas

Langelaar

et al. 2022

Struct Multidisc Optim

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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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Controlling local overheating in topology optimization for additive manufacturing

Ranjan

Ayas

Langelaar

et al. 2022

Struct Multidisc Optim

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“…In addition, such implementation only considers the current layer time without reflection on the temperature of the substrate. Ranjan et al (2017) investigated another approach to avoid overheating in which a combination of a mathematical formulation and density-based topology optimisation was used to adapt a geometry for thermal hotspot formation (Ranjan et al, 2020). In performance-related industries, such as the aerospace industry, weight is an essential aspect in the design and sizing of components.…”

Section: Introductionmentioning

confidence: 99%

In-situ adaptive thermal simulation method for predicting and avoiding hotspots in material extrusion processes

Driezen¹,

Herrmann²

2022

RPJ

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Purpose This study aims to design a novel strategy to avoid thermal defects in three-dimensional (3D) printing processes. A combination of subroutines and utility routines allows for in situ variations of the key process parameters (KPP) in the thermal simulation and produces by post-processing the output an updated machine code for enhanced quality of the printed part in a single iteration. Design/methodology/approach The input data for the thermal simulation were obtained by characterising an acrylonitrile butadiene styrene filament and calibrating an Ultimaker S5 printer. Abaqus subroutines were used to accurately simulate the continuous deposition of molten material. A utility routine extracted the nodal temperatures during simulation and detected regions that were prone to overheating. We developed a method, enabling the introduction of variable process parameters in the thermal simulation and validated it by printing several test geometries. Findings The results of the thermal simulation indicate that decreasing the print speed enhances the amount of heat dissipated to the environment. Therefore, it is an efficient way to avoid overheating of the printed geometry. The validation geometries showed improvements when adapting the print speed. Originality/value This approach is the first to demonstrate the potential of variable process parameters using implemented routines in the thermal process simulation. Here, the focus is on predicting and avoiding thermal hotspots. However, more potential can be obtained by enabling the prediction and adaptation of KPP to ensure mechanical performance. This would be an alternative way to tackle the cost- and time-inefficient post-processing of 3D-printed parts.

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“…A detrimental change of the heat conduction through the part towards the base plate, as well as a significant change of the inter layer time (ILT), can lead to severe heat accumulation of the part or areas of local overheating. This, in turn, results in deviations of the thermal history and eventually affects part quality [5,10,13]. In addition to the geometry, there are many other influencing factors on the thermal history of a L-PBF component.…”

Section: Introductionmentioning

confidence: 99%

“…Figure13. Oxygen concentration in the process chamber during the first 300 min of the short ILT process.…”

mentioning

confidence: 99%

Process Induced Preheating in Laser Powder Bed Fusion Monitored by Thermography and Its Influence on the Microstructure of 316L Stainless Steel Parts

Mohr

Sommer

Knobloch

et al. 2021

Metals

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Undetected and undesired microstructural variations in components produced by laser powder bed fusion are a major challenge, especially for safety-critical components. In this study, an in-depth analysis of the microstructural features of 316L specimens produced by laser powder bed fusion at different levels of volumetric energy density and different levels of inter layer time is reported. The study has been conducted on specimens with an application relevant build height (>100 mm). Furthermore, the evolution of the intrinsic preheating temperature during the build-up of specimens was monitored using a thermographic in-situ monitoring set-up. By applying recently determined emissivity values of 316L powder layers, real temperatures could be quantified. Heat accumulation led to preheating temperatures of up to about 600 °C. Significant differences in the preheating temperatures were discussed with respect to the individual process parameter combinations, including the build height. A strong effect of the inter layer time on the heat accumulation was observed. A shorter inter layer time resulted in an increase of the preheating temperature by more than a factor of 2 in the upper part of the specimens compared to longer inter layer times. This, in turn, resulted in heterogeneity of the microstructure and differences in material properties within individual specimens. The resulting differences in the microstructure were analyzed using electron back scatter diffraction and scanning electron microscopy. Results from chemical analysis as well as electron back scatter diffraction measurements indicated stable conditions in terms of chemical alloy composition and austenite phase content for the used set of parameter combinations. However, an increase of the average grain size by more than a factor of 2.5 could be revealed within individual specimens. Additionally, differences in feature size of the solidification cellular substructure were examined and a trend of increasing cell sizes was observed. This trend was attributed to differences in solidification rate and thermal gradients induced by differences in scanning velocity and preheating temperature. A change of the thermal history due to intrinsic preheating could be identified as the main cause of this heterogeneity. It was induced by critical combinations of the energy input and differences in heat transfer conditions by variations of the inter layer time. The microstructural variations were directly correlated to differences in hardness.

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Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

Cited by 28 publications

References 40 publications

Controlling local overheating in topology optimization for additive manufacturing

Controlling local overheating in topology optimization for additive manufacturing

In-situ adaptive thermal simulation method for predicting and avoiding hotspots in material extrusion processes

Process Induced Preheating in Laser Powder Bed Fusion Monitored by Thermography and Its Influence on the Microstructure of 316L Stainless Steel Parts

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