scholarly journals Autonomous Robotic Feature-Based Freeform Fabrication Approach

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 247
Author(s):  
Xinyi Xiao ◽  
Hanbin Xiao
Keyword(s):  
Feature Recognition ◽  
In Situ Monitoring ◽  
Additive Process ◽  
Loop Control ◽  
Model Decomposition ◽  
Freeform Fabrication ◽  
Material Deposition ◽  
Effective Manner ◽  
Avoidance Condition ◽  
Continuous Material

Robotic additive manufacturing (AM) has gained much attention for its continuous material deposition capability with continuously changeable building orientations, reducing support structure volume and post-processing complexity. However, the current robotic additive process heavily relies on manual geometric reasoning that identifies additive features, related building orientations, tool approach direction, trajectory generation, and sequencing all features in a non-collision manner. In addition, multi-directional material accumulation cannot ensure the nozzle always stays above the building geometry. Thus, the collision between these two becomes a significant issue that needs to be solved. Hence, the common use of a robotic additive is hindered by the lack of fully autonomous tools based on the abovementioned issues. We present a systematic approach to the robotic AM process that can automate the abovementioned planning procedures in the aspect of collision-free. Typically, input models to robotic AM have diverse information contents and data formats, hindering the feature recognition, extraction, and relations to the robotic motion. Our proposed method integrates the collision-avoidance condition to the model decomposition step. Therefore, the decomposed volumes can be associated with additional constraints, such as accessibility, connectivity, and trajectory planning. This generates an entire workspace for the robotic additive building platform, rotatability, and additive features to determine the entire sequence and avoid potential collisions. This approach classifies the uniqueness of autonomous manufacturing on the robotic AM system to build large and complex metal components that are non-achievable through traditional one-directional AM in a computationally effective manner. This approach also paves the path in constructing an in situ monitoring and closed-loop control on robotic AM to control and enhance the build quality of the robotic metal AM process.

scholarly journals Influence of a closed-loop controlled laser metal wire deposition process of S Al 5356 on the quality of manufactured parts before and after subsequent machining

2021 ◽  
Author(s):  
Dina Becker ◽  
Steffen Boley ◽  
Rocco Eisseler ◽  
Thomas Stehle ◽  
Hans-Christian Möhring ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Closed Loop ◽  
Deposition Process ◽  
Metal Wire ◽  
Machining Process ◽  
Machining Processes ◽  
Initial State ◽  
Additive Process ◽  
Shape Accuracy ◽  
Loop Control

AbstractThis paper describes the interdependence of additive and subtractive manufacturing processes using the production of test components made from S Al 5356. To achieve the best possible part accuracy and a preferably small wall thickness already within the additive process, a closed loop process control was developed and applied. Subsequent machining processes were nonetheless required to give the components their final shape, but the amount of material in need of removal was minimised. The effort of minimising material removal strongly depended on the initial state of the component (wall thickness, wall thickness constancy, microstructure of the material and others) which was determined by the additive process. For this reason, knowledge of the correlations between generative parameters and component properties, as well as of the interdependency between the additive process and the subsequent machining process to tune the former to the latter was essential. To ascertain this behaviour, a suitable test part was designed to perform both additive processes using laser metal wire deposition with a closed loop control of the track height and subtractive processes using external and internal longitudinal turning with varied parameters. The so manufactured test parts were then used to qualify the material deposition and turning process by criteria like shape accuracy and surface quality.

Distributed-Parameter Modeling for Geometry Control of Manufacturing Processes With Material Deposition

1998 ◽  
Vol 122 (1) ◽  
pp. 71-77 ◽  
Author(s):  
Charalabos Doumanidis ◽  
Eleni Skordeli
Keyword(s):  
Solid Freeform Fabrication ◽  
Surface Topology ◽  
Distributed Parameter ◽  
Surface Geometry ◽  
Mass Source ◽  
Freeform Fabrication ◽  
Geometry Model ◽  
Material Deposition ◽  
Solid Objects ◽  
3D Solid

Recent solid freeform fabrication methods generate 3D solid objects by material deposition in successive layers made of adjacent beads. Besides numerical simulation, this article introduces an analytical model of such material addition, using superposition of unit deposition distributions, composed of elementary spherical primitives consistent with the mass transfer physics. This real-time surface geometry model, with its parameters identified by in-process profile measurements, is used for Smith-prediction of the material shape in the unobservable deposition region. The model offers the basis for a distributed-parameter geometry control scheme to obtain a desired surface topology, by modulating the feed and motion of a moving mass source. The model was experimentally tested on a fused wire deposition welding station, using optical sensing by a scanning laser stripe. Its applications to other rapid prototyping methods are discussed. [S0022-0434(00)02301-7]

Uniaxial High-Speed Micro-Scale Three-Dimensional Surface Topographical Measurements Using Fringe Projection

2020 ◽  
Author(s):  
Yi Zheng ◽  
Beiwen Li
Keyword(s):  
High Speed ◽  
Sample Surface ◽  
3D Scanning ◽  
In Situ Monitoring ◽  
Fringe Projection ◽  
Depth Information ◽  
Projection Technique ◽  
Projection System ◽  
Loop Control

Abstract In-situ inspection has drawn many attentions in manufacturing due to the importance of quality assurance. Having an accurate and robust in-situ monitoring can assist corrective actions for a closed-loop control of a manufacturing process. The fringe projection technique, as a variation of the structured light technique, has demonstrated significant potential for real-time in-situ monitoring and inspection given its merits of conducting simultaneous high-speed and high accuracy measurements. However, high-speed 3D scanning methods like fringe projection technique are typically based on triangulation principle, meaning that the depth information is retrieved by analyzing the triangulation relationship between the light emitter (i.e., projector), the image receiver (i.e., camera) and the tested sample surface. Such measurement scheme cannot reconstruct 3D surfaces where large geometrical variations are present, such as a deep-hole or a stair geometry. This is because large geometrical variations will block the auxiliary light used in the triangulation based methods, which will resultantly cause a shadowed area to occur. In this paper, we propose a uniaxial fringe projection technique to address such limitation. We measured a stair model using both conventional triangulation-based fringe projection technique and the proposed method for comparison. Our experiment demonstrates that the proposed uniaxial fringe projection technique can perform high-speed 3D scanning without shadows appearing in the scene. Quantitative testing shows that an accuracy of 1.15% can be obtained using the proposed uniaxial fringe projection system.

A novel technique for in-situ monitoring of crystallinity and temperature during rapid thermal annealing of thin Si/Si-Ge films on quartz/glass

1996 ◽  
Vol 424 ◽  
Author(s):  
V. Subramanian ◽  
F. L. Degertekin ◽  
P. Dankoski ◽  
B. T. Khuri-Yakub ◽  
K. C. Saraswat
Keyword(s):  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Acoustic Waves ◽  
Liquid Crystal Display ◽  
In Situ Monitoring ◽  
Loop Control ◽  
Active Matrix ◽  
Novel Technique ◽  
End Point Detection ◽  
Point Detection

AbstractA novel technique is presented to simultaneously measure temperature and crystallinity insitu during the rapid thermal annealing of thin Si / SiGe films on transparent substrates for active matrix liquid crystal display applications. The technique uses acoustic waves to monitor temperature, by measuring changes in velocity with temperature. The technique enables accurate tracking of crystalline phase transitions along with temperature, since it is independent of emissivity. This provides a methodology for closed-loop control and end-point detection. The experiments on thin amorphous Si on Quartz demonstrate temperature repeatability of 2%. Also, the technique proved sensitive enough to detect the onset of nucleation, as evidenced by TEM.

scholarly journals Combination of Laser Material Deposition and Laser Surface processes for the manufacture of sculptured surface components

2018 ◽  
Author(s):  
Jon Iñaki Arrizubieta ◽  
Magdalena Cortina ◽  
Jose Exequiel Ruiz ◽  
Aitzol Lamikiz
Keyword(s):  
Surface Quality ◽  
Dimensional Accuracy ◽  
Laser Machining ◽  
Additive Process ◽  
Laser Polishing ◽  
Material Deposition ◽  
Laser Heat Source ◽  
Near Net Shape ◽  
Machining Operations

The present work proposes a novel manufacturing technique based on the combination of Laser Metal Deposition, Laser Beam Machining and Laser Polishing processes for the complete manufacturing of complex parts. Therefore, the complete process is based on the application of a laser heat source both for the building of the preform shape of the part by additive manufacturing and for the finishing operations. Their combination enables to manufacture near-net-shape parts and afterwards, remove the excess material via laser machining, which has resulted to be capable of eliminating the waviness resulting from the additive process. Besides, surface quality is improved via laser polishing to reduce the roughness of the final part. Therefore, conventional machining operations are eliminated, what results in a much cleaner process. In order to validate the capability of this new approach, the dimensional accuracy and surface quality of the resulting parts are evaluated. The process has been validated on an Inconel 718 test part, where a previously additively built up part has been finished by means of laser machining and laser polishing.

Abstraction of Semantic Mid-Surface Based on Rib-Feature Recognition

2015 ◽  
Author(s):  
Huawei Zhu ◽  
Yusheng Liu
Keyword(s):  
Feature Recognition ◽  
High Efficiency ◽  
Surface Patch ◽  
Surface Model ◽  
Thin Wall ◽  
Wall Model ◽  
Element Analysis ◽  
Model Decomposition ◽  
Surface Patches ◽  
Surface Regeneration

Mid-surface abstraction is an effective simplification method for thin-wall models. The complexity of finite element analysis (FEA) for a mid-surface model can be reduced greatly after abstraction. Although the model decomposition method is adopted for mid-surface extraction, it is hard to obtain the correct mid-surface model for complex models since the existing heuristic rule based methods lack of design intention. In addition, the mid-surface model is not easy to reuse. In this study, a semantic based mid-surface model representation and generation method is proposed. Firstly, a hierarchical semantic mid-surface model based on rib-feature decomposition is proposed. Secondly, based on the reorganization of rib-features and decomposition of the thin-wall model, the rib-features’ semantic information are obtained by the abstraction of the structure and connection in the thin-wall model. Then the hierarchical structure is generated by connection semantics. According to the various structure semantics, different abstraction methods will be employed to get the mid-surface patch for each sub region. Finally, the hierarchical semantic mid-surface model is constructed by the generation of the connection relationship between mid-surface patches based on the connection semantics between the rib-features. This semantic model ensures the high efficiency and accuracy of mid-surface regeneration when local modifications occur to a thin-wall model. A typical example is given to demonstrate the process.

A Process Map for Consistent Build Conditions in the Solid Freeform Fabrication of Thin-Walled Structures

2000 ◽  
Vol 123 (4) ◽  
pp. 615-622 ◽  
Author(s):  
Aditad Vasinonta ◽  
Jack L. Beuth ◽  
Michelle L. Griffith
Keyword(s):  
Solid Freeform Fabrication ◽  
Numerical Models ◽  
Thermal Control ◽  
Process Map ◽  
Freeform Fabrication ◽  
Thin Walled Structures ◽  
Melt Pool ◽  
Material Deposition ◽  
Thin Walled ◽  
Net Shaping

In solid freeform fabrication (SFF) processes involving thermal deposition, thermal control of the process is critical for obtaining consistent build conditions and in limiting residual stress-induced warping of parts. In this research, a nondimensionalized plot (termed a process map) is developed from numerical models of laser-based material deposition of thin-walled structures. This process map quantifies the effects of changes in wall height, laser power, deposition speed and part preheating on melt pool length, which is an essential process parameter to control in order to obtain consistent build conditions. The principal application of this work is to the Laser Engineered Net Shaping (LENS) process under development at Sandia Laboratories; however, the general approach and a subset of the presented results are applicable to any SFF process involving a moving heat source. Procedures are detailed for using the process map to predict melt pool length and predictions are compared against experimentally measured melt pool lengths for stainless steel deposition in the LENS process.

scholarly journals Closed-Loop Control of Droplet Transfer in Electron-Beam Freeform Fabrication

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 923
Author(s):  
Shuhe Chang ◽  
Haoyu Zhang ◽  
Haiying Xu ◽  
Xinghua Sang ◽  
Li Wang ◽  
...  
Keyword(s):  
Electron Beam ◽  
Real Time ◽  
Closed Loop ◽  
Deposition Process ◽  
Closed Loop Control ◽  
Droplet Transfer ◽  
Loop Control ◽  
Freeform Fabrication ◽  
Transfer Distance ◽  
Transfer State

In the process of electron-beam freeform fabrication deposition, the surface of the deposit layer becomes rough because of the instability of the feeding wire and the changing of the thermal diffusion condition. This will make the droplet transfer distance change in the deposition process, and the droplet transfer cannot always be stable in the liquid bridge transfer state. It is easy to form a large droplet or make wire and substrate stick together, which makes the deposition quality worsen or even interrupts the deposition process. The current electron-beam freeform fabrication deposition is mostly open-loop control, so it is urgent to realize the real-time and closed-loop control of the droplet transfer and to make it stable in the liquid bridge transfer state. In this paper, a real-time monitoring method based on machine vision is proposed for the droplet transfer of electron-beam freeform fabrication. The detection accuracy is up to ± 0.08 mm. Based on this method, the measured droplet transfer distance is fed back to the platform control system in real time. This closed-loop control system can stabilize the droplet transfer distance within ± 0.14 mm. In order to improve the detection stability of the whole system, a droplet transfer detection algorithm suitable for this scenario has been written, which improves the adaptability of the droplet transfer distance detection method by means of dilatation/erosion, local minimum value suppression, and image segmentation. This algorithm can resist multiple disturbances, such as spatter, large droplet occlusion and so on.

Modeling of Multifunctional Porous Tissue Scaffolds With Continuous Deposition Path Plan

2012 ◽  
Author(s):  
A. K. M. B. Khoda ◽  
Ibrahim T. Ozbolat ◽  
Bahattin Koc
Keyword(s):  
Pore Size ◽  
Tool Path ◽  
Medial Axis ◽  
Tissue Scaffolds ◽  
Fabrication Process ◽  
Free Form ◽  
Tissue Scaffold ◽  
Medial Axis Transformation ◽  
Material Deposition ◽  
Continuous Material

A novel modeling technique for porous tissue scaffolds with targeting the functionally gradient variational porosity with continuous material deposition planning has been proposed. To vary the porosity of the designed scaffold functionally, medial axis transformation is used. The medial axis of each layers of the scaffold is calculated and used as an internal feature. The medial axis is then used connected to the outer contour using an optimum matching. The desired pore size and hence the porosity have been achieved by discretizing the sub-regions along its peripheral direction based on the pore size while meeting the tissue scaffold design constraints. This would ensure the truly porous nature of the structure in every direction as well as controllable porosity with interconnected pores. Thus the desired controlled variational porosity along the scaffold architecture has been achieved with the combination of two geometrically oriented consecutive layers. A continuous, interconnected and optimized tool-path has been generated for successive layers for additive-manufacturing or solid free form fabrication process. The proposed methodology has been computationally implemented with illustrative examples. Furthermore, the designed example scaffolds with the desired pore size and porosity has been fabricated with an extrusion based bio-fabrication process.

Improving solid freeform fabrication by laser-based additive manufacturing

2002 ◽  
Vol 216 (9) ◽  
pp. 1253-1264 ◽  
Author(s):  
D Hu ◽  
H Mei ◽  
R Kovacevic
Keyword(s):  
Additive Manufacturing ◽  
Metal Powder ◽  
Laser Cladding ◽  
Closed Loop ◽  
Solid Freeform Fabrication ◽  
Three Dimensional ◽  
Closed Loop Control ◽  
Loop Control ◽  
Freeform Fabrication ◽  
Laser Cladding Process

Solid freeform fabrication (SFF) methods for metal part building, such as three-dimensional laser cladding, are generally less stable and less repeatable than other rapid prototyping methods. A large number of parameters govern the three-dimensional laser cladding process. These parameters are sensitive to the environmental variations, and they also influence each other. This paper introduces the research work in Research Center for Advanced Manufacturing (RCAM) to improve the performance of its developed three-dimensional laser cladding process: laser-based additive manufacturing (LBAM). Metal powder delivery real-time sensing is studied to achieve a further controllable powder delivery that is the key technology to build a composite material or alloy with a functionally gradient distribution. An opto-electronic sensor is designed to sense the powder delivery rate in real time. The experimental results show that the sensor's output voltage has a good linear relationship with the powder delivery rate. A closed-loop control system is also built for heat input control in the LBAM process, based on infrared image sensing. A camera with a high frame rate (up to 800frame/s) is installed coaxially to the top of the laser—nozzle set-up. A full view of the infrared images of the molten pool can be acquired with a short nozzle—substrate distance in different scanning directions, eliminating the image noise from the metal powder. The closed-loop control results show a great improvement in the geometrical accuracy of the built feature.

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