Overhang Support Structure Design for Electron Beam Additive Manufacturing

2017 ◽  
Author(s):  
Bo Cheng ◽  
Y. Kevin Chou
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Design Process ◽  
Heat Dissipation ◽  
Design Method ◽  
Solid Substrate ◽  
Structure Design ◽  
Process Time ◽  
Support Structure ◽  
Powder Bed

Overhang structures are commonly found in Powder-bed metal additive manufacturing (AM) such as electron beam additive manufacturing (EBAM) process. The EBAM is assumed to build overhang structure without support features since powder bed could provide support. However, heat dissipation difference by sintered powder and solid substrate for overhang feature actually causes severe part distortion and requires support structure. Current support generation methods usually used certain types of structure to cover the overhang space. They may overestimate the support volume or put a large amount of supports, which could not be necessary and increase the post process time. Thus, the object of this task is to enhance the performance and efficient usage of the EBAM technology through effective support structure designs. In this study, a combined heat support and support anchor design method has been proposed. Numerical model has been used to evaluate stress and deformation during the design process. The detailed design process has been presented for a typical overhang and the simulation results have indicated that overhang deformation can be greatly reduced using this new method.

Deformation Evaluation of Part Overhang Configurations in Electron Beam Additive Manufacturing

2015 ◽  
Author(s):  
Bo Cheng ◽  
Kevin Chou
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Beam Current ◽  
Solid Substrate ◽  
Industrial Applications ◽  
Deformation Condition ◽  
Fe Model ◽  
Porosity Level ◽  
Powder Bed ◽  
Thermomechanical Process

Powder-bed electron beam additive manufacturing (EBAM) has emerged as a cost-effective process for many industrial applications. Intuitively, EBAM would not require support structures for overhang geometry because the powder bed would self-support the overhang weight. However, without a proper support structure, overhang warping actually occurs in practices. In this study, a two dimensional (2D) finite element (FE) model was developed to study the thermomechanical process of EBAM. The model was applied to evaluate (1) the process parameter effect, (2) the overhang and support configuration effect, and (3) the powder porosity effect on overhang deformations. The major results are summarized as follows. (1) Increasing the beam speed and diameter will result in less deformation in an overhang area, while increasing the beam current will worsen the deformation condition. (2) A smaller tilt angle will cause a larger overhang deformation. (3) A support column, even placed away from the solid substrate side, will minimize overhang deformations. (4) An anchor-free solid piece beneath the overhang can reduce the deformation with an appropriate gap. (5) A lower powder porosity level may alleviate overhang deformations.

Thermomechanical Investigation of Overhang Fabrications in Electron Beam Additive Manufacturing

2014 ◽  
Author(s):  
Bo Cheng ◽  
Ping Lu ◽  
Kevin Chou
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Heat Dissipation ◽  
Element Model ◽  
Full Density ◽  
Support Structures ◽  
Powder Bed ◽  
Thermomechanical Process ◽  
Root Cause

Electron beam additive manufacturing (EBAM) is one of powder-bed-fusion additive manufacturing processes that are capable of making full density metallic components. EBAM has a great potential in various high-value, small-batch productions in biomedical and aerospace industries. In EBAM, because a build part is immersed in the powder bed, ideally the process would not require support structures for overhang geometry. However, in practice, support structures are indeed needed for an overhang; without it, the overhang area will have defects such as warping, which is due to the complex thermomechanical process in EBAM. In this study, a thermomechanical finite element model has been developed to simulate temperature and stress fields when building a simple overhang in order to examine the root cause of overhang warping. It is found that the poor thermal conductivity of Ti-6Al-4V powder results in higher temperatures, also slower heat dissipation, in an overhang area, in EBAM builds. The retained higher temperatures in the area above the powder substrate result in higher residual stresses in an overhang area, and lower powder porosity may reduce the residual stresses associated with building an overhang.

scholarly journals PARAMETERS ON SUPPORT STRUCTURE DESIGN FOR METAL ADDITIVE MANUFACTURING

2020 ◽  
Vol 1 ◽  
pp. 1145-1154
Author(s):  
S. Weber ◽  
J. Montero ◽  
M. Bleckmann ◽  
K. Paetzold
Keyword(s):  
Additive Manufacturing ◽  
Design Of Experiments ◽  
Structure Design ◽  
Design Parameters ◽  
Powder Bed Fusion ◽  
Design For Additive Manufacturing ◽  
Laser Powder Bed Fusion ◽  
Support Structure ◽  
Powder Bed ◽  
Metal Additive

AbstractThe topic of support structure design in the Design for Additive Manufacturing (DfAM) field is not addressed with the same relevance as the topic of part design. Therefore, this contribution investigates parameters for both the manufacturing and support structure design for the Laser Powder Bed Fusion (L-PBF) process. Matrices for cause-effect-relations of manufacturing and design parameters on build properties as well as correlations of them are presented. Based on these, recommendations for actions for experimental procedures are derived following the Design of Experiments method.

On Process Temperature in Powder-Bed Electron Beam Additive Manufacturing: Model Development and Validation

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Bo Cheng ◽  
Steven Price ◽  
James Lydon ◽  
Kenneth Cooper ◽  
Kevin Chou
Keyword(s):  
Thermal Conductivity ◽  
Electron Beam ◽  
Additive Manufacturing ◽  
Thermal Characteristics ◽  
Pool Size ◽  
Process Temperature ◽  
Thermal Imager ◽  
Powder Bed ◽  
Melt Pool ◽  
Melt Pool Size

Powder-bed beam-based metal additive manufacturing (AM) such as electron beam additive manufacturing (EBAM) has a potential to offer innovative solutions to many challenges and difficulties faced in the manufacturing industry. However, the complex process physics of EBAM has not been fully understood, nor has process metrology such as temperatures been thoroughly studied, hindering part quality consistency, efficient process development and process optimizations, etc., for effective EBAM usage. In this study, numerical and experimental approaches were combined to research the process temperatures and other thermal characteristics in EBAM using Ti–6Al–4V powder. The objective of this study was to develop a comprehensive thermal model, using a finite element (FE) method, to predict temperature distributions and history in the EBAM process. On the other hand, a near infrared (NIR) thermal imager, with a spectral range of 0.78 μm–1.08 μm, was employed to acquire build surface temperatures in EBAM, with subsequent data processing for temperature profile and melt pool size analysis. The major results are summarized as follows. The thermal conductivity of Ti–6Al–4V powder is porosity dependent and is one of critical factors for temperature predictions. The measured thermal conductivity of preheated powder (of 50% porosity) is 2.44 W/m K versus 10.17 W/m K for solid Ti–6Al–4V at 750 °C. For temperature measurements in EBAM by NIR thermography, a method was developed to compensate temperature profiles due to transmission loss and unknown emissivity of liquid Ti–6Al–4V. At a beam speed of about 680 mm/s, a beam current of about 7.0 mA and a diameter of 0.55 mm, the peak process temperature is on the order around 2700 °C, and the melt pools have dimensions of about 2.94 mm, 1.09 mm, and 0.12 mm, in length, width, and depth, respectively. In general, the simulations are in reasonable agreement with the experimental results with an average error of 32% for the melt pool sizes. From the simulations, the powder porosity is found critical to the thermal characteristics in EBAM. Increasing the powder porosity will elevate the peak process temperature and increase the melt pool size.

A Novel Structure Design Method Based on Knowledge Template

2012 ◽  
Vol 159 ◽  
pp. 18-22
Author(s):  
Rui Song Jiang ◽  
Xin Fa Chen ◽  
Da Yong Feng ◽  
Feng Jun Wang
Keyword(s):  
Turbine Blade ◽  
Design Process ◽  
Investment Casting ◽  
Design Method ◽  
Structure Design ◽  
Design System ◽  
Construction Methods ◽  
Novel Structure ◽  
Base Design

In this study, a novel structure design method based on knowledge template was prompted. The notion and construction methods of knowledge template were introduced. Moreover, the knowledge template based design process was represented. The knowledge templates of investment casting die bases of turbine blade were established and a design system for die base was developed. The system provides designers with a semi-automated approach for the die base design. Finally, several sample applications for investment casting die base of turbine blade were presented for demonstration.

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