Electrochemical Additive Manufacturing (ECAM)
Electrochemical Additive Manufacturing (ECAM) is an emerging, nontraditional additive manufacturing (AM) process currently under study in the UCMAN laboratory. With significant advantages over conventional AM processes, the ECAM process is a promising candidate for future commercial adoption of AM.
Why Electrochemical Additive Manufacturing (ECAM)?
The term additive manufacturing typically brings to mind a traditional, laser-powered curing or sintering process of layer-by-layer material addition. Inherent limitations of conventional processes include thermal defects (which compromise the integrity of the geometry and material properties) and reliance on support structures (which introduce extra cost, labor, and risk of part damage). These issues pose a barrier to commercial adoption, prompting study into alternative approaches of part fabrication by AM. The nontraditional nature of the ECAM process allows for overcoming these challenges during part fabrication.
| Attributes | MJ | ME | SLA | SLS | ECAM |
|---|---|---|---|---|---|
| Avoid support structures | Somewhat | No | No | Somewhat | Yes |
| Can deposit metal parts | Somewhat | No | No | Yes | Yes |
| Avoids residual stress/thermal effects | Somewhat | Somewhat | No | No | Yes |
| Avoids post processing steps | No | Somewhat | No | No | Yes |
| Can achieve resolution | No | No | No | No | Yes |
What is the working principle behind material addition in ECAM?
Figure 1. Working principle of ECAM
Material addition by the ECAM process is achieved using the principle of electrodeposition between an anode and cathode submerged in a metal plating bath. In contrast to processes that deposit over a large area (ie: electroplating or electroforming), the deposit is deliberately localized between a tool of localized geometry (anode) and a flat substrate (cathode). An externally-applied voltage bias drives the ions in solution to migrate to the substrate near the tool, reduce in charge, and form a solid deposit on the substrate.
| Process | Process makes up the entire part | Cathode is removable after the process | Geometry can deviate from that of a cathode | Deposited area can be localized |
|---|---|---|---|---|
| Electroplating | No | No | No | No |
| Electroforming | Yes | Yes | No | No |
| ECAM | Yes | Yes | Yes | Yes |
This entire process occurs at room temperature, which avoids the thermal defects seen in conventional processes. Prior work has shown residual stresses in ECAM-built parts to be several orders of magnitude lower than those found in conventional AM parts.
Figure 2. Study of residual stress control in ECAM
What is a voxel in the ECAM process?
A voxel is the 3D unit and fundamental “building block” of parts that are manufactured by ECAM. The filling-in of a given tool-substrate gap by deposited metal is defined as a voxel, or volumetric pixel. Voxel size and properties are programmatically controlled by the relative position between tool and substrate and applied voltage parameters (ie: amplitude, duty cycle, frequency) in the given solution environment. Properties of interest include material composition, microstructure (ie: porosity), hardness, and yield strength.
Figure 3. Study of porosity control in ECAM
Figure 4. Study of structural control using variable frequencies
Figure 5. Study of hardness and strength control in ECAM parts
Figure 6. Study of composition control of multi-material ECAM parts
Extension of electrodeposition to voxel-by-voxel additive manufacturing
A three-dimensional part printed by ECAM consists of a series of voxels built in a defined programmatic sequence by adjusting the relative tool-substrate position in response to completion of each voxel (detected as a current spike). This programmatic sequence is the tool path that is set up to build the desired computer-generated 3D model. This voxel-by-voxel method of material addition is what enables ECAM to print free-standing parts without reliance on support structures.
Figure 7. Integration of the localized deposition with 3-axis control and current feedback to enable deposition of complex 3D CAD parts
Figure 8. Study of support structureless tool path planning for ECAM
Figure 9. Example of a free-standing structure built in a voxel-by-voxel manner with variable build directions, as opposed to a traditional layer-by-layer manner.
View a timelapse of the deposition.
Figure 10. A showcase of the variety of three-dimensional forms built using ECAM
Modeling and simulation studies
Underlying the brief explanation of voxel build is an extremely complex, localized electrochemical environment. The information an experimenter has access to is limited to single in-process current signal and a post-process view of the deposit. However, this leaves questions as to the nature of what is occurring at the interface during deposition. How do the ions move and redistribute throughout the solution near the deposit? Why do they deposit in a certain manner under certain process parameters? Modeling and simulation, provided they are physically-justified by experimental observation and scientific laws, serve as additional tools to gain insight into these phenomena which are otherwise not possible to observe directly. The scale of simulations has ranged from continuum level (to understand diffusion behavior in the gap and its effect on the deposit) to atomic level (to gain insight into the atom-by-atom nature of electrodeposition).
Figure 11. Showcase of finite element simulation (continuum-level) studies of ECAM
Figure 12. Showcase of atomic-scale simulation studies of ECAM
Acknowledgments
This work has been accomplished under the support of NSF grants CMMI-1400800, CMMI-1454181 (CAREER), and CMMI-1955842.