NASA’s EBF3: The Future of Art-to-Part Manufacturing

Medical
Human bone replacement parts


Automotive and motorsports
Custom and replacement parts


Aerospace structural components
New structural components with high buy-to-fly ratios (such as bulkheads or complex housings)
Replacement parts for aging aircraft


Replacement parts in remote or hostile locations
Military forward-operating locations
Seafaring ships
Offshore oil rigs
Polar research stations


Three-dimensional models for new designs
Rapid iterative prototyping


Metals deposition and treating
Plating, structural mending, and spot etching and heating

NASA’s innovative e-beam freeform fabrication system, which was developed to enable parts manufacturing in the zero-gravity environment of space, offers significant benefits for rapid prototyping and manufacturing here on Earth.

Companies currently providing only laser-based services (e.g., 3D stereolithography, direct metal laser sintering [DMLS]) can use NASA’s EBF3 system to expand their offerings, take advantage of the benefits of e-beam manufacturing (e.g., a wide variety of metal-based parts, reduced waste), and eliminate common drawbacks associated with laser/powder-based e-beam systems (e.g., lengthy cooling periods, part size restricted by fixed powder box dimensions).

Companies offering e-beam fabrication will find that EBF3’s need for lower accelerating voltages (typically 20kV or less) eliminates many of the safety and shielding requirements necessary with higher power (typically 60-200 kV) systems that are derived from e-beam welding technologies.

How It Works

The Core Technology

The core of the EBF3 system is an electron-beam gun, wire feeder, and positioning system enclosed in an aluminum vacuum chamber. Like other e-beam systems, the NASA system focuses the beam to melt a material, in this case metal wire, which is then accurately deposited layer by layer according to computer-aided design (CAD) data to fabricate a three-dimensional structural part without the need for a die or mold.

Unlike other e-beam systems, which operate at 60–200 kV, NASA’s technology can create parts using about 20 kV accelerating voltage. The system can be used to make parts from a wide range of materials (e.g., titanium, aluminum, nickel, stainless steel, etc.) as well as alloyed and layered parts via multiple wire feeds. The size of parts will be dependent upon the size of the system’s build envelope, which can be scalable from a few inches to tens of feet or even larger.

Unique Enhancements

In addition to the core system, NASA has developed the following innovations, which can be licensed either with NASA’s EBF3 or individually for use in other applications:

• Automated Process Control: Monitors deposition and automatically adjusts the parameters to correct for anomalies, resulting in more consistent deposition for higher quality parts.
  
  
• Ion/E-Beam Deflection Control System: Uses beam rastering to provide a high level of precision and accuracy while reducing power requirements.
  
  
• Vapor-Barrier Vacuum-Isolation System: Eliminates the need for a single high-vacuum chamber, thereby allowing larger, low-pressure operating enclosures to be used.

Why It Is Better

The EBF3 system offers the promise of a nearly unrestricted part build envelope. Due to the low power requirements, the complete unit can be as small as an office desk. For very small and lightweight operational environments, the deposition unit can be reduced to the size of a desktop computer, with an umbilical cord to provide connection to the required power supply and vacuum pumps. A system that integrates EBF3’s vacuum-isolation enhancement with a maneuverable, positioning platform (e.g., an industrial robotic arm) eventually will be capable of building any size or shape complex part.

NASA’s EBF3 system is less expensive than other systems. NASA installed its system for $250K; however, a commercialized system is expected to cost significantly less. Furthermore, the EBF3’s low-power design offers significantly reduced operating costs and minimizes the shielding required to comply with radiation safety regulations.

Other cost savings are possible because of the NASA system’s reduced use of material compared to other systems. EBF3 uses a full 100% of the material for the part with no residual material contamination. This offers an advantage over powder-based e-beam systems, which require residual material to be recaptured and recertified before it can be reused. In addition, parts made with NASA’s EBF3 system can be used or shipped immediately with only minimal need for cooling.

Because two or more wires can be fed into the system, EBF3 enables the manufacturing of multi-material parts. The system can create a wide variety of never-before-possible alloy-based parts by feeding two wires simultaneously (at either constant or variable rates). Alternatively, the wires can be fed sequentially to create layered parts with better surface properties. In the case of industrial plating, EBF3 could offer a high-quality alternative to traditional plating (e.g., chrome plating) while allowing manufacturers to better comply with environmental regulations.

The technology works exceptionally well with such alloys as Ti-6Al-4V and Al 2219.

Patent

NASA has patented this technology under U.S. Patent No. 7,168,935 (link opens new browser window) and has applied for additional patents.

EBF3 Core Technology Technical Specifications

Frequenty Asked Questions

What kind of part quality can be expected from the NASA EBF3?

NASA’s part quality is better than other electron-beam systems because NASA’s system works at a slower deposition rate (typically in the range of 1–6 lb/hr [0.45–2.72 kg/hr]) with a smaller bead. NASA’s measured surface roughness is approximately RMS 256, but a roughness of RMS 8 has been achieved via glazing with a 5-minute post-deposition treatment directly after completing the deposition in the e-beam chamber. NASA’s wire-fed EBF3 system provides a smoother sidewall for the part compared to powder-based systems, which yield parts with a sandpaper-like finish due to unmelted powder sticking to the sides of the deposit.

2. Mechanical Properties

What are the mechanical properties that occur during a melt when using NASA’s EBF3?

Tests after standard heat treatments demonstrated that products made using NASA’s EBF3 have properties similar to plate products when subjected to equivalent heat treatments. For example, Ti-6Al-4V as deposited using NASA’s EBF3 system is similar to a mill-annealed plate of Ti-6Al-4V—that is, 90–100 ksi (620–690 MPa) tensile yield, 120 ksi (825 MPa) tensile ultimate, >10% total elongation.

3. Residual Stress

Does NASA’s EBF3 system cause any residual stress during electron-beam deposition?

In running the EBF3 system, NASA researchers have encountered residual stresses and distortion in the baseplate. If the baseplate is sacrificial (i.e., removed during post-processing), such stresses and distortion are not an issue—very little stress is observed in the deposited material itself. However, for baseplates that remain attached to the part, the stress extends about 0.25 in. (6.35 mm) from the deposit location. The extent of the stress is affected by the e-beam heating parameters as well as the deposition rate. Research is underway to understand and mitigate these stresses.

4. Variety of Metals

What metals has NASA deposited using its EBF3 system?

NASA’s EBF3 system could be used to deposit the following metals:

NASA has graded from pure Al to 2219 and from pure Al to 2195 both parallel to and perpendicular to the build plate. The starting wires were standard alloy wires, but by controlling the wire-feed system and feeding two wires simultaneously, the chemistry of the deposition could be easily tailored at any location within the deposit (either at the surface or within the bulk, depending on the end application requirements).

In using its EBF3 system, NASA has not enriched the metal wire to be deposited, although NASA does use standard welding wire, which has been enriched in fugitive alloying elements that tend to boil off during welding or deposition.

The only materials that have been problematic for NASA’s EBF3 system to date are magnetic materials (the beam uses magnetism for beam control, so magnetic ferrous-based alloys are challenging to deposit) and non-weldable alloys (such as 7xxx aluminum alloys which are sensitive to hot cracking).

What is the typical bead size and the deposition rates that pertain to accuracy?

The typical bead size for NASA’s EBF3 system is between 0.1 and 0.25 in. (between 2.54 and 6.35 mm) across using wires ranging from 0.03 in. to 0.09 in. (0.762 mm to 2.29 mm) in diameter. This dictates the level of fine detail that NASA’s system can achieve. The process is scalable, so NASA’s system could work with very fine diameter wires and get an even smaller melt pool and thus a better surface finish and part precision (albeit at a slower deposition rate). The smallest bead size that NASA has demonstrated so far is 0.1 in. (2.54 mm), and experience suggests that the technology could be advanced to where the bead is as narrow as 0.05 in. (1.27 mm) across. (More about “Scalability” is presented below.)

6. Building Complex, Intricate Parts

What kind of part detail is possible with NASA’s EBF3 system?

NASA’s system is more flexible than other wire-based e-beam systems in its ability to build complex near–net shape parts. It works best in a 2.5-dimensional arrangement, where a layer of the part is drawn in the x and y planes then the part is dropped down in z for the next layer. Small details, such as holes, are best created via drilling after the part is fabricated rather than attempting to build holes into the design.

What standoff supports are required to build intricate parts, such as jewelry?

Rather than incorporate support structures into its design, NASA’s EBF3 system uses a positioning system to orient the part with respect to the deposition head to build it directly. By tilting the deposition head perpendicular to the feature being deposited, overhangs of practically any angle can be built directly, eliminating the need for structural standoffs, which would be an ideal approach for manufacturing jewelry.

The parts made using NASA’s EBF3 so far have had geometries that were “open” enough to allow access of the beam and wire-feed nozzle. NASA’s system has built unsupported overhangs of 45 degrees without difficulty in a 2.5-D orientation. Steeper angles (e.g., straight out, parallel to the baseplate) can be built by setting either the part or the gun on an angle/tilt. A small melt pool can be built upside down (assuming the positioning system is designed to allow “overhead” access) due to surface tension holding the bead in place.

Can NASA’s EBF3 system be used to manufacture custom dental implants?

At this time, NASA’s system does not appear to have the precision needed for custom dental implants. Furthermore, a small amount of metal vapor is created at the surface of the puddle and redeposits in a line-of-sight onto other parts of the piece being built. The redeposited metal vapor can form a very thin (angstroms thick) metal coating that bonds securely to the piece and is hard to remove.

7. Tolerances

What kind of tolerances can be expected when building a part using NASA’s EBF3 system?

Tolerance is dictated by bead size (see “Feature Size and Accuracy” above) and by the positioning system’s resolution/accuracy. Because the automatic positioning system used in NASA’s EBF3 system is accurate to ±0.005 in. (0.127 mm), the bead size dominates the tolerance specification for features smaller than 0.1 in. (2.54 mm). For features whose size is equivalent to or larger than the 0.1-in. (2.54-mm) bead diameter, the tolerance can be expected to be within 0.01 in. (0.254 mm) in x and y and around 0.03 in. (0.762 mm) in z. (Note: The z tolerance is dictated by the bead height, so it is not as fine as x or y.)

What is the build time for a 6x6x6 in. (15.24x15.24x15.24 cm) part of average complexity?

Part build time is highly dependent upon whether it is a solid build or hollow/thin-wall build. The longest time to build a solid cube of this size would be approximately 5 hours. A hollow cube with a wall thickness of 0.25 in. (6.35 mm) would take 2.5 to 3 hours to build. (Note: Hollow parts could be built without leaving openings to remove trapped loose feedstock since all of the feedstock is captured in the puddle.)

No time is needed for material recovery because all of the melted material is captured in the part (unlike the post-treatment required to remove excess powder in powder-based systems). Typically, the vacuum chamber can be vented and the part cool enough to handle within 15–20 minutes of completion. (Large parts retain more heat and would require more time to cool down.)

9. Power Consumption

What is the wattage?

NASA’s patented system uses 208-V three-phase power and has a maximum power of 3 kW.

10. Scalability

To what extent can NASA’s EBF3 system be scaled up?

NASA’s EBF3 system can be used to make parts ranging from a few inches/centimeters across to up to tens of feet (several meters) long, restricted only by the size of the vacuum chamber and positioning system. Although some components, such as the wire feeder and the positioning system, need to be replaced when making larger parts, these are inexpensive and readily available commercial-off-the-shelf (COTS) components. The e-beam gun does not need to be “up-sized,” although fabricating larger pieces requires higher power to achieve higher deposition rates.

What is needed in terms of post-processing, improving the quality of surface finish, honing, and/or polishing?

The following steps are commonly used when making parts with NASA’s EBF3 system:

1. Assuming the baseplate is sacrificial, some type of cutting operation (e.g., band saw, wire electrical discharge machining [EDM], water jet cutter, hacksaw) is required to free the part from the baseplate.
2. Heat treatment is used as needed to boost the part’s mechanical properties and to relieve any residual stresses generated within the part either during the deposition or during the removal operation from the baseplate. Standard heat-treatment practices can be used, but parts made with NASA’s EBF3 system (particularly those with fine features) typically should not go through quenching unless it is performed by an experienced technician since the parts are near-net shape.
3. Between 0.1 and 0.125 in. (2.54 and 3.175 mm) must be machined off, as needed for final tolerances. Final surface machining may be required for fine details (e.g., holes, threads) and final surface finish tolerance/accuracy. A surface glaze can be used to eliminate the ridges from the layers but may result in long-range waviness.
   
   

Has NASA started the certification process for aerospace parts?

NASA’s industrial partners are collecting “A basis allowables” data to submit for pursuing aerospace certification in the next 2 years. NASA continues to work to further refine the process to ensure repeatability necessary to meet industrial standards.

This technology is part of NASA’s Innovative Partnerships Program, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry.

NASA invites companies to consider licensing the Wire-Feed E-Beam Freeform Fabrication technology (MSC-23518-1) described here for commercial applications.

Companies also may license any or all of the following additional technologies in conjunction with the above technology:

• Method for Closed-Loop Process Control for Electron Beam Freeform Fabrication and Deposition Processes (LAR-17766-1)
  
  
• Use of Beam Deflection to Control Electron Beam Wire Deposition Processes (LAR-17245-1)
  
  
• Vapor-Barrier Vacuum-Isolation System (LAR-17695-1)

If you would like more information or want to pursue transfer of this technology, please contact us by phone or email: (919) 249-0327, .

For more information about other technology licensing and partnering opportunities, please visit:

Innovations Partnership Office
NASA Johnson Space Center
http://technology.jsc.nasa.gov (link opens new browser window)