Large Format 3D Printing for Aluminum and Inconel Parts

Posted On October 15, 2021 By Protolabs

We’re pretty proud of our newest 3D printer. And who wouldn’t be? According to its maker, GE Additive, the Concept Laser X Line 2000R is “the largest metal laser melting machine” on the planet. It’s equipped with a pair of 1000-watt fiber lasers, a 31.5 in. x 15.7 in. x 19.7 in. (800mm x 400mm x 500mm) build volume, and it’s very well-suited for all manner of end-use aerospace, automotive, and industrial components.

Oh, and did we mention we have two?

Large Format, Production Printing

What’s more important to you is what types of parts these massive printers can produce, what kinds of metals they can print, and what you need to know about designing large-format 3D-printed parts.

Let’s start with the first question, which is easy to answer. Anyone who follows GE Additive knows that its team is all about lowering manufacturing costs, improving product performance, and decreasing time to market. So are we. Simply put, the X Line 2000R has a bunch of cool features that make it easier to operate and maintain, thus increasing our ability to crank out otherwise impossible parts—big, complex, highly accurate metal parts made directly from a 3D model.

 

Meet the Materials: Aluminum vs. Inconel

So what are the metals? We've dedicated the newest machine to AlSi10Mg, an aluminum alloy defined under ASTM standard F3318. Though considered by some to be a casting alloy, it has also proven to be top of the list for anyone searching for a strong yet lightweight 3D printing metal that also excellent thermal conductivity. It contains roughly 10% silicon by weight, so is a bit more abrasive to machine than 6061-T6 aluminum, but offers comparable tensile strength (around 50 ksi). Depending on the heat treatment used, it’s also a bit harder—approximately 72 on the Rockwell B scale, compared to 60 or so for 6061—leading to a slightly lower elongation at break (between 5% to 8%, based on the shear direction).

  Tensile Strength* Elongation at Break Hardness*
Inconel 718 139-208 ksi 1818-40% 27-46 HRC
Aluminum (AlSi10Mg) 45-50 ksi 8% 46-59 HRB

*Varies by resolution and heat treatment

These properties help make AlSi10Mg the de facto standard within the additive manufacturing (AM) world for a range of aluminum components. It's an ideal choice for thin-walled heat exchangers, ductwork, and radiators, as well as brackets, levers, and other mechanical or structural components. Further, GE Additive has developed build parameters that deliver a good balance between print speed, part density, and surface quality.

Then, there’s Inconel 718—the workhorse of the aerospace and energy industries. This nickel-based superalloy is intended for high-stress, high-temperature, or highly corrosive environments (sometimes all three at once). ASTM standard F3055 defines “INCO 718” 3D-printed parts as having physical properties on par with their forged or cast counterparts. This means ultimate tensile strength of 139-208 ksi, elongation at break up to 40%, and a melting point of at least 2300° F (1260° C), making it extremely suitable for gas turbine components, rocket engines, and other mechanically or thermally demanding environments.

Decision Time

So which one should you use? Unfortunately, the decision is not simply about weight. Because 3D printing can create very complex lattice-like and honeycomb structures, designers can produce lightweight parts compared to those made subtractively, even when using relatively dense, heavy metals like Inconel 718. On the flip side, modern design tools and printing processes tend to make all 3D-printed structures much stronger than they otherwise would be, putting aluminum in the running for applications that were once unthinkable.

Much of the decision comes down to cost. The aluminum powder used in all 3D printers is less expensive than any superalloy, Inconel included. And due to its lower melting point, the particles are a bit easier to fuse than Inconel, decreasing processing time somewhat. Lower temperatures also mean fewer concerns over thermal growth and curling, an important consideration on any laser-based 3D printer. However, given that raw material expense represents a smaller portion of the total 3D-printed part cost compared to machined or cast components, designers should focus instead on the specific material properties needed for their application

Benefit Comparison: Inconel 718 vs. Aluminum

In summary, Inconel 718 should be used in extreme temperature environments (hot or cold), where corrosion and chemical attack are likely, or where this highly capable alloy's superior strength and hardness are necessary. AlSi10Mg aluminum, on the other hand, is the first choice where weight is the primary consideration (assuming that the finished part will meet all physical demands) or where piece-price is a key driver. As always, determining the cost delta is a simple matter of uploading the CAD model to our quoting system, selecting the different materials, and comparing the quotes for each.

  Cost Tolerance to Extreme Temp. Lightweighting Corrosion Resistance
Inconel 718   X   X
Aluminum (AlSi10Mg) X   X  


Better 3D Printing Builds for Large Parts

Some might wonder if large-format 3D-printed metal parts come with a different design playbook. Not really. Design for Additive Manufacturing (DfAM) guidelines tell us that the thick, bulky parts with which traditional manufacturers are familiar should be optimized for 3D printing. Eliminate heavy cross-sections and excess material in favor of the honeycombs and lattice structures mentioned earlier. Avoid unsupported horizontal planes wherever possible—if not, additional post-processing will be needed to remove build supports, driving up costs.

And as with all additive manufacturing, look for opportunities for part consolidation. This last bit of advice is especially true on large-format parts, where what was once a multi-piece assembly containing perhaps hundreds of individual components and fasteners can be printed as a single part. The potential cost and lead-time savings are enormous, as is the advantage of shortening the supply chain. If you have any questions or need a hand with your part design, you know where to find us.