Protolabs Gives Metal 3D Printing a Size Boost

High-volume production of complex isotropic parts of all sizes is now possible with GE’s X Line 2000R. (Image courtesy of Protolabs.)

When it comes to additive manufacturing, there is often a trade-off between how isotopically complex a printed part is and how large it can be printed. Whether it’s fused filament fabrication (FFF) or Carbon Digital Light Synthesis (DLS), 3D-printed parts can be extremely complex in their geometry, but efforts in translating this complexity to larger parts have seen limited success. To make matters worse, even if the printed part can retain its complexity when scaled upwards in size, the high-volume production rate of such parts has been a severe challenge.

Protolabs, a polymer and metal manufacturing solutions company, is addressing this limitation by incorporating industrial 3D printers that can not only scale geometric complexity to larger parts but also maintain a steady production rate.

Since its inception in 1999, Protolabs has focused on expediting injection-molding and CNC machining processes. In 2014, the company launched an industrial-grade 3D printing service geared towards simple prototyping for complex, low-volume production. As of today, Protolabs offers 3D printing, CNC machining, injection molding and sheet metal fabrication solutions. (Image courtesy of Protolabs.)

Aluminum—An Economic 3D Printing Option

Earlier in 2021, Protolabs added GE’s X Line 2000R 3D printer to their repertoire of 3D printers. The X Line 2000R boasts large-volume printing capabilities as high as 80cm x 40cm x 50cm. Aside from the large size of the printed part, the printer uses Inconel 718—a nickel-chromium alloy that is extremely durable, corrosion-resistant, heat- and cold-resistant at temperatures ranging between –253°C and 705°C. Given its versatility, there has been an influx of Inconel 718’s applications in aerospace and automotive industries as well as in the medical sector.

The GE’s X Line 2000R printer being transported. This year, Protolabs is adding two X Line 2000R printers to its repertoire of more than 120 additive manufacturing machines, including GE’s M2 Series 5. Each month, Protolabs prints more than 124,000 parts. (Image courtesy of Protolabs.)

However, there remains a need for inexpensive, light-weight metal printing options that still retain Inconel 718’s performance qualities—ergo, aluminum. Not only is aluminum almost four times lighter than Inconel 718, but one kilogram of aluminum costs around $2.50—nearly 25 times less than Inconel 718’s $65 per kg. What had prevented Protolabs from meeting this demand was that many requested parts were simply too large to be produced through additive manufacturing. To meet these demands, Protolabs has received its second X Line 2000R machine from GE that will focus entirely on producing large-scale aluminum parts.

“Looking back at our historical quote request activity, we found that we had a large number of requests in aluminum that we had to turn down in the past due to the sheer size of the parts,” explained David Giebenhain, Global Product Director for Protolabs. “Aluminum is generally one of the key materials in our portfolio. It’s very well suited to provide the benefits from metal 3D printing. It’s an extremely lightweight material and it has really good thermal conductivity. Aluminum is also our least expensive material offering.”

Large aluminum products can now be 3D printed using GE’s X Line 2000R. (Image courtesy of Protolabs.)

A Continuous Production Cycle

The X Line 2000R uses the Direct Metal Laser Melting (DMLM) method for additive manufacturing. Whether it’s Inconel 718 or aluminum, the process involves using high-power lasers to melt the desired shape into a bed of powdered metal. First, a layer of the metal is evenly deposited onto the build tray. The powder is extremely fine, with each particle ranging between 15–65 microns. Next, two powerful 1000W lasers draw the cross-section shape of the part onto this layer, after which another layer of the powdered metal is deposited and the process is repeated. The lasers can be programmed to melt different cross-sections in the powdered layer, allowing multiple parts to be printed in a single build.

Two lasers work in tandem to melt the required shape into the metal powder. Note that while DMLM and Direct Metal Laser Sintering (DMLS) are frequently used interchangeably, the difference is that in DMLS the laser partially melts the metal powder. In DMLM, the metal powder is melted completely. (Image courtesy of GE.)

The X Line 2000R has a build volume of 160 liters and features a dual-build module where a part can be printed on one build tray while another build is simultaneously being prepared. Once the first build is complete, the trays can simply rotate 180 degrees so that the second build can begin without any downtime. Furthermore, the closed-circuit vacuuming sucks the excess metal powder, processes it in the sieving station, and stores it in an external silo to be reused in subsequent builds. The silo can store thousands of pounds of powdered material—which, coupled with the X Line 2000R’s dual-build module—grants users the ability to print continuously. This addresses the high-volume production limitations that have marred metal 3D printing in the past.

The powdered metal is first treated in the sieving station where the powder is separated from any larger parts that may accidentally have been sucked in during vacuuming. The refined powder is then sent to the silo for storage and can be reused for future builds. The rotating mechanism is the part of the printer that can revolve 180 degrees to maintain continuous production. (Image courtesy of GE.)

“The X Line platforms produce parts faster than the other platforms that we have. They’ve got two lasers and they’re high-power lasers, so they can sinter metal at a much faster rate than a smaller M2 platform,” said Giebenhain. “One additional benefit of having the very large platform, especially as it relates to speed, is that it simply takes fewer builds. So, if you’ve got a set quantity—let’s say 100—that might take 10 M2 platforms, we have to turn over that platform 10 times, whereas with an X Line, we may only have to do two builds.”

Scalable Parameters

Depending on the material used and the complexity of the part produced, the X Line 2000R can print as much as 120 cm³ in an hour. As the printer can build with a variety of metals—stainless steel, aluminum, Inconel 718, titanium, cobalt and nickel—GE and Protolabs have come up with printing parameters for each material. X Line 2000R’s dual lasers are scalable in their intensity, based on the material being used. Aluminum, for example, can be melted using the 1000W setting on the lasers. However, using this intensity for a titanium build can not only cause porosity issues in the parts, but can pose safety concerns since titanium burns very intensely.

“How fast do they want the laser to move?” elaborated Marques Franklin, Senior Systems Manufacturing Engineer at GE. “How much laser power do they want when they’re building, when they look at lasers moving from one side of the part to the other side? How much space do they want in between passes of the laser or what's affected by that is porosity in the part? So, what happens is you can get porosity in the part that will affect your tensile properties or your physical properties. And so, the parameters that are developed are converted into physical characteristics of the parts that are created. This requires a lot of time to determine what is the correct recipe for a given material.”

Establishing such parameters maximizes the efficiency of production, ensures that the part’s performance is not compromised in any way, and also increases the efficacy of the manufacturing process itself.

For more information on Protolabs and the manufacturing services they offer, click here.