Push-Button DED System Aims for Machine Shop Workflow in Metal Additive Manufacturing

Metal additive manufacturing (AM) would seem to be a fitting capability for a CNC machine shop. After all, both 3D printing and machining offer means of producing discrete metal parts. But get closer, and the fit is less apparent. The most common metal AM capability for production, laser powder bed fusion (LBPF), involves material handling and workflow considerations very different from machining, not to mention an equipment cost that tends to be high relative to machine tools. As a result, for many machine shops, their use of 3D printing is limited to deposition-style fused filament fabrication (FFF) in polymer. They leverage this low-cost, easy-to-use 3D printing method to make fixtures, prototypes and work aids — and this is as far as additive goes for a large number of shops.

But a new system from metal AM equipment maker Meltio illustrates what could be seen as a next increment of metal 3D printing technology, promising to let AM go farther for shops. The company’s M600 metal 3D printer, among other things, offers a direct response to the compromise described above. The system looks and operates much like an FFF polymer 3D printer, but makes metal 3D printed parts across the spectrum of weldable alloys. The machine offers an example of the continued advance of metal additive in terms of its accessibility to a broader range of users.

The new Meltio 3D printer (like all the company’s machines) uses directed energy deposition (DED), not LPBF. That is, material is deposited through a nozzle. The material form is wire, loaded into the machine in spools, and while the machine maker supplies this material, commonly available welding wire can also be used. The machine employs a laser to melt this metal and relies on argon gas for an inert environment — two elements peculiar to metal AM — so the comparison with a polymer 3D printer only goes so far. But the operator’s straightforward interaction with the machine and the lack of any necessary downstream steps (for example, no sintering is needed) resemble the use of 3D printing as machine shops experience it today.

Meanwhile, the system will not do machining; this is still left to machine tools. The DED 3D printer is not available as a “hybrid,” and Meltio R&D director Lukas Hoppe says it is unlikely it ever will be. “In production, the problem with a hybrid is the shop only gets access to 50% of the machine [either 3D printing or machining] at any time,” he says. Instead, this is a metal 3D printing unit for about the same price as a mid-range machine tool, and it is intended for operation in conjunction with, and within the same workflow as, CNC machines.

The Problems Metal AM Solves for Machine Shops

I attended a launch of the new machine held near the company’s headquarters in Linares, Spain. At this event, company applications engineer Manuel Calvache gave a talk making the case for metal 3D printing in a machine shop. The capability provides a solution to three challenges machining businesses today routinely confront, he notes. They are:

1. The need to interrupt production on machine tools to make custom workholding using those same machines.
2. Long lead times for parts made of high-value metals, often resulting from a wait for castings or forgings in those materials.
3. Work that must be turned down, because the job involves a challenging material or geometry the shop is not confident it can economically machine.

All these challenges suggest AM, he says. And adopting AM presents shops with a choice of polymer or metal 3D printing. Polymer is easier, but of limited use — it can address problem one, but not two or three. By contrast, metal 3D printing has tended to ask a lot of shops, he says. LPBF generally involves a high initial investment, safety considerations around handling powder, operator skill beyond what is involved in machining and the need to design and produce part geometries not typical of a machine shop. Calvache says Meltio developed the M600 as a bridge between these two realms.

In fact, applying DED to problems two and three from the list above offers solutions that go well beyond the range of choices machining makes available. The M600 system provides capacity for four spools of wire, meaning up to four different materials can be applied in a single 3D printing build. The operation of the nozzle, which melts material outside the nozzle itself and can therefore change wire just by retracting the feed without any nozzle clearing, allows for switching back and forth between metals as a programmed part of the build. The system’s use of a blue laser extends the range of metals, allowing for melting reflective metals (like copper and aluminum) precluded by earlier systems. All of this together brings the potential for multi-metal solutions. One option could be to 3D print a part inexpensively by using a lower-cost metal for bulk, applying a more expensive metal only at the outer surface where hardness or corrosion resistance is needed. Or, for heat-conducting parts, the bulk of the part could be 3D printed from copper for heat transfer, while the outer form is made from a more durable material such as Inconel or stainless steel.

Adding AM to Machine Shop Workflow

Meanwhile, certain other possibilities are new to this machine but long-established for machine shops. Because Meltio’s M600 is larger than an earlier model, the company’s M450, new features are possible. For example, the machine makes full use of probing like a machine tool. The company’s earlier system used probing only in the Z-axis to locate the surface of the build plate, whereas the new machine features probing in three axes.

In addition, “The newer machine is big enough to incorporate industrial workholding solutions,” Hoppe says, such as quick-change zero-point clamping using the same third-party system that might be in use on a shop’s machine tools.

These two capabilities together — machine tool workholding and probing — allow for a workflow that can cleanly integrate additive and subtractive operations, Hoppe says. A part could be machined, then sent to 3D printing for a complex feature to be added to the part, then sent back to the machine tool for finish machining of that new feature. Zero-point clamping and probing for location would ensure minimal delay at each of these steps.

Indeed, in broad terms, it is this different workflow the M600 makes possible (compared to other metal AM systems) that suits it for use in an existing production environment such as a machine shop. Hoppe says, “Once you generate a slice file, you are only a minute from 3D printing. The bed is probed, but no other step like heating up the chamber is needed. That means one-piece flow makes a lot of sense.”

He adds, “I do not see metal AM fully succeeding if it does not ultimately find a way to go into machine shops.”