Integrating Metal Additive Manufacturing – 10 Questions to Ask
Ian Wright posted on October 02, 2017 | 4431 views
(Left) An early CNC fed by paper tape. (Right) a metal 3D printer.
(Left) An early CNC fed by paper tape. (Right) A laser sintering machine.
Imagine you could go back to the 1970s knowing where computers were headed.

What would you do with that knowledge, aside from buying stock in Apple and Microsoft?

If you happened to work in manufacturing, you might push for adopting computer numerical control (CNC). Of course, even armed with several decades of foreknowledge, that’s no simple task: adding CNC capabilities isn’t just a matter of plunking controls down onto existing manual machines.

Integration is a difficult and complex task—just ask an integrator.

Now, flash forward to metal additive manufacturing (AM) today—another technology poised to make a huge impact on manufacturing, and sooner than you might think.

“The technology is moving fast and has already spread from significant penetration in the aerospace industry to now beginning to penetrate the fabrication of almost all metal components,” said Jack Beuth, professor of mechanical engineering and director of the NextManufacturing Center at Carnegie Mellon. “The analogy I make is that, with respect to metals AM, we are where personal computing was back in the 1980s. It is just getting started.”

As it was with CNC, manufacturers seem to be faced with the following choice when it comes to metal AM: get on board or risk being left behind. But before you board the hype train, there are ten questions you need to ask.


1) Is Your Application Suitable for Metal AM?

Despite the enthusiasm surrounding metal additive manufacturing, it’s not a magic bullet that makes any part better. It isn’t necessarily worthwhile to use additive manufacturing for a part that’s been reliably produced through conventional, subtractive processes for years.

So how do you know if your particular part would benefit from metal AM?

To start, it helps to take a step back and look at the industries that are using it the most.

 

Metal Additive Manufacturing Industries

CFM International’s 3D-printed fuel nozzle. (Image courtesy of GE.)
CFM International’s 3D-printed fuel nozzle. (Image courtesy of GE.)
The aerospace and medical device industries are probably the two best known for using metal additive manufacturing. GE’s renowned 3D-printed fuel nozzles for its LEAP family of engines used to be made from 20 discrete parts coming from independent suppliers, but using direct metal laser sintering (DMLS) resulted in a single-piece component that’s 25 percent lighter and five times stronger than the original.

On the medical side, Renishaw has been developing custom hip implants with metal printed in a lattice structure for stiffness and strength. Dentistry also increasingly involves metal AM, particularly for bridges and crowns. Even dogs are benefiting from medical implants made with metal 3D printing, thanks to 3D Systems’ Direct Metal Printing (DMP) technology.

Although these industries are leading the way, metal AM can be fruitfully applied in almost any industry, provided the application meets certain criteria. Beuth explained it this way:

“We break it down into three factors that can lead to adoption of AM over conventional processing. First, AM can win on cost per part, particularly if a current part or collection of parts are redesigned to exploit additive. The consolidation of parts can yield major cost savings. Small production lots can also be cost-effective for AM.

“Second, AM can win on time to market. In some industries, getting to market first is more important than cost per part (first-in usually wins).

“Third, AM can win if it is able, through part redesign, to enhance the performance of the component or components. Often it is some combination of these three that makes a part a prime candidate for fabrication by AM.”

These three factors (part consolidation, production time and performance) are exemplified by applications in the aerospace and medical device industries, but they generalize to most other industries.

A selection of metal additive parts. (Image courtesy of NextManufacturing Center/Carnegie Mellon University.)
A selection of metal additive parts. (Image courtesy of NextManufacturing Center/Carnegie Mellon University.)
Moreover, metal AM can be applied to more than just end-use parts. There’s also a home for 3D printing in maintenance, repair and overhaul applications. “After production, maintenance operations also benefit from AM, which allows spare parts to be manufactured as needed, avoiding investment required for storage of parts and production tools,” said Ingo Uckelmann, technical manager for metal 3D printing at the Materialise Competence Center in Breman. “As awareness of metal AM’s possibilities grows, new applications continue to emerge.”

Uckelmann also offered a helpful guide for deciding whether your part would be better served by additive or subtractive processes: “When compared to milling, metal AM is cost competitive if the buy-to-fly ratio is higher than 10:1, especially for titanium products. If turnaround time is critical, metal AM is the best manufacturing solution, as lead times are as short as 10 working days.”

 

2) Should You Outsource Your Metal AM Parts?

Once you’ve decided that metal AM is the way to go, you immediately run into one of the most common quandaries in manufacturing: to outsource or stay in-house. The answer to this question hinges on a whole host of other factors, including setup costs, shipping costs, inspection and quality control requirements, intellectual property, security and more.

This object was made with direct metal laser melting (DMLM). (Image courtesy of Star Rapid.)

This object was made with direct metal laser melting (DMLM). (Image courtesy of Star Rapid.)

Gordon Styles, president and founder of Star Rapid, a provider of rapid prototyping, rapid tooling and low-volume manufacturing of custom parts, offered the following insight on the issue of outsourcing metal AM:

“When does it make sense to add 3D metal printing to a conventional machine shop production environment?  That depends on a lot of caveats, of course, but for me the choice can be reduced to a few essential considerations.”

“First, you must have a skilled and experienced technologist or engineer on staff to run the metal printing process.  This is not subtractive machining and it requires a completely different skill set.  Without that the effort is doomed to be a disappointment at best.” 

“Secondly,” Styles continued, “you must remember that there are substantial upfront costs that can possibly justify the investment only if there is sufficient volume of parts or a high margin built into the finished product.”

Beuth agreed, emphasizing the time lag between installing a metal 3D printer and having it set up and running at capacity:

“The biggest mistake new users make is not understanding what really goes into making a part before buying a machine or targeting an application for it. Even well-staffed companies experience a delay of 6 months to a year between the time a machine is delivered and the time where they are regularly producing components.”

Uckelmann pointed out another significant barrier to integrating metal AM into an existing production line:

“Where companies are in development can also be an issue; ideally a company would decide on metal AM at the new design introduction stage, not later in the development and engineering process. The level of standardization in the industry also needs to catch up and the rate of obsolescence in metal AM machines needs to come down in order for companies to install their own machines instead of turning to a metal AM service provider.”

Styles also touched upon the more general issues with outsourcing:

“If a company is making parts for themselves, such as GE printing advanced fuel pump nozzles for their engines, then they can control their proprietary design as well as directly monitor the quality of the results – important considerations for such a sophisticated part performing a critical function.” 

One last caveat from Styles bears emphasizing:

“It also needs to be said that virtually all 3D metal printed parts will require some form of post-machining, so there are advantages to having both processes available on one shop floor.  I would caution anyone, however, to take on such an investment only after doing extensive research on the costs, the design requirements of the technology, and what exactly you hope to achieve.”

Even if you decide that you’re better off outsourcing when it comes to metal additive manufacturing, several of the questions that apply to those working with metal AM in-house will still apply to you. The most pressing is the question of which metal AM technology will work best for your application.

 

3) Powder Bed Fusion or Directed Energy Deposition: Which is Right for You?

Broadly speaking, there are two main approaches to metal 3D printing: powder bed fusion (PBF) and directed energy deposition (DED). There’s also Desktop Metal’s relatively new bound metal deposition (BMD) technology. Although the prospects for BMD are exciting—the company boasts that its tech offers a hundred times the speed of selective laser melting (SLM) at a tenth of the cost—it’s still in the relatively early stages compared to PBF and DED.

For that reason, we’ll focus here on powder bed fusion and directed energy deposition.

(For an in-depth look at Desktop Metal’s BMD, click here.)

Aluminum part created using DMLS. (Image courtesy of Materialise.)

Aluminum part created using DMLS. (Image courtesy of Materialise.)

Powder bed fusion involves selectively consolidating a powdered material using a heat source such as a laser or electron beam. The unfused powder around the printed part acts as a support for overhanging features. This approach offers the ability to make highly complex parts from a variety of materials, including plastics and ceramics as well as metals. Subtypes of metal PBF include direct metal laser sintering (DMLS), electron beam melting (EBM) and selective laser sintering (SLS).

In contrast, directed energy deposition involves feeding a powder or wire into a melt pool generated on the surface of a part using a laser or electron beam. The process is essentially a form of automated build-up welding. This approach has the advantage of being able to operate in more than three axes and can combine multiple materials into a single part. Subtypes of DED include laser metal deposition (LMD) and direct metal deposition (DMD).

Broadly speaking, PBF is better for making entire parts from scratch, whereas DED is better for adding features or conducting repairs.

Jason Jones, CEO of Hybrid Manufacturing Technologies, elaborated on the relative strengths of PBF and DED:

“Being able to vary the material that you’re putting down on the fly is mostly unique to directed energy deposition,” he said. “In contrast, with powder bed fusion you’re typically growing an entire part from scratch. Its capability at making internal passages is very good, so if you’re looking at parts that have internal passages, there were probably made with powder bed fusion.”

Cabin brackets for the Airbus A350 XWB. (Image courtesy of Concept Laser.)
Cabin brackets for the Airbus A350 XWB. (Image courtesy of Concept Laser.)
Jones went on to explain that, as it currently stands, DED is behind PBF in terms of technological maturity and application. “The reason for that is very simple,” he said.

“The original 3D printing mentality was: ‘This thing comes out of the box and it’s a finished part.’ That’s why its killer application was prototyping. But directed energy deposition was so coarse in comparison to machining that its volumetric productivity was overshadowed by the post processing you had to do.”

For Jones, the solution to this tension between DED’s high deposition rate and relative roughness of its parts is the raison d’être of his company. “By merging directed energy deposition with CNC machining, you can de-couple surface roughness from volumetric productivity, and that’s what Hybrid did,” he said.

This raises another important question to ask before purchasing your first 3D metal printer.

 

4) Should You Use Hybrid CNC Machines or Standalone 3D Printers?

(Image courtesy of PADT, Inc.)
(Image courtesy of PADT, Inc.)
Once you’ve determined which metal AM technology makes the most sense for your particular manufacturing application, the next question to ask is whether to go the hybrid route and use a machine that combines additive and subtractive capabilities or invest in a standalone metal 3D printer.

If your application demands PBF, then you’re likely looking at a standalone machine. DED naturally lends itself to hybrid setups. However, as a PBF hybrid machine, Matsurra Machinery’s LUMEX Series is an exception to this general rule.

The topic of hybrid machines is a controversial one. Uckelmann, for example, pointed out that a machine combining milling with metal AM cannot perform both functions simultaneously. That’s why he predicts that, “In the future, hybrid machining will likely consist of a combined line of AM printers and CNC milling machines, where parts move from one system to another.”

Dhruv Bate, senior technologist at PADT, agreed: “Here is the crux of the challenge that I pose to folks who want to go hybrid,” he said. “Unless it is able to do everything for me in one step—that means support removal and finishing—then I do not see the advantage in investing in a hybrid machine, because it’s very likely that I will still need all these downstream operations to truly get my part production-ready.”

Jones has a unique insight into this question. His company produces deposition modules that can be added to existing machine tools, turning conventional CNC machines into hybrid additive/subtractive setups. When asked about the choice between hybrid machines and dedicated 3D printers, Jones granted that there are instances where an independent additive machine makes sense.

Hybrid Manufacturing Technology's deposition modules are designed to be integrated into existing machine tools. (Image courtesy of Hybrid Manufacturing Technologies.)
Hybrid Manufacturing Technologies' deposition modules are designed to be integrated into existing machine tools. (Image courtesy of Hybrid Manufacturing Technologies.)
However, he added that “We’ve pioneered a new space where you’re able to do everything in a single setup, and for a catchment of applications that’s tremendously beneficial. For example, the company I just visited in South America has historically been making a product which requires a traditional pre-heat prior to adding metal by manual welding. With our technology, they’re going to skip that entirely.”

“So,” Jones continued, “they’re going to almost half of the capital equipment requirements to produce their parts by going to a single-setup approach. They’re working on castings coming from a foundry, which will go onto a hybrid all-in-one machine and what has historically been three or four difference setups will now be merged into one.”

Jones suggested one way to determine whether hybrid machining makes sense for your application: “The first question is: ‘What percentage of material are you adding to the part?’ If you’re only adding 5-15 percent of the volume, then an all-in-one machine could very well be a better business case for you. In contrast, if you’re going to building something from scratch, where it’s virtually all built from powder, then separate machines might make more sense.”

Additive manufacturing on Tongtai's AMH-350 5-axis machine. (Image courtesy of Tongtai.)
Additive manufacturing on Tongtai's AMH-350 5-axis machine. (Image courtesy of Tongtai.)
One final point is worth noting on the topic of hybrid vs. standalone metal printers. Several of the largest machine tool manufacturers, including DMG MORI, ELB-Schliff, Mazak and Tongtai now have their own hybrid machines on offer.

As with adding one of Hybrid Manufacturing Technologies’ deposition modules to a machine you already have, opting for a hybrid machine from a major manufacturer has the benefit of minimizing the amount of additional training required to get a new additive system up and running. This may not be the most essential consideration, but it is worth keeping in mind, especially if you’re hesitant to go all-in on your first foray into additive manufacturing.

 

5) What are Your Material Limitations?

So, you’ve determined that metal additive manufacturing is a good fit your application, you’ve decided between outsourcing and printing in-house, you’ve selected your additive technology and the machine that’s going to use it.

What’s next?

Rhodium metal: powder, pressed pellet 3*105 psi) remelted. (Image courtesy of Heinrich Pniok.)
Rhodium metal: powder, pressed pellet (3*105 psi) and remelted. (Image courtesy of Heinrich Pniok.)
At this point, take the time to consider your material requirements as well as the availability and characteristics of the metal(s) you’ll be using as feedstock. There are plenty of metals to choose from, but your choice of DED or PBF technology may put some constraints on the materials available to you, since DED can work with welding wire products in addition to metal powders, depending on the system.

“A common mistake for new users comes from a lack of understanding of which alloys can be used for metal AM,” said Uckelmann. “New users often think in terms of the classic alloy portfolio, not all of which can be used in metal AM.”

Generally speaking, wire products are more varied and easier to obtain than metal powders, due in large part to the former’s use in welding applications.

Sciaky, Inc., a developer of metal 3D printing technology, including Electron Beam Additive Manufacturing (EBAM), lists the following raw materials as being available in wire feedstock:

  • Titanium and Titanium Alloys
  • Inconel 600, 625, 718
  • Nickel and Copper Nickel Alloys
  • Stainless Steels 300 Series
  • Aluminum Alloys 1100, 2318, 2319, 3000 Series, 4043, 4047, 5183, 5356, 5554, 5556
  • Alloy Steels
  • Cobalt Alloys
  • 4340 Steel
  • Zircalloy
  • Tantalum
  • Tungsten
  • Niobium
  • Molybdenum

Sandvik Materials Technology, which suppliers metal powders for additive manufacturing, lists the following materials as its most popular products:

  • Austenitic Stainless Steels and Duplex Steels
  • Cobalt Alloys
  • Low-Alloy Steels
  • Nickel Alloys
  • Tool Steels (including Maraging Steels)

Other common powder materials include:

  • Aluminum Alloys
  • Titanium and Titanium Alloys
  • Copper Alloys
  • Precious Metals (Gold, Platinum, Palladium, Silver)

Selecting the right supplier is almost as important as selecting the right feedstock type and material. Beuth has previously predicted that growth in the metal powder supply chain will struggle to keep pace with supply. The lack of high-quality, defect-free metal powder could very well be the principal bottleneck for metal additive manufacturing in the near term.

(Image courtesy of TRUMPF.)
(Image courtesy of TRUMPF.)
This is why it’s important to qualify your feedstock, potentially in ways that are unfamiliar to those coming from traditional subtractive backgrounds.

“People from the machine world aren’t used to being responsible for the volumetric quality of metal,” said Jones. “Right now, when you buy a billet of material, you’re assuming it’s fully dense. But with additive processes, you’re forming the internal microstructure as you go. It’s a new space for somebody who runs machine tools to say, ‘Oh, I’ve got to make sure my powder is dry so I don’t introduce any defects into the volume of the material.”

Paul Browning, president and CEO of Mitsubishi Hitachi Power Systems Americas, Inc. and a metallurgist by training, emphasized the difficulties that come with investing in metal 3D printing:

“My biggest piece of advice to new adopters is to hire a good metallurgist. The biggest challenge of additive is getting the metallurgy right. Printing something that looks like what you want it to look like is actually not that hard, but printing something that performs the way you want it to perform—that’s the real challenge. In the metallic space, all of the challenges are in materials engineering.”

 

Metal Additive Manufacturing: Taking the Plunge

(Image courtesy of NextManufacturing Center/Carnegie Mellon University.)
(Image courtesy of NextManufacturing Center/Carnegie Mellon University.)
If you can confidently answer all five of the preceding questions, congratulations! You’re ready to start integrating 3D metal printing into your manufacturing operations.

That being said, there’s still a lot to do before you’ll be able to take full advantage of that shiny new additive process. In addition to the five questions above, you’ll also need to answer these questions:

  • What ancillary equipment do you need?
  • What about training or certifications?
  • What are your post-processing requirements?
  • How do you qualify your metal parts?
  • What are the safety risks?

Check out our eBook on metal additive manufacturing for more information.

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