Design for Additive Manufacturability

How to combine designing for manufacturability with designing for additive manufacturing.

(Image courtesy of EOS.)

An injector head baseplate.  Redesigning with additive manufacturing reduced the number of components from 248 to 1. (Image courtesy of EOS.)

Leonardo da Vinci has long been a patron saint of engineers, and for good reason.

Da Vinci’s designs combine insights from mechanics and the natural world into concepts that were centuries ahead of their time. Of course, that’s not always a good thing. For all his innovations, there’s one thing da Vinci didn’t anticipate: designing for manufacturability (DfM).

These days DfM is almost a given, although its implementation differs widely depending on the manufacturing technologies at play. 3D printing, for example, introduces an almost entirely different set of constraints on manufacturability compared to injection molding or CNC machining. In fact, 3D printing technology is so different from these more conventional techniques that it’s spawned its own design philosophy, known as designing for additive manufacturing (DfAM).

Using additive manufacturing for production opens up a host of new possibilities, including new challenges, which is why Gregory Hayes, Director of Applications and Consulting at EOS North America, advises new users to take their time with the technology.

“Crawl, walk, run,” he said. “I think there’s a need—especially when it comes to additive manufacturing—to have both feet on the ground and take a pragmatic approach to a new manufacturing capability. Oftentimes, companies are very quick to talk about Industry 4.0, digitalizing a supply chain or making data-driven decisions based on a fully digitalized manufacturing environment. These things are all possible, but if you want to implement them, it needs to be well planned.”

The Factory of the Future. (Image courtesy of EOS.)

The Digital Factory of the Future. (Image courtesy of EOS.)

As is often the case in innovation, a change in mindset can help smooth the transition. In addition to designing for additive manufacturing, engineers can also think in terms of designing for additive manufacturability (DfAMy). While the former tends to focus on utilizing the unique capabilities of 3D printing, such as blind holes and internal passages with complex geometries, designing for additive manufacturability is about minimizing the cost and maximizing the efficiency of volume production for 3D-printed parts.

To put it another way, DfAM principles can be applied even when you’re producing prototypes or one-offs; DfAMy doesn’t really come until play until you’re ready for production.

Designing for Manufacturability (DfM)

In order to understand what DfAMy is and how it differs from DfAM, it helps to begin with the acronym that started it all: DfM. Designing for manufacturability comes after the initial mechanical and/or electrical design, but before the design is released to the supplier for fabrication. For this reason, it can also be supplier-specific, taking the capabilities of each supplier into account. In any case, the goal is always to minimize cost and maximize production efficiency.

However, some factors that affect manufacturability go beyond the limits of DfM. These include the necessary material type and form, dimensional tolerances, regulatory constraints and post-processing. While it may be possible to accommodate some of these factors in the DfM phase, others may be fixed by the requirements of the initial design specifications.

Nevertheless, the particular production technology at play still makes the biggest impact on designing for manufacturability. For example, in order to minimize costs when CNC machining, engineers need to minimize the time it takes for programming, fixturing, set-up and machining time. Typically, the simplest way to do this is minimize the number of operations needed to make a part.

Volume also plays an important role in determining manufacturability. For CNC machining, the law of diminishing returns kicks in around volumes of 100-300 parts, depending on the application. Material type constitutes another significant factor, since parts made from softer metals—such as aluminum or brass—will also be easier to machine.

Designing for Additive Manufacturing (DfAM)

Like DfM, DfAM is all about optimization. However, unlike other industrial processes, additive manufacturing requires a very different mindset. For example, the first step in DfAM is most often asking whether you should really be using additive manufacturing in the first place. The cost of an industrial 3D printer is comparable to a moderate or high-end machine tool, so your investment in AM will need to be thoroughly justified.

Oftentimes, AM is a production method of last resort: engineers turn to additive when there’s no other way to achieve the functionality they need. Fortunately, once you’re using 3D printing as a production process, there are several benefits that come along for free. For example, there’s no additional cost to most aesthetic details. If you want to add a logo or part number, or just make the part look better, DfAM encourages that. Why not make your part more beautiful if you can do it for free?

Image courtesy of EOS.)

EOS direct metal laser sintering for additive manufacturing. (Image courtesy of EOS.)

“One of the biggest hurdles when it comes to getting designers and engineers to think differently is to really start with a blank sheet of paper,” Hayes explained. “Many times, when companies are considering additive manufacturing, the paper isn’t blank. They’re starting with a component made traditionally and redesigning it. You can do a lot of interesting things when you redesign a component: you can lightweight it, you can change the structure, you can combine assemblies—but you’re still not starting with a blank sheet of paper and designing for function with limited constraints.”

Of course, additive manufacturing, like any production process, requires you to take more than just the design of the part itself in mind. Print orientation is just as important for 3D printing as workholding is for machining, if not more. As a rule of thumb, engineers are encouraged to design parts that will minimize the amount of support material, and one of the easiest ways to do that is to change your print orientation. For similar reasons, large masses of material should be avoided, since they add material cost to each part as well as introducing more residual stress.

The key takeaway here is that DfAM aims to answer two basic questions:

  • Should you use additive manufacturing to produce your part?
  • How can you use AM to make your part better?

Designing for Additive Manufacturability (DfAMy)

“It’s a shame that we still need to make a difference between designing for manufacturability and designing for additive manufacturing,” Hayes commented. “The industry is heading to a point where these ideas will be indistinguishable in the near future. For now, we see that design for additive manufacturing involves pushing the boundaries of what’s possible in terms of design—taking advantage of organic shapes, reducing assemblies from multiple parts into just a few—and most of the time these are utilized for proof of concepts and part prototyping.”

A look at EOSPRINT 2 for optimizing CAD data. (Image courtesy of EOS.)

A look at EOSPRINT 2 for optimizing CAD data. (Image courtesy of EOS.)

“Design for manufacturability comes into play when you’re thinking about production and bills of materials—it’s where the price per part is considered,” he continued. “So, people use design for additive manufacturing for prototyping and demonstration, and design for manufacturability for the real-world problem of ‘Okay, we’re going to make this thing. How much will it cost?”

If we compare the examples of principles for DfM with those of DfAM, a clear contrast emerges. Designing for manufacturability is about making parts as efficiently as possible; designing for additive manufacturing is about making the parts themselves as efficient as possible. But a stronger, lighter and more beautiful part isn’t necessarily more manufacturable than its weaker, heavier and uglier competitor.

So, what does it mean to design not just for additive manufacturing, but additive manufacturability?

Like DfM, DfAMy is all about minimizing costs and maximizing production efficiency, which means taking the entire production process into account. For example, some level of post-processing is basically a given for additive manufacturing, but you can adjust the time and cost of post-processing operations by adjusting your part orientation.

Although DfAM suggests that you should minimize the number of supports a part will need to be printed, printing a part with supports on a hidden surface—rather than one which may need to be painted or otherwise finished—could be worthwhile if it significantly reduces your post-processing time.

Thinking in terms of DfAMy may be difficult for new users, but there are plenty of resources available that can help you get into the additive mindset. “At EOS, we have the Additive Minds engineering group, which is specifically set up to carry out projects and help companies with this transition,” Hayes explained. “We approach this with a crawl-walk-run strategy. It’s not always our advice that customers run out and buy an additive machine. The capex requirement there is quite high, and it should only be done when a business plan backs up the decision.”

Additive Minds  (Image courtesy of EOS.)

The Additive Minds engineering group at EOS is an applied engineering consultancy that helps companies carry out projects and transition to using DfAMy. (Image courtesy of EOS.)

“However,” Hayes continued, “in almost every business we engage with—whether small, medium or large—there is business case to start using additive in one way or another which is financially advantageous. For a small company, that might mean starting out with redesigns and prototyping, working with a service provider until their needs ramp up and they get to a point where it makes sense to bring the technology in-house.”

As Hayes described it, the Additive Minds group is an applied engineering consultancy. It’s made up of roughly 25 engineers in North America and more than 100 worldwide. Although the group services multiple industries—including aerospace, automotive and medical—Hayes emphasized that its members are, first and foremost, additive manufacturing engineers.

“We’re industry agnostic, and we are not a sales team,” he said. “Our goal isn’t to sell products or projects; it’s the higher-order goal of growing additive manufacturing in all industries. We work with our customers to help them crawl, walk and run when it comes to additive manufacturing.”

Crawl, Walk, Run

The transition from DfM to DfAM to DfAMy parallels Hayes’ developmental analogy. Anyone who’s compared an old part made with conventional methods to a new one made with additive manufacturing has probably had a similar realization as someone who’s watched a child go from crawling to walking: it’s like seeing all the possibilities and potential, all at once.

Similarly, the transition from DfAM to DfAMy is much like the transition from walking to running: even if it’s not quite as game-changing as the preceding transition, it’s still a major adjustment. Ask anyone who’s had to chase a sprinting toddler.

Companies are starting to run with additive manufacturing, and no one wants to be left behind, but that doesn’t mean to you to start sprinting now.

“Additive manufacturing is coming, and companies need to engage with it, but they can do that in a smart way,” Hayes said. “You don’t need to run right away. We’re shifting away from redesigning to designing from the ground up, and eventually I think additive manufacturing will be just another tool in the engineer’s toolkit, and the Additive Minds group is here to help us get there.”

For more information, visit the EOS website.

EOS has sponsored this article.  All opinions are mine.  –Ian Wright