Powder Bed Fusion vs. Binder Jetting

 

Powder Bed Fusion and Binder Jetting are two of the most common classes of metal 3D Printing technology. Each one provides unique advantages and considerations as it relates to meeting the needs of different applications. Powder Bed Fusion has grabbed headlines in the industry for the longest, but binder jetting's emergence has grabbed its fair share of headlines as well. Could either process be the solution for one of your applications? Here we provide a quick tale of the tape, comparing these two popular metal 3D Printing process families.

Process Overview

Powder Bed Fusion

 

Powder Bed Fusion involves the use of a focused energy source - commonly an infrared laser or electron beam - to selectively melt layers of metal powder.  This process results in highly dense parts that provide strengths typically surpassing cast parts (and occasionally forged parts).

binder jetting metal 3d printing process

Binder Jetting

 

As its name would suggest, Binder Jetting involves the targeted jetting of a binding agent to hold particles of powdered material together. This process takes place layer-by-layer to produces a "green part," basically a fragile matrix of metal held together with adhesive. This part can then be used for non-stress applications or more commonly undergoes post-processing steps, most notably sintering.

Accuracy

How accurate are these processes? How reliably do they deliver that accuracy? Or said in the most straightforward engineering terms, which tolerances can they hold?

As Low As .001"

Powder Bed Fusion technologies are very accurate, with some technologies capable of achieving tolerances as tight at .001" (25 microns). It should be noted that metal Powder Bed Fusion is generally expected to meet tolerances of .005" +/- .002" per inch, and certain powder bed technologies like Electron Beam Melting have global tolerances that are looser than that. Generally speaking, Powder Bed Fusion is more accurate than Full Sinter Binder Jetting.

+/- 3%

Binder Jetting is a relatively accurate 3D Printing technology, but much of its accuracy depends on what level of post-processing you have in mind for your print. Since we are specifically looking at metal 3D Printing, then for the purposes of this discussion we are weighing Full Sinter Binder Jetting and Infiltrated Binder Jetting.  Full sinter involves the creation of a green part, but then sintering that part in an oven once the shape is set — which results in roughly 20% shrinkage and creates a challenge in delivering tight tolerances. This is not as noticeable with certain types of geometries and smaller parts. Additionally, this can be improved through repeated manufacturing. Nonetheless, its default tolerances are higher. Infiltrated Binder Jetting doesn't experience the same degree of shrinkage because the metal matrix is filled with another lower-melting-temperature metal instead of allowing the matrix to sinter down on itself.  Still, the nod generally goes to powder bed when we talk about accuracy.

Cost

How expensive are these processes? Both relative to each other and to more traditional metal manufacturing processes like CNC, Casting, or Metal Injection Molding?

Cost Effective for Intricate Designs

Powder Bed Fusion prints are generally pretty expensive. The underlying energy source - an expensive laser or electron beam - is quite expensive. The powder commonly required for these machines is also more refined than that required for binder jetting, also driving up cost. Generally speaking, Powder Bed Fusion becomes the most cost effective solution when a part has been designed with the process in mind. This means the designer has eliminated unnecessary mass and structured the part to be self-supporting throughout the build.

Lower Cost Inputs = Lower Cost Outputs

By jetting binding agent rather than accurately tracing a path, Binder Jetting can effectively arrive at a geometry much faster than Powder Bed Fusion. While this analogy oversimplifies things (especially for Electron Beam Melting), Binder Jetting is a paint brush to Powder Bed Fusion's pen or pencil. This approach gives Binder Jetting particular usefulness for chunkier parts that still have a good bit of complexity. Augmenting this reduction in machine time, Binder Jetting leans on lower cost solutions to create geometries. Glue and an oven are decidedly cheaper than a fiber laser or electron beam. Additionally, Binder Jetting doesn't require the same fine granulated powders that powder bed systems do — this means cost savings as well.

Electron Beam Powder Bed Fusion

Materials

Which materials can each technology process? Is there a broader range of materials available to one process or the other? How do material options compare to traditional manufacturing technologies?

Selective Due to Economics

Nearly every metal can be used in Powder Bed Fusion systems. Certain powder bed systems are better at processing high temperature materials whereas others are more conducive to lower-melting-temperature materials. Generally driving this is the extent to which the powder bed chamber is heated during manufacturing. Lower temperature chambers can be more prone to cracking and internal stress when processing high temperature materials. More than capability is actually economics when it comes to commonly available materials for Powder Bed Fusion. Materials commonly associated with less critical applications (e.g., iron) are not as prevalent as higher value metals like Titanium, Aluminum, Stainless Steel, Copper, and Nickel Inconel superalloys (e.g., 625, 718).

Limited Due To Nascency

Because the first step of Binder Jetting's process simply involves binding particles of metal together with glue, it offers tremendous material flexibility, in theory.1 Materials such as sand, gypsum, metal, and plastic can be bound with the Binder Jetting process. With regards to the next step — sintering — some limitations emerge. The extreme temperatures required for melting titanium, for instance, are challenging within a sinter furnace. Stainless Steel is the most common material used in the Full Sinter Binder Jetting process, in part because its behavior with regards to shrinkage in the sintering step is perhaps best understood.

Sand Print to Cast

Density

Will the process deliver me the density I need for repeated cycles and fatigue?

99.5% and Up

Powder Bed Fusion delivers dense parts.  Straight off the machine, density is typically north of 99.5%.  This is significantly above the density of cast parts, which typically run around 98% dense. This is one key consideration in how PBF parts can deliver better-than-cast material properties. Additionally, parts can undergo a Hot Isostatic Press (HIP) post-processing step to bring density within a hair of 100%.

93%-98%

The Binder Jetting process generally cannot deliver the same density as Powder Bed Fusion parts. Quite simply, while the sintering process can create density typically on par with cast parts, it does not achieve complete density. This level of density is appropriate for many applications. However, for certain tasks with high cycle time fatigue concerns, this may be a limiting factor. Again, Hot Isostatic Press (HIP) as a post-process step can be used to improve overall density.

Design Constraints

Does one process provide unique advantages when it comes to available geometries? Do each operate with the same design constraints?

Master of Complex Lattices

When it comes to design, Powder Bed Fusion offers a great deal of design freedom. Relative to traditional manufacturing processes, powder bed is capable of processing extraordinarily complex designs just as fast - actually faster - than standard blocks of material. Especially with laser systems, very fine features can be achieved. We generally don't recommend features smaller than 1mm, although we commonly can resolve them. In general, this allows for extraordinarily complex lattice structures to eliminate weight while retaining strength. Notable to consider is that Powder Bed Fusion systems generally require the inclusion of supports, made from the same material as the part, to prevent the metal from warping under the rapid heating and cooling that occurs during the process. Certain powder bed platforms operate with a heated chamber which reduces the need for such supports, but that can create other design considerations. Either way, you should try to design your part to be self-supporting. Just imagine if your part was a skyscraper — would any aspect of it need scaffolding to be built? This is critical, because parts designed without supports in mind can drive the price of a part up more than 50%.

Support Needs Reduced, But Sintering Must Be Considered

The Binder Jetting process does not have the same support restrictions as powder bed systems because there isn't a thermal component to creating the green part. With that being said, the post-processing step can be problematic for fine features, as the green part shrinks in size by 15-20%. This can also come with the threat of internal stresses. As a result, binder jetting parts are generally limited to sizes smaller than a fist for cost-effective printing and sintering.

The Bottom Line

It's really a tie.  Depending on the part you've designed, the quantities you seek, the material you desire, and the performance you require, either process might carry the day. The good news is that 3Diligent offers both of these 3D printing technologies (any many more!), and our experts can help you design to take advantage of either process.

 

Takeaways From Our Discussion at Atlantic Design and Manufacturing: 3D Printing Goes Heavy Metal

I had the pleasure of participating in the 3D Printing Goes Heavy Metal session and its panel discussion at the Atlantic Design and Manufacturing show this past Wednesday at the Javits Center in New York City. The discussion covered a wide range of metal 3D Printing topics, with a few specific discussions regarding design considerations, overall cost, and post-process requirements. For those of you who couldn't make it to the discussion, we will share a few of those thoughts here.

Cullen Speaking at 3D Printing Goes Heavy Metal

Design for Metal 3D Printing

Additive design became a topic of increasing interest as 3D Printing broke away from strictly prototyping uses and into a manufacturing technology for functional applications such as tooling, spare parts, and production parts. I think a primary takeaway from that panel was the consensus that designs should begin with a particular machine and material combination in mind — as well as the broad concepts of additive to achieve an optimized part.

Practically speaking, every process undergoes its additive step and post-processing requirements in slightly different ways. Hence, understanding and incorporating those key considerations is particularly relevant to developing a good product. This can be challenging and may often require an expert's support. The session highlighted some exciting advances in topological optimization and generative design software, which can help you take full advantage of a 3D printers' capabilities. With that being said, there was also consensus that, currently, no software could deliver ready-made parts that were suitable to go straight to the printer. A degree of expert interaction with the designs was warranted.

Metal Additive and Costs

Obviously, metal 3D Printing is generally expensive and justifiably so. The leading technology in the metal additive space, powder bed fusion (PBF), is quite costly due to the requirement for highly refined powder and expensive underlying lasers with extraordinarily high optical requirements. However, an advancement of competing technologies in recent years has brought competition to PBF.

Metal binder jetting and extrusion technologies leverage less refined powders to deliver more cost-effective parts for certain geometries. These powders utilize sintering furnaces that, on the whole, lower costs compared to high-power lasers. A final group of additive processes scraps both furnaces and lasers altogether: sheet lamination, cold spray, and metal stirring. These technologies, though not as developed, potentially open the door to cost savings as well. There are also different hybrid solutions that can take rougher outputs from an additive process and achieve a degree of post-processing on the fly.

Cullen Speaking at 3D Printing Goes Heavy Metal

Post-Processing Requirements

3D Printing is famously known for requiring a significant amount of post-processing, tied in part to laser powder bed fusion; but it's not unreasonable to say that post-processing requirements are prevalent across the metal 3D Printing industry. The big takeaway from this portion of the discussion was that designing for your particular process can be extraordinarily valuable in eliminating post-processing costs. If your design does not account for a particular additive process, then it will likely require the removal of support structures. Similarly, things like trapped powder can wreak havoc on a finishing station; avoidable with appropriate "design for manufacturing" thinking ahead of time.

So if you couldn't make it to the show or join us at the panel discussion, I hope it was helpful hearing some of the key inputs to how 3D Printing is going heavy metal. If you have other questions, don't hesitate to reach out, look around our site here, or leave comments in the section below.

-Cullen Hilkene, CEO

3Diligent at Javits Center Speaking Session: 3D Printing Goes Heavy Metal

 

Today at 2:00 P.M. Eastern, our CEO Cullen Hilkene will be speaking at the Javits Center‘s 3D Printing Goes Heavy Metal panel. Among the topics included in the overall 3D Printing session will be how it is:

Highlighting this pervasive topic in medical manufacturing and beyond so you can walk away prepared for the changes ahead. You’ll find it all, including design software, hardware, services, post-printing manufacturing solutions, and more.

Our panel discussion, entitled “3D Printing Goes Heavy Metal” will explore:

Which materials hold the most promise while considering case studies from industries that are leading the adoption of metal printing.

Swing by if you are in New York, we hope you’ll come join the conversation and sync with us!

 

3Diligent at the World Economic Forum; The Challenges and Solutions for the Future of Additive

I had the distinct privilege of being invited to and attending a recent session at the World Economic Forum — Center for the Fourth Industrial Revolution in San Francisco. It was a remarkable experience for a handful of reasons; and I thought that I would take this opportunity to share a bit about the experience with our blog readers.

The World Economic Forum and 3Diligent

So for starters, I figure it best to establish what the World Economic Forum is, what it does, and what its goals are. Frankly, my understanding of the World Economic Forum prior to this event was largely that of a trade organization — it pulls together leaders from across the world of business. For that reason, I know that there seem to be annual protests at their event in Davos, Switzerland because the folks participating are in decision-maker positions. Upon arrival, I realized that the World Economic Forum is focused on advancing the standing of humankind. Obviously, they view trade as a key means of doing that. However, important to the purpose is understanding the way that new technologies are impacting the world, the disruption that it may potentially have on humanity, and articulating potential solutions so that governmental organizations — who are typically slower to act than businesses — can effectively govern and minimize adverse impacts.

Therefore, it was with this context that I was invited to the 3D Printing and Trade Logistics working session at the world economic forum's center for the Fourth Industrial Revolution in San Francisco earlier this week. We at 3Diligent were honored to be invited as a company that possesses significant visibility into the market and a very active day-to-day role in engaging with those companies and the manufacturing organizations that are making use of the technology.

3Diligent World Economic Forum Badge

What Will 3D Printing Headlines Look Like in 20-50 Years?

The first thing that we did at the World Economic Forum, after a few introductory remarks, was to think about headlines from 20-50 years in the future that might be related to 3D Printing. The ideas that the group landed on were really interesting…

Changing of the Guard

One set of thinkers anticipated a complete "changing of the guard" in terms of leadership in the aerospace industry — tied to upstart organizations who had advanced 3D Printing to a point where there planes were almost entirely 3D printed to provide unmatched fuel savings and price competitiveness in the transport market.

Bio 3D Printing to Prevent Remote, Fatal Accidents 

Another group of thinkers anticipated a hypothetical calamitous event in a National Park where an individual had lost an appendage. New arms, ears, or eyes could be printed on demand and airlifted to the site of the carnage so that they can make a rapid recovery — instead of what would have normally been almost certain death.

Bio 3D Printing for Survival in Extreme Environments

Yet another group of thinkers anticipated a colony of autonomous humanoid beings, derived from advanced Bio 3D Printing technologies, capable of living in the depths of the Marianas Trench — tens of thousands of feet underwater — due to adaptations that 3D printers were capable of providing to them.

In brief, some pretty crazy stuff — but "crazy" only in so far that this group of industry leaders felt that the stories were entirely plausible within the next 30 Years.

A Challenge Resulting from Future Developments

Next, we began considering some of the key challenges that such future developments would have on human society, as well as actions that could be taken to address those challenges. Our group listed out a healthy set of challenges, broadly tied to themes including the workforce, security, business models, ethical/moral, cross-border flows, and standardization.

Workforce Displacement from Robots and AI

By far the consensus concern was something that we hear regularly in this day and age, and it is the disruption to the workforce that the rise of robots and AI may bring about. The group, on the whole, was not extraordinary concerned about this displacement in the near-term. As the number of studies have called out, the rise of digital manufacturing is actually creating many more jobs than it is eliminating; and this is especially true for developed economies.

In places like the United States, Europe, and Japan, the possibility of eliminating a chunk of the "labor cost input" to a digitally manufactured part means that new levels of competitiveness are possible. These more expensive countries still suffer from the need to cover the cost of more expensive real estate on for their plants to sit on. However, the ability of 3D printers — especially to occupy very small spaces while still achieving near peak efficiency — is what mitigates this issue on some level.

Therefore, there is a higher likelihood that the market penetration of these machines has the effect of localizing or at least regionalizing manufacturing and restoring a lot of jobs. This obviously has the counterpoint of potentially preventing less-developed nations from coming up the curve that other countries have through serving as a source of low-cost manufacturing labor.

Consensus

I got the feeling in the room that the net good would outweigh the net harm, at least over the next couple decades. With that in mind, the consensus opinion was that governmental organizations and private organizations — as well as public-private partnerships — could do a lot in the very near future by investing in training and retraining programs to empower a new generation of digital manufacturing experts. The remarkable opportunities that digital manufacturing is opening up will only be realized if we have an educated workforce — capable of understanding and taking full advantage of these technologies.

In Summary

We dug in on each of the other major thematic areas, but I think that's enough for one blog. Perhaps we'll post them at a future date but for now, I'm interested to hear if anyone reading this article has their own perspective on the biggest challenges that the rise of digital manufacturing — and especially 3D printing — will bring about in the decades to come. If so, then what they view as the best solutions to addressing these future challenges.