The researchers tested four different printing patterns, with the lasers either melting the powdered metal back and forth continuously or in distinct square islands and either running parallel to the long side of the part or diagonal to it. (Image: Lawrence Livermore National Laboratory/M. Strantza)

A senior product development engineer at MAGNET, part of the National Institute of Standards and Technology’s Manufacturing Extension Partnership National Network, explains how additive manufacturing—or 3D printing—can help small and medium-sized manufacturer realize design benefits, improve part performance, and achieve greater cost- and time-saving efficiencies.

By Dave Pierson

“I’ve heard additive manufacturing is key to driving innovation in our industry, but how does it really deliver value?”

“We’ve looked at some additive manufacturing machines, but how can we justify the expense when we’re trying to eliminate our capital expenditures?”

“Is additive manufacturing worth the investment?”

I field questions like these every time I host or attend additive manufacturing conferences for small and medium-sized manufacturers (SMMs) through the MEP National Network™. As the senior product development engineer at MAGNET (Manufacturing Advocacy and Growth Network), part of the Ohio Manufacturing Extension Partnership (MEP), my goal is to educate SMMs and other MEP Centers on how additive manufacturing can help small businesses compete against larger industrial players.

I do this, in part, because of Ohio MEP’s participation in a 2017 NIST MEP award to Pennsylvania MEP to partner with America Makes, the Manufacturing USA Institute focused on additive manufacturing. This Institute works with industry, academia, government, and non-government agencies to innovate and accelerate additive manufacturing and 3D printing to increase U.S. global manufacturing competitiveness. And through our partnership, Ohio MEP is assisting MEP Centers and SMMs with adopting additive manufacturing strategies, including guidance on ROI benefits and affordable options for equipment purchases.

So, what’s the big deal about additive manufacturing? Additive manufacturing is the next step for those already familiar with three-dimensional (3D) CAD technology. In essence, 3D CAD is foundational to using additive manufacturing. Once you’ve mastered the core competencies of 3D CAD, you’re ready to transition to additive manufacturing.

Ways That Smaller Manufacturers Reap ROI from Additive Manufacturing

Originally developed by MITadditive manufacturing adds layer upon layer of materials to “print” a 3D object or part. These parts can be created from a variety of materials, including plastics, metals, ceramics, or concrete.

Additive manufacturing can provide significant ROI to SMMs by helping them improve their industrial tooling processes, produce more high-value, low-run parts, and create highly customized products for their industry and their customers. The technology also empowers manufacturers to conduct more cost-effective prototyping for R&D processes. Additive manufacturing can quickly and efficiently distill user experiences into a mockup, so manufacturers can produce and evaluate a 3D-printed prototype. Repeated feedback cycles can yield more ideas for more value-added parts.

Aerospace and medical manufacturers are already seeing the ROI benefits from additive manufacturing. Today, a growing number of smaller manufacturers are using it to transition to a more digital inventory, where you can support 40 parts that each have different SKUs, versus 5,000 parts with the same SKU.

Say you’re a company who produces sand casting or specialty tools. I help companies like these learn how to use additive manufacturing to print those parts in a couple of weeks, instead of months. With less lead time needed to create parts, it’s easier to transition to a digital inventory.

Strategic-minded manufacturers are turning to additive manufacturing to compete with larger players in their industry. But the majority of SMMs still have a lot of questions on how this technology will really deliver value in both the short term and for the long haul.

Here are some of the most common additive manufacturing questions I’ve received from SMMs and other MEP Centers.

 

What Specific Applications Can Benefit from Additive Manufacturing?

Does your facility use injection molding? Additive manufacturing allows cooling channels to be designed and built to contour to the mold, thus improving cooling performance. This process extends the life of the mold and reduces waste. The technology is also more efficient for lightweighting, with more material options available, such as lightweight plastics and composites. The process also uses less material, while improving part performance.

If you’re currently using metal castings, you can use additive manufacturing to print sand molds and cores from a CAD design without the need for a pattern or core box. Unlike typical industrial casting tools, additive manufacturing can significantly reduce the time and expense for producing molds and cores.

Can Additive Manufacturing Save Lead Time and Production Costs?

Additive manufacturing provides the ability to print customized, just-in-time parts. It reduces tool development time and costs, with less material and less waste. Potential uses include holding, guiding, aligning, locating, and clamping, as well as simple “go/no-go” gauges to check the fit and quality of components.

The precise nature of additive manufacturing means it dramatically increases time savings for the production of fixture-making for first-article inspections. As a result, machine tools, jigs, fixtures, or gauges can then be produced more quickly and with fewer defects.

This technology also improves the ability to [make fixtures for] coordinate measurement machine (CMM) inspections. Orek has used additive manufacturing to make hundreds of inspection fixtures for its CMMs. On average, the company estimates it saves $200 and six-and-a-half days versus having the fixtures machined. By using additive manufacturing, Oreck has removed fixture making and CMM programming from the critical path.

Can Additive Manufacturing Help Repair High-Value Parts More Cost-Effectively?

 Do you have high-value metal parts that are costly to replace? Directed energy deposition (DED) is a specific additive manufacturing application that can repair turbine blades and other high-end parts and equipment by rapidly depositing material on existing parts to extend their life.

This technology can also be combined with existing CNC equipment. The DED machinery builds the part and then the CNC equipment mills the part down to the right size and smoothness.

Taking Advantage of Your Additive Manufacturing Resources

There are numerous hands-on opportunities for SMMs to learn more about additive manufacturing and how this technology can help smaller manufacturers compete in today’s 3D-driven industrial landscape. I would suggest starting with learning events provided by the Additive Manufacturing Users Group (AMUG) and the RAPID + TCT Conference produced in partnership with the Society of Manufacturing Engineers (SME).

The National Institute of Standards and Technology (NIST) also offers multiple educational resources on its additive manufacturing database, such as workshops for metal and polymer-based applications. Additionally, MAGNET is currently working with MIT to develop a curriculum for about 60 MEP Center personnel for online additive manufacturing training.

 

About the Author

Dave Pierson is a senior design engineer for MAGNET, part of the National Institute of Standards’ Manufacturing Extension Partnership (MEP) National Network, and a notable figure in the advanced manufacturing (AM) community. He has 25 years of varied and practical additive manufacturing training experience that covers seven AM standards categories as set by the American Society for Testing and Materials.

Source: Manufacturing Innovation Blog, National Institute of Standards’ Manufacturing Extension Partnership (MEP) program (NIST.gov). Published online July 13, 2021. 

 

 

New Research Could Help Manufacturers Avoid 3D-Printing Pitfall

Researchers at NIST, Lawrence Livermore, and Los Alamos examined ‘island scanning.’ Their findings may surprise you.

 A research team has found that a method commonly used to skirt one of metal 3D printing’s biggest problems may be far from a silver bullet.

For manufacturers, 3D printing, or additive manufacturing, provides a means of building complex-shaped parts that are more durable, lighter, and more environmentally friendly than those made through traditional methods. The industry is burgeoning, with some predicting it to double in size every three years, but growth often goes hand-in-hand with growing pains.

Residual stress, a byproduct of the repeated heating and cooling inherent to metal printing processes, can introduce defects into parts and, in some cases, damage printers. To better understand how residual stress forms, and how it might be curbed, researchers at the National Institute of Standards and Technology (NIST), Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and other institutions closely examined the effects of different printing patterns in titanium alloy parts made with a common laser-based method.

Their results, published in Additive Manufacturing, show that a printing pattern often used in industry to decrease residual stress, known as island scanning, had the worst showing among the approaches studied, defying the team’s expectations. The data they produced could help manufacturers test and improve predictive models for 3D printing, which, if accurate, could steer them away from destructive levels of residual stress.

“This was very surprising and underscores the complexity of the problem,” said NIST Materials Research Engineer Thien Phan, a co-author of the study. “It shows that, although island scanning may work in many cases, it did not work in ours, which really highlights the fact that we need to have accurate modeling.”

The team’s research centered on a prevalent additive manufacturing method called laser powder bed fusion (LPBF), in which a laser scans over a layer of metal powder in a predetermined pattern, melting and fusing particles at the surface together. As the molten metal cools into a solid, a stage supporting the material lowers and the printer adds a new coat of powder on top, allowing the laser to continue building the part layer by layer.

Once the second layer of a build begins, residual stress starts to rear its unpleasant head. The metals used in LPBF cool off quickly, meaning that by the time a printer’s laser begins heating up a new layer, the metal from the previous layer is already solid. The melted layers contract inward as they cool, pulling on the solid metal below and creating stress. And the greater the difference in temperature, the more the melted layer pulls. This process repeats for every layer until the part is complete, locking the stresses into solid metal.

“You end up with an incredible amount of residual stresses inside your piece,” said Phan. “So it’s sitting there, tearing itself apart. The residual stress could crack the part and lift it up during the build, which could actually crash the machine.”

The most straightforward printing pattern in LPBF is a continuous scan, where the laser scans back and forth from one end of the part to the other. But an alternative option called island scanning has emerged as a way to mitigate stress. The idea behind this approach is that melting small sections, or islands, of metal one at a time rather than an entire layer would result in less metal contracting at the same time, reducing the overall stress.

Island scanning has gained traction with manufacturers, but past studies on the technique have been inconsistent. And more broadly, the relationship between scanning strategies and residual stress largely remains a mystery. To begin filling in these gaps, the multi-institution team set out to analyze the effects of island scanning on stress in great detail.

The authors of the new study printed four titanium alloy bridges just over 2 centimeters (0.8 inches) in length. The samples were built via either continuous or island scanning, with lasers running along their length and width or at a 45-degree angle.

At a glance, the bridges looked similar coming out of the printer, but rather than take them at face value, the researchers scrutinized them in close detail.

They beamed high-energy X-rays, generated by a powerful tool called a synchrotron, deep into the samples. By measuring the wavelengths of X-rays that reflected off of the metal, the team extracted the distances between the metal atoms with high accuracy. From there the researchers calculated stress. The greater the distances, the more stressed the metal was. With that critical information in hand, they generated maps showing the location and degree of stress throughout the samples.

All samples contained stresses close to the titanium alloy’s yield strength — the point at which a material undergoes permanent deformation. But the maps revealed something else that caught the researchers by surprise.

“The island scan samples have these really large stresses on their sides and tops, which are missing or much less pronounced in the continuous scan samples,” said NIST physicist and co-author Lyle Levine. “If island scanning is a way that industry is trying to mitigate these stresses, I would say, for this particular case, it is far from successful.”

In another test, they detached a leg of each bridge from the metal base plates it was stuck to. The study’s authors measured the distance the legs sprung upward, obtaining another indicator for how much residual stress was stored inside of the arch of each bridge. Again, the island scan samples performed poorly, their legs deflecting by more than twice as much as the other samples.

The authors propose that island scanning could be a double-edged sword. Although the small size of the islands may reduce contraction, the islands might also cool much faster than the larger melt pools, creating greater temperature differences and thus greater stress.

Although island scanning was not well suited to the particular part, material, and equipment used in the study, it could still be a good choice under different circumstances, Phan said. The results do indicate it is not a cure-all for residual stress, however. To keep stress at bay, manufacturers may need to tailor the scanning strategy and other parameters to their specific build — an effort that would be greatly aided by computer models.

Rather than optimize a print through trial and error, manufacturers could use models to quickly and cheaply identify the best parameters, if their predictions are accurate. Modelers could boost confidence in their tools by testing them against rigorously produced benchmark measurements, not unlike the data obtained in the new study, Levine said.

Paper: M. Strantza, R.K. Ganeriwala, B. Clausen, T.Q. Phan, L.E. Levine, D.C. Pagan, J. Ruff, W.E. King, N.S. Johnson, R.M. Martinez, V. Anghel, G. Rafailov and D.W. Brown. Effect of the scanning strategy on the formation of residual stresses in additively manufactured Ti-6Al-4V. Additive Manufacturing.

Source: National Institute of Standards and Technology (NIST.gov). Published online May 19, 2021. DOI: 10.1016/j.addma.2021.102003

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