The Do’s and Don’ts of Metal 3D Printing

Star Trek aficionados are well versed in the wonder of the “Replicator,” a machine that initially synthesized meals on demand, but eventually evolved to magically produce any number of complex objects, from clothing to the USS Enterprise’s spare parts.

3D printing, and in particular, recent advances in metal additive manufacturing (AM), have many likening what’s possible with the technology to the sci-fi promises of the Star Trek universe. Proponents of metal 3D printing are bullish on the potential, touting the ability to accommodate complex structures, decrease materials waste and reduce lead times for specific classes of traditionally manufactured metal parts. 

However, the general lack of understanding of the process, especially the need to redesign parts to achieve the true benefits, remains a significant hurdle to adoption as well as an ongoing inhibitor to metal AM return on investment (ROI).

While metal 3D printing is indeed a game changer, most companies haven’t fully capitalized yet because they aren’t taking the opportunity to redesign parts, contends Tom Houle, director of LUMEX NA for Matsuura USA. 

“When we see parts that are designed to be metal 3D printed instead of converted to metal 3D printing then the result is a part that is lighter, uses less materials, creates less scrap and waste and runs on a machine 24/7, lights out,” he explains. “Those are four game-changing aspects of metal 3D printing and why the technology will eventually be commonplace.” 

Designing for Metal AM is Key

For now, metal AM is not exactly a manufacturing floor or engineering department staple, but it is making headway. A recent survey from Market Reports World projects the metals 3D printing market to grow at a compound annual growth rate (CAGR) of almost 22% from 2021 to 2025, increasing revenue by $1.3 billion. Grandview Research is projecting 27.8% CAGR growth between 2020 and 2027, fueled by increased adoption in the medical, automotive, and aerospace and defense sectors.

Despite the uptick, the high-cost and complex nature of traditional metal 3D printers have put them out of reach for a large segment of manufacturers and engineering shops. That dynamic has shifted over the last few years as prices have declined and a spate of next-generation models have made the technology more accessible. 

Yet, as companies start to test-drive metal 3D printing, they encounter an array of challenges that leave many disappointed with results.

“The core challenge of metal 3D printing is education and expectation setting,” says Lishan Mu, product manager at Markforged. “Because of the novelty of metal 3D printing, the manufacturing world doesn’t know what to print or how to design for the metal AM process. They are taking parts meant for [computer numerically controlled] machining and expecting the same results from metal 3D printing. It just doesn’t work that way as metal 3D printing is a completely new fabrication process that has its own capabilities, strengths and shortcomings.”

To help counter that scenario, Markforged advises engineering teams to embrace a redesign approach, reevaluating parts by drilling down into why a particular feature was designed the way it was. 

“Ask yourself, ‘Why is the hole round? Is it because it’s a through hole for a screw or because the drill to create the hole is round? Does it actually need to be round?’” asks Mu. “Most conventionally-designed parts are concepted to require as little material removal as possible, which is the exact opposite of what Design for AM (DfAM) suggests. If you ask enough of the right questions, you’ll quickly find areas to optimize for a successful output with metal 3D printing.” 

To assist customers in this process, the Markforged University program helps identify the right parts to print as well as how to implement DfAM techniques to ensure print success.

Best Practices for Metal AM

Beyond the No. 1 best practice of redesigning parts for metal AM, experts in the field have various recommendations for what measures to avoid along with guidelines to ensure the best value and to optimize printed parts. Among them are:

Don’t underestimate post-processing. Because it’s still relatively unknown in broad market circles, many companies tend to look at 3D printing, and metal AM in particular, as a black box. Experts say it’s a misconception to assume most offerings are a plug-and-play machine and that there won’t be significant machining and finishing work required to ensure a part comes out finished as intended.

Companies diving into metal AM need to cultivate an understanding about how particular materials operate in terms of structural integrity as well as gain a clear picture of what’s required for surface finishing and heat treatment to ensure there is no deformation and that parts will meet required tolerances. Often, companies don’t factor in the need for machine shop capabilities as an integral part of the metal AM process.

Those firms that go into metal AM with a strategy that starts with design and goes all the way through inspection and testing have better results with implementation, Houle says. 

“Those that have a plan from the ground up for implementing metal 3D printing have a strong track record of ROI,” he says. “Those that bring in the technology and try to find different parts or applications they can convert do not.”

Matsuura’s LUMEX Avance-25 and Avance-60 metal laser sintering system focus on a hybrid approach, which streamlines post-processing work, Houle contends. The systems combine a powder bed metal AM platform with subtractive machining capabilities to ensure quality parts are finished with maximum precision.

SPEE3D’s supersonic 3D powder deposition (SP3D) process also helps defray post-processing challenges while operating up to 100 to 1,000 times faster than traditional 3D metal printing processes, according to Bruce Colter, vice president and general manager for the Americas region of the company. 

SPEE3D is based on cold spray technology, typically used for parts repair and coating, which combines high-pressure carrier gas with metal powders and operates below the melting point of the metal in use so it achieves a high density of deposits and low residual stresses. The resulting process requires far less heat treatment or post-processing work to get a quality finished result.

“The dirty little secret of metal AM is that often 60% of the process time is spent at the back end, de-stressing, heat treating or HIP (Hot Isostatic Pressing) parts as part of the finish work,” Colter says. HIP refers to a process that exposes components to simultaneous application of heat and high pressure to help form the part by compacting the metal powder and eliminating porosity.

Make use of simulation to help optimize print processes. As companies expand use of simulation, simulation can also play a role in helping companies understand the metal AM process, specifically to optimize the printing process. SPEE3D just released SPEE3D Craft, a 3D printing simulator that takes users through the entire process, from part design to picking materials and removing parts from the build plate. It also provides instruction for use of the equipment.

Desktop Metal also sees simulation as a critical step for successful metal AM. The company’s Live Sinter software simulates the complex forces and deformation of parts during sintering, helping users with limited experience with the technology to achieve defect-free parts. To foster better parts design for metal AM, the company offers Live Parts generative design software. 

“We focus on simulation before and during the simulation process,” says Jonah Myerberg, Desktop Metal CTO. “We want the designer to only put materials where they need to be and design the part around the manufacturing process, and Live Sinter shows how parts distort and change so engineers can make minor tweaks and get better results.”

Don’t forget metal AM is an end-to-end process, not just a machine. The specific features and functions of a metal AM system are important, but it’s critical to look at how the platform addresses the entirety of the process to ensure the best results. At Velo3D, for example, the Sapphire 3D printer is integrated tightly with Flow print preparation software and Assure, a quality assurance and control system. Flow employs simulation to ensure predicable print outcomes directly from a native CAD workflow. 

The software also features standardized recipes for parts, negating the need to develop new process parameters for every print job, saving time and reducing the need for 3D printing specialists. Assure uses a multi-sensor defect detection system to predict bulk material properties for each part and to determine print health in real time, ensuring companies can move to production with verifiable part-to-part consistency. 

“Historically, engineers have had to wait for something to be printed to scan and check results,” says Zach Murphree, vice president of technical partnerships at Velo3D.

Do embrace an iterative approach to design and manufacturing. That’s at the heart of the benefits of 3D printing of all types. “Don’t be afraid to put something on the machine,” says Patrick Dunne, vice president of advanced application development at 3D Systems. “Maybe it doesn’t work, maybe it breaks, but it’s the ability to iterate at a high frequency and embrace Agile as a design approach that’s so interesting.”

Do get your feet wet with a service bureau. To determine whether metal AM makes sense for your applications, consider enlisting the help of a service bureau that has already gone through the learning curve and codified best practices to address complexities like part orientation or how to best plan for supports. 

“We’ve already been through the growing pains,” contends David Bentley, senior manufacturing engineer for 3D printing at Protolabs, a contract manufacturer. “Right now metal 3D printing isn’t a dark art, but there’s definitely some art to it. We can look at a part and come up with a solution that works on the first print and avoid a lot of that trial and error.”

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