Clash of the Recoaters: Overcoming Failed AM Builds

April 4, 2022

If you’re looking to manufacture a part, there are countless paths and processes to explore, each with their own benefits and pitfalls. When working in an industry like metal additive manufacturing (AM), it can be easier to draw distinctions between new technologies and more traditional forms of manufacturing like casting, brazing, and welding, because the processes are so wildly different.

The world of metal AM isn’t a monolith, however. There are numerous points of distinction that define each printer’s solution, but unfortunately many of those distinctions go overlooked if you were to consider metal 3D printing an industry where the brand names change but the technology stays the same.

At Velo3D, we specialize in an advanced metal AM solution that has surpassed conventional AM technologies. This Velo3D brand of advanced AM is made possible by a confluence of next-generation hardware and software advances that build upon weaker points in those conventional AM systems; one of those advances is Velo3D’s non-contact recoater.

In this article we’ll look at how Velo3D’s approach to recoater technology separates itself from conventional AM systems, and what a non-contact recoater means—particularly when paired with Velo3D’s other advances in AM technology—to help ensure part quality.

The Function of Recoater Blades

Metal AM, specifically the powder bed fusion form of it, works through the precise melting of powdered alloy to weld into a dense substrate. Within a metal 3D printer (which has a precisely calibrated, inert atmosphere), a recoater lays down a layer of powder as thin as the diameter of a human hair. This thin layer of powder is then precisely melted by the lasers forming tiny melt pools, which cool and solidify into solid material. The recoater then iteratively passes back over the build plane, layer by layer, adding more feedstock powder each time. As each layer is densified, they fuse together to create a part from the ground up.

Where Recoaters Can Go Wrong and How They Can Be Improved

During the metal AM process, we’re rapidly turning metal from a powder to a liquid, and then to a dense solid. That’s a lot of evolution in a short amount of time.

When melt pools are formed, they function as most liquids do; they have a propensity to dome like the meniscus on a glass of water. When the melt pool solidifies, the once liquid meniscus is now solid, domed material and depending on the size of the melt pool, can be a significant, solid metal protrusion. Protrusions of course, can also occur from macro-warping of solid material. This is common with insufficient supporting of certain geometries and can protrude higher in magnitude than melt pool protrusions.

A recoater passing over the surface, layer by layer, is working in near-close contact to the build plane; again, roughly the diameter of a strand of hair. In legacy metal AM systems, if the recoater encounters one of these protrusions, it may ‘hop’ over it, continuing to distribute a layer of powder over the substrate. The area near this “hop” will likely receive an excess amount of powder, which may be too thick for the laser to melt through, leaving porosity in the part. Additionally, when hopping over a protrusion, the recoater blade may also incur some damage to its underside, which may impact its functionality in the future.

These recoater “clashes” aren’t as dramatic as the name implies; it isn’t as if the recoater is smashing into the part like a car into a crash test wall. Rather, subtle deviations which traditional recoaters fail to accommodate, and possibly resulting in inconsistencies and porosity in the structure of a part.

Velo3D has pioneered what’s known as a non-contact recoater. By allowing the blade slightly more clearance off of the build plate, Sapphire printers mitigate the risk of contact when protrusions form, without sacrificing the precise consistency of powder bed layer height. While the non-contact recoater is an essential part of the printing process, it’s the technology surrounding it that makes Velo3D an advanced AM system. 

The Worst-Case Scenario for a Recoater Clash

In a less-than-ideal print scenario like the one outlined above—where the recoater hops over a protrusion, creating inconsistent thicknesses or porosity in the part—the worry isn’t a failed build. If a part is faulty and the build is unsuccessful, engineers can recalibrate the machine, start over, and hope for better results the next time.

The real worry is if the build is completed and the resulting part is riddled with undetected errors on a foundational level. This part may go through costly post-processing and make its way into an engine or some other machine and then fail because it wasn’t sound to begin with. This is the absolute worst-case scenario of a recoater clash in a legacy metal AM system. It’s not a failed build but a successful build of a failing part.

How Velo3D Overcomes Recoater Failure

While Velo3D’s non-contact recoater is important for mitigating clashes, where the technology shines is in its in-situ process monitoring. Within Velo3D Sapphire printers, every layer of the build is height mapped to detect protrusions and inform the operator. This gives engineers a unique ability to quickly detect print anomalies and perform corrective action.

By integrating Assure quality assurance software into the printers themselves, should there be errors within the build, they won’t go unnoticed. The behavior of additively manufactured metal can be difficult to predict. Even on the most advanced technology, things can go awry, however, with the RIGHT technology, anomalies are captured candidly, reported explicitly, and delivered seamlessly to the user, allowing rapid troubleshooting and problem solving.

Advanced metal AM, as pioneered by Velo3D, is made possible through the synergy of next-generation hardware like the non-contact recoater, and best-in-class process monitoring software like Assure. In many legacy metal AM systems, the failure isn’t necessarily in the way a part is built, it’s in the fact that that quality can’t be guaranteed. Velo3D avoids those pitfalls to ensure a quality build time and time again.

Interested in learning more about metal AM? Get in touch with our team of experts today.

Was this article helpful?

About the Author

Gene Miller

Technical Sales Manager

Gene Miller has held various high-level positions in foundry and process engineering. He joined Velo3D in 2016 as a process engineer, developing unique laser parameters for the company's flagship Sapphire 3D metal AM printer, and helped elevate Velo3D's SupportFree technology. He holds a BS in Mechanical Engineering from Colorado State University.