Layer by Layer: Assuring Metal AM Part Quality with Velo3D’s Process Monitoring Controls

November 22, 2021

Additive manufacturing (3D printing) was supposed to herald a new era of performance and supply chain agility, but what we’ve experienced with many conventional AM systems has fallen short of hopes and expectations for the technology. This frustrating reality is hammered home even further when examining the varying quality and control measures (or lack thereof) offered by conventional AM systems.

To achieve the best possible parts, at the consistency and quality needed by the most demanding and innovative industries, it’s imperative to move beyond conventional AM and look to the benefits of advanced AM and the technology’s more comprehensive quality assurance and process controls.

The above has long been a cornerstone of Velo3D’s end-to-end solution. Working in concert with one another, Velo3D’s revolutionary quality control system enables visibility into every layer of the part build through real-time, multi-sensor, physics-based excursion detection algorithms.

Our focus to provide customers with the best quality control and monitoring has perhaps teetered on obsession, but that’s because we’re keenly aware of how these two factors can, when it comes to AM, literally make, or break a build.

The importance of part quality

Unlike conventional AM systems, Velo3D was designed as a true end-to-end solution. That means both software and hardware are fully integrated and built to work together from the ground up. In fact, we’ve simplified complications that make conventional AM systems inefficient and non-repeatable, creating conditions for a more agile, less costly, supply chain that can revolutionize the parts production process without compromise.

All Velo3D Sapphire® printers feature our proprietary Assure™ quality assurance software, which is accessed through a web-based interface.

Before a build even starts, Assure™ takes all the metrology signals collected and distills it down into a simple dashboard for the user to look at and indicate whether or not the system is healthy and ready to start building the desired part.

During the build, Assure™ monitors and ensures the system is healthy and operating within nominal specifications. As we like to say at Velo3D, it’s one thing to have sensors that give you all this information, but it’s another thing to be able to process them and distill them down into metrics that are actionable.

With Assure™, we’re able to translate all the information, coming off the printer into discrete actions that the operator can use to determine whether the build is going be successful.

Of course, it’s all for good reason—for greater industry-wide acceptance and adoption, AM processes and parts need to be validated, reliable, and repeatable. This is especially true of heavily regulated industries, such as aviation and space, where 3D printed parts must pass rigorous qualifications and inspections.

The role of metrology for AM

Metrology is analyzing what happens during a build. Simply put, we rely on the metrology to know whether the printing process is going well or not.

With metrology, it’s crucial to verify the starting point of the system when it begins the build, and whether the starting point is identical to when that part or process was initially qualified.

To do that, we need a lot of good data to ensure that everything about the optical system is the same as what it was, or within nominal limits, when it was originally qualified. This helps ensure that you don’t end up with some defectivity that you didn’t intend or originally characterize.

Mitigating failure with comprehensive analysis 

But how does this all ultimately affect part quality? The expectation during the Laser Powder Bed Fusion (LPBF) printing process is to leave a uniform layer of new powder, which then melts and fuses to the layer underneath it.

If there are any issues over the course of the build—for instance, if something happens with the mechanism that deposits powder on that layer—you can have either an excess of powder or local starvation of powder in a particular area.

This discrepancy causes problems for the lasing process. Recall that if you don’t have the same starting conditions, in terms of the amount of material that was expected, you can end up with a lack of fusion defect on the interior of the part.

Alternatively, there can be subtle changes during the build such as the thermal expansion of the chamber which causes an increase in the optical path length which can result in lasers becoming misaligned relative to one another.

A change in the optical path length or beam profile can also change the incoming energy density in the meltpool which can cause either overheating and balling of the melt surface or underheating and lack of fusion to the metal substrate

While there are many opportunities for things to veer off course during the printing process, Velo3D’s end-to-end AM solution and its Sapphire® 3D metal printer were designed to mitigate failures and monitor for issues that may prevent a successful build.

Without these built-in safeguards, it would be very easy for something to go wrong, resulting in tens, even hundreds of thousands of dollars that you ultimately must scrap because it fails final inspection.

Metrology that matters

The way Velo3D handles metrology is unique in that there are different components that we monitor at different times. One of the most sensitive aspects is the laser alignment between lasers.

It’s essential to have consistent, reliable metrology to ensure that the lasers are pointing at the same X and Y coordinates so that when you’re making a single, monolithic part with different lasers, you get good overlap, and you don’t end up with a stitch line.

That is the type of thing that can change on a layer-to-layer basis because it basically can scale as the temperature of the system changes. As a result, the entire optics are heating and expanding and contracting, which can cause errors to spread.

For the above example, Sapphire® measures this alignment on every single layer and actively corrects for it to make sure that the two lasers don’t drift from each other, while Assure™ reports the results.

There are other metrics that we use that don’t have to be monitored as frequently, but we still do to ensure we’re providing the best process monitoring possible. These pre-built routines can measure very accurately, for instance, what the spot size of the laser is over the build plate relative to nominal.

That’s the type of measurement that in most cases does not change in the middle of a build, but it’s extremely helpful for whenever you’re doing maintenance activity that might require, say, changing the recoater.

Ensuring proper process controls layer by layer

There’s a lot of metrologies built into our solution that are unique and don’t exist on other systems—all which give insight into what’s happening during a build.

One of the most novel is the height mapper utility found on all Sapphire® printers, which allows the system to automatically measure the Z position as a function of X, Y on the build plane.

During the build, the height mapper provides an accurate topographical map of what the powder bed looks like and what the part looks like while you’re printing it.

This metrology provides a lot of important insights, like whether the process is starting to drift away from you. It also lets you know whether there’s any risk of the system potentially damaging itself from a piece of metal protruding significantly from the powder bed, which could then lead to a recoater collision.

There are several other similar sensors. For example, there are optical sensors that are looking at melt pool monitoring, we have other optical sensors in the system as well, which all provide different feedback in terms of laser health and that frequently scan and analyze for these types of quality excursions.

The benefit of actionable process monitoring and controls

It’s no secret there’s a fear among additive manufacturing technology in general. This fear stems from a lack of trust, confidence, and whether the parts that are being manufactured ultimately meet the quality standards required of the original design intent.

From OEM to CM, our goal has been to provide a level of quality assurance and control that instills confidence and ensures quality. We want our customers to print parts, take additional orders, and push those parts out to their customers without worrying about quality issues getting escalated back to them.

At the end of the day, all this quality assurance software is to give our customers greater confidence in the quality of the parts that they manufacture on our systems.

OEMS, CMs and supply chain logistics

It doesn’t seem like it, but flexibility is another way that Velo3D ensures proper process monitoring and controls to deliver the best quality possible.

We know that a lot of OEMs are ultimately going to put these parts into finished products. However, while some may look to bring manufacturing in house, others may not have the resources to go that route, choosing instead to leverage Velo3D’s trusted and experienced contract manufacturing network.

Customers who want to shop their parts to different contract manufacturers can do so knowing that they can send a print file to any CM anywhere in the world and achieve the same quality end part, regardless of where that Velo3D Sapphire® is located.

Furthermore, Assure™ provides an independent report detailing that the build happened within specifications. This includes a report of what the sensors are saying during the build, whether the system was calibrated prior to starting—giving customers more confidence when they’re shopping the parts out to different CMs and knowing the part they receive back is of consistent and verified quality.

Why it all matters

There remains a lot of unnecessary ambiguity and complexity in additive manufacturing. Sending a design file to a CM, or even utilizing a different machine located in the same manufacturing center, can yield unexpected, inconsistent, and undesired results.

At Velo3D, we’ve worked tireless to remove that ambiguity from the AM equation with a complete end-to-end solution that provides unparalleled metrology and process controls to ensure the best part outcome, every time.

That’s because our customers are true innovators who want to push beyond the limits of conventional AM, and it’s our mission to help them do so without compromising the quality and repeatability they need.

With conventional AM, that remains a real challenge. And the absence of a truly integrated solution means customers looking to design, develop, and manufacture new parts will simply continue to experience unnecessary friction until they move beyond incumbent technologies.

Want to learn more about the Velo3D end-to-end solution? Contact one of our expert engineers today.

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About the Author

Amir Iliaifar

Director of Content

Amir Iliaifar is the Director of Content at Velo3D where he oversees the production and distribution of Velo3D’s global digital content marketing initiatives. Prior to joining the company, Amir worked for a leading professional drone manufacturer, several SaaS companies, and as an automotive tech journalist. He holds a Master of Arts in Digital Communication from the University of North Carolina at Chapel Hill.