Metal 3D Printing Simulation Arrives with exaSIM Ultimate
Michael Molitch-Hou posted on October 03, 2017 | 5502 views

Since its founding in 2014, 3DSIM has been on a mission to address problems of quality and repeatability in metal additive manufacturing (AM) by creating software that makes it possible to properly 3D print a part in the first go. Now, the Park City, Utah, firm has released the final piece of its exaSIM package, exaSIM Ultimate, which provides unprecedented simulations of the thermal strain created at every point in a metal part as it’s being printed.

To learn more about this important technology, ENGINEERING.com spoke to Brent Stucker, co-founder and CEO of 3DSIM.

Trial and Error in Metal 3D Printing

Aerospace companies like Airbus, GE, Arconic, Boeing and GKN Aerospace are aware of the powerful trend taking place. Metal AM is proving itself capable of producing a new generation of components that may be lighter and more efficient than those made with traditional manufacturing technologies.

While Airbus is trying to cram as many 3D-printed parts into its A350 XWB and A320 neo aircraft as possible, metal AM has some fatal flaws that are preventing its widespread adoption. Quality, repeatability and ease-of-use are just a few of the biggest issues with the technology in its current state.

Due to the physical stresses that occur in metal AM, printing a component isn’t as easy as clicking “print” and getting a finished part. Metal parts require properly placed support structures to absorb some of the thermal strain and, even then, warpage can occur.

As a result, machine operators and designers often have to reorient the part, test out support structure placement and redesign the component to compensate for warpage. For this reason, it can take a machine operator or designer multiple tries before a decent print is obtained.

“In metal AM, you rarely get what you want the first time you try. In particular, if you’re a new metal AM user and you don’t have a lot of history with failed builds, you find that whenever you try a new geometry, your success rate is really low,” Stucker explained. “Even experts have to build a part over and over to figure out the best orientation, exactly where supports are needed and how to avoid blade crashes.”

exaSIM Until Now

To address this issue and more, Stucker and his co-founder Deepankar Pal, 3DSIM chief science officer, have been researching how to simulate metal AM for years. The science behind 3DSIM’s software dates back to 2009, but Stucker has been studying metal AM the past 24 years.

exaSIM is used to simulate how part orientation will affect thermal stress. The first image shows orientation, which is followed by the stress simulation, followed by supports automatically generated by exaSIM. (Images courtesy of exaSIM.)
exaSIM is used to simulate how part orientation will affect thermal stress. The first image shows orientation, which is followed by the stress simulation, followed by supports automatically generated by exaSIM. (Images courtesy of exaSIM.)

The company’s first release was exaSIM, which can perform a simulation of a part being printed by laser powder bed fusion in a birds-eye manner. The software, like other metal AM simulation software that has been released, takes the printing parameters and generalizes the thermal effects throughout the part. It does so by assuming that these effects will be the same at every point throughout a print.

“We assumed that every point had the exact same amount of strain that occurred in it or we gave it a scan vector orientation-dependent strain, where we increased the strain parallel to the scan direction and decreased it perpendicular to the scan,” Stucker said. “Every scan vector had the exact same average strain as the prior ones. All of our case studies to date have used those averages to show how you can get very good predictions just from the average effect.”

Once such a simulation has been performed. exaSIM tools make it possible to determine the optimal orientation and place the proper number of support structures—the fewer support structures, the less post-processing work will be required.

More recently, 3DSIM introduced its powerful Distortion Compensation Tool, which predicts the amount of warpage which will occur in a part. It then applies a “reverse warp” to compensate for any distortion caused by the thermal stresses.

In the first image, you can see a bulge in a 3D-printed filter made by Croft Filters, along with an exaSIM simulation that accurately predicts this bulge. The next image shows distortion compensation, in which the bulged area is purposefully shrunken to compensate for the bulge. This is followed by a successfully printed part with distortion compensation. (Images courtesy of exaSIM.)
In the first image, you can see a bulge in a 3D-printed filter made by Croft Filters, along with an exaSIM simulation that accurately predicts this bulge. The next image shows distortion compensation, in which the bulged area is purposefully shrunken to compensate for the bulge. This is followed by a successfully printed part with distortion compensation. (Images courtesy of exaSIM.)

This reverse warp can be applied to a part before it is removed from the build platform—a process that often requires CNC machining or wire electrical discharge machining—or even after. This can help when making important decisions regarding post-print heat treatment, which can be used to relieve stress caused by the printing process.

“If you can get the machine to build the right shape while it’s attached to the supports, but you know it’s going to warp significantly when you cut it off, then you would know that you need a heat treatment to relieve the stress before you cut it off. If you predict that you can cut it off and it’s not going to go anywhere, then you know that you don’t have to do a heat treatment for that geometry,” Stucker said.

exaSIM Ultimate

As beneficial as this may have been, it’s obvious that—as heat builds up, as the part geometry changes and as the laser’s behavior changes—the thermal strain will not be the same at every point throughout a build. What 3DSIM has introduced with exaSIM Ultimate is something that no other simulation software has. The program actually predicts the thermal strain point-by-point throughout a print.

“We’re basically solving how much shrinkage strain occurs in each location in space, depending upon how the temperature goes up and down,” Stucker said. “From that we get a much more accurate prediction of the part and how it’s going to deform.”

According to Stucker, this is particularly important when it comes to objects with complex geometries, including thin and thick regions, and the complex laser scan patterns that may be deployed to print them.

To obtain the complex physics that occur when an energy source melts a metal powder in a sophisticated laser system, exaSIM Ultimate has machine profiles from different manufacturers or the user can input laser scan parameters (such as laser power, scan speed and the scan pattern) into the software. 3DSIM plans to eventually incorporate all of the systems from the major manufacturers into the software.

The software then runs a simulation that mimics what the machine actually does when printing. These simulations are based on two custom finite element (FE) solvers written by 3DSIM, one that performs thermal calculations for every scan vector and another that accumulates strain layer by layer.

For the user, this means that it’s possible to use high-level, less-detailed simulations to determine the proper part orientation and support structure placement. Then, the user can run the detailed thermal analysis provided by exaSIM Ultimate to understand the stresses at a point-by-point basis. This is particularly useful if you want to produce multiple parts and ensure the quality is very high.

Considering such a complex set of variables—bed size, layer thickness, scanning time—would theoretically require a 16 teraflop computer and 5.7x1018 years to solve. However, by implementing a number of mathematical and computational tricks, exaSIM is able to perform these simulations quickly.

“There’s certain phenomena that are occurring over and over in the printing process. Mathematically, we can then solve that problem once and reuse the answer over and over where it applies throughout the simulation and then solve the difference discretely every time,” Stucker said.

Another important variable is the fact that Stucker has been studying metal AM 24 years and understands the physics well, which allows him to understand “just the right amount of physics to predict only what a user wants.”

Stucker estimated that the model in the graphic above would take about 10 to 15 minutes to simulate at a high level and 24 to 48 hours when fully detailed. This graphic is from a research initiative launched by America Makes, in which the partners involved saw a 75 percent reduction in product development time. (Image courtesy of America Makes.)
Stucker estimated that the model in the graphic above would take about 10 to 15 minutes to simulate at a high level and 24 to 48 hours when fully detailed. This graphic is from a research initiative launched by America Makes, in which the partners involved saw a 75 percent reduction in product development time. (Image courtesy of America Makes.)

To run the high-level simulations, Stucker estimated that it might take 10 to 15 minutes. To get the most detailed simulation with the highest accuracy possible might take somewhere between 24 to 48 hours. The simulations can currently be run on 3DSIM’s cloud, but the firm also will be releasing a desktop version of its software for use with CAD computers.

The Benefits of Simulating Metal 3D Printing

The benefits of bypassing the trial-and-error method associated with metal AM are substantial. By simulating a part, there will be less, often very expensive, material wasted by producing failed prints. This cost-savings may be compounded by avoiding blade crashes that require repairing the machine. Additionally, it can save a great deal of time.

“For metal AM experts, the reason they’ve become successful with the technology is really based on a lot of built-up tribal knowledge of what doesn’t work and what works,” Stucker explained. “They simulate a print mentally and say, ‘I‘ve seen this problem or geometry before. If we try this trick we found it would work in the past.’ For people who are new to metal AM, exaSIM can actually help them overcome those years of disadvantage they have compared to the more established AM users.”

The technology may not only help new users catch up to the likes of GE and Boeing but also help those established users avoid trial-and-error associated with new geometries and material. Stucker pointed to a recent study performed as a part of a project hosted by America Makes, the public-private U.S. 3D printing institute.

The study saw GE, Honeywell and United Technologies Research Center collaborate with 3DSIM, Pan Computing and CDI Corporation to validate the simulation software. The result saw that such a simulation tool could reduce product development time by 75 percent. When applied to the costly and critical aerospace or medical sector, this number is substantial.

FLEX and the Future of 3DSIM

Currently, 3DSIM’s software is suited for laser powder bed systems, but 3DSIM is actively adapting the tools to work with directed energy deposition (DED) and electron beam melting (EBM), two crucial metal AM technologies.

According to Stucker, the software can already be used for these technologies; it’s just a matter of users tweaking exaSIM’s inputs to better reflect these processes. However, 3DSIM aims to create machine profiles that accommodate the differences between laser powder bed and DED and EBM.

exaSIM can simulate the majority of standard metals used in AM, including Inconel superalloys, Ti64, steel alloys, aluminum alloys and cobalt chrome, but Stucker said that this list will expand as customers request new metals be added.

Beyond exaSIM, 3DSIM will be releasing what could prove to be another crucial technology for simulating metal AM. Dubbed FLEX, the next software, likely to be released in October 2017, goes beyond distortion in metal AM and provides insight into other variables, such as meltpool sizes and shapes. This is geared toward predicting the microstructure of a component so porosity that might result in cracks and part failure can be predicted.

This will be key for the next step in the exaSIM vision, which is incorporating sensor technology into the exaSIM workflow. With the release of FLEX, users will be able to simulate what various sensor technologies—such as sensor systems from Sigma Labs, IR cameras or pyrometers—see in the printing process.

Such simulations make it possible for companies to then develop qualification procedures that match the as-built printing process with the simulated process. In turn, it will be easier for companies that are 3D printing parts for industries such as aerospace and medicine to achieve regulatory approval.

In the not too distant future, it will be possible for FLEX to predict a part’s microstructure and physical properties, further adding to this qualification effort. If it’s possible to predict that a 3D-printed part, such as an airframe bracket, will have the correct microstructure without porosity, there will be less destructive and non-destructive testing of printed parts required. Simulations can be increasingly used to show regulators that a part will perform well.

Not long after that, it may even be possible for FLEX to be used to perform actual in-process quality control within 3D printers. By inputting sensor data into real-time simulations of the printing process as it is taking place, it may be possible for the machines to regulate themselves in order to avoid any issues. Such an implementation could be developed as early as 2019, according to Stucker—that is, after FLEX is fully validated.

In the meantime, 3DSIM is working to package its software with metal AM systems on the market with the goal of integrating it into the machines’ own software. In the future, metal AM 3D printing may be as perfect as we can expect them to be.

To learn more about 3DSIM, visit the company website.


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