3D Printing Simulation (Part 1)
3D printing simulation is a fairly broad term that covers any simulation aspect of the 3D printing process, ranging from the melting of particles in a feedstock to the actual toolpath simulation required to build a part.
As you can imagine, there is a range of different companies offering simulation solutions for each and every aspect of the process. The target demographics of each of these software packages are as wide and varied as the software products themselves. Some are code-heavy products aimed at researchers, while others feature simplified operations with fancy GUIs and are designed for the manufacturing environment proper.
Which Is Which? And Who Is Who?
Let’s take a look at five different companies in the broad field of additive manufacturing (AM) simulation and see what they are offering.
First up, let’s take a look at Amphyon from Germany-based software company Additive Works GmbH.
Amphyon is aimed at users of metal AM systems, specifically those using laser beam melting. Figure 1 shows the software’s user interface.
Figure 1. Amphyon’s user interface. Image courtesy of Additive Works.
“Our software aims at all users of the laser beam melting technology, but [focuses on] the pre-processing and automation in production,” said Nils Keller, CEO of Additive Works GmbH.
“The idea is that every build job can be optimal and fully automated [and] prepared based on numerical simulation. However, the software can also be used for research and education and [to assist] in the design and construction stages.”
Amphyon is used for laser-based AM processes, including selective laser melting (SLM), direct metal laser sintering (DMLS) and LaserCUSING, and can simulate various stages of the manufacturing process, such as the buildup process itself, post-processing stages: base plate cutting, support removal and heat treatment of parts.
So, what makes Amphyon different from other metal-based AM simulation software solutions on the market?
“We rely on pragmatic simulation approaches and methods to generate more information [about] how pre-processing can be done in the best way and also provide the direction generation of build jobs based on this data,” said Keller.
“Compared to other simulation software, it’s not an extensive tool for all process issues users may want to simulate, but is a complete pre-processing software. We’ve AM-optimized solvers with several AM-specific enhancements to achieve very accurate and reliable results based on an experimental calibration routine,” explained Keller.
Additive Works is a member of the Altair Partner Alliance, and so HyperWorks customers can access Amphyon as part of their existing Altair/HyperWorks subscriptions.
Simufact, which is one of the leading companies working in the field of manufacturing simulation, offers a range of packages aimed at welding simulation and forming simulation, and the company recently released a package for metal AM named Simufact Additive (the current release is version 3.1 at time of writing). Figure 2 shows a Simufact Additive displacement plot. Of course, it’s a natural evolution for the company, because metal AM is a little bit like welding, isn’t it?
Figure 2. Simufact Additive displacement plot. Image courtesy of Simufact.
Simufact was so innovative with its products that MSC Software bought the entire company out in 2015, and so now Simufact is a defacto part of MSC Software. This is a fairly common theme in AM simulation—someone comes up with a great product, and the big guns come in and gobble the entire company up. The result is that the smaller company gains access to the parent company’s huge resources, while the parent company obtains the rights to some awesome software. Essentially, everyone is happy.
Whereas Amphyon focuses largely on pre-processing simulation, Simufact covers a range of stages, including modeling and distortion compensation. How does the distortion compensation process work? Well, the simulation shows how the part will undergo thermal deformation, and then designs the part pre-deformed to compensate for this. And it works, too. According to the Simufact website, displacement from distortion can be reduced by 50 percent and eliminates the need for printing test pieces.
We spoke to Volker Mensing, director of Marketing & Communications at Simufact, to get the lowdown on its offering.
“Simufact Additive is a specialized simulation solution for metal AM manufacturing addressing both manufacturers and researchers,” said Mensing.
“The software offers different simulation approaches: Depending on the aspects to examine, the user can choose between or combine a fast mechanical (inherent strain) approach, a thermal approach, and a thermo-mechanical approach for highest accuracy.”
As mentioned previously, Simufact covers a range of process stages in the AM workflow.
“Simufact Additive puts its focus on build simulation and subsequent steps, including heat treatment, cutting the base plate, removing supports and HIP [hot isostatic pressing],” said Mensing. “The software is open for interfacing with third-party solutions in the AM process chain such as Materialise Magics and OEM build preparation software (e.g., Renishaw´s QuantAM). The software can export results in 3D solid format, e.g., for structural analyses.”
So, what makes Simufact Additive different from all the other solutions available? We asked Simufact for its elevator pitch.
“Simufact Additive claims to be the best overall simulation package concerning speed, accuracy, functionality and usability,” confirmed Mensing.
“The software comes with a workflow-oriented user interface, which customers report as the best-in-class GUI. The software helps the user to identify the best build orientation, compensate final part distortion automatically, optimize support structures automatically and identify manufacturing issues such as cracks, shrinklines and recoater contact. Simufact Additive is ready for high performance computing based on Linux clusters.”
So, in summary, Simufact Additive is both user friendly and cloud enabled, and can reduce the time needed to develop parts.
One of the more well-known AM simulation packages is the Netfabb product line from Autodesk. Autodesk offers three tiers of Netfabb software that provide simulation of the printing process: Netfabb Premium, Netfabb Ultimate and Netfabb Local Simulation. Figure 3 shows a Netfabb displacement plot.
We spoke to Brian Frank, senior product line manager for Simulation at Autodesk, for more information on Netfabb’s features.
“The Netfabb family of products allows for simulation of the powder bed fusion method of metal additive manufacturing,” said Frank.
Figure 3. Netfabb displacement plot. Image courtesy of Autodesk.
“Netfabb Premium provides users with our simulation capabilities as a cloud service. Netfabb Ultimate provides all of the cloud capabilities and introduces the ability to perform simulations with your local compute resources, dependent on the complexity and size of the part you want to simulate. And Netfabb Local Simulation provides the ability to solve locally any geometric complexity for powder bed fusion and also includes the ability to simulate the Direct Energy Deposition method for metal additive manufacturing.”
For those who aren’t familiar with Netfabb, it is a platform that covers a range of processes starting with modeling, which includes the awesome Netfabb Generative Design feature (which we have covered in great detail), model import/repair/editing, deformation studies, auto-packing, and much more.
“The simulation capabilities in Netfabb are fully predictive, using multiscale simulation results to inform the predicted outcome from the start of the process, and it eliminates the need to create and measure test prints.” elaborated Frank.
“Other offerings on the market leverage an inherent strain approach, where the user is required to first print a test sample of the geometry, scan the print, and identify deformations, then adjust and tune the solver to product an output that matches the test print. That approach is costly and time-consuming. Netfabb users are able to get accurate results without wasting time and money on initial prints and examination in order to get accurate results.”
This is an interesting point to make regarding tuning the solver. As a personal anecdote, my old avionics professor used to call this tuning of math to suit the outcome the “fudge factor.” Apparently, Autodesk has eliminated the need for fudging, and is focusing on making the actual simulations more robust with regards to the real-life outcomes. This is critical in any simulation. For an efficient and accurate simulation, you first need to understand the mathematical model that defines the process…and then you need to make sure that your inputs are accurate.
As we like to say in simulation…“if you put garbage in, you get garbage out.”
Frank went on to elaborate further on this concept.
“In our experience, variations between predicted performance and observed results can typically be attributed to errors in providing the right data to the simulation process, such as fully understanding material properties and how it will behave during the printing process, the machine itself, and the characteristics of the machine environment components, etc. Once these items are fully understood, correlation between a predictive simulation result and observed performance can be achieved reliably.”
Reliability, robustness, accuracy and, most importantly, repeatability for the manufactured part are all things you want from a simulation package.
So, exactly how accurate are the simulations compared to real life?
“Autodesk invests heavily in undertaking verification of simulation results,” said Frank.
“This pedigree of doing in-house verification started with our Moldflow products, where we leverage our own laboratory facilities to do material and process testing, informing our simulation technology. We have continued this practice as we have built our additive manufacturing simulation technologies. We use both internal resources and external partnerships to continue to gain access to machines and materials to ensure the accuracy of our simulation capabilities. We also leverage these capabilities in our own facilities, like our Advanced Manufacturing Facility in Birmingham, UK, as well as our other technology centers in San Francisco, Toronto and Boston.”
What’s the next innovation Autodesk is aiming for in AM simulation?
“Autodesk will to continue to enhance and extend the capabilities and robustness of our additive simulation technologies. One particular area of focus is thin-walled parts and geometries, which currently present users of additive manufacturing [with] tremendous difficulties in production and high failure rates if they are not leveraging simulation. We are also incorporating simulation to aid in support creation and part orientation to limit post-processing operations. These efforts dovetail into our larger efforts for the manufacturing industry. As part of our vision for the Future of Making Things, we are building support for a full-featured “Design-to-Make” pipeline of capabilities, including generative design, automation, validation, toolpathing, production planning and more.”
GENOA 3DP is a software package from the awesomely futuristically named AlphaStar Corporation, which sounds a little bit like something from a Philip K. Dick novel.
Unlike most of the other software mentioned in this article, which are focused primarily on metal AM processes, GENOA3DP supports the virtual simulation and analysis of polymers, metals and ceramics.
“GENOA3DP is a tool that is needed by and targeted at researchers, OEM manufacturers and contract manufacturers for the optimized, trial and error-free fabrication of AM parts.” said Rashid Miraj, director of Technical Operations at AlphaStar.
“It simulates material and process parameters associated with an AM build in order to identify an optimized AM build solution.”
The software provides users with the ability to import an STL file/G-code; generate a structural mesh; run analysis and optimize the build in order to reduce weight; reduce scrap rate; improve performance; and meet specification.
Features of GENOA 3DP include the ability to predict the presence of residual stress, deformation and delamination (initiation/propagation); and predict fracture, failure type and percentage of contribution by a failure type.
In addition, the software provides the ability to identify location and extent of damage and fracture, that is, diffusion creep, void and surface roughness. It also allows parameters to be changed to improve the manufacturing process, that is, printing speed, intrusion distance, material temperature, ambient temperature and material type. Figure 4 shows the GENOA 3DP failure analysis.
Figure 4. GENOA3DP failure analysis. Image courtesy of AlphaStar Corp.
“GENOA3DP combines a detailed dehomogenized thermal-structural material model with Multi-Scale Progressive Failure Analysis to accurately predict the presence of voids, delamination, deflection, residual stress, damage initiation and crack growth that may arise during an AM build.” concluded Miraj.
FLOW-3D is a complete AM process simulation package from Flow Science, Inc.
Flow Science is headquartered in New Mexico and has been in the business of providing laser welding and AM process simulations to customers for the last six years. Its customers include machine manufacturers, end users of AM technology in the automotive and aerospace industries, and research labs and academic universities.
“FLOW-3D simulates the entire AM process by accounting for powder packing, power spreading with a roller, laser melting of powder, melt pool formation and solidification, and sequentially repeating these steps for a multilayer powder bed fusion process,” said Paree Allu, CFD engineer at Flow Science.
“FLOW-3D’s multilayer simulations are unique in that they save the thermal history of the previously solidified layer. Simulations are then carried out for a new set of powder particles spread onto the previously solidified bed. Although thermal distortions and residual stresses in the solidified bed can be evaluated using FLOW-3D, it is also possible to export pressure and temperature data into other FEA software.
“Additionally, FLOW-3D simulates binder jetting and Direct Energy Deposition and processes. In a binder jetting 3D printing process, FLOW-3D models resin infiltration and lateral spreading in a powder bed. In Direct Energy Deposition, process parameters such as the powder injection rate, particle size distribution, laser power and scan speed can influence the printed layer thickness and crystal growth and orientation, all of which can be simulated using FLOW-3D.”
FLOW-3D simulates a wide range of processes across the AM work pipeline, including:
For laser powder bed fusion (PBF), FLOW-3D simulates powder packing and spreading (see Figure 5), melt pool dynamics, onset of balling and porosity, surface morphology, microstructure evolution and process parameter development.
Figure 5. Powder spreading simulation. Image courtesy of Flow Science.
For Direct Energy Deposition (DED), the software simulates melt pool dynamics (see Figure 6), clad shape and dimensions, surface morphology, and microstructure evolution.
Figure 6. Simulating the melt pool generation in FLOW-3D. Image courtesy of Flow Science.
And for binder jetting, it can simulate inkjet printhead design, powder spreading and packing, binder infiltration and spreading.
“Using FLOW-3D and its discrete element method (DEM) and WELD modules, it is possible to simulate at the powder level and melt pool scale,” continued Allu.
“Relevant physics include laser-particle interactions, melting and solidification, recoil pressure, shield gas pressure, surface tension, and powder/particle dynamics. This multiphysics approach enables successful development of process windows for alloys and provides insight into microstructure evolution.”
And so we asked Flow Science what sets its product apart from the others.
“The status quo in additive manufacturing simulation software is focused on thermo-mechanical simulations that help with part-scale modeling such as thermal distortions, residual stresses and generation of support structures,” said Allu.
“While useful, information about melt pool dynamics and related defects such as balling, porosity and keyholing is usually outside the realm of such approaches. Fluid flow, heat transfer and surface tension within the melt pool affect the thermal gradients and cooling rates, which in turn influence the microstructure evolution.
“With FLOW-3D, it is possible to accurately simulate powder spreading and packing, laser/particle interactions, melt pool dynamics, surface morphology and the subsequent microstructure evolution. FLOW-3D captures the melt pool scale accurately by accounting for all the major physics involved. These detailed analyses help the user understand the role of process parameters such as scan speed, laser power and distribution, and powder packing density in affecting build quality of the 3D-printed part.
“These capabilities are unique to FLOW-3D and are achieved in a highly computationally efficient manner. FLOW-3D bridges the gap between the different scales in an AM process by implementing the critical physics, as well as generating results in time frames that are acceptable by industry standards. Finally, FLOW-3D can also simulate direct energy deposition and binder jetting processes in detail.”
The ANSYS 3D printing simulation options are called “Additive Suite” and “Additive Print,” and are focused on metal AM. In particular, they specialize in powder bed AM simulation. Figure 7 shows the ANSYS AM workflow.
Figure 7. ANSYS AM workflow. Image courtesy of ANSYS.
We spoke to Masha Petrova of Product Marketing Additive Simulation at ANSYS to get the latest on the company’s offerings.
“ANSYS currently has two products that are available. One is called “Additive Print” and the other product is called “Additive Suite,” said Petrova.
“Additive Suite is not a tool by itself; it’s actually a suite of software tools that ANSYS offers that includes everything under the sun for additive manufacturing. So, Additive Suite includes Additive Print; topology optimization; lattice optimization (available in workbench); Workbench Additive, which is a mechanical workbench tool that is available for the additive manufacturing process; and then there is something called Additive Science, which is a new tool coming out that is for simulation of microstructure and understanding the properties of the final printed part.”
Like most of the other companies in this article, ANSYS is currently focusing on metal AM processes, and specifically powder bed fusion. The company is currently looking into Direct Energy Deposition processes, as this is what the aerospace industry is interested in right now. Figure 8 shows an ANSYS print simulation.
“Technologically, there is no issue with simulation AM of plastics, but the issue is that plastic parts are so cheap to manufacture anyway that if you have a few failures, then it doesn’t really matter.”
Indeed. Metal powders and the machines that print them are very expensive. The philosophy of “Right First Time” definitely comes into play in this regard.
Figure 8. ANSYS print simulation. Image courtesy of ANSYS.
What sets the ANSYS tools apart from the tools offered by competitors?
“For print simulation specifically, we offer two tools that support powder bed metal AM print processes, and the number one goal is to reduce failed builds,” said Petrova.
“Failed builds are absolutely an issue for everybody, and it needs to be resolved. If simulation can truly allow you to simulate the process and let you understand where you need to put your supports and how you need to redesign the part so it doesn’t fail, and so you don’t get distortions or a plate crash and so on…you know, that simulation has a ton of value.
“The problem is, that of the other tools that are out there are not specifically designed just for operators and designers and people who have nothing to do with simulation, or just for people who are analysts who do simulation all the time…they try and cover both. Whereas ANSYS now offers two tools and there are two different solvers.
“So, one is the APDL solver, which is used in Workbench Additive, and that is designed specifically for analysts. ANSYS knows analysts and … what analysts need, so [it has] designed this tool that sits perfectly in the workflow of engineering analysts.
“So that’s the Workbench Additive product.
“But in addition to that, we have a tool that also came from the 3DSIM acquisition that uses a very different simulation process where it takes the scan pattern from a particular machine (because each different AM machine has their own scan pattern logic), and so we take that logic into consideration when running simulations. So, it gives you a very different look at the print process. From these two different approaches, we end up with two different approximations of the same physics…and the interfaces and user experiences are designed for two different groups of people [analysts and engineers], even though it’s the same process.
“And that’s something that nobody else is doing at the moment. And secondly, nobody has anything close to what Additive Science offers, which is basically being able to play around with the laser power and the scan speed, to see how these factors affect the final properties of the part.”
Obviously, robustness in terms of simulation is an integral part of making sure that the simulation results mirror the real-life processes. Garbage in, garbage out is a mantra known to simulation engineers the world over.
ANSYS have some other thoughts on the causes of variance between the simulation and the real-world processes that they emulate.
“Probably a big source of variation comes from a lack of knowledge,” continued Petrova, “and we’re trying to fix that by putting together some really good courses for our customers. We’re doing online courses, and we’ve partnered with the University of Louisville, who have a really great AM lab, so we can do courses on location. So, yes, I think a lot of the variation comes from a lack of knowledge from users.”
These products are available to users of ANSYS 19.1, except for Additive Science, which will be included in the ANSYS 19.2 release, which will be available in September 2018.