@ANSYS #ANSYS

## Efficient and Accurate Simulation of Antenna Arrays in HFSS

### Unit-cell in HFSS

HFSS offers different method of creating and simulating a large array. The explicit method, shown in Figure 1(a) might be the first method that comes to our mind. This is where you create the exact CAD of the array and solve it. While this is the most accurate method of simulating an array, it is computationally extensive. This method may be non-feasible for the initial design of a large array. The use of unit cell (Figure 1(b)) and array theory helps us to start with an estimate of the array performance by a few assumptions. Finite Array Domain Decomposition (or FADDM) takes advantage of unit cell simplicity and creates a full model using the meshing information generated in a unit cell. In this blog we will review the creation of unit cell. In the next blog we will explain how a unit cell can be used to simulate a large array and FADDM.

In a unit cell, the following assumptions are made:

• The pattern of each element is identical.
• The array is uniformly excited in amplitude, but not necessarily in phase.
• Edge affects and mutual coupling are ignored

A unit cell works based on Master/Slave (or Primary/Secondary) boundary around the cell. Master/Slave boundaries are always paired. In a rectangular cell you may use the new Lattice Pair boundary that is introduced in Ansys HFSS 2020R1. These boundaries are means of simulating an infinite array and estimating the performance of a relatively large arrays. The use of unit cell reduces the required RAM and solve time.

Primary/Secondary (Master/Slave) (or P/S) boundaries can be combined with Floquet port, radiation or PML boundary to be used in an infinite array or large array setting, as shown in Figure 3.

To create a unit cell with P/S boundary, first start with a single element with the exact dimensions of the cell. The next step is creating a vacuum or airbox around the cell. For this step, set the padding in the location of P/S boundary to zero. For example, Figure 4 shows a microstrip patch antenna that we intend to create a 2D array based on this model. The array is placed on the XY plane. An air box is created around the unit cell with zero padding in X and Y directions.

You notice that in this example the vacuum box is larger than usual size of quarter wavelength that is usually used in creating a vacuum region around the antenna. We will get to calculation of this size in a bit, for now let’s just assign a value or parameter to it, as it will be determined later. The next step is to define P/S to generate the lattice. In AEDT 2020R1 this boundary is under “Coupled” boundary. There are two methods to create P/S: (1) Lattice Pair, (2) Primary/Secondary boundary.

Lattice Pair

The Lattice Pair works best for square lattices. It automatically assigns the primary and secondary boundaries. To assign a lattice pair boundary select the two sides that are supposed to create infinite periodic cells, right-click->Assign Boundary->Coupled->Lattice Pair, choose a name and enter the scan angles. Note that scan angles can be assigned as parameters. This feature that is introduced in 2020R1 does not require the user to define the UV directions, they are automatically assigned.

### Primary/Secondary

Primary/Secondary boundary is the same as what used to be called Master/Slave boundary. In this case, each Secondary (Slave) boundary should be assigned following a Primary (Master) boundary UV directions. First choose the side of the cell that Primary boundary. Right-click->Assign Boundary->Coupled->Primary. In Primary Boundary window define U vector. Next select the secondary wall, right-click->Assign Boundary->Couple->Secondary, choose the Primary Boundary and define U vector exactly in the same direction as the Primary, add the scan angles (the same as Primary scan angles)

### Floquet Port and Modes Calculator

Floquet port excites and terminates waves propagating down the unit cell. They are similar to waveguide modes. Floquet port is always linked to P/S boundaries. Set of TE and TM modes travel inside the cell. However, keep in mind that the number of modes that are absorbed by the Floquet port are determined by the user. All the other modes are short-circuited back into the model. To assign a Floquet port two major steps should be taken:

Defining Floquet Port

Select the face of the cell that you like to assign the Floquet port. This is determined by the location of P/S boundary. The lattice vectors A and B directions are defined by the direction of lattice (Figure 7).

The number of modes to be included are defined with the help of Modes Calculator. In the Mode Setup tab of the Floquet Port window, choose a high number of modes (e.g. 20) and click on Modes Calculator. The Mode Table Calculator will request your input of Frequency and Scan Angles. After selecting those, a table of modes and their attenuation using dB/length units are created. This is your guide in selecting the height of the unit cell and vaccume box. The attenation multiplied by the height of the unit cell (in the project units, defined in Modeler->Units) should be large enough to make sure the modes are attenuated enough so removing them from the calcuatlion does not cause errors. If the unit cell is too short, then you will see many modes are not attenuated enough. The product of the attenuatin and height of the airbox should be at least 50 dB. After the correct size for the airbox is calcualted and entered, the model with high attenuation can be removed from the Floquet port definition.

The 3D Refinement tab is used to control the inclusion of the modes in the 3D refinement of the mesh. It is recommended not to select them for the antenna arrays.

In our example, Figure 8 shows that the 5th mode has an attenuation of 2.59dB/length. The height of the airbox is around 19.5mm, providing 19.5mm*2.59dB/mm=50.505dB attenuation for the 5th mode. Therefore, only the first 4 modes are kept for the calculations. If the height of the airbox was less than 19.5mm, we would need to increase the height so accordingly for an attenuation of at least 50dB.

A simpler alternative for Floquet port is radiation boundary. It is important to note that the size of the airbox should still be kept around the same size that was calculated for the Floquet port, therefore, higher order modes sufficiently attenuated. In this case the traditional quarter wavelength padding might not be adequate.

Perfectly Matched Layer

Although using radiation boundary is much simpler than Floquet port, it is not accurate for large scan angles. It can be a good alternative to Floquet port only if the beam scanning is limited to small angles. Another alternative to Floquet port is to cover the cell by a layer of PML. This is a good compromise and provides very similar results to Floquet port models. However, the P/S boundary need to surround the PML layer as well, which means a few additional steps are required. Here is how you can do it:

1. Reduce the size of the airbox* slightly, so after adding the PML layer, the unit cell height is the same as the one that was generated using the Modes Calculation. (For example, in our model airbox height was 19mm+substrte thickness, the PML height was 3mm, so we reduced the airbox height to 16mm).
2. Choose the top face and add PML boundary.
3. Select each side of the airbox and create an object from that face (Figure 10).
4. Select each side of the PML and create objects from those faces (Figure 10).
5. Select the two faces that are on the same plane from the faces created from airbox and PML and unite them to create a side wall (Figure 10).
6. Then assign P/S boundary to each pair of walls (Figure 10).

*Please note for this method, an auto-size “region” cannot be used, instead draw a box for air/vacuum box. The region does not let you create the faces you need to combine with PML faces.

The advantage of PML termination over Floquet port is that it is simpler and sometimes faster calculation. The advantage over Radiation Boundary termination is that it provides accurate results for large scan angles. For better accuracy the mesh for the PML region can be defined as length based.

Seed the Mesh

To improve the accuracy of the PML model further, an option is to use length-based mesh. To do this select the PML box, from the project tree in Project Manager window right-click on Mesh->Assign Mesh Operation->On Selection->Length Based. Select a length smaller than lambda/10.

Scanning the Angle

In phased array simulation, we are mostly interested in the performance of the unit cell and array at different scan angles. To add the scanning option, the phase of P/S boundary should be defined by project or design parameters. The parameters can be used to run a parametric sweep, like the one shown in Figure 12. In this example the theta angle is scanned from 0 to 60 degrees.

Comparing PML and Floquet Port with Radiation Boundary

To see the accuracy of the radiation boundary vs. PML and Floquet Port, I ran the simulations for scan angles up to 60 degrees for a single element patch antenna. Figure 13 shows that the accuracy of the Radiation boundary drops after around 15 degrees scanning. However, PML and Floquet port show similar performance.

S Parameters

To compare the accuracy, we can also check the S parameters. Figure 14 shows the comparison of active S at port 1 for PML and Floquet port models. Active S parameters were used since the unit cell antenna has two ports. Figure 15 shows how S parameters compare for the model with the radiation boundary and the one with the Floquet port.

### Conclusion

The unit cell definition and options on terminating the cell were discussed here. Stay tuned. In the next blog we discuss how the unit cell is utilized in modeling antenna arrays.

## Test, Design & Analyze From Home With Ansys Simulation Software – Webinar

As companies are closing their doors in order to help ensure the health and safety of their employees and customers, those that can are pivoting to working form home.

But what about those working on product design, testing, and analysis that require a physical presence?

Here at PADT we know that the show must go on, and companies working across various technical professions are needed to keep the world moving forward, especially in these trying times. Thus we would like to introduce a solution: Ansys Engineering Simulation Software.

Join The PADT team for a panel discussion on how you can use simulation to move your in-person workflow to a digital environment, as well as what specific Ansys tools can be used to access your work from home.

All of this will be followed by a live Q&A in which our expert staff will take any questions regarding your specific concerns with transitioning your workflow and all other things related to working from home.

Register Here

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

## Ansys Sherlock: A Comprehensive Electronics Reliability Tool

As systems become more complex, the introduction and adoption of detailed Multiphysics / Multidomain tools is becoming more commonplace. Oftentimes, these tools serve as preprocessors and specialized interfaces for linking together other base level tools or models in a meaningful way. This is what Ansys Sherlock does for Circuit Card Assemblies (CCAs), with a heavy emphasis on product reliability through detailed life cycle definitions.

In an ideal scenario, the user will have already compiled a detailed ODB++ archive containing all the relevant model information. For Sherlock, this includes .odb files for each PCB layer, the silkscreens, component lists, component locations separated by top/bottom surface, drilled locations, solder mask maps, mounting points, and test points. This would provide the most streamlined experience from a CCA design through reliability analysis, though any of these components can be imported individually.

These definitions, in combination with an extensive library of package geometries, allow Sherlock to generate a 3D model consisting of components that can be checked against accepted parts lists and material properties. The inclusion of solder mask and silkscreen layers also makes for convenient spot-checking of component location and orientation. If any of these things deviate from the expected or if basic design variation and optimization studies need to be conducted, new components can be added and existing components can be removed, exchanged, or edited entirely within Sherlock.

Figure 1: Sherlock’s 2D layer viewer and editor. Each layer can be toggled on/off, and components can be rearranged.

While a few of the available analyses depend on just the component definitions and geometries (Part Validation, DFMEA, and CAF Failure), the rest are in some way connected to the concept of life cycle definitions. The overall life cycle can be organized into life phases, e.g. an operating phase, packaging phase, transport phase, or idle phase, which can then contain any number of unique event definitions. Sherlock provides support for vibration events (random and harmonic), mechanical shock events, and thermal events. At each level, these phases and events can be prescribed a total duration, cycle count, or duty cycle relative to their parent definition. On the Life Cycle definition itself, the total lifespan and accepted failure probability within that lifespan are defined for the generation of final reliability metrics.  Figure 1 demonstrates an example layout for a CCA that may be part of a vehicle system containing both high cycle fatigue thermal and vibration events, and low cycle fatigue shock events.

Figure 2: Product life cycles are broken down into life phases that contain life events. Each event is customizable through its duration, frequency, and profile.

The remaining analysis types can be divided into two categories: FEA and part specification-based. The FEA based tests function by generating a 3D model with detail and mesh criteria determined within Sherlock, which is then passed over to an Ansys Mechanical session for analysis. Sherlock provides quite a lot of customization on the pre-processing level; the menu options include different methods and resolutions for the PCB, explicit modeling of traces, and inclusion or exclusion of part leads, mechanical parts, and potting regions, among others.

Figure 3: Left shows the 3D model options, the middle shows part leads modeled, and right shows a populated board.

Each of the FEA tests, Random Vibration, Harmonic Vibration, Mechanical Shock, and Natural Frequency, correspond to an analysis block within Ansys Workbench. Once these simulations are completed, the results file is read back into Sherlock, and strain values for each component are extracted and applied to either Basquin or Coffin—Manson fatigue models as appropriate for each included life cycle event.

Part specification tests include Component Failure Analysis for electrolytic and ceramic capacitors, Semiconductor Wearout for semiconductor devices, and CTE mismatch issues for Plated Through-Hole and solder fatigue. These analyses are much more component-specific in the sense that an electrolytic capacitor has some completely different failure modes than a semiconductor device and including them allows for a broad range of physics to be accounted for across the CCA.

The result from each type of analysis is ultimately a life prediction for each component in terms of a failure probability curve alongside a time to failure estimate. The curves for every component are then combined into a life prediction for the entire CCA under one failure analysis.

Figure 4: Analysis results for Solder Fatigue including an overview for quantity of parts in each score range along with a detailed breakdown of score for each board component.

Taking it one step further, the results from each analysis are then combined into an overall life prediction for the CCA that encompasses all the defined life events. From Figure 5, we can see that the life prediction for this CCA does not quite meet its 5-year requirement, and that the most troublesome analyses are Solder Fatigue and PTH Fatigue. Since Sherlock makes it easy to identify these as problem areas, we could then iterate on this design by reexamining the severity or frequency of applied thermal cycles or adjusting some of the board material choices to minimize CTE mismatch.

Figure 5: Combined life predictions for all failure analyses and life events.

Sherlock’s convenience for defining life cycle phases and events, alongside the wide variety of component definitions and failure analyses available, really cement Sherlock’s role as a comprehensive electronics reliability tool. As in most analyses, the quality of the results is still dependent on the quality of the input, but all the checks and cross-validations for components vs life events that come along with Sherlock’s preprocessing toolset really assist with this, too.

@ANSYS #ANSYS

## Update on PADT and COVID-19

Dear Customers, Vendors, and Partners,

Here at PADT, we want to deal with the Coronavirus/COVID-19 situation in a timely and frank manner. We will ensure that the needs of our employees, customers, and suppliers are met to the best of our ability. We know that it is never too early to plan, and that how everyone in the supply chain reacts impacts every other participant in that network.

The key to getting through this experience is frequent, open, and honest communication. We will make an effort to reach out to everyone in our ecosystem, but please do not hesitate to contact us with your concerns and needs.

The collective health and safety of everyone involved is our first priority.  We will also strive to continue to deliver the products and services you count on PADT to perform in the most effective and timely manner possible. The good news is that PADT is a technology-driven company with the established infrastructure already in place to keep consulting projects and transactions moving forward, provide critical support, and deliver your parts and products on time.

We have the following restrictions currently in place:

1. Travel Restrictions
PADT has stopped all travel until further notice.
2. Face-to-Face Meetings
In addition to travel, PADT has canceled all face-to-face meetings with non-employees.
3. Events
4. Field Service

We have replaced all travel and face-to-face interactions with virtual or phone meetings. Every employee is available via video conferencing, email, or over the phone.

In addition, the following measures will be put into place as needed:

1. Work from Home
PADT has an existing and proven infrastructure in place that enables employees to work from home.  It is secure and follows our established cybersecurity policies. If we feel the need to assignemployees to work from home, you will be able to contact them via email, and voice mails will be sent to them electronically. Every employee has access to Microsoft Teams and can also interact using your virtual meeting preferred tool.
2. Order Fulfillment
There are currently no issues with order fulfilment
We are working closely with our suppliers to identify any upstream supply chain disruptions as soon as possible.  We will quickly communicate any potential issues to all impacted parties.

The key to getting through this situation with minimal disruption is focusing on the health and safety of everyone, adapting flexibly to an ever-changing situation, and communicating effectively.

## MAPDL – Elements, Contact & Solver Updates in Ansys 2020 R1 – Webinar

The ANSYS finite element solvers enable a breadth and depth of capabilities unmatched by anyone in the world of computer-aided simulation. Thermal, Structural, Acoustic, Piezoelectric, Electrostatic and Circuit Coupled Electromagnetics are just an example of what can be simulated. Regardless of the type of simulation, each model is represented by a powerful scripting language, the ANSYS Parametric Design Language (APDL).

APDL is the foundation for all sophisticated features, many of which are not exposed in the Workbench Mechanical user interface. It also offers many conveniences such as parameterization, macros, branching and looping, and complex math operations. All these benefits are accessible within the ANSYS Mechanical APDL user interface.

Join PADT’s Principle & Co-Owner Eric Miller for a look at what’s new for MAPDL in ANSYS 2020 R1, regarding:

• Linear Dynamics
• Elements
• Contacts
• Post Processing
• Solver Components
• And Much More

Register Here

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

## ANSYS Discovery Live: A Focus on Topology Optimization

For those who are not already familiar with it, Discovery Live is a rapid design tool that shares the Discovery SpaceClaim environment. It is capable of near real-time simulation of basic structural, modal, fluid, electronic, and thermal problems. This is done through leveraging the computational power of a dedicated GPU, though because of the required speed it will necessarily have somewhat less fidelity than the corresponding full Ansys analyses. Even so, the ability to immediately see the effects of modifying, adding, or rearranging geometry through SpaceClaim’s operations provides a tremendous value to designers.

One of the most interesting features within Discovery Live is the ability to perform Topology Optimization for reducing the quantity of material in a design while maintaining optimal stiffness for a designated loading condition. This can be particularly appealing given the rapid adoption of 3D printing and other additive manufacturing techniques where reducing the total material used saves both time and material cost. These also allow the production of complex organic shapes that were not always feasible with more traditional techniques like milling.

With these things in mind, we have recently received requests to demonstrate Discovery Live’s capabilities and provide some training in its use, especially for topology optimization. Given that Discovery Live is amazingly straightforward in its application, this also seems like an ideal topic to expand on in blog form alongside our general Discovery Live workshops!

For this example, we have chosen to work with a generic “engine mount” geometry that was saved in .stp format. The overall dimensions are about 10 cm wide x 5 cm tall x 5 cm deep, and we assume it is made out of stainless steel (though this is not terribly important for this demonstration).

Figure 1: Starting engine mount geometry with fixed supports and a defined load.

The three bolt holes around the perimeter are fixed in position, as if they were firmly clamped to a surface, while a total load of 9069 N (-9000 N in X, 1000 N in Y, and 500 N in Z) is applied to the cylindrical surfaces on the front. From here, we simply tell Discovery Live that we would like to add a topology optimization calculation onto our structural analysis. This opens up the ability to specify a couple more options: the way we define how much material to remove and the amount of material around boundary conditions to preserve. For removing material, we can choose to either reduce the total volume by a percent of the original or to remove material until we reach a specific model volume. For the area around boundary conditions, this is an “inflation” length measured as a normal distance from these surfaces, easily visualizable when highlighting the condition on the solution tree.

Figure 2: Inflation zone shown around each fixed support and load surface.

Since I have already planned out what kind of comparisons I want to make in this analysis, I chose to set the final model volume to 30 cm3. After hitting the simulate button, we get to watch the optimization happen alongside a rough structural analysis. By default, we are provided with a result chart showing the model’s volume, which pretty quickly converges on our target volume. As with any analysis, the duration of this process is fairly sensitive to the fidelity specified, but with default settings this took all of 7 minutes and 50 seconds to complete on my desktop with a Quadro K4000.

Figure 3: Mid-optimization on the top, post-optimization on the bottom.

Once optimization is complete, there are several more operations that become available. In order to gain access to the optimized structure, we need to convert it into a model body. Both options for this result in faceted bodies with the click of a button located in the solution tree; the difference is just that the second has also had a smoothing operation applied to it. One or the other may be preferable, depending on your application.

Figure 4: Converting results to faceted geometry

Figure 5: Faceted body post-optimization

Figure 6: Smoothed faceted body post-optimization

Though some rough stress calculations were made throughout the optimization process, the next step is typically a validation. Discovery Live makes this as a simple procedure as right-clicking on the optimized result in the solution tree and selecting the “Create Validation Solution” button. This essentially copies over the newly generated geometry into a new structural analysis while preserving the previously applied supports and loads. This allows for finer control over the fidelity of our validation, but still a very fast confirmation of our results. Using maximum fidelity on our faceted body, we find that the resulting maximum stress is about 360 MPa as compared to our unoptimized structure’s stress of 267 MPa, though of course our new material volume is less than half the original.

Figure 7: Optimized structure validation. Example surfaces that are untouched by optimization are boxed.

It may be that our final stress value is higher than what we find acceptable. At this point, it is important to note one of the limitations in version 2019R3: Discovery Live can only remove material from the original geometry, it does not add. What this means is that any surfaces remaining unchanged throughout the process are important in maintaining structural integrity for the specified load. So, if we really want to optimize our structure, we should start with additional material in these regions to allow for more optimization flexibility.

In this case, we can go back to our original engine mount model in Discovery Live and use the integrated SpaceClaim tools to thicken our backplate and expand the fillets around the load surfaces.

Figure 8: Modified engine mount geometry with a thicker backplate and larger fillets.

We can then run back through the same analysis, specifying the same target volume, to improve the performance of our final component. Indeed, we find that after optimizing back down to a material volume of 30 cm3, our new maximum stress has been decreased to 256 MPa. Keep in mind that this is very doable within Discovery Live, as the entire modification and simulation process can be done in <10 minutes for this model.

Figure 9: Validated results from the modified geometry post-optimization.

Of course, once a promising solution has been attained in Discovery Live, we should then export the model to run a more thorough analysis of in Ansys Mechanical, but hopefully, this provides a useful example of how to leverage this amazing tool!

One final comment is that while this example was performed in the 2019R3 version, 2020R1 has expanded Discovery Live’s optimization capability somewhat. Instead of only being allowed to specify a target volume or percent reduction, you can choose to allow a specified increase in structure compliance while minimizing the volume. In addition to this, there are a couple more knobs to turn for better control over the manufacturability of the result, such as specifying the maximum thickness of any region and preventing any internal overhangs in a specified direction. It is now also possible to link topology optimization to a general-purpose modal analysis, either on its own or coupled to a structural analysis. These continued improvements are great news for users, and we hope that even more features continue to roll out.

@ANSYS #ANSYS

## Icepak in Ansys Electronic Desktop – Why should you know about it?

The role of Ansys Electronics Desktop Icepak (hereafter referred to as Icepak, not to be confused with Classic Icepak) is in an interesting place. On the back end, it is a tremendously capable CFD solver through the use of the Ansys Fluent code. On the front end, it is an all-in-one pre and post processor that is streamlined for electronics thermal management, including the explicit simulation and effects of fluid convection. In this regard, Icepak can be thought of as a system level Multiphysics simulation tool.

One of the advantages of Icepak is in its interface consistency with the rest of the Electronic Desktop (EDT) products. This not only results in a slick modern appearance but also provides a very familiar environment for the electrical engineers and designers who typically use the other EDT tools. While they may not already be intimately familiar with the physics and setup process for CFD/thermal simulations, being able to follow a very similar workflow certainly lowers the barrier to entry for accessing useful results. Even if complete adoption by these users is not practical, this same environment can serve as a happy medium for collaboration with thermal and fluids experts.

Figure 1: AEDT Icepak interface. The same ribbon menus, project manager, history tree, and display window as other EDT products.

So, beyond these generalities, what does Icepak actually offer for an optimized user experience over other tools, and what kinds of problems/applications are best suited for it?

The first thing that comes to mind for both of these questions is a PCB with attached components. In a real-world environment, anyone that has looked at the inside of a computer is likely familiar with motherboards covered with all kinds of little chips and capacitors and often dominated by a CPU mounted with a heatsink and fan. In most cases, this motherboard is enclosed within some kind of box (a computer case) with vents/filters/fans on at least some of the sides to facilitate controlled airflow. This is an ideal scenario for Icepak. The geometries of the board and its components are typically well represented by rectangular prisms and cylinders, and the thermal management of the system is strongly related to the physics of conjugate heat transfer. For the case geometry, it may be more convenient to import this from a more comprehensive modeler like SpaceClaim and then take advantage of the tools built into Icepak to quickly process the important features.

Figure 2: A computer case with motherboard imported from SpaceClaim. The front and back have vents/fans while the side has a rectangular patterned grille.

For a CAD model like the one above, we may want to include some additional items like heatsinks, fan models, or simple PCB components. Icepak’s geometry tools include some very convenient parameterized functions for quickly constructing and positioning fans and heatsinks, in addition to the basic ability to create and manipulate simple volumes. There are also routines for extracting openings on surface, such as the rectangular vent arrays on the front and back as well as the patterned grille on the side. So, not only can you import detailed CAD from external sources, you can mix, match, and simplify it with Icepak’s geometry, which streamlines the entire design and setup process. For an experienced user, the above model can be prepared for a basic simulation within just a matter of minutes. The resulting configuration with an added heatsink, some RAM, and boundary conditions, could look something like this:

Figure 3: The model from Figure 2 after Icepak processing. Boundary conditions for the fans, vents, and grille have been defined. Icepak primitives have also been added in the form of a heatsink and RAM modules.

Monitor points can then assigned to surfaces or bodies as desired; chances are that for a simulation like this, temperature within the CPU is the most important. Additional temperature points for each RAM module or flow measurements for the fans and openings can also be defined. These points can all be tracked as the simulation proceeds to ensure that convergence is actually attained.

Figure 4: Monitoring chosen solution variables to ensure convergence.

For this simple system containing a 20 W CPU and 8 RAM modules at 2 W each, quite a few of our components are toasty and potentially problematic from a thermal standpoint.

Figure 5: Post-processing with Icepak. Temperature contours are overlaid with flow velocities to better understand the behavior of the system.

With the power of a simulation environment in Icepak at our fingertips, we can now play around with our design parameters to improve the thermal management of this system! Want to see what happens when you block the outlet vents? Easy, select and delete them! Want to use a more powerful fan or try a new material for the motherboard or heatsink? Just edit their properties in the history tree. Want to spin around the board or try changing the number of fins on the heatsink? Also straightforward, although you will have to remesh the model. While these are the kinds of things that are certainly possible in other tools, they are exceptionally easy to do within an all-in-one interface like Icepak.

The physics involved in this example are pretty standard: solid body conduction with conjugate heat transfer to a turbulent K-Omega fluid model. Where Icepak really shines is its ability to integrate with the other tools in the EDT environment. While we assumed that the motherboard was nothing more than a solid chunk of FR-4, this board could have been designed and simulated in detail with another tool like HFSS. The board, along with all of the power losses calculated during the HFSS analysis, could have then been directly imported into the Icepak project. This would allow for each layer to be modeled with its own spatially varying thermal properties according to trace locations as well as a very accurate spatial mapping of heat generation.

This is not at all to say that Icepak is limited to these kinds of PCB and CCA examples. These just often tend to be convenient to think about and relatively easy to geometrically represent. Using Fluent as the solver provides a lot of flexibility, and there are many more classes of problems that could be benefit from Icepak. On the low frequency side, electric motors are a good example of a problem where electronic and thermal behavior are intertwined. As voltage is applied to the windings, currents are induced and heat is generated. For larger motors, these currents, and consequently the associated thermal losses, can be significant. Maxwell is used to model the electronic side for these types of problems, where the results can then be easily brought into an Icepak simulation. I have gone through just such an example rotor/stator/winding motor assembly model in Maxwell, where I then copied everything into an Iecpak project to simulate the resulting steady temperature profile in a box of naturally convecting air.

Figure 6: An example half-motor that was solved in Maxwell as a magnetostatic problem and then copied over to Icepak for thermal analysis.

If it is found that better thermal management is needed, then extra features could then be added on the Icepak side as desired, such as a dedicated heatsink or external fan. Only the components with loads mapped over from Maxwell need to remain unmodified.

On the high frequency side, you may care about the performance of an antenna. HFSS can be used for the electromagnetic side, while Icepak can once again be brought in to analyze the thermal behavior. For high powered antenna, some components could very easily get hot enough for the material properties to appreciably change and for thermal radiation to become a dominant mode of heat transport. A 2-way automatic Icepak coupling is an excellent way to model this. Thermal modifiers may be defined for material properties in HFSS, and radiation is a supported physics model in Icepak. HFSS and Icepak can then be set up to alternately solve and automatically feed each other new loads and boundary conditions until a converged result is attained.

What all of this really comes down to is the question: how easy is it for the user to set up a model that will produce the information they need? For these kinds of electronics questions, I believe the answer for Icepak is “extraordinarily easy”. While functional on its own merit, Icepak really shines when it comes to the ease of coupling thermal management analysis with the EM family of tools.

## GrabCAD Print Software, Part Two: Simplify Set-ups, Save Time, and Do Cool Stuff You Hadn’t Even Considered

You haven’t really lived in the world of 3D printing until you’ve had a part fail spectacularly due to open faces, self-intersecting faces or inverted normals. Your part ends up looking more like modern art than technical part. Or perhaps the design you have in mind has great geometry but you wish that some parts could have regions that are dense and strong while other regions would work with minimal infill.

In Part One of this blog post about GrabCAD Print software, we covered the basics of setting up and printing a part; now we’ll look at several of the advanced features that save you set-up time and result in better parts.

Behind the Scenes Repairs

Stratasys GrabCAD Print software, available as a free download, is crafted for users setting up solid models for 3D printing on Stratasys FDM and PolyJet printers. Once you’ve started using it, you’ll find one of its many useful advanced features is the automated STL file-repair option.

Most people still create solid models in CAD software then convert the file to the industry-standard STL format before opening it in a given 3D printer’s own set-up software. Every CAD package works a little differently to generate an STL file, and once in a while the geometry just doesn’t get perfectly meshed. Triangles may overlap, triangles may end up very long and very skinny, or the vector that signals “point in” or “point out” can get reversed.

Traditionally, the 3D printer set-up program reacts to these situations by doing one of two things: it prints exactly what you tell it to print (producing weird holes and shifted layers) or it simply refuses to print at all. Both situations are due to tiny errors in the conversion of a solid CAD model to a tessellated surface.

GrabCAD Print, however, gives your file a once-over and immediately flags sections of the model in need of repair. You can see a color-coded representation of all the problem areas, choose to view just some or all, and then click on Automatic Repair. No hand-editing, no counting layers and identifying sections where the problems reside – just a click of the virtual button and all the problem regions are identified, repaired and ready for the next processing steps.

GrabCAD Print also uniquely allows users to bring in their models in the original CAD file-format (from SolidWorks, Autodesk, PTC, Siemens, etc.) or neutral formats, with no need to first convert it to STL. For FDM users, this means GrabCAD recognizes actual CAD bodies, faces, and features, letting you make build-modifications directly in the print set-up stage that previously would have required layer-by-layer slice editing, or couldn’t have been done at all.

For example, with a little planning ahead, you can bring in a multi-body CAD model (i.e., an assembly), merge the parts, and direct GrabCAD to apply different parameters to each body. This way you can reinforce some areas at full density then change the infill pattern, layout, and density in other regions where full strength is unnecessary.

Here’s an example of a SolidWorks model intended for printing with a solid lower base but lighter weight (saving material) in the upper sections. It’s a holder for Post-It® notes, comprising three individual parts – lower base, upper base and upper slot – combined and saved as an assembly.

Here was my workflow:

1 – I brought the assembly into GrabCAD and merged all the bodies, selected an F370 Stratasys FDM printer, chose Print Settings of acrylonitrile butadiene styrene (ABS) and 0.005 inches layer height, and oriented the part.

2 -To ensure strength in the lower base, I selected that section (you can do this either in the model tree or on the part itself) and opened the Selection Settings menu at the right. Under Body>Advanced, I chose Solid Infill and slid Rigidity to High.

3 – Then I selected the upper base, chose Hexagram, and changed the Infill Density to 60%.

4 – Lastly, I selected the upper slot section, chose Single Dense, and changed the Infill Density to 35%.

5 – With all three sections defined, I clicked on Slice Preview, sliced the model and used the slider bar on the left to step through each section’s toolpath. For the screenshots, I turned off showing Support Material; the yellow bits indicate where seams start (another parameter that can be edited).

Here is each section highlighted, with screenshots of the parameter choices and how the part infill looks when sliced:

So that you can really see the differences, I printed the part four times, stopping as the infill got partway through each section, then letting the final part print to completion. Here are the three partial sections, plus my final part:

Automated Hole Sizing Simplifies Adding Inserts

But like the old advertisements say, “But wait – there’s more!” Do you use heat-set inserts a lot to create secure connections between 3D printed parts and metal hardware? Planning ahead for the right hole size, especially if you have different design groups involved and fasteners may not yet be decided, this is the feature for you.

In your CAD part model, draw a hole that is centered where you know the insert will go, give it a nominal diameter and use Cut/Extrude so that the hole is at least the depth of your longest candidate insert. Now bring your part into GrabCAD Advanced FDM (soon all these features will be available in a single Model Interface) and go to Selection Settings in the right-hand menu.

This time, click on Face (not Body) and Select the inner cylindrical wall of your hole. Several options will become active, including Apply Insert. When you check that box, a new drop-down will appear, giving you the choice of adding a heat-set insert, a helicoil insert or a custom size. Below that you select either Inch or Metric, and for either, the appropriate list of standard insert sizes appears.

Choose the insert you want, click Update in the upper middle of the GrabCAD screen, and you’ll see the hole-size immediately changed (larger or smaller as needed). The new diameter will match the required oversized dimensions for the correct (melted into place) part-fit. You can even do this in a sidewall! (For tips on putting inserts into FDM parts, particularly with a soldering iron, see Adding Inserts to 3D Printed Parts: Hardware Tips.)

Note that this way, you can print the overall part with a sparse infill, yet reinforce the area around the insert to create just the right mass to make a solid connection.

To document the selected choices for whoever will be doing the insert assembly, GrabCAD also generates a numbered, manufacturing-footnote that lists each insert’s size; this information can be exported as a PDF file that includes a separate close-up image of each insert’s location.

## Press Release: 3D Printing Glossary Now Available from PADT Provides Most Comprehensive Online Resource for Additive Manufacturing Terminology

3DPrinting-Glossary.com Covers Everything from Machines and Materials to Pre- and Post-Processing Terms

After searching the internet for a resource you can’t find, have you ever sat at your desk and said to yourself “I wish someone would take the time to create this. I could really use it.” Here at PADT, we have been saying that for many years about the need for a comprehensive reference on the terms used in Additive Manufacturing. Then we realized that the only way to get it done was to roll up our sleeves and do it ourselves. And so we did.

The result is www.3DPrinting-Glossary.com

This free online resource contains over 250 terms with definitions for each one. We write each definition and reviewed it amongst our team of long term users of Additive Manufacturing. After over 25 years in the business, we should know the difference between direct laser melting and selective laser sintering. And even if we are off a little, it is a start and we encourage the community to send us corrections, recommendations, and especially new terms to add to this compendium.

The site is free for use, and the contents are licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. This allows anyone to use the content how they wish as long as they say where it came from and don’t make money directly off of it.

Check it out and let us know what you think. More details are below in the official Press Release, which you can also find in PDF and HTML.

And do not hesitate to contact PADT for any of your Additive Manufacturing, Product Development, or Simulation needs. The same expertise that went into creating this resource is applied to every project we work on and every product we sell.

## 3D Printing Glossary Now Available from PADT Provides Most Comprehensive Online Resource for Additive Manufacturing Terminology

3DPrinting-Glossary.com Covers Everything from Machines and Materials to Pre- and Post-Processing Terms

TEMPE, Ariz., March 3, 2020 PADT, a globally recognized provider of numerical simulation, product development, and 3D printing products and services, today announced the launch of the most comprehensive online Glossary of industry terms relevant to additive manufacturing. The new site, www.3dprinting-glossary.com, includes more than 250 definitions in nine different categories.

“In addition to being an outstanding partner to our customers, PADT strives to be a trusted advisor on all things additive manufacturing,” said Eric Miller, co-founder and principal, PADT. “Our goal for the glossary is to help educate the community on the evolving terminology in our industry and serve as a critical resource for students and professionals seeking 3D printing knowledge and clarification.”

The company has been a provider of additive manufacturing services since 1994. They are also a Stratasys Platinum Partner that has sold and supported Stratasys equipment in the Southwest for over fifteen years. Many of their employees are recognized and award-winning experts in the AM community.

The creation of PADT’s 3D Printing Glossary was the result of a companywide effort to gather and define the terms used in the industry daily. The user-friendly website allows visitors to search for terms directly or by category. PADT will continue to support and update the glossary as the industry grows and innovates.

The nine glossary categories include:

• Build Characteristics
• General
• Manufacturing Term
• Material
• Post-Processing
• Pre-Processing
• Product Definition
• System Characteristic

Since founding PADT in 1994, the company’s leadership has made a great effort to become more than just a reseller or service provider.  They want to be a resource to the community. In addition to investing in entrepreneurs, serving on technology boards and committees, and speaking at industry events, PADT donates a great deal of money, time and resources to STEM-focused educational initiatives. The 3D Printing Glossary is another resource that PADT has created for the benefit of students as well as up and coming professionals in the engineering and manufacturing industry.

PADT is also asking the community to contribute to this effort If users notice a term is missing, disagree with the definition, or have more to add to the definition, they ask that readers email additions or changes to info@padtinc.com.

PADT is an engineering product and services company that focuses on helping customers who develop physical products by providing Numerical Simulation, Product Development, and 3D Printing solutions. PADT’s worldwide reputation for technical excellence and experienced staff is based on its proven record of building long-term win-win partnerships with vendors and customers. Since its establishment in 1994, companies have relied on PADT because “We Make Innovation Work.” With over 90 employees, PADT services customers from its headquarters at the Arizona State University Research Park in Tempe, Arizona, and from offices in Torrance, California, Littleton, Colorado, Albuquerque, New Mexico, Austin, Texas, and Murray, Utah, as well as through staff members located around the country. More information on PADT can be found at www.PADTINC.com.

# # #

Media contact: Alec Robertson Brodeur Partners arobertson@brodeur.com 585-281-6399

Organization Contact:
Eric Miller
480-813-4884

The ANSYS Discovery 3D Design family of products enables CAD modeling and simulation for all design engineers. Since the demands on today’s design engineer to build optimized, lighter and smarter products are greater than ever, using the appropriate design tools is more important than ever. With ANSYS you can explore ideas, iterate, and innovate with unprecedented speed early in your design process. Delve deeper into design details, refine concepts and perform multiple physics simulations — backed by ANSYS solvers — to better account for real-world behaviors.

Capabilities in this tool-set allow engineers to increase speed and reduce costs from the start of the design cycle, all the way to product launch. Improve engineering productivity and accelerate development time, create higher-quality products while reducing development & manufacturing costs, and respond quickly to changing customer demands while bringing new products to market faster than the competition.

Join PADT’s Training & Support Application Engineer, Robert McCathren for a look at whats new & improved when it comes to these tools in ANSYS 2020 R1. This update includes new releases for ANSYS Discovery Live, AIM, and SpaceClaim, focusing on areas including:

• Simulation of Thin Parts
• Topology Optimization in Discovery Live
• Structural Material Properties
• Physics Aware Meshing
• Beam and Shell Modeling
• And much more

Register Here

## All Things ANSYS 057: Simulation for Additive Manufacturing in ANSYS 2020 R1

 Published on: February 24th, 2020 With: Eric Miller & Doug Oatis Description: In this episode your host and Co-Founder of PADT, Eric Miller is joined by Lead Mechanical Engineer Doug Oatis for a discussion on the latest advancements in simulation for additive manufacturing and topology optimization in ANSYS 2020 R1. If you would like to learn more about what this release is capable of, check out our webinar on the topic here: https://www.brighttalk.com/webcast/15747/384528 If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you! Listen: Subscribe:

@ANSYS #ANSYS

## ANSYS Mechanical: Mesh Time Metric Display

The things you find out from poking around the Enhancement Request list…

Did you know that you can get ANSYS Mechanical to report the amount of time that the meshing takes? I didn’t until I stumbled across this little gem on the request to show mesh time metrics.

This option is already available for many releases now. Users can turn performance diagnostics by setting to Tools -> Options -> Miscellaneous -> “Report Performance Diagnostics in Messages” to Yes inside Mechanical.

So, of course, I tried it out.

This was in version 2020R1, but it says that the option has been there since R19.0.  Now they just need to add it to the Statistics section of the Mesh Details so that we can use it as an output parameter.