Fighting COVID-19 with Ansys Simulation – Webinar

Simulation has been and continues to be a powerful tool for helping to drive innovation in the medical industry. Everything from medical devices, to hospital equipment, and even pharmaceutical and clinical practices can benefit from the introduction of simulation technology. This is true now more than ever, as the we all are facing such turbulent times.

During the COVID-19 pandemic, Ansys is striving to combat the spread of the coronavirus, by backing the ongoing initiatives of customers and partners working in the medical sphere. In order to support healthcare professionals, policy makers, and communities around the world in this endeavor, Ansys is sharing key insights gained from their own analyse, along with those of partners and other collaborators, regarding how to prevent future spread, and treat those already effected by the virus.

Join PADT’s Co-founder and Principal engineer Eric Miller, along with Marc Horner, Principal Healthcare Engineer at Ansys, for a discussion on what the company is doing to combat the virus, as well as a look at some models that effectively illustrate how the tools are being used.

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Advanced Capabilities to Consider when Simulating Blow Molding in Ansys Polyflow or Discovery AIM

Ansys Polyflow is a Finite Element CFD solver with unique capabilities that enable simulation of complex non-Newtonian flows seen in the polymer processing industry. In recent releases, Polyflow has included templates to streamline two of its most common use cases: blow molding and extrusion. Similarly, Ansys Discovery AIM offers a modern user interface that guides users through blow molding and extrusion workflows while still using the proven Polyflow solver under the hood. It is not uncommon for engineers to be unsure about which tool to pursue for their specific application. In this article, I will focus on the blow molding workflow. More specifically, I will point out three features in Polyflow that have not yet been incorporated into Discovery AIM:

  1. The PolyMat curve fitting tool to derive viscoelasticity model input parameters from test data
  2. Automatic parison thickness mapping onto an Ansys Mechanical shell mesh
  3. Parison Programming to optimize parison thickness subject to final part thickness constraints

Keep in mind that either tool will get the job done in most applications, so let us first quickly review some of the core features of blow molding simulations that are common to Polyflow and AIM:

  • Parison/Mold contact detection
  • 3-D Shell Lagrangian automatic remeshing
  • Generalized Newtonian viscosity models
  • Temperature dependent and multi-mode integral viscoelastic models
  • Time dependent mold pressure boundary conditions
  •  Isothermal or non-isothermal conditions

For demonstration purposes, I modeled a sweet submarine toy in SpaceClaim. Unfortunately, I think it will float, but let’s move past that for now.  

Figure 1: Final Submarine shape (Left), Top View of Mold+ Parison (Top Left), Side View of Mold+Parison (Bottom Right)

At this point, you could proceed with Discovery AIM or with Polyflow without any re-work. I’lll proceed with the Polyflow Blow Molding workflow to point out the features currently only available in Polyflow.

PolyMat Curve Fitting Tool

With the blow molding template, you can select whether to treat the parison as isothermal or non-isothermal and whether to model it as general Newtonian or viscoelastic. Suppose we would like to model viscoelasticity with the KBKZ integral viscoelastic model because we were interested in capturing strain hardening as the parison is stretched. The inputs to the KBKZ model are viscosity and relaxation times for each mode. If they are known, the user can input the values directly. This is possible in Discovery AIM as well. However, the PolyMat tool is unique to Polyflow. PolyMat is a built-in curve fitting tool that helps generate input parameters for the various viscosity model available in Polyflow using material data. This is particularly useful when you do not explicitly have the inputs for a viscoelastic model, but perhaps you have other test data such as oscillatory and capillary rheometry data. In this case I have with the loss modulus, storage modulus and shear viscosity for a generic high density polyethylene (HDPE) material. For this material, four modes are enough to anchor the KBKZ model to the data as shown below. We can then load the viscosity/relaxation time into Polyflow and continue. 

Figure 2: Curve Fitting of G’(Ω),G’’(Ω),η() [Left], KBKZ Viscoelastic Model inputs (Right)

The main output of the simulation is the final parison thickness distribution. For this sweet submarine, the initial parison thickness is set to 3mm and the final thickness distribution is shown in the contour plot below.

Figure 3a: Animation of blow molding process

Figure 3b: Final Part Thickness Distribution

Thickness Mapping to Ansys Mechanical

The second Polyflow capability I’d like to point out is the ability to easily map the thickness distribution onto an Ansys mechanical shell mesh. You can map the thickness onto an Ansys Mechanical shell mesh by connecting the polyflow solution component to a structural model in workbench as shown below. The analogous work flow in AIM, would be to create a second simulation for the structural analysis, but you would be confined to specifying a constant thickness.

Figure 4: Polyflow – Ansys Mechanical Parison Thickness Mapping

In Ansys Mechanical, the mapping comes through within the geometry tree as shown below. The imported Data Transfer Summary is a good way to ensure the mapping behaves as expected. In this case we can see that 100% of the nodes were mapped and the thickness contours qualitatively match the Polyflow results in CFD -Post.

Figure 5: Imported Thickness in Ansys Mechanical

Figure 6: Thickness Data Transfer Summary

A force is applied normal to front face of the sail and simulated in Mechanical. The peak stress and deformation are shown below. The predicted stresses are likely acceptable for a toy, especially since my toy is a sweet submarine. Nonetheless, suppose that I was interested in reducing the deformation in the sail under this load condition by thickening the extruded parison. A logical approach would be to increase the initial parison thickness from 3mm to 4mm for example. Polyflow’s parison programming feature takes the guesswork out of the process. 

Figure 7: Clockwise from Top Left: Applied Load on Sail, Stress Distribution, total Deformation, Thickness Distribution

Parison Programming

Parison programming is an iterative optimization work flow within Polyflow for determining the extruded thickness distribution required to meet the final part thickness constraints. To activate it, you create a new post processor sub-task of type parison programming.   

Figure 8: Parison Programming Setup

The inputs to the optimization are straight forward. The only inputs that you typically would need to modify are the direction of optimization, width of stripes, and list of (X,h) pairs. The direction of optimization is the direction of extrusion which is X in this case. If the extruder can vary parison thickness along “stripes” of the parison, then Polyflow can optimize each stripe thickness. The list of (X,h) pairs serves as a list of constraints for the final part thickness where X is the location on the parison along the direction of extrusion and h is the final part thickness constraint.

Figure 9: Thickness Constraints for Parison Programming

In our scenario, the X,h pairs form a piecewise linear thickness distribution to constrain the area around the sail to have a 3.5mm thickness and 2mm everywhere else. After the simulation, Polyflow will write a csv file with to the output directory containing the initial thickness for each node for the next iteration. You will need to copy over the csv file from the output directory of iteration N to the input directory of iteration N+1. The good news is the optimization converges within 3-5 iterations.

Figure 10: Defining the Initial Thickness for the Next Parison Programming Iteration

Polyflow will print the parison strip thickness distribution for the next iteration in the .lst file. The plot below shows the thickness distribution from the first 3 iterations. Note from the charts below that the distribution converged by iteration 2; thus iteration 3 was not actually simulated. The optimized parison thickness distribution is also plotted in the contour plot below.

Figure 11: Optimized Parison Thickness (Top), Final Part Thickness (Bottom)

Figure 12: % of Elements At or Above Thickness Criteria

As a final check, we can evaluate how the modification to the parison thickness reduced the deformation of the submarine. The total deformation contour plot below confirms that the peak deformation decreased from 2mm to 0.8mm.

Figure 13: Total Deformation in Ansys Mechanical After Parison Programming

Summary

Ansys Discovery AIM is a versatile platform with an intuitive and modern user interface. While Aim has incorporated most of the blow molding simulation capabilities from Polyflow, some advanced functionality has not yet been brought into AIM. This article simulated the blow molding process of a toy submarine to demonstrate three capabilities currently only available in Polyflow: the PolyMat curve fitting tool, automatic parison thickness mapping to Ansys Mechanical, and parison programming. Engineers should consider whether any of these capabilities are needed in their application next time they are faced with the decision to create a blow mold simulation using Ansys Discovery AIM or Polyflow.

Five Ways to Save Time and Money in Your Product Development Process Using the Stratasys J55

Is your current prototyping process costing you more time and money than it should?

Bring higher quality modeling in-house at your team’s elbow, and straight into the design process. Using traditional production methods is costing your product development teams time and money.

Quality model shops have a long queue and large price tag, traditional modeling by hand is laborious and time consuming, and outsourcing comes with a laundry list of communication headaches, IP theft concerns, and extra costs.


Ready to learn more?


Make communication easier, improve design quality, and reduce time to market.

Click the link below to download the solution guide and discover five ways the Stratasys J55 can help you save time and money during the product development process. 

Download Here

All Things Ansys 063: Fighting COVID-19 with Ansys Simulation

 

Published on: May 18th, 2020
With: Eric Miller, Thierry Marchal & Marc Horner
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by two leaders in the Ansys response to COVID-19 – Thierry Marchal, Global Industry Director for Healthcare, Consumer Products & Construction, and Marc Horner, Principal Healthcare Engineer – for a discussion on what the company is doing to combat the spread of the virus, as well as give our listeners a more complete understanding regarding the specific applications that Ansys tools are being used for during this global pandemic.

If you would like to learn more about Ansys and their response to COVID-19, check out the following link: https://bit.ly/36bs8rR

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!

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Panel Discussion: Fighting COVID-19 with 3D Printing

When the virus that causes COVID-19 started to spread around the world, supply chains started to fail. The made access to personal protective equipment, or PPE, even more difficult. That is when Additive Manufacturing stepped up and said: “We can help.”

PADT held a panel discussion with three customers and our partner, Stratasys, to hear how each of them met the challenges posed by COVID-19 and responded with 3D Printing. It was a fantastic discussion and well worth a listen.

Designing Better Rocket Engines with Ansys – Webinar

In 2017 Colorado based company Ursa Major Technologies put together an expert team of designers and engineers to realize its vision of providing the microsatellite industry with the best rocket engines in the business. Utilizing Ansys simulation software, additive manufacturing, and modernizing staged combustion, the company successfully designed and built two liquid oxygen and kerosene engines and has a third engine in development.

With Ansys, Ursa Major Technologies is accomplishing design goals faster and more efficiently than ever before. Using Finite Element Analysis (FEA), the company can run models with 30-40 unique parts to analyze entire turbo pumps in one simulation. Thrust analysis, which the company had previously done with 2D models, can now be done all in the Ansys CFX tool more cost-effectively.

Join PADT and Ursa Major Technologies for a brief overview of applications for Ansys in the aerospace industry, followed by an exploration of how they are using these simulation tools to better design and optimize the next generation of rocket engines.

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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!

Changes to Licencing at ANSYS 2020R1

There are three main goals of the licensing changes in the latest release of ANSYS:

  • Deliver Ansys licensing using the FlexLM industry standard
  • Eliminate the Ansys licensing interconnect
  • Provide modular licensing options that are easier to understand
  • Finally – and this is the whopper (or Double Double if you’re an In-N-Out kind of analogy person) – this new licensing model eliminates the need for upgrading the Ansys License Manager with every software update. (please pause for shock recovery)
If you’re still shocked and would to like see a “shocked groundhog” compilation, check this out.

Why is this significant? Well, this was always a sticking point for our customers when upgrading from one version to the next.

Here’s how that usually plays out:

  1. Engineers eager to try out new features or overcome software defects, download the software and install it on their workstations.
    1. Surprise – software throws an obscure licensing error.
    2. Engineer notifies IT or Ansys Channel partner of issue.
    3. After a few calls, maybe a screenshare or two, its determined that the license server needs to be upgraded.
    4. The best-case scenario – IT or PADT Support can get it installed in a few minutes and engineer can be on his way.
    5. The usual scenario – it will take a week to schedule downtime on the server and notify all stakeholders and the engineer is left to simmer on medium-low until those important safeguards are handled.

What does this all mean?

  • Starting in January 2020, all new Ansys keys issued will be in the new format and will require upgrading to the 2020R1 License manager. This should be the last mandatory license server upgrade for a while.
  • Your Ansys Channel Partner will contact you ahead of your next renewal to discuss new license increments and if there are any expected changes.
  • Your IT and Ansys support team will be celebrating in the back office the last mandatory Ansys License Manager upgrade for a while.

How to upgrade the Ansys License Manager?

Download the latest license manager through the Ansys customer portal:

Follow installation instructions and add the latest license file:

  • Ansys has a handy video on this here
  • Make sure that you run the installed as an administrator for best results.

Make sure license server is running and has the correct licenses queued:

  • Look for the green checkmark in the license management center window.
  • Start your application and make sure everything looks good.

This was a high-level flyover of the new Ansys Licensing released with version 2020R1. For specifics contact your PADT Account manager or support@padtinc.com .

Introducing the Stratasys J55 3D Printer – Possibilities at Every Turn

From perfecting products to applying concepts learned in the classroom, Stratasys can help you realize any number of design ideas. The new J55 introduces a rotating print platform for outstanding surface finish and printing quality, and features multimaterial capabilities and material configurations for both industrial and mechanical design.

The Stratasys J55 3D Printer is a huge leap forward for accessible, full color 3D printing and allows designers to have multiple iterations of a prototype ready and at their fingertips throughout every phase of the design process.

Enhanced 3D printing capabilities include – static print head, rotating build tray, UV LED illumination technology, new material cartridge design, and more. The full reliability and quality of PolyJet technology created for an office or studio environment, at an affordable price.

Designed for consistent, stable performance, the J55 requires zero mechanical calibrations and features a “ready-to-print” mode, so you can make ideas a reality without interruption.

Click the link below to download the product brochure and learn how this innovative new machine is revolutionizing the world of additive manufacturing. 

All Things Ansys 062: Optimizing Materials Selection for Additive Manufacturing with Ansys Granta

 

Published on: May 4th, 2020
With: Eric Miller, Pam Waterman & Robert McCathren
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Pam Waterman and Robert McCathren for a discussion on how Ansys Granta can be used to help optimize hardware selection for additive manufacturing. The Senvol Database details 1,000 AM machines and more than 850 compatible materials. Using this tool within Granta Selector, you can search and compare materials based on properties, type, or compatible machines.

If you would like to learn more about the Ansys tool and it’s applications for additive, check out our webinar on the topic here: https://bit.ly/2SAZN8G

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!

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Example of full color part with mapped image, created from 3MF file format brought into GrabCAD Print and printed on a Stratasys PolyJet 3D printer. (Image courtesy GrabCAD)

3MF Printing Format Comes to GrabCAD Print

Example of full color part with mapped image, created from 3MF file format brought into GrabCAD Print and printed on a Stratasys PolyJet 3D printer. (Image courtesy GrabCAD)

Example of full color part with mapped image, created from a 3MF file-format brought into GrabCAD Print and set up to print on a Stratasys PolyJet 3D printer. (Image courtesy GrabCAD)

What is the 3MF format? How does it differ from the standard STL format? And what can you do with it, especially if your 3D printers run GrabCAD Print software from Stratasys?

For most designers, engineers and users involved in 3D printing, regardless of the 3D CAD software you use, you save (convert) your model to print as an STL format file. A lot has been written about it, including a PADT post from back in 2012 – and STL-wise, things really haven’t changed. This format approximates the native CAD solid model as a closed surface comprising small triangles of various shapes and sizes. STL has been the standard since the AM industry began, and although different CAD packages use different algorithms to create the mesh, for the most part, it’s worked pretty well.

A Sample STL File Segment

However, an STL file is simply a large text file listing the Cartesian coordinates for each vertex of the thousands of triangles, along with info on the normal direction:

Sample code from saving a CAD model in STL format.

A modest number of large triangles produces relatively small files but doesn’t do a good job of reproducing curves (think highly faceted surfaces); conversely, big files of many small triangles produce much smoother transitions but can take a long time to process in slicing software.

And, perhaps the biggest negative is that an STL file cannot include any other information: desired color, desired material, transparency, internal density gradient, internal fine structure or more.

What is 3MF?

In early 2015, Microsoft and a number of other major corporations including Autodesk, Dassault Systèmes, HP, Shapeways and SLM Group created a consortium to address these issues. They decided to overhaul a little-used file format called the 3D Modeling Format (3MF), to make it support highly detailed 3D model information and be more useful for 3D printing and related processes.

Logo 3MF Consortium

This ongoing consortium project defines 3MF as “a set of conventions for using XML to describe the appearance and structure of 3D models for the purpose of manufacturing (3D printing).”

In developer language, 3MF is a standard package or data that follows a core specification and may include some task-specific extensions.

In user terms, a 3MF file contains some or all of the following information in ASCII format:

  • Metadata about part name, creator and date
  • Information on the mesh of triangles (yes, it still creates and uses these, but does it better for a number of reasons, one of which is that it cannot create non-manifold edges (i.e., triangles that share endpoints with more than one triangle, which confuses the printer))
  • Color information (throughout the complete part body or in sub-sections)
  • Ways to define multiple materials combined as a composite
  • Texture information – what it is and where to place it
  • Ways to assign different materials to different sections of a part
  • Ways to duplicate information from one section of a part to another section, to save memory
  • Slicing instructions

Without getting into the nitty gritty, here are just two examples of XML code lines from 3MF metadata sections:

Example code of saving a solid CAD model in 3MF format.

Meaning, information about the part number and the part color rides along with the vertex coordinates! For a deep-dive into the coding schema, including a helpful glossary, see the 3MF github site; to learn how 3MF compares to STL, OBJ, AMF, STEP and other formats, check out the consortium’s About Us page.

Exporting 3MF Files

Now, how about using all of this? Where to start? Many 3D CAD software packages now let you save solid models as 3MF files (check out your “Save As” drop-down menu to verify), but again, they can vary as to what information is being saved. For example, a SolidWorks 3MF file can generate data on color and material but does not yet support transparency.

Here are all the options that you see in SolidWorks when you click the arrow next to “Save As”:

Second step in SolidWorks for saving a file in 3MF format: check off “include materials” and “include appearance.” (Image courtesy PADT)

“Save As” window in SolidWorks 2019, where step number one is to select “.3mf” format. (Image courtesy PADT)

You can select “.3mf” but don’t Save yet. First, click on the “Options” button that shows up below the Save as File Type line, opening this window:


Second step in SolidWorks for saving a file in 3MF format: check off “include materials” and “include appearance.” (Image courtesy PADT)

You need to check the boxes for “Include Materials” and “Include Appearances” to ensure that all that great information you specified in the solid model gets written to the converted file. A good, short tutorial can be found here.

Another interesting aspect of 3MF files is that they are zipped internally, and therefore smaller than STL files. Look at the difference in file size between the two formats when this ASA Omega Clip part is saved both ways:

Comparison of file size for STL versus 3MF formats.

The 3MF-saved file size is just 13% the size of the standard STL file, which may be significant for file manipulation; for files with a lot of detail such as texture information, the difference won’t be as great, but you can still expect to save 30 to 50%.

Working with 3MF files in GrabCAD Print

Okay, so CAD programs export files in 3MF format. The other half of the story addresses the question: how does a 3D printer import and use a 3MF file? Developers of 3D printing systems follow these same consortium specifications to define how their software will set up a 3MF file to print. Some slicers and equipment already act upon some of the expanded build information, while others may accept the file but still treat it the same as an STL (no additional functions enabled so it ignores the extra data). What matters is whether the system is itself capable of printing with multiple materials or depositing material in a way that adds color, texture, transparency or a variation in internal geometry.

GrabCAD Print (GCP), the cloud-connected 3D Printer interface for today’s Stratasys printers – both FDM and PolyJet – has always supported STL and native CAD file import. However, in GCP v.1.40, released in March 2020, GrabCAD has added support for 3MF files. For files created by SolidWorks software, this adds the ability to specify face colors, body colors and textures and send all that data in one file to a PolyJet multi-material, multi-color 3D printer. (Stratasys FDM printers accept 3MF geometry and assembly structure information.)

For a great tutorial about setting up SolidWorks models with applied appearances and sending their 3MF files to GrabCAD Print, check out these step-by-step directions from Shuvom Ghose.

Example of setting up a textured part in SolidWorks, then saving the file in 3MF format and importing it into GrabCAD Print, for printing on a full-color Stratasys PolyJet printer. (Image courtesy GrabCAD)

Example of setting up a textured part in SolidWorks, then saving the file in 3MF format and importing it into GrabCAD Print, for printing on a full-color Stratasys PolyJet printer. (Image courtesy GrabCAD)

At PADT, we’re starting to learn the nuances of working with 3MF files and will be sharing more examples soon. In the meantime, we suggest you download your own free copy of GrabCAD Print to check out the new capabilities, then email or call us to learn more.

PADT Inc. is a globally recognized provider of Numerical Simulation, Product Development and 3D Printing products and services. For more information on Stratasys printers and materials, contact us at info@padtinc.com.

Optimizing Materials Selection for Additive with ANSYS Granta – Webinar

There are hundreds of industrial AM machines and materials. New products come to market weekly, and picking the best option for a manufacturing or research project is a tough call. A wrong direction can be costly. This is where Ansys Granta and the Senvol Database come in handy. 

The Senvol Database details 1,000 AM machines and more than 850 compatible materials. Using this tool within Granta Selector, you can search and compare materials based on properties, type, or compatible machines. Identify and compare machines based on supported processes, manufacturer, required part size, cost, or compatible materials (and their properties). Quickly focus on the most likely routes to achieve project goals, save time and get new ideas as you research AM options.

Join PADT’s Application Engineer Robert McCathren for an overview of Ganta Material Selector, along with its importance and applications for those working with or interested in additive manufacturing.

Register Here

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All Things Ansys 061: Bring Your Simulation Home with Ansys Cloud Solutions

 

Published on: April 20th, 2020
With: Eric Miller & Sina Ghods
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Senior Simulation Support & Application Engineer Sina Ghods for a look at what is new with Ansys Cloud and how the tool provides access to higher fidelity models, faster turnaround, and multiple supported solvers, anywhere and anytime.

If you would like to learn more about the Ansys tool offering access to simulation on the go, check out our webinar on the topic here: https://bit.ly/3al5PjH

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!

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Making Sense of DC IR Results in Ansys SIwave

In this article I will cover a Voltage Drop (DC IR) simulation in SIwave, applying realistic power delivery setup on a simple 4-layer PCB design. The main goal for this project is to understand what data we receive by running DC IR simulation, how to verify it, and what is the best way of using it.

And before I open my tools and start diving deep into this topic, I would like to thank Zachary Donathan for asking the right questions and having deep meaningful technical discussions with me on some related subjects. He may not have known, but he was helping me to shape up this article in my head!

Design Setup

There are many different power nets present on the board under test, however I will be focusing on two widely spread nets +1.2V and +3.3V. Both nets are being supplied through Voltage Regulator Module (VRM), which will be assigned as a Voltage Source in our analysis. After careful assessment of the board design, I identified the most critical components for the power delivery to include in the analysis as Current Sources (also known as ‘sinks’). Two DRAM small outline integrated circuit (SOIC) components D1 and D2 are supplied with +1.2V. While power net +3.3V provides voltage to two quad flat package (QFP) microcontrollers U20 and U21, mini PCIE connector, and hex Schmitt-Trigger inverter U1.

Fig. 1. Power Delivery Network setting for a DC IR analysis

Figure 1 shows the ‘floor plan’ of the DC IR analysis setup with 1.2V voltage path highlighted in yellow and 3.3V path highlighted in light blue.

Before we assign any Voltage and Current sources, we need to define pin groups for all nets +1.2V, +3.3V and GND for all PDN component mentioned above. Having pin groups will significantly simplify the reviewing process of the results. Also, it is generally a good practice to start the DC IR analysis from the ‘big picture’ to understand if certain component gets enough power from the VRM. If a given IC reports an acceptable level of voltage being delivered with a good margin, then we don’t need to dig deeper; we can instead focus on those which may not have good enough margins.

Once we have created all necessary pin groups, we can assign voltage and current sources. There are several ways of doing that (using wizard or manual), for this project we will use ‘Generate Circuit Element on Components’ feature to manually define all sources. Knowing all the components and having pin groups already created makes the assignment very straight-forward. All current sources draw different amount of current, as indicated in our setting, however all current sources have the same Parasitic Resistance (very large value) and all voltage source also have the same Parasitic Resistance (very small value). This is shown on Figure 2 and Figure 3.

Note: The type of the current source ‘Constant Voltage’ or ‘Distributed Current’ matters only if you are assigning a current source to a component with multiple pins on the same net, and since in this project we are working with pins groups, this setting doesn’t make difference in final results.

Fig. 2. Voltage and Current sources assigned
Fig. 3. Parasitic Resistance assignments for all voltage and current sources

For each power net we have created a voltage source on VRM and multiple current sources on ICs and the connector. All sources have a negative node on a GND net, so we have a good common return path. And in addition, we have assigned a negative node of both voltage sources (one for +1.2V and one for +3.3V) as our reference points for our analysis. So reported voltage values will be referenced to that that node as absolute 0V.

At this point, the DC IR setup is complete and ready for simulation.

Results overview and validation

When the DC IR simulation is finished, there is large amount of data being generated, therefore there are different ways of viewing results, all options are presented on Figure 4. In this article I will be primarily focusing on ‘Power Tree’ and ‘Element Data’. As an additional source if validation we may review the currents and voltages overlaying the design to help us to visualize the current flow and power distribution. Most of the time this helps to understand if our assumption of pin grouping is accurate.

Fig. 4. Options to view different aspects of DC IR simulated data

Power Tree

First let’s look at the Power Tree, presented on Figure 5. Two different power nets were simulated, +1.2V and +3.3V, each of which has specified Current Sources where the power gets delivered. Therefore, when we analyze DC IR results in the Power tree format, we see two ‘trees’, one for each power net. Since we don’t have any pins, which would get both 1.2V and 3.3V at the same time (not very physical example), we don’t have ‘common branches’ on these two ‘trees’.

Now, let’s dissect all the information present in this power tree (taking in consideration only one ‘branch’ for simplicity, although the logic is applicable for all ‘branches’):

  • We were treating both power nets +1.2V and +3.3V as separate voltage loops, so we have assigned negative nodes of each Voltage Source as a reference point. Therefore, we see the ‘GND’ symbol ((1) and (2)) for each voltage source. Now all voltage calculations will be referenced to that node as 0V for its specific tree.
  • Then we see the path from Voltage Source to Current Source, the value ΔV shows the Voltage Drop in that path (3). Ultimately, this is the main value power engineers usually are interested in during this type of analysis. If we subtract ΔV from Vout we will get the ‘Actual Voltage’ delivered to the specific current source positive pin (1.2V – 0.22246V = 0.977V). That value reported in the box for the Current Source (4). Technically, the same voltage drop value is reported in the column ‘IR Drop’, but in this column we get more details – we see what the percentage of the Vout is being dropped. Engineers usually specify the margin value of the acceptable voltage drop as a percentage of Vout, and in our experiment we have specified 15%, as reported in column ‘Specification’. And we see that 18.5% is greater than 15%, therefore we get ‘Fail_I_&_V’ results (6) for that Current Source.
  • Regarding the current – we have manually specified the current value for each Current Source. Current values in Figure 2 are the same as in Figure 5. Also, we can specify the margin for the current to report pass or fail. In our example we assigned 108A as a current at the Current Source (5), while 100A is our current limit (4). Therefore, we also got failed results for the current as well.
  • As mentioned earlier, we assigned current values for each Current Source, but we didn’t set any current values for the Voltage Source. This is because the tool calculates how much current needs to be assigned for the Voltage Source, based on the value at the Current Sources. In our case we have 3 Current Sources 108A, 63A, 63A (5). The sum of these three values is 234A, which is reported as a current at the Voltage Source (7). Later we will see that this value is being used to calculate output power at the Voltage Source.  
Fig. 5. DC IR simulated data viewed as a ‘Power Tree’

Element Data

This option shows us results in the tabular representation. It lists many important calculated data points for specific objects, such as bondwire, current sources, all vias associated with the power distribution network, voltage probes, voltage sources.

Let’s continue reviewing the same power net +1.2V and the power distribution to CPU1 component as we have done for Power Tree (Figure 5). The same way we will be going over the details in point-by-point approach:

  • First and foremost, when we look at the information for Current Sources, we see a ‘Voltage’ value, which may be confusing. The value reported in this table is 0.7247V (8), which is different from the reported value of 0.977V in Power Tree on Figure 5 (4). The reason for the difference is that reported voltage value were calculated at different locations. As mentioned earlier, the reported voltage in the Power Tree is the voltage at the positive pin of the Current Source. The voltage reported in Element Data is the voltage at the negative pin of the Current Source, which doesn’t include the voltage drop across the ground plane of the return path.

To verify the reported voltage values, we can place Voltage Probes (under circuit elements). Once we do that, we will need to rerun the simulation in order to get the results for the probes:

  1. Two terminals of the ‘VPROBE_1’ attached at the positive pin of Voltage Source and at the positive pin of the Current Source. This probe should show us the voltage difference between VRM and IC, which also the same as reported Voltage Drop ΔV. And as we can see ‘VPROBE_1’ = 222.4637mV (13), when ΔV = 222.464mV (3). Correlated perfectly!
  2. Two terminals of the ‘VPROBE_GND’ attached to the negative pin of the Current Source and negative pin of the Voltage Source. The voltage shown by this probe is the voltage drop across the ground plane.

If we have 1.2V at the positive pin of VRM, then voltage drops 222.464mV across the power plane, so the positive pin of IC gets supplied with 0.977V. Then the voltage at the Current Source 0.724827V (8) being drawn, leaving us with (1.2V – 0.222464V – 0.724827V) = 0.252709V at the negative pin of the Current Source. On the return path the voltage drops again across the ground plane 252.4749mV (14) delivering back at the negative pin of VRM (0.252709V – 0.252475V) = 234uV. This is the internal voltage drop in the Voltage Source, as calculated as output current at VRM 234A (7) multiplied by Parasitic Resistance 1E-6Ohm (Figure 3) at VRM. This is Series R Voltage (11)

  • Parallel R Current of the Current source is calculated as Voltage 724.82mV (8) divided by Parasitic Resistance of the Current Source (Figure 3) 5E+7 Ohm = 1.44965E-8 (9)
  • Current of the Voltage Source report in the Element Data 234A (10) is the same value as reported in the Power Tree (sum of all currents of Current Sources for the +1.2V power net) = 234A (7). Knowing this value of the current we can multiple it by Parasitic Resistance of the Voltage Source (Figure 3) 1E-6 Ohm = (234A * 1E-6Ohm) = 234E-6V, which is equal to reported Series R Voltage (11). And considering that the 234A is the output current of the Voltage Source, we can multiple it by output voltage Vout = 1.2V to get a Power Output = (234A * 1.2V) = 280.85W (12)
Fig. 6. DC IR simulated data viewed in the table format as ‘Element Data’

In addition to all provided above calculations and explanations, the video below in Figure 7 highlights all the key points of this article.

Fig. 7. Difference between reporting Voltage values in Power Tree and Element Data

Conclusion

By carefully reviewing the Power Tree and Element Data reporting options, we can determine many important decisions about the power delivery network quality, such as how much voltage gets delivered to the Current Source; how much voltage drop is on the power net and on the ground net, etc. More valuable information can be extracted from other DC IR results options, such as ‘Loop Resistance’, ‘Path Resistance’, ‘RL table’, ‘Spice Netlist’, full ‘Report’. However, all these features deserve a separate topic.

As always, if you would like to receive more information related to this topic or have any questions please reach out to us at info@padtinc.com.

Bring Your Simulation Home with Ansys Cloud Solutions – Webinar

Engineering simulation has long been constrained by fixed computing resources available on a desktop or cluster. Today, however, cloud computing can deliver the on-demand, high performance computing (HPC) capacity required for faster high-fidelity results offering greater performance insight, all from the comfort of your home.

Ansys Cloud delivers the speed, power and compute capacity of cloud computing directly to your desktop — when and where you need it. You can run larger, more complex and more accurate simulations to gain more insight into your product — or you can evaluate more design variations to find the optimal design without long hardware/software procurement and deployment delays.

Join PADT’s Senior Application & Simulation Support Engineer Sina Ghods for a look at how Ansys is working to drive adoption by providing users a ready to use cloud service that provides:

  • Higher Fidelity Models
  • Faster Turnaround Time
  • Improved Productivity
  • Flexible Licensing
  • Multiple Supported Solvers
  • 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!

All Things Ansys 060: Tips For Making Working From Home More Productive

 

Published on: April 6th, 2020
With: Eric Miller & Matt Sutton
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s seasoned expert at working with Ansys from home Matt Sutton for a quick discussion on tips and best practices that make working from home more productive and effective.

If you would like to learn more about how PADT and Ansys can help you to better run your simulation from your home office, check out our webinar on the topic here: https://bit.ly/3dSa8WN

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!

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