## Desktop Engineering: Your Optimization Software Respectfully Suggests a Revision

When Desktop Engineering needed a subject matter expert on Topological Optimization and its use to drive product development, they called on PADT’s Manoj Mahendran.  The article “Your Optimization Software Respectfully Suggests a Revision” gives a great overview of how designs can be driven by the use of Topological Optimization. They also mention a few of the more common tools, and with Manoj’s help, discuss the importance of 3D Printing to the process. An important take away is how these tools can be used to suggest design changes to the designer.

## Constitutive Modeling of 3D Printed FDM Parts: Part 1 (Challenges)

As I showed in a prior blog post, Fused Deposition Modeling (FDM) is increasingly being used to make functional plastic parts in the aerospace industry. All functional parts have an expected performance that they must sustain during their lifetime. Ensuring this performance is attained is crucial for aerospace components, but important in all applications. Finite Element Analysis (FEA) is an important predictor of part performance in a wide range of indusrties, but this is not straightforward for the simulation of FDM parts due to difficulties in accurately representing the material behavior in a constitutive model. In part 1 of this article, I list some of the challenges in the development of constitutive models for FDM parts. In part 2, I will discuss possible approaches to addressing these challenges while developing constitutive models that offer some value to the analyst.

It helps to first take a look at the fundamental multi-scale structure of an FDM part. A 2002 paper by Li et. al. details the multi-scale structure of an FDM part as it is built up from individually deposited filaments all the way to a three-dimensional part as shown in the image below.

This multi-scale structure, and the deposition process inherent to FDM, make for 4 challenges that need to be accounted for in any constitutive modeling effort.

• Anisotropy: The first challenge is clear from the above image – FDM parts have different structure depending on which direction you look at the part from. Their layered structure is more akin to composites than traditional plastics from injection molding. For ULTEM-9085, which is one of the high temperature polymers available from Stratasys, the datasheets clearly show a difference in properties depending on the orientation the part was built in, as seen in the table below with some select mechanical properties.
• Toolpath Definition: In addition to the variation in material properties that arise from the layered approach in the FDM process, there is significant variation possible within a layer in terms of how toolpaths are defined: this is essentially the layout of how the filament is deposited. Specifically, there are at least 4 parameters in a layer as shown in the image below (filament width, raster to raster air gap, perimeter to raster air gap and the raster angle). I compiled data from two sources (Stratasys’ data sheet and a 2011 paper by Bagsik et al that show how for ULTEM 9085, the Ultimate Tensile Strength varies as a function of not just build orientation, but also as a function of the parameter settings – the yellow bars show the best condition the authors were able to achieve against the orange and gray bars that represent the default settings in the tool.  The blue bar represents the value reported for injection molded ULTEM 9085.
• Layer Thickness: Most FDM tools offer a range of layer thicknesses, typical values ranging from 0.005″ to 0.013″. It is well known that thicker layers have greater strength than thinner ones. Thinner layers are generally used when finer feature detail or smoother surfaces are prioritized over out-of-plane strength of the part. In fact, Stratasys’s values above are specified for the default 0.010″ thickness layer only.
• Defects: Like all manufacturing processes, improper material and machine performance and setup and other conditions may lead to process defects, but those are not ones that constitutive models typically account for. Additionally and somewhat unique to 3D printing technologies, interactions of build sheet and support structures can also influence properties, though there is little understanding of how significant these are. There are additional defects that arise from purely geometric limitations of the FDM process, and may influence properties of parts, particularly relating to crack initiation and propagation. These were classified by Huang in a 2014 Ph.D. thesis as surface and internal defects.
• Surface defects include the staircase error shown below, but can also come from curve-approximation errors in the originating STL file.
• Internal defects include voids just inside the perimeter (at the contour-raster intersection) as well as within rasters. Voids around the perimeter occur either due to normal raster curvature or are attributable to raster discontinuities.

Thus, any constitutive model for FDM that is to accurately predict a part’s response needs to account for its anisotropy, be informed by the specifics of the process parameters that were involved in creating the part and ensure that geometric non-idealities are comprehended or shown to be insignificant. In my next blog post, I will describe a few ways these challenges can be addressed, along with the pros and cons of each approach.

For our Christmas parties at PADT we generally have over 40 employees so a traditional secret Santa gift exchange takes to long. So a couple of years ago we downloaded a right-left gift exchange story from the internet and it was a big hit. We ran out of stories on the internet, so we started writing our own, usually in some sort of over-the-top style.  This year, 2015, we had started the day of the party by attending the new Star Wars movie, so the story had to be Star Wars related.

Everyone gets their gift and forms a big circle in the middle of the room.  Someone with a strong voice reads the story and every time the world LEFT is read, everyone passes the package they have to the left. Every time the world RIGHT is read, everyone passes the package they have to their right.  You should pause a bit at each LEFT/RIGHT to give people a chance to pass.

You can find our older stories here

– Elf Family Christmas (2017)
– Western Christmas (2016)
– Star Wars Christmas (2015)
– Fairy Tail Christmas (2014)
– Science Fiction Christmas (2013)
– Romance Christmas (2012)
– Film Noir Christmas (2011)

## A long time ago in a galaxy far far, away…

San To Claas is in trouble. Right next to the Right-torna system on the left side of the Galaxy, the planet Northpoliax, in a left hand orbit around the star Leftonia 37, was the galactic hub for all thing Christmas. Gifts left the system right after the planet’s winter solstice. But nothing left on this orbit. Because right above the largest continent on Northpoliax, a Death Star hovered. Threatening Christmas for everyone, no one was left out.

A new Sith lord, Darth Rightis, hated Christmas. All that cheer and spirit left him cold inside. Two much of the light side of the force. Just the thought of all those gifts left for younglings left him angry. But help was right around the corner. A squadron of Xwing fighters was following right behind the Millennium Falcon.

“Arffhhhhdghgg ” said Chewy.

“What? The moon on the left or the one on the right?” Asked Han Solo. Chewy gestured and Hans went to the left.

“Your other left” yelled Princess Leia. Han dived right behind the moon on the left and slingshoted right toward the Death Star, the Xwings right behind them.

The lead pilot said: “Red leader this is blue leader. You take the left side. We will take the left as well, right after you attack, those bastards won’t expect that.”

Han added: “We will soften up that left side for you. Then let loose the “big present” after both your attacks on the left. The warhead should go right in and end this madness. “

As they approached the Millennium Falcon put covering fire to the right, then veered to the right, leaving the left open. The Xwings attacked, diving right into the slot and trying not to hit either side, the left or the right. The first attack on the left left the defenses damaged. The second attack on the left was right on target. That left the run of the Millennium Falcon. It released a plasma bomb that was wrapped in a big red package, with a bow right on top. As Han pulled up and to the left, and then the right, the warhead exploded right on inside of the main power coupler. Chewy, sitting in the right seat, bellowed in victory as the Death Star exploded right under them. As the debris clears a hologram image appeared right in the middle of the cabin.

It showed Admiral San To Clause, wearing his red uniform with white fur epilets on the right and left shoulders.

“Thank you all for coming right when we needed you. Right now, Christmas is saved and the dark side is left with one less Sith Lord. May the force, be right with you. And Merrrrrry Christmas to all!

## 3D Printed Plastics in Functional Aerospace Parts

Fused Deposition Modeling (FDM) is the most widely used 3D printing technology today, ranging from desktop printers to industrial scale manufacturing tools. While the use of FDM for prototyping and rapid tooling is well established, its use for manufacturing end-use parts in aerospace is a more recent phenomenon. This has been brought about primarily due to the availability of one material choice in particular: ULTEM. ULTEM is a thermoplastic that delivers compliance with FAA FAR 25.853 requirements. It features inherent flame retardant behavior and provides a high strength-to-weight ratio, outstanding elevated thermal resistance, high strength and stiffness and broad chemical resistance (official SABIC press release).

During an industry scan I conducted for a recent research proposal PADT submitted, I came across several examples of the aerospace industry using the FDM process to manufacture end-use parts. Each of these examples is interesting because they demonstrate the different criteria that make FDM preferable over traditional options, and I have classified them accordingly into: design opportunity, cost and lead-time reduction, and supply complexity.

Design Opportunity: In this category, I include parts that were primarily selected for 3D printing because of the unique design freedom that layer-wise additive manufacturing offers. This applies to all 3D printing technologies, the two examples below are for FDM in ducts.

ULA Environmental Control System (ECS) duct: As reported in a prior blog post, United Launch Alliance (ULA) leveraged FDM technology to manufacture an ECS duct and reduce the overall assembly from 140 parts to only 16, while reducing production costs by 57%. The ECS ducts distribute temperature and humidity controlled air onto sensitive avionics equipment during launch and need to withstand strong vibrations. The first Atlas V with these ducts is expected to launch in 2016.

Orbis Flying Eye Hospital aircraft duct: The Flying Eye Hospital is an amazing concept from Orbis, who use a refurbished DC-10 plane to deliver eye care around the world. The plane actually houses all the surgical rooms to conduct operations and also has educational classrooms. The refurbishment posed a particular challenge when it came to air conditioning: a duct had to transfer air over a rigid barrier while maintaining the volume. Due to the required geometric complexity, the team selected FDM and ULTEM to manufacture this duct, and installed it and met with FAA approval. The story is described in more detail in this video.

Supply Complexity: 3D printing has a significant role to play in retro-fitting of components on legacy aircraft. The challenge with maintaining these aircrafts is that often the original manufacturer either no longer is in business or makes the parts.

Airbus Safety belt holder: Airbus shared an interesting case of a safety belt holder that had to be retrofitted for the A310 aircraft. The original supplier made these 30 years ago and since went out of business and rebuilding the molds would cost thousands of dollars and be time-consuming. Airbus decided to use FDM to print these safety belt holders as described in this video. They took a mere 2 hours to design the part from existing drawings, and had the actual part printed and ready for evaluation within a week!

Incidentally, the US Air Force has also recognized this as a critical opportunity to drive down costs and reduce the downtime spent by aircrafts awaiting parts, as indicated by a recent research grant they are funding to enable them to leverage 3D printing for the purpose of improving the availability of parts that are difficult and/or expensive to procure. As of 2014, The Department of Defense (DOD) reported that they have maintenance crews supporting a staggering 31,900 combat vehicles, 239 ships and 16,900 aircraft – and identified 3D printing as a key factor in improving parts availability for these crews.

Cost & Lead-time Reduction: In low-volume, high-value industries such as aerospace, 3D printing has a very strong proposition to make as a technology that will bring products to market faster and cheaper. What is often a surprise is the levels of reduction that can be obtained with 3D printing, as borne out by the three examples below.

Airbus A350 Electric wire covers: The Airbus A350 has several hundred plastic covers that are 3D printed with FDM. These covers are used for housing electric wires at junction boxes. Airbus claims it took 70% less time to make these parts, and the manufacturing costs plunged 80%. See this video for more information.

Kelly Manufacturing Toroid housing: Kelly Manufacturing selected FDM to manufacture toroid housings that are assembled into their M3500 instrument, which is a “turn and bank” indicator which provides the pilot information regarding the rate of aircraft turn. These housings were previously made of urethane castings and required manual sanding to remove artifacts from the casting process, and also had high costs and lead times associated with tooling. Using FDM, they were able to eliminate the need to do sanding and reduced the lead time 93% and also reduced per-piece costs by 5% while eliminating the large tooling costs. See the official case study from Stratasys here.

These examples help demonstrate that 3D printing parts can be a cost savings solution and almost always results in significant lead time reduction – both of vital interest in the increasingly competitive aerospace industry. Further, design freedom offered by 3D printing allows manufacturing geometries that are otherwise impossible or cost prohibitive to make using other processes, and also have enormous benefit in overcoming roadblocks in the supply chain. At the same time, not every part on an aircraft is a suitable candidate for 3D printing. As we have just seen, selection criteria involve the readily quantifiable metrics of part cost and lead time, but also involve less tangible factors such as supply chain complexity, and the design benefits available to additive manufacturing. An additional factor not explicitly mentioned in any of the previous examples is the criticality of the part to the flight and the safety of the crew and passengers on board. All these factors need to be taken into consideration when determining the suitability of the part for 3D printing.

## Arizona Chief Science Officers Design Their Own 3D Printed Name Badges

The Chief Science Officer program is a program for 6th-12th grade students to represent their school in STEM. And what better way is there for them to identify themselves then with 3D Printed name badges?  The program’s sponsors, the AZ SciTech Festival offer a training retreat for the kids who get elected as their school’s CSO and we all thought introducing design and 3D Printing would be a great activity.

As part of the 2015 Fall CSO Institute, PADT’s Jeff Nichols joined local designer and artist John Drury to spend some time with the kids explaining how to work with logos and shapes to convey an idea, and how to design for 3D Printing.  The kids worked out their own design and sent it to PADT for printing.

We converted their sketch into a 3D Model, starting in Adobe Illustrator. The sketch was traced with vector geometry and then a generic name was added. This was then copied 144 times and each name was typed in, with a few extras. This step was the only boring part.

The design worked great because it is a simple extrusion with no need for support material.    The outline of their names were exported as DXF from Illustrator and then imported onto the 3D Model and extruded up to make a solid model of a badge. This was then copied to make a badge for each student. Then the names were imported and extruded on the patterned badges.

STL files were then made and sent off to one of our Stratasys FDM 3D Printers. The FDM (Fused Deposition Modeling) process extrudes an ABS plastic filament, and you can change material during the build. So, to add a bit of contrast, we changed the filament color after the base of the design was done, making the logo and student names stand out.  The final results came out really nice.

This project was a lot of fun because we were able to work with the students. They got what John and Jeff taught them and did a great job.  We know they will be placed with pride on back backs and jackets across Arizona.

To learn more about the CSO program, visit their website: http://chiefscienceofficers.org/ Check out the blog.  Some of these kids can really write well and their insight into Science, Technology, Math, and Education is insightful.

## Star Wars – The Force Awakens with PADT

For an engineer, there are certain TV and Movie experiences that border on the religious – Star Wars is of course one of those.  That is why PADT’s main office in Tempe closed down today to head down the freeway to the Chandler to see Star Wars VII: The Force Awakens.

Around 370 employees, family members, friends, vendors, former employees, and customers showed up for the 10:00 am showing.  We were confident that JJ Abrams would do a great job, because he did so well with an even more important franchise to PADT, Star Trek.  We were not disappointed.  There were cheers, there was laughter, and several of us confessed in the lobby afterwards that we teared up a bit.  A true treat.

I want to thank Josh Heaps here for putting it all together and for dealing with our constantly asking him about when and where it was and how many seats the theater had.

This is also a great venue to thank our customers and vendors for coming and for bringing your families.  We don’t get to see many of you often enough, and rarely outside of a meeting or a phone call.  Seeing the smiles on everyone’s face after the movie was, as they say, worth the price of admission.

May the Force Be With You

If you want to organize similar event to your colleagues, hire team building company in Singapore!

## Activating Hyperdrive in ANSYS Simulations

With PADT and the rest of the world getting ready to pile into dark rooms to watch a saga that we’ve been waiting for 10 years to see, I figured I’d take this opportunity to address a common, yet simple, question that we get:

“How do I turn on HPC to use multiple cores when running an analysis?”

For those that don’t know, ANSYS spends a significant amount of resources into making the various solvers it has utilize multiple CPU processors more efficiently than before.  By default, depending on the solver, you are able to use between 1-2 cores without needing HPC licenses.

With the utilization of HPC licenses, users can unlock hyperdrive in ANSYS.  If you are equipped with HPC licenses it’s just a matter of where to look for each of the ANSYS products to activate it.

## ANSYS Mechanical

Whether or not you are performing a structural, thermal or explicit simulation the process to activate multiple cores is identical.

1. Go to Tools > Solve Process Settings
2. The Solve Process Settings Window will pop up
4. You will see an option for Max number of utilized cores
5. Simply change the value to your desired core count
6. You will see below an option to allow for GPU acceleration (if your computer is equipped with the appropriate hardware)
7. Select the GPU type from the dropdown and choose how many GPUs you want to utilize
8. Click Ok and close

### Distributed Solve in ANSYS Mechanical

One other thing you’ll notice in the Advanced Settings Window is the option to turn “Distributed” On or Off using the checkbox.

In many cases Distributing a solution can be significantly faster than the opposite (Shared Memory Parallel).  It requires that MPI be configured properly (PADT can help guide you through those steps).  Please see this article by Eric Miller that references GPU usage and Distributed solve in ANSYS Mechanical

## ANSYS Fluent

Whether launching Fluent through Workbench or standalone you will first see the Fluent Launcher window.  It has several options regarding the project.

1. Under the Processing Options you will see 2 options: Serial and Parallel
2. Simply select Parallel and you will see 2 new dropdowns
3. The first dropdown lets you select the number of processes (equal to the number of cores) to use in not only during Fluent’s calculations but also during pre-processing as well

## ANSYS CFX

For CFX simulations through Workbench, the option to activate HPC exists in the Solution Manager

1. Open the CFX Solver Manager
2. You will see a dropdown for Run Mode
3. Rather than the default “Serial” option choose from one of the available “Parallel” options.
4. For example, if running on the same machine select Platform MPI Local Parallel
5. Once selected in the section below you will see the name of the computer and a column called Partitions
6. Simply type the desired number of cores under the Partitions column and then either click “Save Settings” or “Start Run”

## ANSYS Electronics Desktop/HFSS/Maxwell

Regardless of which electromagnetic solver you are using: HFSS or Maxwell you can access the ability to change the number of cores by going to the HPC and Analysis Options.

1. Go to Tools > Options > HPC and Analysis Options.
2. In the window that pops up you will see a summary of the HPC configuration
3. Click on Edit and you will see a column for Tasks and a column for Cores.
5. To simply increase the number of cores you want to run the simulation on, change the cores column to your desired value
6. Click OK on all windows

There you have it.  That’s how easy it is to turn on Hyperdrive in the flagship ANSYS products to advance your simulations and get to your endpoint faster than before.

If you have any questions or would like to discuss the possibility of upgrading your ship with Hyperdrive (HPC capabilities) please feel free to call us at 1-800-293-PADT or email us at support@padtinc.com.

## New Enhancements to Flownex 2015: Even Better Fluid-Thermal Simulation

The developers of Flownex have been hard at work again and have put out a fantastic update to Flownex 2015.  These additions go far beyond what most simulation programs include in an update, so we thought it was worth a bit of a blog article to share it with everyone.  You can also download the full release notes here: FlownexSE 2015 Update 1 – Enhancements and Fixes

## What is Flownex?

Some of you may not be familiar with Flownex. It is a simulation tool that models Fluid-Thermal networks.  It is a 1-D tool that is very easy to use, powerful, and comprehensive. The technology advancements delivered by Flownex offer a fast, reliable and accurate total system and subsystem approach to simulation that complements component level simulation in tools like ANSYS Fluent, ANSYS CFX, and ANSYS Mechanical.  We use it to model everything from turbine engine combustors to water treatment plants. Learn more here

# Major Enhancements

A lot went in to this update, much hidden behind the scenes in the forms of code improvements and fixes.  There are also a slew of major new or enhanced features worth mentioning.

## Shared Company Database

One of the great things about Flownex is that you can create modeling objects that you drag and drop into your system model. Now you can share those components, fluids, charts, compounds, and default settings across your company, department, or group.    There is no limit on the number of databases that are shared and access can be controlled. This will allow users to reuse information across your company.

## Static Pressure Boundary Conditions

In the past Flownex always used a total pressure boundary condition. Based on user requests, this update includes a new boundary condition object that allows the user to specify the static pressure as a boundary condition. This is useful because many tests of real hardware only provide static pressure. It is also a common boundary condition in typical rotational flow fields in turbo machinery secondary flow.

## Subdivided Cavities

Another turbo machinery request was the ability to break cavities up into several radial zones, giving a more accurate pressure distribution in secondary flow applications for Rotor-Rotor and Rotor-Stator cavities.  These subdivisions can be automatically created in the radial direction by Flownex.

## Excel Input Sheets and Parameter Tables

The connection between Microsoft Excel and Flownex has always been strong and useful, and it just get even better.  So many people were connecting cells to their Flownex model parameters that the developers decided to directly connect the two programs so the user no longer has to establish data connection links.  Now an properties in Flownex can be hooked to a cell in Excel.

The next thing users wanted was the ability to work with tables of parameters, so that was added as well.  The user can hook a table of values in Excel to Flownex parameters and then have Flownex solve for the whole table, even returning resulting parameters.  This makes parametric studies driven from Excel simple and powerful.

## Component Enhancements

Users can now create component defaults and save them in a library. This saves time because in the past the user had to specify the parameters for a given component. Now thy just drag and job the existing defaults into their model.

Compound components have also been enhanced by the development team so you no loner have to restart Flownex when you move, export, or import a compound component.

## Find Based on Property Values

Users can now search through properties on all the objects in their model based on the value assigned to those properties.  As an example, you can type > 27.35 to get a list of all properties with an assigned value that is larger than 27.35.  This saves time because the user no longer has to look through properties or remember what properties were assigned.

## Network Creation through Programming

Users can now write programs through the API or scripting tool to build their network models. This will allow companies to create vertical applications or automate the creation of complex networks based on user input. Of all the enhancements in this update, this improvement has the potential to deliver the greatest productivity improvements.

## Automatic Elevations Importing in GIS

Users who are specifying flow networks over real terrain can now pull elevation data from the internet, rather than requiring that the data be defined when the network is specified. This enhancement will greatly speed up the modeling of large fluid-thermal systems, especially when part of the simulation process is moving components of the system over terrain.

## Multiple Fluid Interface Component

A very common requirement in fluid-thermal systems is the ability to model different fluids or fluid types and how they interact. With this update users can now model two separate fluid networks and define a coupling between the two. The mass balance and resulting pressure at the interface is maintained.

## Static Condition Calculation Improvements

Many simulation require an accurate calculation of static pressures. To do this, the upstream and downstream areas and equivalent pipe diameters are needed to obtain the proper values.  Many components now allow upstream and downstream areas to be defined, including restrictors and nozzles.

## Scaled Drawing

The ability to create a scale 2-Dimensional drawing was added to Flownex. The user can easily add components onto an existing scaled drawing that is used as a background image in Flownex. These components will automatically detect and input lengths based on the drawing scale and distance between nodes. This results in much less time and effort spent setting up larger models where actual geometric sizes are important.

# How do I Try this Out?

As you can see by the breadth and depth of enhancements, Flownex is a very capable tool that delivers on user needs.  Written and maintained by a consulting company that uses the tool every day, it has that rare mix of detailed theory and practical application that most simulation engineers crave.  If you model fluid-thermal systems, or feel you should be simulating your systems, contact Brian Duncan at 480.813.4884 or brain.duncan@padtinc.com. We can do a quick demo over the internet and learn more about what your simulation needs are.  Even if you are using a different tool, you should look at Flownex, it is an great tool.

## Stuff I Learned about Injection Molding with 3D Printed Tooling

Making injection molding tools using 3D Printing has been a long term goal for the industry.  I knew the technology had advanced recently, but was really not aware how far it had come until I attended two seminars in Utah on the subject. In this post I’ll share what I learned, and share some content that goes into greater detail.

## The Seminars

The reason for my update on this subject was a visit to PADT’s Utah office.  Our two people there, Anthony Wagoner (sales) and James Barker (engineering), told me they were doing a seminar on injection molding and I should go. I figured why not, I’m in town. Maybe I’ll meet a couple of customers.  Almost 30 people showed up to the Salt Lake Community College Injection Molding lab for the event.  Gil Robinson from Stratasys presented a fantastic overview (included in the download package) on where the technology is, how to apply it, and gave some great real world examples.  There were some fantastic questions as well which allowed us to really explore the technology

Then the best part happened when we walked into the shop and saw parts being made right there on the machine. They had recently printed a tool and were shooting polypropylene parts while we were in the classroom next door. During the hour long presentation, Richard Savage from ICU Medical was able to fine-tune the injection molding machine and good parts were popping out. As you can imagine, what followed next was they type of discussion would expect with  a room full of injection molding people. “What material? How hot? What pressure? What is the cooling time? Do you use compressed air to cool it? Not a lot of flash, how hard are you clamping it? These features here, what draft did you need?”  Good stuff.  I got caught up in everything and forgot to grab some pictures.

I learned so much at that event that I decided to head north along the Wasatch Range to Clearfield and the Davis Applied Technology College.  About the same number of people were able to make it from medical, aerospace, and consumer products companies in Northern Utah.  Gil presented the same material, but this time we got some different questions so I learned a bit more about material options and some other lessons learned.

Then we visited their lab where I did remember to take some pictures:

Here is a shot of different shots that Jonathan George from DATC did to dial in the parameters.  It took him about an hour, not bad for the first time using a 3D Printed tool.

The part is actually a clam shell assembly for Christmas lights, in the shape of a snow flake. Here is what they look like on the tree itself.

And here is a video they made showing the process. He was able to get 950 shots out of the tool.

In talking to attendees at both events I learned of several great applications that they were going to try, varying from medical devices for clinical trials to making rubber masking tools for surface treatments. The injection molding community in Utah is very sophisticated and forward thinking.

## What I Learned

I’ll spare you the details on what we had for dinner Monday night for the Utah office holiday celebration and jump right in to what I learned.

1. For  the right applications, you can get some very nice parts from 3D Printed tools
2. You do need to take the process in to account and oriented the tools facing upward in the machine, add a bit more draft than usual, and keep your pressures and temperature down when compared to metal tools.
3. For some parts, you can get over 1,000 shots from a tool, but most poeple are getting a couple of hundred parts.
4. As with any injection molding, the magic is in the tool design and setting up the right parameters on the injection molding press.
5. Tricky parts can be made by using metal inserts
6. Some machining may be required on your 3D printed tool to get it just right, but that is mostly reaming holes for ejector pins and metal inserts
7. Plastic is an insulator (duh) so plastic tools have to be cooled more slowly and with air.
8. Conformal cooling is a great idea, but some work still needs to be done to get it to work.
9. The mold usually fails during part ejection, so using mold release, good draft, and proper design can reduce the loading during ejection and get more parts from the tool.
10. The material of choice for this is DigitalABS on Stratasys Connex Machines.

There was a ton more, and you can find most of it in the download package.

The big take-away from both events was that this technology works and it really does allow you to create an injection molding tool in a couple of hours on a 3D Printer. In the time it normally takes to just get the order figured out for a machined tool (RFQ, Quote, Iterate, PO, etc…) you can have your parts.

## Next Steps

Interested in trying this out yourself or learning more?  We have put together an injection molding package with the following content:

• Polyjet Injection Molding Application Brief
• 18 Page Polyjet Injection Molding Technical Guide
• 12 Page White Paper: Precision Prototyping – The Role of 3D Printed Molds in the Injection Molding Industry
• 3D Printed Injection Molding Application Guide from PADT and Stratasys
• Presentation from Seminars
• List of Relevant Videos
• Four Real World Case Studies
• Link List for Other Resources  on the Web

We have spent some time putting all this information in one place and put it into one convenient ZIP file.  Please click here to download this very useful content.

## PID Thermostat Boundary Condition ACT Extension for ANSYS Mechanical

PADT is pleased to announce that we have uploaded a new ACT Extension to the ANSYS ACT App Store.  This new extension implements a PID based thermostat boundary condition that can be used within a transient thermal simulation.  This boundary condition is quite general purpose in nature.  For example, it can be setup to use any combination of (P)roportional (I)ntegral or (D)erivate control.   It supports locally monitoring the instantaneous temperature of any piece of geometry within the model.  For a piece of geometry that is associated with more than one node, such as an edge or a face, it uses a novel averaging scheme implemented using constraint equations so that the control law references a single temperature value regardless of the reference geometry.

The set-point value for the controller can be specified in one of two ways.  First, it can be specified as a simple table that is a function of time.  In this scenario, the PID ACT Extension will attempt to inject or remove energy from some location on the model such that a potentially different location of the model tracks the tabular values.   Alternatively, the PID thermostat boundary condition can be set up to “follow” the temperature value of a portion of the model.  This location again can be a vertex, edge or face and the ACT extension uses the same averaging scheme mentioned above for situations in which more than one node is associated with the reference geometry.  Finally, an offset value can be specified so that the set point temperature tracks a given location in the model with some nonzero offset.

For thermal models that require some notion of control the PID thermostat element can be used effectively.  Please do note, however, that the extension works best with the SI units system (m-kg-s).

## A Guide to Crawling, Walking, and Running with ANSYS Structural Analysis

At PADT, we apply a Crawl, Walk, Run philosophy to just about everything we do. Start with the basics, build knowledge and capability on that, and then continue to develop your skills throughout your career. Unfortunately, all too often I run across some poor new grad, two weeks out of school, contending with a problem that’s more befitting someone with about a decade of experience under his or her belt.

Now, the point of this article isn’t to call anyone out. Rather, I sincerely hope that managers and supervisors see this and use it as a guideline in assigning tasks to their direct reports. Note that the recommendations are relative and general. Some people may be quite competent in the “run” categories after just a few months of usage and study while others may have been using the software for a decade and still have trouble figuring out how to even start it. It’s also possible that, for certain projects, the “crawl” categories may actually end up being more difficult to contend with than the “run” categories.

With those caveats in mind, here is our list of recommendations for Crawling, Walking, and Running with ANSYS. Note that these apply to structural analysis. I fully plan to hit up my colleagues for similar blog posts about heat transfer, CFD, and electrical simulation.

## Crawl

• Linear static
• Basic modal
• Eigenvalue (linear) buckling, but don’t forget to apply a knock-down factor

## Walk

• Nonlinearities
• Large Deflection
• Rate-independent plasticity
• Nonlinear contact (frictionless and frictional)
• Dynamics
• Modal with linear perturbation
• Spectrum analyses (running the analysis is easy; understanding what you’re doing and interpreting results correctly is hard)
• Shock/Single point response
• Random Vibration (PSD)
• Harmonic analysis
• Fatigue

## Run

• Nonlinearities
• Hyperelasticity
• Rate-dependent phenomena
• Creep
• Viscoelasticity
• Viscoplasticity
• Other advanced material models such as shape memory alloy and gaskets
• Element birth and death
• Dynamics
• Transient dynamics (implicit)
• Explicit dynamics (e.g. LS-Dyna and Autodyn)
• Rotordynamics
• Fracture and crack growth

So what’s the best, quickest way to move from crawling to walking or walking to running? Invest in general or consultative (or even better, both) ANSYS training with PADT. We’ll help you get to where you need to be.

## Seminar: Additive Manufacturing & the Honeywell Global Initiative

Donald Godfrey, Honeywell Engineering Fellow for Additive Manufacturing will be presenting a seminar at Arizona State University on the status of metal Additive Manufacturing (AM) within the company worldwide.  This live event, being held at the ASU Polytechnic Campus in Mesa, Arizona, will be a fantastic opportunity to learn how this exciting technology is used in the real world to change the way aerospace parts are designed and made.

## GCOI 2015 – Celebrating Arizona’s Technology Community

For those of us that are part of the Arizona Technology community, the official kickoff of holiday and end of year celebrations is the Governor’s Celebration of Innovation, or GCOI.  A who’s who of key people from startups to large aerospace firms gather at the convention center to recognize students, academicians, companies, and individuals who have had a significant impact on the State’s high tech industries.  This is always a special evening for PADT because many of the attendees, and usually a few of the award winners, are our customers.

In fact, for 2015 we are proud to congratulate the following long time PADT customers who were recognized last night:

• Medtronic Tempe Campus for Innovator of the Year, Large Company
• Raytheon Missile Systems for winning the Pioneering Award
• ASU’s Michael Crow, the OneNeck IT Services People’s Choice Lifetime Achievement Award winner (ASU is a large PADT customer… so we feel Dr. Crow is our customer as well.)

You can find a full list of winners and some great pictures  from the event in Tishin Donkersley’s article at AZ Tech Beat.

This fantastic event is put on by the Arizona Technology Council and the Arizona Commerce Authority.  For those that were there: Mac & Cheese bar FTW.

As in past years, PADT was honored to be able to fabricate the awards that were handed out. This year we used the overall design for the event, created by Atom, as our starting point. We used our Stratasys FDM printers to make the stair steps and “tech guy silhouette” The graphics are then printed on large stickers that are adhered to the back of an Arizona’ish shaped piece of plexiglass.

This year we decided to not bring a 3D Printer and instead focus on parts made on a wider variety of printers. The hit for visitors were the metal parts that were made on ConceptLaser Direct Laser Melting systems.  In addition we got to talk about the great work that our product development team did for GlobalStar on the Spot devices and Orthosensor for their intelligent orthopedic sensors. We even had a few simulation people come by to talk ANSYS.

Hopefully you had a chance to talk with Andrew Miller, Kathryn Pesta, or Mario Vargas. If you missed us and want to know more about PADT, what we do, or the Arizona Technology Community, reach out and we will be happy to chat.

## Be a Pinball Wizard with Contact Regions in ANSYS Mechanical

I had a very cool music teacher back in 6th or 7th grade in the 1970’s in upstate New York.  Today we’d probably say she was eclectic.  In that class we listened to and discussed fairly recent songs in addition to general music studies.  Two songs I remember in particular are ‘Hurdy Gurdy Man’ by Donovan and ‘Pinball Wizard’ by The Who.  If you’re not familiar with Pinball Wizard, it’s from The Who’s rock opera Tommy, and is about a deaf, mute, blind young man who happens to be adept at the game of pinball.  Yes, he is a Pinball Wizard.  This sing popped into my head recently when we had some customer questions here at PADT regarding the pinball region concept as it pertains to ANSYS contact regions.

I’m not sure if the developers at ANSYS, Inc. had this song in mind when they came up with the nomenclature for the 17X (latest and greatest) series of contact elements in ANSYS, but regardless, you too can be a pinball wizard when it comes to understanding contact elements in ANSYS Mechanical and MAPDL.

Fans of this blog may remember one of my prior posts on contact regions in ANSYS that also had a musical theme (bringing to mind Peter Gabriel’s song “I Have the Touch”):

In this current entry we will go more in depth on the pinball region, also known as the pinball radius.  The pinball region is involved with the distance from contact element to target element in a given contact region.  Outside the pinball region, ANSYS doesn’t bother to check to see if the elements on opposite sides of the contact region are touching or not.  The program assumes they are far away from each other and doesn’t worry about any additional calculations for the most part.

Here is an illustration.  The gray elements on the left represent the contact body and the red elements on the right represent the target body (assuming asymmetric contact).  Target elements outside the pinball radius will not be checked for contact.  The contact and target elements actually ‘coat’ the underlying solid elements so they are shown as dashed lines slightly offset from the solid elements for the sake of visibility.  Here the pinball radius is displayed as a dashed blue circle, centered on the contact elements, with a radius of 2X the depth of the underlying solid elements.

So, outside the pinball region, we know ANSYS doesn’t check to see if the contact and target are actually in contact.  It just assumes they are far away and not in contact.  What about what happens if the contact and target are inside the pinball region?  The answer to that question depends on which contact type we have selected.

For frictionless contact (aka standard contact in MAPDL) and frictional contact, the program will then check to see if the contact and target are truly touching.  If they are touching, the program will check to see if they are sliding or possibly separating.  If they are touching and penetrating, the program will check to see if the penetration exceeds the allowable amount and will make adjustments, etc.  In other words, for frictionless and frictional contact, if the contact and target elements are close enough to be inside the pinball region, the program will make all sorts of checks and adjustments to make sure the contact behavior is adequately captured.

The other scenario is for bonded and no separation contact.  With these contact types, the program’s behavior when the contact and target elements are within the pinball region is different.  For these types, as long as the contact and target are close enough to be within the pinball region, the program considers the contact region to be closed.  So, for bonded and no separation, your contact and target elements do not need to be line on line touching in order for contact to be recognized.  The contact and target pairs just need to be inside the pinball region.  This can be good, in that it allows for some ‘slop’ in the geometry to be automatically ignored, but it also can have a downside if we have a curved surface touching a flat surface for example.  In that case, more of the curved surface may be considered in contact than would be the case if the pinball region was smaller.  This effect is shown in the image below.  Reducing the pinball radius to an appropriate smaller amount would be the fix for eliminating this ‘overconstraint’ if desired.

There is a default value for the pinball region/radius.  It can be changed if needed.  We’ll add more details in a moment.  First, why is it called the “pinball” region?  I like to think it’s because when it’s visualized in the Mechanical window, it looks like a blue pinball from an actual pinball arcade game, but I’ll admit that the ANSYS terminology may predate the Mechanical interface.  The image below shows what I mean.  The blue balls are the different pinball radii for different contact regions.

Note that you don’t see the pinball region displayed as shown in the above image unless you have manually changed the pinball size in Mechanical.  The pinball region can be changed in the Mechanical window in the details view for each contact region by changing Pinball Region from Program Controlled to Radius, like this:

In MAPDL, the pinball radius value can be changed by defining or editing the real constant labeled PINB.

By now you’re probably wondering what is the default value for the pinball radius?  The good news is that it is intelligently decided by the program for each contact region.  The default is always a scale factor on the depth of the underlying elements of each contact region.  In the first pinball region image shown near the beginning of this article, the example plot shows the pinball region/radius as two times the depth of the underlying elements.

The table below summarizes the default pinball radius values for most circumstances for 2D and 3D solid element models.  More detailed information is available in the ANSYS Help.

Default Pinball Radius ValuesLarge Deflection Off
Flexible-Flexible
Large Deflection On
Flexible-Flexible
Frictionless and Frictional1* Underlying Element Depth2*Underlying Element Depth
Bonded and No Seperation0.25*Underlying Element Depth0.5*Underlying Element Depth
Rigid-Flexible Contact: Typically the Default Values are Doubled

Summing it all up:  we have seen how the default values are calculated and also how to change them.  We have seen what they look like as blue balls in a plot of contact regions in Mechanical if the pinball radius has been explicitly defined.  We also discussed what the pinball radius does and how it’s different for frictionless/frictional contact and bonded/no separation contact.

You should be well on your way to becoming a pinball wizard at this point.

Does performing simulation in ANSYS make you think of certain songs, or are there songs you like to listen to while working away on your simulations an addition to The Who’s “Pinball Wizard” and Peter Gabriel’s “I Have the Touch”?  If so, we’d love to hear about your song preferences in the comments below.

## Video: Automated Test Fixture for Biopsy Device

How do you figure out when and why a product is failing?  When the failure is due to repetitive operation the only practical way is to build a machine that operates the product over and over again. Designing, building, and running this type of device is one of the many services that PADT offers its customers.

The video below is an example of how PADT’s Medical Device team developed an automated text fixture for a customer that needed to understand the failure mechanisms of a biopsy device. The fixture was designed to operate the device, repeating field operations, and capture behavior over time with the goal of capture which components failed, the nature of each failure, and the nature of each failure.

The apparatus repeats four operations that constitute one operation of the device. Video is used with a counter to determine when a failure occurred and how. The project brought together test, controls, and mechanical design engineers. It also utilized PADT’s in-house 3D Printing and machining capability.

This is also a perfect example of how a customer can hand over an entire project that they need done, but don’t have the resources to do in-house. PADT’s team created the test specification, designed the hardware, conducted the tests, and delivered actionable information to the customer.

If you have a project you do not have the resources to complete in-house, consider having our engineers take a look at it to see how we can help.