Advanced ANSYS Functionality

Just like any other marketplace, there are a lot of options in simulation software.  There are custom niche-codes for casting simulations to completely general purpose linear algebra solvers that allow you to write your own shape functions.  Just like with most things in life, you truly get what you pay for.

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For basic structural and thermal simulations pretty much any FE-package should suffice.  The difference there will be in how easy it is to pre/post process the work and the support you receive from the vendor.  How complicated is the geometry to mesh, how long does it take to solve, if you can utilize multiple cores how well does it scale, how easy is it to get reactions at interfaces/constraints…and so on.  I could make this an article about all the productivity enhancements available within ANSYS, but instead I’ll talk about some of the more advanced functionalities that differentiate ANSYS from other software out there.

  • Radiation

You can typically ignore radiation if there isn’t a big temperature gradient between surfaces (or ambient) and just model your system as conduction/convection cooled.  Once that delta is large enough to require radiation to be modeled there are several degrees of numerical difficulty that need to be handled by the solver.

First, radiating to ambient is fairly basic but the heat transfer is now a function of T^4.  The solver can also be sensitive to initial conditions since large DT results in a large heat transfer, which can then result in a large change in temperature from iteration to iteration.  It’s helpful to be able to run the model transiently or as a quasi-static to allow the solver to allow some flexibility.

Next, once you introduce surface to surface radiation you now have to calculate view factors prior to starting the thermal solution. If you have multiple enclosures (surfaces that can’t see each other, or enclosed regions) hopefully there are some processes to simplify the view factor calculations (not wasting time calculating a ‘0’ for elements that can’t radiate to each other).  The view factors can sometimes be sensitive to the mesh density, so being able to scale/modify those view factors can be extremely beneficial.

Lastly you run into the emissivity side of things.  Is the emissivity factor a function of temperature?  A function of wavelength?  Do you need to account for absorption in the radiation domain?

Luckily ANSYS does all of this.  ANSYS Mechanical allows you to easily define radiation to ambient or surface-to-surface.  If you’re using symmetry in your model the full radiating surface will be captured automatically.  You can define as many enclosures as possible, each with different emissivity factors (or emissivity vs Temperature).  There are more advanced features that can help with calculating view factors (simplify the radiating surface representation, use more ray traces, etc) and there is functionality to save the calculated view factors for later simulations.  ANSYS fluid products (CFX and Fluent) can also account for radiation and have the ability to capture frequency-based emissivity and participating media.

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Automatic expansion of radiating surfaces across symmetry planes

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Different enclosures to simplify view factor calculations

Long story short…you don’t have to know what the Stefan-Boltzman constant is if you want to include radiation in your model (bonus points if you do).  You don’t have to mess with a lot of settings to get your model to run.  Just insert radiation, select the surface, and run.  Additional options and technical support is there if necessary.

  • Multiple/Multi-physics

I’d expect that any structural/thermal/fluids/magnetics code should be able to solve the basic fundamental equations for the environment it simulates.  However, what happens when you need to combine physics, like a MEMs device.  Or maybe you want to take some guess-work/assumptions out of how one physics loads another, like what the actual pressure load is from a CFD simulation on a structural model.  Or maybe you want to capture the acoustic behavior of an electric motor, accounting for structural prestress/loads such as Joule heating and magnetic forces.

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ANSYS allows you to couple multiple physics together, either using a single model or through data mapping between different meshes.  Many of the data mapping routines allow for bi-directional data passing so the results can converge.  So you can run an magnetic simulation on the holding force between a magnet and a plate, then capture the deflected shape due to an external load, and pass that deformed shape back to the magnetic simulation to capture the updated force (and repeat until converged).

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If you have vendor-supplied data, or are using another tool to calculate some other results you can read in point cloud data and apply it to your model with minimal effort.

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To make another long story short…you can remove assumptions and uncertainty by using ANSYS functionality.

  • Advanced Material Models

 

Any simulation tool should be able to handle simple linear material models.  But there are many different flavors of ‘nonlinear’ simulation.  Does the stiffness change due to deflection/motion (like a fishing rod)?  Are you working with ductile metals that experience plastic deformation?  Does the stiffness change due to parts coming into/out-of contact?  Are surfaces connected through some adhesive property that debonds under high loads?  Are you working with elastomers that utilize some polynomial form hyper-elasic formulation?  Are you working with shape memory alloys?  Are you trying to simulate porous media through some geomechanical model?  Are you trying to simulate a stochastic material variation failure in an impact/explosive simulation?

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Large deflection stiffness calculations, plasticity, and contact status changes are easy in ANSYS.  Debonding has been available since ANSYS 11 (reminder, we’re at release 18.0 now).  ANSYS recently integrated some more advanced geomechanical models for dam/reservoir/etc simulations.  The explicit solver allows you to introduce stochastic variation in material strengths for impact/explosive simulations.

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ANSYS also has all the major flavors of hyper-elastic material models.  You can choose from basic Neo-Hookean, Arruda-Boyce, Gent, all the way through multiple variations of Mooney-Rivlin, Yeoh, Ogden, and more.  In addition to having these material models available (and the curve fitting routines to properly extract the constants from test data) ANSYS also has the ability to dynamically remesh a model.  Most of the time when you’re analyzing the behavior of a hyperelastic part there is a lot of deformation, and what starts out as a well-shaped mesh can quickly turn into a bad mesh.  Using adaptive meshing, you can have the solve automatically pause the solution, remesh the deformed shape, map the previous stress state onto the new nodes/elements, and continue with the solution.  I should note that this nonlinear adaptive remesh is NOT just limited to hyperelastic simulations…it is just extremely helpful in these instances.

The ending of this story is pretty much the same as others.  If you have a complicated material response that you’re trying to capture you can model it in ANSYS.  If you already know how to characterize your material, just find the material model and enter the constants.  We’ve worked with several customers in getting their material tested and properly characterized.  So while most structural codes can do basic linear-elastic, and maybe some plastic…very few can capture all the material responses that ANSYS can.

  • MEMs/Piezo/Etc

I know I’ve already discussed multiple physics and advanced materials, but once you start making parts smaller you start to get coupling between physics that may not work well for vector-based coupling (passing load vectors/deformations from one mesh to another).  Luckily ANSYS has a range of multi-physics elements that can solve use either weak or strong coupling to solve a host of piezo or MEM-related problems (static, transient, modal, harmonic).  Some codes allow for this kind of coupling but either require you to write your own governing equations or pay for a bunch of modules to access.

If you have the ANSYS Enterprise-level license you can download a free extension that exposes all of these properties in the Mechanical GUI.  No scripting, no compiling, just straight-up menu clicks.

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Using this extension you can define the full complex piezoelectric matrix, couple it with an anisotropic elasticity matrix, and use frequency dependent losses to capture the actual response of your structure.  Or if you want you can use simplified material definitions to get the best approximation possible (especially if you’re lacking a full material definition from your supplier).

 

Long story short…there are a lot of simulation products out there.  Pretty much any of them should be able to handle the basics (single part, structural/thermal, etc).  What differentiates the tools is in how easy it helps you implement more real-world conditions/physics into your analysis.  Software can be expensive, and it’s important that you don’t paint yourself into a corner by using a single point-solution or low-end tool.

Silicon Desert Insider: Are you ready for artificial intelligence to change your business?

Artificial intelligence has been a Science Fiction staple for decades, and has been the focus of much marketing hype more recently.  While all this was going on however, AI sort of happened. It is here, it is part of our every day, and “Are you ready for artificial intelligence to change your business?”  This is one of those fundamental technology shifts that impacts everything, and smart business will understand and adapt.

Phoenix Business Journal: ​Automation is here and we need to pay attention

People talk about automation, mostly with respecte to manufacturing, like it is something that is comming.  But “Automation is here and we need to pay attention.” If you don’t understand how computer software, robotics, and sensors are changing every aspect of our lives, odds are you will miss how it will change your business.

Installing a Metal 3D Printer: Part 3A (Safety: Risks)

Download all 5 parts of this series as a single PDF here.

What are the safety risks in laser powder bed fusion metal 3D printing?

This is the first half of the 3rd post in a series of 5 on things we learned installing a metal 3D printer (laser powder bed fusion). Links to previous posts are below:

The most important discussions around installing and operating a metal 3D printer involve safety. The requirements can be difficult to pin down since they depend on several things: whether you are using reactive or non-reactive alloys (read a previous post on this subject here), the risk perception of your local building safety director and fire marshal, local regulations (and exceptions) and the volume of material you are dealing with. As with all things safety and more so because of how nascent metal 3D printing technology is, I list a few disclaimers at the bottom of this page.

There is so much to say about safety in this process that half-way through writing this post, it became clear it would not fit in one post. Therefore, I have split the content into two: in this post (3A) I talk about the risks: where they come from and why they matter. In the next post (3B), I will discuss how these risks can be mitigated.

1. Sources of Risk

Broadly speaking, I like to think of two sources of risk in this process since as an operator of these machines you have to think differently about how you interact with these sources.

1.1 Metal Powder

Metal 3D printing involves fusing together powder in a bed. Typical metal powders used for laser based 3D printing are spherical in shape and range from 10-70 microns in diameter, as shown in Figure 1. At this size, a metal can be prone to fire and explosion (under the right circumstances) and there is also the physiological concern of long-term inhalation of, and contact with, these powders. The powder also has a long life cycle and requires human interaction at many steps – from arriving in a container (as shown in Figure 2), through multiple recycling steps through final disposal. These risks come into play just when handling the powder (independent of its use in the process) – an additional risk comes from the melting process itself.

Fig 1. Typical powder particle size distribution is in the range of 10-70 microns for the laser powder bed fusion process.
Fig 2. Metal powders are delivered and stored in plastic containers such as the one shown above

1.2 The Laser Fusion Process

The powder in the bed described before is fused together into a solid using a laser that locally melts the powder one layer at a time. This is conducted in an inert atmosphere (Argon or Nitrogen) and is the second source of risk since these gases can displace Oxygen from a closed environment. Additionally, the process of laser melting of metals creates vaporized soot (see video below), some of which deposits on the process chamber and in the extraction module and filter. The smoke particles can be even finer than the powder itself, and need to be cleaned out with care on a regular basis.

2. Risks

There are 4 main risks arising from the laser powder bed fusion process: fire and explosion, powder inhalation and contact, inert gas asphyxiation and the environmental impact of the wastes generated.

2.1 Fire and Explosion

In May 2014, OSHA cited a 3D printing company for 10 violations deriving from the workplace safety standards surrounding the operation of a metal 3D printer (including not having the proper Class D fire extinguisher). The disregard of multiple safety measures during a routine build setup procedure resulted in a fire which caused life-threatening burns to the operator of the printer. While this incident was the result of gross negligence, it is nonetheless a cautionary tale that should drive us to understand the fundamental reasons why a metal 3D printer can cause fires and to appreciate the underlying reasons for why suppliers recommend the safety measures they do.

Fire and explosion require a combination of conditions as shown in the commonly cited image below used by OSHA and other agencies to communicate risks of powder handling.
As shown in Fig. 3, when handling powder in ambient atmospheres (with oxygen), all that is needed is a suitable ignition source to initiate a fire. Further, if this occurs in the presence of a dust cloud with many particles dispersed in a contained area (such as a small room or an air duct), this could lead to a more damaging explosion.

Fig 3. The oft cited fire triangle and explosion pentagon. Users of powder based metal 3D printing are often working with 2 of the 3 elements in the triangle and the key is to avoid the third.
  • Fire: When handling metal powder, the user needs to be aware that she/he already has 2 of the 3 requirements of a fire met and the main aim must be to ensure protection against any ignition source. There are several sources that could cause an ignition, the most likely one for a user of a metal 3D printer is static electricity. Additionally, it is possible that a fire can be initiated by hot surfaces, flames, hot gases and particles, mechanically generated sparks and strayelectrical currents.
  • Explosion: With regard to explosions, in addition to the 3 requirements above, dust clouds in contained areas can exacerbate any ignition to a much larger impact within milliseconds. Therefore, the prevention of the formation of metal dust clouds (as unlikely as that may seem), is of paramount importance.

In addition to the requirements above, there are levels associated with each requirement that need to be met together for an actual fire or explosion to occur. The risk of ignition increases with reducing particle diameter and given a certain particle size, the most significant factor governing risk is the nature of the metal. Reactive metals (Aluminum alloys, Titanium and its alloys, as well as smoke particles from both reactives and non-reactives) pose much higher risk than non-reactive metals (steels, Inconels, bronze, Cobalt Chrome alloys) – this is a subject I wrote about in more detail in a previous post.

2.2 Powder Inhalation & Contact

As discussed before, most metal 3D powder particles range in size from 10-70um. This is at the very edge of what is considered respirable and damaging to our lungs. While contact physically is to be avoided since it may initiate irritation and potential dermatitis, there is greater concern about the long-term inhalation exposure risks of these powders. Particles of the size range in this process can get deposited in the tracheo-bronchial region per Jenson [1] and Goldich [2]. Ultimately, these particles are discharged from the body or swallowed, but effects of long term exposure for the wide range of metals and alloys is not fully studied – which is why suppliers insist on respirators (more on that in the next post). It is worth pointing out though, from the work published by Jenson and Goldich, that it appears that while metal 3D printing powders are small enough to travel past the nasal cavity if inhaled, their sizes are large enough that respiratory damage in the lungs is highly unlikely – only particles under 2 microns are at risk of making it all the way to the alveoli and causing lung disease [2].

Fig 4. The human respiratory system. Particles in the 20-100 micron range, if inhaled, can make it to the trachea and bronchial regions [1, 2]  (Image Credit – public domain: National Institute of Health: National Heart, Lung and Blood Institute)

2.3 Inert Gas Asphyxiation

Inert gases are used in laser metal 3D printers to reduce the reactivity of the metal for processing purposes. Most metal 3D printers either use Nitrogen or Argon. Inert gas asphyxiation is the main risk due to oxygen being displaced by either of these gases that have leaked for some reason. Since both gases are not detectable by humans, victims do not realize that they are inhaling air depleted of oxygen and as a result this can have a serious impact. The human body is used to atmospheric percentages of oxygen (21%) and values below 19.5% can be harmful and are defined as oxygen-deficient per OSHA [3]. Thus, any user of nitrogen or argon gas (and this applies not just to any process using inert gases), especially in small spaces such as a closed room, needs to be aware of this risk and protect against it.

2.4 Environmental Impact

A key challenge with powder based processes lies in collecting and disposing the stray or “fugitive” powder from different locations such as the tool, PPE, containers and vacuum systems into temporary storage, during which the above risks of fire/explosion and inhalation remain. Additionally, the storage typically results in loose powder and solid waste as well as water with powder particles, both of which need to be disposed into the outside world and could pose an environmental hazard. I will discuss this further in a future post, when I attempt to look at some of the environmental aspects around this technology.

Fig 5. Metal powder settled at the bottom of the water column in the wet separator (vacuum cleaner). Where does it go next?

3. Disclaimers

  • This is intended to supplement the supplier training you must receive before using the equipment and not meant to replace it – in case of conflicting information, your supplier’s training and equipment requirements override any discussion here. PADT assumes no legal responsibilities for any decisions or actions taken by the readers of this document.
  • My personal experience derives specifically from the use of Laser-based metal 3D printing tools, specifically Concept Laser’s MLab Cusing R equipment. I expect majority of this information to be of use to users of other laser based powder bed fusion metal systems and to a lesser extent to Electron Beam systems, but have no personal experience to vouch for this.
  • Local, state and federal regulations vary, and are important – partner with your local fire marshal (or equivalent authority) as a starting point and take them along with you every step of the way. If in the US, familiarize yourself in particular with OSHA’s guidance on dust explosions [4] and NFPA 484 [5], the National Fire Protection Association’s standard for combustible metals (links below).

4. References

  1. J.M. Benson, “Safety considerations when handling metal powders,” Southern African Institute of Mining and Metallurgy, 2012
  2. R. G. Goldich, “Fundamentals of Particle Technology,” Chapter 15, Midland IT and Publishing, UK, 2002
  3. OSHA on Oxygen Deficiency
  4. OSHA’s Guidance on Dust Explosions
  5. National Fire Protection Association’s standard for combustible metals, NFPA 484
  6. D. Bhate, “Reactive and Non-Reactive Metal Alloys in Laser-based Powder Bed Fusion,” PADT Blog Post, 2016

Acknowledgements

Thank you to Perry Harlow-Leggett, the AM team at UL whose articles and webinars I have benefited from, and all the folks behind the scenes at OSHA and NFPA.

~

Continue to Part 3B here, where I address mitigation strategies to address the risks described in this post. In the meantime, please read my prior posts below if you haven’t already, or send your inputs to me via message on LinkedIn. Thank you!

Stratasys – PolyJet Agilus 30 Webinar

Introducing New PolyJet Material: Agilus30

PADT is excited to introduce the newest polyjet material available from Stratasys, Agilus30! Agilus30 is a superior Rubber-like PolyJet photopolymer family ideal for advanced design verification and rapid prototyping.

Get more durable, tear-resistant prototypes that can stand up to repeated flexing and bending. With a Shore A value of 30 in clear or black, Agilus30 accurately simulates the look, feel and function of Rubber-like products. 3D print rubber surrounds, overmolds, soft-touch coatings, living hinges, jigs and fixtures, wearables, grips and seals with improved surface texture.

Agilus30 has applications in a number of areas, including:

  • Medical Models

  • Tooling needing rubber-like characteristics

  • Consumer Goods

  • Sporting Goods

  • General Prototyping

  • Overmolding & many more!

Want to know more about PolyJet’s toughest flexible material to date? 

Join PADT’s 3D Printing Application Engineer James Barker along with Stratasys Materials Business Manager Ken Burns for a presentation on the various benefits and attributes that Agilus30 has to offer, which machines are compatible with it, and how companies are making use of it’s unique capabilities.

Phoenix Business Journal: ​Technical training for employees is changing, is that a good thing?

Like so much else these days, the way that we deliver training to employees has changed over time to take advantage of new technologies. This is especially true for technical training on how to use hardware and software. The traditional classroom approach has been replaced with online and on-demand training. In “Technical training for employees is changing, is that a good thing?” I put on my curmudgeon hat and talk about why the traditional way has advantages that outway the negatives.

Phoenix Business Journal: ​5 things to think about when implementing a database product at your business

If you have ever implemented a Database appcliation at your business you know it can be a pain.  In “​5 things to think about when implementing a database product at your business” I go over some lessons that we have learned over time to make the whole process and outcome better.

3D Metal Printing: A Role in Military Fleet Readiness

The project to keep a 1944 P-51 Mustang flying was covered again, this time in 3D Metal Printing Magazine (Pg 23-33).   Concept Laser worked with PADT to reverse engineer and print the exhaust manifold from a P-51 to keep it flying.  Unlike the other article and video on the project, this reporter used this example as a great way to look at the readiness of military aircraft, and not just antique planes.

As PADT’s Rey Chu says ““This was a great exercise that’s suitable for numerous military applications and very relevant to the future use of 3D metal printing to maintain fleets in the field,” Chu says. “Maintaining spare-parts inventory has become a significant challenge, for example, to the Air Force. Additive manufacturing could be the solution.”

PADT Startup Spotlight – The Speed of Simulation

The Speed of Simulation  with Velox Motorsports

With thoroughly engineered components including the use of Finite Element Analysis (FEA), thermodynamics, heat transfer, and Computational Fluid Dynamics (CFD), PADT Startup Spotlight Velox Motorsports strives to produce aftermarket parts that can effectively outperform the factory components.

Join Velox Co-Owners Eric Hazen and Paul Lucas for a discussion on what they use ANSYS simulation software for and how they have benefited from it’s introduction into their manufacturing process.

This webinar will focus on two projects within which the engineers at Velox have see the impact of ANSYS, including:

Using Finite Element Analysis (FEA) to reverse engineer a Subaru fork, find the cause of failure and develop an improved replacement part.

Using Computational Fluid Dynamics (CFD) to rub a shape sensitivity study on Nissan GT R strakes, and develop a replacement that increases down-force without significantly increasing drag.

ANSYS 18 – SpaceClaim Webinar

In its latest release, ANSYS SpaceClaim further integrates its ease of use and rapid geometry manipulation capabilities into common simulation workflows. From large changes to behind the scenes enhancements, you’ll notice efficiency improvements across the board. You’ll save time automating geometry tasks with the expanded recording and replay capabilities of SpaceClaim’s enhanced scripting environment.

Join PADT’s Application Engineer Tyler Smith  for this webinar and learn about several improvements that are guaranteed to save time, enhance your designs and improve overall usability. We’ll cover:

  • Continued development of SpaceClaim’s scripting environment. With expanded recording capabilities and replayability of scripts on model versions, you’ll save time in the steps needed to automate geometry tasks.

  • Faceted data optimization and smoothing enhancements. You can greatly simplify and smooth topology optimized STL data for downstream printing, while preserving the integrity of localized regions.

  • Lattice Infilling for additive manufacturing. The Infilling functionality has greatly expanded to include several lattice infill types, all with custom options to ensure your 3-D printed component has an ideal strength-to-weight relationship.

  • Exploration of inner details of a model with the new fly-through capability. Without hiding components or using cross sections, this capability provides graphical feedback at your fingertips while making it even more enjoyable to work in a 3-D environment.

Kidneys and Child Hearts – Our Recent Real World Experiences with 3D Printing in Medicine

Mostly we make boxes.  Pretty boxes but the bulk of what we 3D Print is some sort of plastic box that people stuff electronics in to. Most of the time we also don’t really know what customers do with the objects we make for them.  But every once in a while you get involved in a project that really makes a difference. That could not be more true than two recent medical applications for 3D Printing that we worked on with Intermountain Healthcare (IHC) in Salt Lake City, Utah.

KSL, a local TV station, did a story on our IHC was deploying 3D Printing to produce better outcomes for their patients. You can view the story here.

PADT was fortunate enough to be part of two of the cases mentioned in the story.  The first was a St George man who was feeling some pain in his back. He had a scan and they found 12 kidney stones.  On top of that, his kidney was not in the right place and was distorted.  PADT helped print a model of the scan so that the doctors could just get a real feel for what they were dealing with, and then plan the surgery.

The second situation really pulled at our heart strings.  A 10 year old boy needs heart surgery and its a complicated problem. They need a model fast so we worked with Stratasy to quickly print an accurate model so that the sugeons could come up with a plan. We still have not heard how it went, they are scheduling things, but the feedback from the team was that the 3D model was extremely helpful.  We are talking life saving.

Both of these recent situations build on years of examples where we have worked the doctors and their technical assistance to convert scans of patients into usable 3D Models. If you are in the surgery or surgery planning space and want to learn more about how accurate 3D models printed directly from scan data can be used to improve patient outcome, contact PADT at info@padtinc.com and we will connect you with our 3D Printing team.

How-To: Creating Matching Faces on Touching Parts with ANSYS SpaceClaim

Sometimes you want to take two parts and and prepare them for meshing so that they either share a surface between them, or have identical but distinct surfaces on each part where they touch.  In this simple How-To, we share the steps for creating both of these situations so you can get a continuous mesh or create a matching contact surface in ANSYS Mechanical.

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How-To: Connecting Shells Elements in Surface Models with ANSYS SpaceClaim and ANSYS Mechanical

By using the power of ANSYS SpaceClaim to quickly modify geometry, you can set up your surface models in ANSYS Mechanical to easily be connected.  Take a look in this How-To slide deck to see how easy it is to extend geometry and intersect surfaces.

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Silicon Desert Insider: Self-driving cars are driving big changes in tech

Everywhere you drive in Phoenix you see autonomous cars being tested.  These are cool and all, but they also are a sign of a whole new boom in technological change. In “Self-driving cars are driving big changes in tech” I go over some of the key disruptive innovations that will be driven by these new vehicles.

Phoenix Business Journal: 3 keys to success for smart home devices

When Cox Communications asked us to be part of its local Smart Home Tour I said yes for one simple reason: I wanted to see a truly connected home. in “3 keys to success for smart home devices” I discuss some of the lessons I learned about IoT devices that actually work in the home.