Increase your throughput and reduce manufacturing costs

Fast, easy to use lightweighting for structural analysis is now only a few clicks away thanks to the introduction of Topology Optimization in ANSYS 18.

Engineers who use Finite Element Analysis (FEA) can reduce weight, materials, and cost without switching tools or environments. Along with this, Topology Optimization frees designers from constraints or preconceptions, helping to produce the best shape to fulfill their project’s requirements.

Topology Optimization also works hand-in-hand with Additive Manufacturing; a form of 3D printing where parts are designed, validated, and then produced by adding layers of material until the full piece is formed. Pairing the two simply allows users to carry out the trend of more efficient manufacturing through the entirety of their process.

Join PADT’s simulation support manager Ted Harris for a live presentation on the full
benefits of introducing Topology Optimization into your manufacturing process. This webinar will cover:

  • A brief introduction into the background of Topology Optimization and Additive Manufacturing, along with an overview of it’s capabilities

  • An explanation of the features available within this tool and a run through of it’s user interface and overall usage

  • An in-depth look at some of the intricacies involved with using the tool as well as the effectiveness of it’s design workflow

Thoughts from my day in a smart home – the importance of connecting right

When I was asked to take part in a demonstration put on by one of our local communication companies, Cox Communications, showing off what a “smart home” looks like, I of course said yes.  I love gadgets, and smart gadgets more.  On top of that it was another chance to evangelise on the power of 3D Printing.  And I got to hang out in a brand new luxury condo in Downtown Phoenix, a post kid lifestyle change that is very appealing.  Plus we deal with customers designing and improving Internet of Things (IoT) devices all the time, and this is the perfect chance to see such products in action.

So I packed up one of our Makerbots, none of our Fortus machines fits in the back of my Prius, and headed downtown.  The first thing that shocked me was that I had the printer, my iPhone, iPad, and laptop connected to their network in about one minute.  The printer showed up on the Makerbot Print app on my iPad and I was printing a part in about three minutes.

My station, showing off 3D Printing in the home.

The whole point of the demonstration was to show how the new high-speed Internet offering from Cox, Gigablast, can enable a true smart home.  So I was focused on the speed of the connection to the Internet, which was fast.  What I didn’t get till I connected was that the speed and bandwidth of the WiFi in the house was even more important.

When everything was connected, we had 55 devices on the local network talking to each other and the Internet. At one point I was downloading a large STL file to the printer while on a teleconference on my iPhone and my “roommate” was giving a violin lesson to one of his students in Canada.

Oh, and the roomba started to vacuum the floor. On the balcony someone was giving a golf lesson and a doctor was diagnosing a patient in the master bedroom.  That was on top of the smart kitchen gadgets.  And it all worked.  Yes, it all worked.

I’m trying to convey shock and surprise because the reality is that nine times out of ten when I show up for some event, at a customer, or at a friends house and we try and connect things to the internet… it doesn’t work.  If you are a technical guy you know that feeling when your vacation or visit for dinner turns into an IT house call.  All I could think of was how awesome it was that everything worked and it was fast.

So I went to work printing little plastic Arizona style houses with COX on the roof. And then a reporter showed up. “3D Printing, interesting.  Hmmmm…  they are cool and all but really, what does that have to do with a smart house?”  Damn reporters and their questions.  I was still reveling in the fact that everything worked so well, I hadn’t taken to time to think about the “so what.”

Then I thought about it.  3D Printing in the home is just now starting to take off, and the reason why is actually high-speed internet connections. If you wanted a 3D Printer in your home in the past you needed the printer, a high end computer, and some good 3D modeling software on that computer.  Basically you had to create whatever you wanted to make.  Unless you are a trained engineer, that may not be so easy.

My “house” that I was printing at the invent sits on the cloud in my Thingiverse account.

But with a well connected home you have access to places like Thingiverse and Grabcad to download stuff you want to print.  And if you do want to create your own, you can go to Tinkercad or Onshape and use a free online 3D modeler to create your geometry.  All over the web, even on a pad, phone (I don’t recommend trying to do modeling on a phone, but it does work), or on a basic computer.  The files are stored in the cloud and downloaded directly to your printer.  No muss, no fuss.  All you need is a reliable and fast connection to the internet and in your home.

High speed internet and a smart 3D printer makes anyone a maker.

And when we had a three hour break, I went downstairs to a coffee shop on the ground floor of the condo and worked, while monitoring my builds using the camera in the smart 3D Printer.

Pretty cool when you step back and think about how far we have come from that first Stereolithography machine that PADT bought in 1994.  We had to use floppy disks to get the data from our high-end Unix workstation to the machine.  Now it sits on the web and can be monitored.

This may be what we have been waiting for when it comes to 3D Printers in the home moving beyond that technologists and makers.

I’ve been focused on my experience with the 3D printing in the smart home, but there was a lot more to look at.  Check out these stories to learn more:

Phoenix Business Journal: Cox shows off a smart home with 55 connected devices and fast gigabyte internet

The Arizona Republic: Cox ‘smart home’ in Phoenix displays future at the push of a button

I also did a piece for the Phoenix Business Journal while I was at the event on “3 keys to success for smart home devices” based on what I learned while playing with the other devices in the smart home.

All and all a good day.  Oh, and being a 10 minute walk from my favorite pub made the idea of living downtown not such a bad idea, which doesn’t have much to do with high speed internet, connected devices, or 3D Printing.  But one of my goals was to check out post-child urban living…

 

 

Installing a Metal 3D Printer: Part 1 (Equipment)

concept-laser-mlab
Fig 1. Concept Laser MLab Cusing R in PADT’s Metal 3D Printing Lab

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

What equipment does one need for metal 3D printing? 

This is the first in a five-part series that brings together the different lessons we learned installing our first metal printer, a Concept Laser MLab Cusing R at PADT, shown in Figure 1. In this post I list the different equipment needed to enable metal 3D printing end-to-end, along with a brief explanation of its purpose. In subsequent posts, I deal with (2) Facilities, (3) Safety, (4) Environmental & (5) Housekeeping aspects of the technology. I hope this information adds to the conversation in a meaningful way and help those who are thinking about, or in the process of installing a metal 3D printer.

The specifics of some of this information will vary depending on the equipment and materials you handle, but my hope is the themes covered here give you a sense of what is involved in installing a metal 3D printer to aid in your preparation for doing the same and for having good discussions with your equipment supplier to ensure these are addressed at a minimum.

One way to look at classifying the equipment needed (beyond the obvious metal 3D printer!) is by its purpose, and I do so here by dividing it into two broad categories: Ancillary Equipment (necessary to the printing itself) and Post-Processing Equipment (focused on the part).

At the outset, it is crucial that the difference between reactive and non-reactive metal alloys be comprehended since a lot of the use of the equipment differs depending on what kind of metal alloy is being used. A previous blog post addressed these differences and these terms will be used in the following sections.

1. Ancillary Equipment

1.1 Wet Separator

wet-separator-ruwac
Fig 2. Wet separator used to vacuum fugitive powder

The wet separator is essentially a vacuum cleaner that is designed to safely vacuum stray (“fugitive”) metal powders that cannot be cleaned up any other way. When dealing with powders, the typical recommendation is to first brush whatever you can into the overflow bin so you can reuse it. The next step is to try and wipe up powder with a moist lint-free cloth (to be covered in the housekeeping post). The wet separator has a water column that passivates the metal powder and renders it non-reactive to allow for easier disposal (to be covered in the environmental post). Wet separators require a significant amount of maintenance, particularly when dealing with reactive metals like Titanium and Aluminum alloys, where the supplier recommends the wet separator be cleaned out on a daily basis. At least one company has developed a kit to help with wet separator cleaning – which gives you an indication of how significant of an issue this is. Most suppliers provide a wet separator along with their equipment.

1.2 Glove Box

glove-box
Fig 3. Glove box used to interact with the build chamber in a safe manner, and in an inert atmosphere for reactive metals

A glove box is a useful piece of equipment for dealing with reactive metals in particular. The glove box allows an operator to manage all the powder handling in the build chamber to be done in a closed environment. For non-reactive metals this is not a necessary piece of equipment but it is highly recommended for reactive metals. The glove box when used in concert with reactive metals will allow for inert gas flushing out of oxygen to low PPM levels prior to operator intervention, and also includes grounding connections for the box to the machine. The nice thing about having a glove box is it reduces the amount of time you need to have a respirator on by allowing you to add powder and unpack builds in a closed environment. The glove box may also be integrated into the machine itself – ours is a stand alone device on wheels that we roll over to the machine when we need it.

1.3 Powder Sieve

Unless you plan on disposing all the powder in each build after it is completed, you need a sieve to separate out the larger particles and contaminants from the powder you wish to reuse in subsequent builds. The sieves are also typically provided with the machine and can be enabled with inerting capability (as shown in Fig 4 on the left, or as shown on the right, come as a small desktop unit that can sieve about 3-5 lbs of powder at a time). While the sieve on the left may be used for reactive metal sieving, it is uncertain if one can safely use the desktop sieve for the same, even with grounding the table it sits on and the operator – this is a gray area and I am keen to hear thoughts on this from those that have the expertise/experience in this space.

sieves
Fig 4. Mechanical sieving: (left) for large quantity sieving, (right) tabletop model for smaller quantities

1.4 Ultrasonic Cleaner

ultrasonic-cleaner
Fig 5. Ultrasonic cleaner used to help isolate metal powder trapped inside parts and supports

The purpose of the ultrasonic cleaner is to remove as much trapped powder as possible before the part and the build plate are subjected to any post-processing – this is to minimize the risk of trapped powder getting airborne during downstream processes – which cannot be completely eliminated (which is why PPE should be used all the way through till the final part is in hand after cleaning).

The Ultrasonic cleaner is used twice: first before the parts are removed from the build plate, and again after they are removed. Sometimes I will even use it a third time after all supports have been removed, if the part has internal p. I typically use the 40 kHz and 60 C temperature setting but have not sought to further optimize the parameters at this time.

2. Post-Processing Equipment

2.1 Furnace

Fig 6. Radiation heating furnace with inert gas capability. The Nabertherm 7/H has a maximum temperature of 1280 C, suitable for stress relief.

The purpose of the furnace is to relieve residual stresses built in the parts prior to removing them from the build plate. So this is the first step after the parts and the plate come out of the ultrasonic cleaner. We use a furnace that allows for nitrogen or argon flushing, and place our parts wrapped in stainless steel foil in a gas box. Instructions for heat treatment (time and temperature profile) are typically provided on the technical specifications that come with the material. Metals like stainless steel can be stress relieved in a nitrogen atmosphere but Inconels and Ti6Al4V for example require higher temperatures of between 800-1000 C and argon atmospheres – so you need to be setup for both gases if you are considering running more than 1 metal in your operation.

2.2 Support Removal

All parts are connected to the build plate by between 3-5mm of supports that need to be removed. This is a two step process: the first step involves removing the parts with supports off the build plate, and this is most commonly done with a table saw or a wire EDM. At PADT, we stumbled upon a third way to do this, using an oscillating hand tool and a carbide blade – which works well for small parts (<3″ in X-Y space). It is important to always wear gloves and a supplier recommended (N95 or higher) respirator while removing supports since there could be trapped powder in the supports that was not removed with the Ultrasonic cleaner. The second step is to use hand tools to pry out the supports from the part – this is why it is important to design supports that have weak mechanical connections to the part itself – ideally you can tear them off with hand tools like a perforated sheet of paper [Video below courtesy Bob Baker at PADT, Inc].

2.3 Die Grinder

Fig 7. Die grinder used for removing burrs at the support interfaces on the part

A carbide die grinder is then used to grind away the support-model interface – for tiny parts, this can be achieved with a hand file as well for some parts but is easier to do with a die grinder. For large parts, this need can be eliminated by designing in regions that are to be machined later and aligning these regions with supported regions, so as to reduce the need for finishing on these surfaces.

2.4 Face Milling

This may come as a bit of a surprise, but you also need some way of replenishing the build plates after use so you can re-use the plates – this involves using a face milling technique to remove all the remnant supports on the build plate and take off a thin slice at the top of the build plate, while retaining flatness to within 100 microns (0.004″). Having this capability in-house will greatly speed-up your ability to start successive prints and reduce the need to keep large inventories of build plates [Video below courtesy Bob Baker at PADT, Inc].

2.5 Surface Finishing

A combination of techniques can be used for surface finishing. At a minimum, you must have the ability to do glass bead blasting – this is both for the printed parts, but also for the build plate itself – a bead blasted finish is recommended to improve the adhesion of the first layer of powder to the build plate.

Fig 8. (left) Bead blaster and (right) post-processed build plates, ready for use again

2.6 Other Capabilities

The list above is what I would consider a minimum list of capabilities one needs to get started in metal 3D printing, but is not comprehensive and does not include facility, safety, environmental and housekeeping requirements which I will cover in future posts. Additional CNC equipment for machining metal AM parts, heat treatment and HIP, and superior surface finishing and cleaning techniques are often called upon for metal AM production, but these are highly dependent on application and part design, which is why I have left them out of the above list.

Move on to part 2 of this series where I discuss the facilities requirements for metal 3D printing (electrical, inert gas etc.). Did I miss anything or do you have a better way of doing the things described above? Please send your thoughts to info@padtinc.com, citing this blog post, or connect with me on LinkedIn.

Acknowledgements:
Garrett Garner at Concept Laser, Inc and Bob Baker at PADT, Inc. for their insight and expertise that helped us select and bring in the above capabilities at PADT.

CLICK HERE for part 2

ASU Polytechnique Deploys Robots in Project for 3D Printing Automation for Orbital ATK

Sometimes we run across some great exampls of industry and academia working together and like to share them as examples of win-win partnerships that can move technology forward and give studends a great oportunity.   A current Capstone Design Project by students at ASU Polytechnique is a great example.  It is also an early exmple of what can be done at the brand new Additive Manufacturing Center that was recently opened at the campus.

I’ll let ASU Mecanical Enginering Systems student Dean McBride tell you in his own words:

Orbital ATK in Chandler currently utilizes two Stratasys Dimension SST 1200es printers to prototype various parts with.  These printers print on parts trays, which must be removed and re-inserted into the printer to start new prints.  Wanting to increase process efficiency, Orbital had the desire of automating this 3D printing process during times when employees are not present to run the printers.  After the idea was born, Orbital presented this project to ASU Polytechnic as a potential senior capstone design project.  Shortly after, an ambitious team was assembled to take on the project.

 Numerous iterations of the engineering design process took place, and the team finally arrived at a final solution.  This solution is a Cartesian style robot, meaning the robot moves in linear motions, similar to the 1200es printer itself.  The mechanical frame and structure of the robot have been mostly assembled at this point.  Once assembly is achieved, the team will focus their efforts on the electrical system of the robot, as well as software coding of the micro-controller control system.  The team will be working to fine tune all aspects of the system until early May when the school semester ends.  The final goal of this project is to automate at least two complete print cycles without human interaction.

Here is a picture of the team with the robot they are building along side the Stratasys FDM printer they are automating.

 

Engineering.com: Metal Additive Manufacturing Keeps Legend Flying

What do you do when you want to replace the exhaust on a 1944 P-51D Mustang warbird and you also happen to be a pioneer in additive manufacturing?  You work with Concept Laser and PADT to can and print a replacement stainless steel part.  In “Metal Additive Manufacturing Keeps Legend Flying” Engineering.com details the project that involved blue light scanning and 3D Printing of new metal part in modern Stainless Steel, replacing the three-piece weldment with a single part.

They also did a fantastic video about the effort:

If you would like to learn how PADT can help you reverse engineering your legacy geometry and recreate it using Additive Manufacturing, contact us.

On the Functions of Cellular Structures in Nature

WHY did nature evolve cellular structures?

In a previous post, I laid out a structural classification of cellular structures in nature, proposing that they fall into 6 categories. I argued that it is not always apparent to a designer what the best unit cell choice for a given application is. While most mechanical engineers have a feel for what structure to use for high stiffness or energy absorption, we cannot easily address multi-objective problems or apply these to complex geometries with spatially varying requirements (and therefore locally optimum cellular designs). However, nature is full of examples where cellular structures possess multi-objective functionality: bone is one such well-known example. To be able to assign structure to a specific function requires us to connect the two, and to do that, we must identify all the functions in play. In this post, I attempt to do just that and develop a classification of the functions of cellular structures.

Any discussion of structure in nature has to contend with a range of drivers and constraints that are typically not part of an engineer’s concern. In my discussions with biologists (including my biochemist wife), I quickly run into justified skepticism about whether generalized models associating structure and function can address the diversity and nuance in nature – and I (tend to) agree. However, my attempt here is not to be biologically accurate – it is merely to construct something that is useful and relevant enough for an engineer to use in design. But we must begin with a few caveats to ensure our assessments consider the correct biological context.

1. Uniquely Biological Considerations

Before I attempt to propose a structure-function model, there are some legitimate concerns many have made in the literature that I wish to recap in the context of cellular structures. Three of these in particular are relevant to this discussion and I list them below.

1.1 Design for Growth

Engineers are familiar with “design for manufacturing” where design considers not just the final product but also aspects of its manufacturing, which often place constraints on said design. Nature’s “manufacturing” method involves (at the global level of structure), highly complex growth – these natural growth mechanisms have no parallel in most manufacturing processes. Take for example the flower stalk in Fig 1, which is from a Yucca tree that I found in a parking lot in Arizona.

Figure 1. The flower stalk (before bloom) of a Yucca plant in Arizona with overlapping surface cellular structure (Author’s image)

At first glance, this looks like a good example of overlapping surfaces, one of the 6 categories of cellular structures I covered before. But when you pause for a moment and query the function of this packing of cells (WHY this shape, size, packing?), you realize there is a powerful growth motive for this design. A few weeks later when I returned to the parking lot, I found many of the Yucca stems simultaneously in various stages of bloom – and captured them in a collage shown in Fig 2. This is a staggering level of structural complexity, including integration with the environment (sunlight, temperature, pollinators) that is both wondrous and for an engineer, very humbling.

Figure 2. From flower stalk to seed pods, with some help from pollinators. Form in nature is often driven by demands of growth. (Author’s images)

The lesson here is to recognize growth as a strong driver in every natural structure – the tricky part is determining when the design is constrained by growth as the primary force and when can growth be treated as incidental to achieving an optimum functional objective.

1.2 Multi-functionality

Even setting aside the growth driver mentioned previously, structure in nature is often serving multiple functions at once – and this is true of cellular structures as well. Consider the tessellation of “scutes” on the alligator. If you were tasked with designing armor for a structure, you may be tempted to mimic the alligator skin as shown in Fig. 3.

Figure 3. The cellular scutes on the alligator serve more than just one function: thermal regulation, bio-protection, mobility, fluid loss mitigation are some of the multiple underlying objectives that have been proposed (CCO public domain, Attr. Republica)

As you begin to study the skin, you see it is comprised of multiple scutes that have varying shape, size and cross-sections – see Fig 4 for a close-up.

Figure 4. Close-up of alligator scutes (Attr: Hans Hillewaert, Flickr, Creative Commons)

The pattern varies spatially, but you notice some trends: there exists a pattern on the top but it is different from the sides and the bottom (not pictured here). The only way to make sense of this variation is to ask what functions do these scutes serve? Luckily for us, biologists have given this a great deal of thought and it turns out there are several: bio-protection, thermoregulation, fluid loss mitigation and unrestricted mobility are some of the functions discussed in the literature [1, 2]. So whereas you were initially concerned only with protection (armor), the alligator seeks to accomplish much more – this means the designer either needs to de-confound the various functional aspects spatially and/or expand the search to other examples of natural armor to develop a common principle that emerges independent of multi-functionality specific to each species.

1.3 Sub-Optimal Design

This is an aspect for which I have not found an example in the field of cellular structures (yet), so I will borrow a well-known (and somewhat controversial) example [3] to make this point, and that has to do with the giraffe’s Recurrent Laryngeal Nerve (RLN), which connects the Vagus Nerve to the larynx as shown in Figure 5, which it is argued, takes an unnecessarily long circuitous route to connect these two points.

Figure 5. Observe how the RLN in the giraffe emerges from the Vagus Nerve far away from the thorax: a sub-optimal design that was likely carried along through the generations in aid of prioritizing neck growth (Attr: Vladimir V. Medeyko)

We know that from a design standpoint, this is sub-optimal because we have an axiom that states the shortest distance between two points is a straight line. And therefore, the long detour the RLN makes in the giraffe’s neck must have some other evolutionary and/or developmental basis (fish do not have this detour) [3]. However, in the case of other entities such as the cellular structures we are focusing on, the complexity of the underlying design principles makes it hard to identify cases where nature has found a sub-optimal design space for the function of interest to us, in favor of other pressing needs determined by selection. What is sufficient for the present moment is to appreciate that such cases may exist and to bear them in mind when studying structure in nature.

2. Classifying Functions

Given the above challenges, the engineer may well ask: why even consider natural form in making determinations involving the design of engineering structures? The biomimic responds by reminding us that nature has had 3.8 billion years to develop a “design guide” and we would be wise to learn from it. Importantly, natural and engineering structures both exist in the same environment and are subject to identical physics and further, are both often tasked with performing similar functions. In the context of cellular structures, we may thus ask: what are the functions of interest to engineers and designers that nature has addressed through cellular design? Through my reading [1-4], I have compiled the classification of functions in Figure 6, though this is likely to grow over time.

Figure 6. A proposed classification of functions of cellular structures in nature (subject to constant change!)

This broad classification into structural and transport may seem a little contrived, but it emerges from an analyst’s view of the world. There are two reasons why I propose this separation:

  1. Structural functions involve the spatial allocation of materials in the construction of the cellular structures, while transport functions involve the structure AND some other entity and their interactions (fluid or light for example) – thus additional physics needs to be comprehended for transport functions
  2. Secondly, structural performance needs to be comprehended independent of any transport function: a cellular structure must retain its integrity over the intended lifetime in addition to performing any additional function

Each of these functions is a fascinating case study in its own right and I highly recommend the site AskNature.org [1] as a way to learn more on a specific application, but this is beyond the scope of the current post. More relevant to our high-level discussion is that having listed the various reasons WHY cellular structures are found in nature, the next question is can we connect the structures described in the previous post to the functions tabulated above? This will be the attempt of my next post. Until then, as always, I welcome all inputs and comments, which you can send by messaging me on LinkedIn.

Thank you for reading!

References

  1. AskNature.org
  2. Foy (1983), The grand design: Form and colour in animals, Prentice-Hall, 1st edition
  3. Dawkins (2010), The greatest show on earth: the evidence for evolution, Free Press, Reprint of 1st edition
  4. Gibson, Ashby, Harley (2010), Cellular Materials in Nature and Medicine, Cambridge University Press; 1st edition
  5. Ashby, Evans, Fleck, Gibson, Hutchinson, Wadley (2000), Metal Foams: A Design Guide, Butterworth-Heinemann, 1st edition

Cellular Design Strategies in Nature: A Classification

What types of cellular designs do we find in nature?

Cellular structures are an important area of research in Additive Manufacturing (AM), including work we are doing here at PADT. As I described in a previous blog post, the research landscape can be broadly classified into four categories: application, design, modeling and manufacturing. In the context of design, most of the work today is primarily driven by software that represent complex cellular structures efficiently as well as analysis tools that enable optimization of these structures in response to environmental conditions and some desired objective. In most of these software, the designer is given a choice of selecting a specific unit cell to construct the entity being designed. However, it is not always apparent what the best unit cell choice is, and this is where I think a biomimetic approach can add much value. As with most biomimetic approaches, the first step is to frame a question and observe nature as a student. And the first question I asked is the one described at the start of this post: what types of cellular designs do we find in the natural world around us? In this post, I summarize my findings.

Design Strategies

In a previous post, I classified cellular structures into 4 categories. However, this only addressed “volumetric” structures where the objective of the cellular structure is to fill three-dimensional space. Since then, I have decided to frame things a bit differently based on my studies of cellular structures in nature and the mechanics around these structures. First is the need to allow for the discretization of surfaces as well: nature does this often (animal armor or the wings of a dragonfly, for example). Secondly, a simple but important distinction from a modeling standpoint is whether the cellular structure in question uses beam- or shell-type elements in its construction (or a combination of the two). This has led me to expand my 4 categories into 6, which I now present in Figure 1 below.

Figure 1. Classification of cellular structures in nature: Volumetric – Beam: Honeycomb in bee construction (Richard Bartz, Munich Makro Freak & Beemaster Hubert Seibring), Lattice structure in the Venus flower basket sea sponge (Neon); Volumetric – Shell: Foam structure in douglas fir wood (U.S. National Archives and Records Administration), Periodic Surface similar to what is seen in sea urchin skeletal plates (Anders Sandberg); Surface: Tessellation on glypotodon shell (Author’s image), Scales on a pangolin (Red Rocket Photography for The Children’s Museum of Indianapolis)

Setting aside the “why” of these structures for a future post, here I wish to only present these 6 strategies from a structural design standpoint.

  1. Volumetric – Beam: These are cellular structures that fill space predominantly with beam-like elements. Two sub-categories may be further defined:
    • Honeycomb: Honeycombs are prismatic, 2-dimensional cellular designs extruded in the 3rd dimension, like the well-known hexagonal honeycomb shown in Fig 1. All cross-sections through the 3rd dimension are thus identical. Though the hexagonal honeycomb is most well known, the term applies to all designs that have this prismatic property, including square and triangular honeycombs.
    • Lattice and Open Cell Foam: Freeing up the prismatic requirement on the honeycomb brings us to a fully 3-dimensional lattice or open-cell foam. Lattice designs tend to embody higher stiffness levels while open cell foams enable energy absorption, which is why these may be further separated, as I have argued before. Nature tends to employ both strategies at different levels. One example of a predominantly lattice based strategy is the Venus flower basket sea sponge shown in Fig 1, trabecular bone is another example.
  2. Volumetric – Shell:
    • Closed Cell Foam: Closed cell foams are open-cell foams with enclosed cells. This typically involves a membrane like structure that may be of varying thickness from the strut-like structures. Plant sections often reveal a closed cell foam, such as the douglas fir wood structure shown in Fig 1.
    • Periodic Surface: Periodic surfaces are fascinating mathematical structures that often have multiple orders of symmetry similar to crystalline groups (but on a macro-scale) that make them strong candidates for design of stiff engineering structures and for packing high surface areas in a given volume while promoting flow or exchange. In nature, these are less commonly observed, but seen for example in sea urchin skeletal plates.
  3. Surface:
    • Tessellation: Tessellation describes covering a surface with non-overlapping cells (as we do with tiles on a floor). Examples of tessellation in nature include the armored shells of several animals including the extinct glyptodon shown in Fig 1 and the pineapple and turtle shell shown in Fig 2 below.
    • Overlapping Surface: Overlapping surfaces are a variation on tessellation where the cells are allowed to overlap (as we do with tiles on a roof). The most obvious example of this in nature is scales – including those of the pangolin shown in Fig 1.
Figure 2. Tessellation design strategies on a pineapple and the map Turtle shell [Scans conducted at PADT by Ademola Falade]

What about Function then?

This separation into 6 categories is driven from a designer’s and an analyst’s perspective – designers tend to think in volumes and surfaces and the analyst investigates how these are modeled (beam- and shell-elements are at the first level of classification used here). However, this is not sufficient since it ignores the function of the cellular design, which both designer and analyst need to also consider. In the case of tessellation on the skin of an alligator for example as shown in Fig 3, was it selected for protection, easy of motion or for controlling temperature and fluid loss?

Figure 3. Varied tessellation on an alligator conceals a range of possible functions (CCO public domain)

In a future post, I will attempt to develop an approach to classifying cellular structures that derives not from its structure or mechanics as I have here, but from its function, with the ultimate goal of attempting to reconcile the two approaches. This is not a trivial undertaking since it involves de-confounding multiple functional requirements, accounting for growth (nature’s “design for manufacturing”) and unwrapping what is often termed as “evolutionary baggage,” where the optimum solution may have been sidestepped by natural selection in favor of other, more pressing needs. Despite these challenges, I believe some first-order themes can be discerned that can in turn be of use to the designer in selecting a particular design strategy for a specific application.

References

This is by no means the first attempt at a classification of cellular structures in nature and while the specific 6 part separation proposed in this post was developed by me, it combines ideas from a lot of previous work, and three of the best that I strongly recommend as further reading on this subject are listed below.

  1. Gibson, Ashby, Harley (2010), Cellular Materials in Nature and Medicine, Cambridge University Press; 1st edition
  2. Naleway, Porter, McKittrick, Meyers (2015), Structural Design Elements in Biological Materials: Application to Bioinspiration. Advanced Materials, 27(37), 5455-5476
  3. Pearce (1980), Structure in Nature is a Strategy for Design, The MIT Press; Reprint edition

As always, I welcome all inputs and comments – if you have an example that does not fit into any of the 6 categories mentioned above, please let me know by messaging me on LinkedIn and I shall include it in the discussion with due credit. Thanks!

Phoenix Business Journal: Installing a metal 3-D printer was a lesson on working with regulators

While installing our new metal 3D Printer we learned a couple of important lessons on working with local inspectors.  In “Installing a metal 3-D printer was a lesson on working with regulators” we share what we captured.

3D Printing Student Projects at PADT: Visit our Open House to Learn More (Thursday, March 2, 5pm)

Thursday, March 2 is PADT’s annual SciTech Festival Open House, from 5-8pm (click HERE to register). This year, three student groups working on a range of projects will be present to showcase their work, all of which involved some level of 3D printing. Please bring friends and families to meet and discuss ideas with these students from our community.

Formula SAE Team (Arizona State University)

ASU’s Formula SAE team will be onsite with their 2016 cardemonstrating specifically how they used 3D printing to manufacture the functional intake manifolds on these cars. What is specifically interesting is how they have modified their manifold design to improve performance while leveraging the advantages of 3D printing, and also they have evaluated multiple materials and processes over the recent years (FDM, SLS).

Prosthetic Arm Project (BASIS Chandler)

Rahul Jayaraman will be back to discuss how he and 30 students at BASIS Chandler manufactured, assembled and delivered about 20 prosthetic hands to an organization that distributes these to children in need across the world. Rahul and PADT were featured in the news for this event.

Cellular Structures in Nature (BASIS Chandler)

A BASIS Chandler High School senior, Amy Zhang, just started her Senior Research Project with PADT, focusing on a project at the intersection of biology and 3D printing, investigating cellular structures that occur on surfaces in nature, like the wing of a dragonfly or the shell on a turtle or the encasing of a pineapple – all of which are comprised of cellular geometries. Using 3D scanning, image analysis and mathematical methods, Amy hopes to develop models for describing these structures that can then be used in developing design principles for 3D printing. You can learn more on Amy’s blog: http://shellcells.blogspot.com/

 

 

Tour ConceptLaser’s Metal 3D Printing lab at AeroDef

Attending AeroDef this year in Fort Worth? Make sure you register to tour Concept Laser on March 6th before AeroDef! You’ll hear an update on the GE acquisition and presentations on customer applications and machine safety. Registration ends February 24th, 2017, so don’t miss this opportunity!

Register now: http://aerodefevent.com/sessions/concept-laser-tour/

Speed, superior quality monitoring, and an open architecture that enables innovation – that is what makes Concept Laser’s Direct Metal Laser Melting (DMLM) technology a leader in the metal additive manufacturing industry. Come and hear about how Concept Laser is investing to bring you innovation through new products and processes that will lead to revenue-generating opportunities for your business.

The Tour is March 6th from 8:30am to 11:30pm and includes round trip transportation from the conference and more.

What you will see on the tour:

  • Direct Metal Laser Melting
  • In-situ Quality Assurance
  • Best-in-class safety guidelines when interacting with reactive and non-reactive materials
3D Printed Exhaust Gas Probe (RSC Engineering and Concept Laser Inc.)
Titanium implant leveraging lattice designs (Concept Laser)

Learn About the New Stratasys 3D Printers and New Orleans

It was my first time visiting New Orleans. I have heard many stories of how good the food is and how everyone is really nice there so I was excited to visit this city for a business trip. Stratasys Launch 2017! There was some buzz going on about some new FDM printers that Stratasys has been working on and I was really excited to see them and hear what sets them apart from the competition. Rey Chu (Co-Owner of PADT), Mario Vargas (Manager of 3D Printer Sales), Norman Stucker (Account Executive in Colorado), and I (James Barker, Application Engineer) represented PADT at this year’s Launch.

The city did not disappoint! I ate the best gumbo I’ve ever tried. Below is a picture of it with some Alligator Bourbon Balls. The gumbo is Alligator Sausage and Seafood. Sooooo Good!!


My last night in New Orleans, Stratasys rented out Mardi Gras World. That is where they build all the floats for Mardi Gras. They had a few dancers and people dressed up festive. I was able to get a picture of Rey in a Mardi Gras costume.

After dinner at Mardi Gras World, I took Rey and Mario down Bourbon Street one last time and then we went to Café Du Monde for their world famous Beignets. Everyone told me that if I come home without trying the Beignets, then the trip was a waste. They were great! I recommend them as well. Below is picture of Mario and me at the restaurant.

As you can see we had a fun business trip. The best part of it was the unveiling of the new FDM printers! Mario and I sat on the closest table to the stage and shared the table with Scott Crump (President of Stratasys and inventor of FDM technology back in 1988). These new printers are replacing some of Stratasys entry level and mid-level printers. What impressed me most is that they all can print PLA, ABS, and ASA materials with the F370 being able to print PC-ABS. You also can build parts in four different layer heights (.005, .007, .010, and .013”), all while utilizing new software called GrabCad Print.

GrabCad Print is exciting because you can now monitor all of you Stratasys FDM printers from this software and setup queues. What made me and many others clap during the unveiling is that with GrabCad Print you no longer have to export STL files! You can import your native CAD assemblies and either print them as an assembly or explode the assembly and print the parts separately.

      

Everyone wants a 3D Printer that can print parts faster, more accurately and is dependable. You get that with the family of systems! Speed has increased big time, they are twice as fast as the Dimension line of FDM printers. Stratasys has published the accuracy of these new printers to be ±.008” up to a 4 inch tall part and then every inch past 4 inches, you add another .002”. These machines are very dependable. They are replacing the Uprint (Uprint SE Plus is still current), Dimension, and Fortus 250 machines that have been workhorses. Many of our customers still have a Dimension from 2002 when they were first launched. In addition to the 43 existing patents that Stratasys has rolled into this phenomenal product, they have an additional 15 new patents that speaks volumes as to the innovation in these 3D printers.

Stratasys Launch was a blast for me. Seeing these new printers, parts that were printed from them, and understanding why these are the best FDM printers on the market was well worth my time! I look forward to helping you with learning more about them. Please contact me at james.barker@padtinc.com for more information. If you would like to hear my recorded webinar that has even more information about the new F170, F270, and F370, here is the link.  Or you can download the brochure here.

Metal 3D Printed Shift Knob: Is It Cool(er)?

I had a really great time designing the Metal 3D printed shift knob from my previous blog post. I was curious what the other benefits of the knob may be besides being cool to look at and show off. What better way than to use the simulation software that we use here at PADT every day!

One of the clear differences between my solid spherical knob and the Metal 3D printed version is surface area. Being that PADT is based in Tempe, AZ, some may say that we have “warm” summers down here. Couple the 120F days with a black car, and the interior can get very hot, at some points feeling like the sun itself has taken up residence inside the back seat. With modern A/C, this heat can be mitigated fairly quickly, only to attempt to shift into gear to be scalded by the shift knob!

I wanted to see what the rate of cooling for the two knobs would be in a basic situation with some basic assumptions. Using ANSYS transient thermal, I initialized the knobs to 150F, temperatures that can be quickly reached in parked cars here in AZ. I added a convection heat transfer boundary condition on the outer surface of each shift knob, assuming a film coefficient of 50 W/m^2C, and that the ambient temp in the car is at a cool 70F.

 

I ran the simulations for 5 minutes, and the results were in line with what I expected. As the 3D printed knob has more surface area for cooling, it’s final temperature was ~84F, compared to the solid spherical knob at a final temperature of 115F!

 

Want to learn more, check out the article in “Additive Manufacturing Media.”

Part Scanning – An Update

3d-optical-scanner-1Did you know that PADT does scanning of parts?  No? You are not alone. We recently ran into several customers who were sending their scanning out of state and didn’t know that they could have it done by PADT, someone who is already a trusted partner. So we thought it would be a good time to do an update on our Scanning services and provide some additional background on what it is.

Part Scanning 101

The idea behind part scanning is that you want to take a part in the real world, and get an accurate model in a computer. To do this you somehow measure the part with a computer, getting a three dimensional representation of the parts surface.  Today, there are six basic ways to do this:


Physical Measurement (CMM)
Measure points on the part relative to some reference. This is great for measure simple geometry where you can reconstruct it by knowing key dimensions.
scanning-laser-scanningLaser Scanning
This process shines a laser on an object and measures the distance to the object. It does this thousands of times to build up a point array of the surface


scanning-structured-lightStructured Light Scanning
This process puts down a series of parallel lines, or a grid of lines, and measures how far they distort from a flat pattern. With this information it can create a massive amount of points on the objects surface.

scanning-cssCross Sectional Scanning
If you need to see inside, light based scanning does not work. In cross sectional scanning you machine away thin slices of an object and take an accurate picture of each layer as you go. This can then be turned in to an accurate representation of both the inside and outside of the object.
scanning-ct-scannerVolumetric Scanning
Another way around the fact that light can not penetrate an object is to use various types of radiation, like X-Rays, that go inside an object. Although new for industrial applications this method is growing for complex parts with internal geometry.
scanning-photometric-scanningPhotometric Scanning
If accuracy is not critical, then software can take pictures taken from dozens of views and reconstruct a 3D shape.  This is used most often for art and entertainment, but is not precise enough for engineering yet.

PADT offers Structured Light and Cross Sectional Scanning

scanning-point-cloud-surfaceAll of these methods create points in space.  The more sophisticated the software, the more automatic the process of assembling the points to define the surfaces of the full object. These points are sometimes called a “point cloud.”

The Point cloud can them be turned in to a faceted representation of the object.  For many people, this is all they need. This faceted representation can be rendered on a computer screen or 3D Printed.  It can also be used with inspection software to determine the accuracy of the part relative to its original specification as well as variations across multiple copies of the same geometry.

scanning-CAD-modelIf users need more, like a full CAD model, that can be created from the point cloud using specialized software.  PADT uses Geomagic DesignX.  This tool not only creates usable geometry, but it can export in the customer’s native CAD format.

To do accurate part scanning you need:

  1. A precision scanning device
  2. Software to take the measured data and create an accurate point cloud. This includes repair and cleanup tools.
  3. Software to convert the point cloud into a usable 3D CAD model
  4. or, Software to conduct accurate inspection on the measured geometry.

All of these tools require some training and practice to use efficiently.  It is fairly easy to get ball park computer models using consumer level tools. But to get accurate, engineering quality results the right tools and processes must be applied.

Why does Part Scanning Take so Long and Cost So Much?

When people ask for their first part scanning quote, they can often be surprised by the cost. The scanning process doesn’t look that hard. And to be honest, the amount of time you actually spend scanning most parts is pretty short.  The time is spent on the preparation, scanning hard-to-reach areas, the clean up, and then converting the data in to usable formats.

scanning-doing-the-workIf we are working with a light based scanner, we have to prepare the parts so that they reflect the light properly. Sometimes we have to cover the part with a find powder, sometimes we may even have to paint it.  What we need is for the reflection and color of the part to not interfere with the scanning.

If we are using cross sectional scanning, the part needs to be cast inside a rigid material, so the part we are scanning does not distort as we remove layers.  In addition, if the part is not a solid light or dark color, it may need to be died to provide contrast for the camera.

Both processes also require some study to determine the orientation of the part relative to the scanner and how the scanning process will take place. Once all this is worked out, the scanning often goes very fast. If there are nasty little parts that are hard to get to or that confuse the device, the engineer may have to modify things, do some special localized scanning, or even make castings that are then scanned.  As is usual with technical processes, a very small portion of the surface being scanned may take up the vast majority of the scanning time.

Once the scanning is done, the real hard work begins. Although software is much better than it was in the past, the resulting point cloud needs to be massaged and cleaned. Stray data is removed, and points from different scans need to be positioned and combined.  Then everything must be checked. If a CAD solid model is needed, then the engineer must spend considerable time dealing with complex features and transition areas. As with the scanning, the bulk of the time spent creating a CAD model is spent on a relatively small percentage of the geometry.

All of this adds up.  Plus, to be honest, things rarely go as planned and unexpected issues arise that need to be dealt with.

Part Scanning Services at PADT

scanning-geomagic-1Now we get to the important part of this post: hiring PADT to do your scanning.  We added this capability to support our 3D Printing customers that wanted copies of physical parts.  But as we looked at it, we found that we also had customers who needed inspection and reverse engineering of legacy parts. We studied the problem for some time and found the right tools and people to make it happen.

Our primary scanner is a Zeiss Comet L3D 5M STructured light scanner.  It used to be called a Steinbichler, till Zeiss bought them in 2015.  Although it is portable and easy to manipulate, the Comet L3D 5M is highly accurate.  It allows us to scan everything from small medical devices to the front end of acar, and to know that the resulting geometry will be accurate and usable. This is the best option for inspection and reverse engineering of high-precision parts.

scanning-padt-partsWe also have a Geomagic Capture scanner. Although less accurate it is more portable and simpler to operate. It is ideal or taking to a customer and getting geometry for reverse engineering or part copying.

If parts have internal features, and are made of plastic, we use our Cross Sectional Scanners. These high precision devices do a fantastic job and are really the best way to capture inside surfaces. Our customers love it to see how injection molded parts are coming out on well used molds.

If anything else is needed, our experts can outsource to a niche supplier.

Want to do it Yourself?

If you need to do your own scanning, no worries. PADT also sells all the tools we use inhouse to customers that need the capability internally.

Next Steps

scanning-inspection-softwareHopefully this posting has answered most of your questions and you are eager to try 3D Part Scanning.  The best place to start is to get a quote from PADT.  However, if you still have questions then feel free to contact us and fire away. We are passionate bout this capability and love talking about it.

Download our brochure here.

Either way, you can email rp@padtinc.com or call 480.813.4884 and ask to talk about Part Scanning. We also have some information on our website at www.padtinc.com/scanning.

Stratasys Release Webinar 2017

We here at PADT are excited to share information on the next big release from Stratasys, the global leader in 3D printing, additive solutions, materials and services.

The name Stratasys has always been synonymous with top of the line machines that meet even the most advanced rapid prototyping needs, and excel at every stage of the design prototyping process.

This new release is no exception.

Keep an eye out for more information on February 6th

Update on ASU 3D Printing Research and Teaching Lab

Two weeks ago we were part of a fantastic open house at the ASU Polytechnic campus for the grand opening of the Additive Manufacturing Research center, a part of the Manufacturing Research and Innovation Hub.  What a great event it was where the Additive Manufacturing community in Arizona gathered in one place to celebrate  this important piece in the local ecosystem.  A piece that puts Arizona in the lead for the practical application of 3D Printing in industry.

I could go on and on, but better writers by far have penned some great stories on the event and on the lab.

ASU’s article is here: New hub’s $2 million in cutting-edge 3-D printing equipment will allow students to stay on forefront of rapidly growing sector

And Hayley Ringle of the Phoenix Business Journal summed it all up, with some great insight into the impact on education and job growth in “See inside the Southwest’s largest 3D printing research facility at ASU

And last but not least, here are some pictures related to PADT that ASU provided: