Additive manufacturing has seen an explosion of material options in recent years. With these new material options comes significant improvements in mechanical properties and the potential for new applications that extend well beyond prototyping; one such application being sacrificial tooling.
Traditional composite manufacturing techniques work well to produce basic shapes with constant cross sections. However, complex composite parts with hollow interiors present unique manufacturing challenges. However, with FDM sacrificial tooling, no design compromise is necessary.
Download the white paper to discover how FDM sacrificial tooling can dramatically streamline the production process for complicated composite parts with hollow interiors.
This document includes insight into:
The advanced composites industry has a continual need for innovative tooling solutions. Conventional tooling is typically heavy, costly and time-consuming to produce. New applications, product improvements and the demand for faster, lower-cost tool creation challenge composite product manufacturers to innovate and remain competitive.
The use of additive manufacturing (or “3D printing”), and specifically FDM, for composite tooling has demonstrated considerable cost and lead time reductions while providing numerous other advantages such as immense design freedom and rapid iteration, nearly regardless of part complexity.
This document includes best practices for:
Additive manufacturing encompasses methods of fabrication that build objects through the successive addition of material, as opposed to subtractive methods such as CNC machining, that remove material until a final shape is achieved. Composite fabrication is one of the most original forms of additive manufacturing.
Whether the process involves wet lay-up, hand lay-up of prepreg materials, or automated fiber placement (AFP), methods of composite manufacture are distinctly additive in nature, building up to final part forms typically one layer at a time. However, the nature of additive manufacturing has been revolutionized with the advent of the 3D printing industry.
Strong, resilient, fiber-reinforced thermoplastics. Lightweight, low-cost composite tooling. Explore these and other characteristics and benefits of additively manufactured composites in the e-book “Introduction to Additive Manufacturing for Composites.”
This e-book covers:
When it comes to delivering accurate, robust, and feature-rich additive manufacturing, commonly called 3D Printing, to professional users, one brand of systems stands above all the rest: Stratasys. For over a decade PADT has been a reseller of these outstanding machines in the four-corners states of Arizona, Colorado, New Mexico, and Utah. In fact, our leadership position in the Additive Manufacturing space is built on the foundation of our sales and support history with Stratasys.
There is one simple reason why Stratasys is the world leader in Additive Manufacturing systems and why so many of our customers keep buying Stratasys systems: They Work. The whole point of 3D Printing is that you can go from a computer model to a real part as quickly and easily as possible. Stratasys has created a complete set of hardware, material, and software to make that happen. For hardware, they offer two additive manufacturing technologies: FDM and PolyJet.
FDM, or Fused Deposition Modeling, is the most common technology because it is reliable, accurate and builds strong parts. FDM was invented by Stratasys over 25 years ago and still forms the foundation of their product line. It is a layered deposition process that melts a variety of plastics that are then extruded through a nozzle to draw the shape of each layer. From the desktop MakerBot machines to the industry favorite FORTUS 900, there is a machine that works for every need. Recently, we have been selling a large number of F370’s to new an existing customers. FMD systems come in a variety of sizes, speeds, costs, and most importantly, material options. And best of all, the majority of FDM systems come with Stratasys’ patented soluble support material that makes support removal as easy as dropping your part into a cleaning system (many of which are made by PADT).
If you need greater refinement, the ability to change material, or color, then PolyJet technology is your ideal solution. The power of PolyJet is that it uses inkjet print heads to deposit tiny dots of liquid material on a build layr. That material is then hardened with an ultraviolet lamp. What is cool is that you can have multiple inkjet print heads and therefore deposit a mix of material within a given layer. This allows you to make parts with very hard, or very soft material in the same build. Or, to mix clear and colors in the same build. Our customers use Polyjet printers to make everything from accurate medical models of organs to molds for plastic injection molding. No other 3D Printing technology is as versatile as the PolyJet machines from Stratasys.
Lots of people sell 3D Printers. We know because we have been doing it for over fifteen years. And as the technology has become more popular, more and more people are getting into the industry. Our experience and technically driven sales approach is why customers keep coming to PADT when they have so many choices. Our sales team is not about this months sales goal. They are about building, and more often than not, growing our relationship with customers new and old. We are all about understanding what you really want to get done, and then finding the right combination of Additive Manufacturing system, accessories, and software that will make it happen.
That expertise comes from the fact that we have been running a 3D Printing service since 1994. We know the real world of Additive Manufacturing. No other reseller can bring our expertise and experience to your aid.
Once you purchase a system, your journey with PADT hits full swing. Our engineers will help you install, train your users, and then be there when you need us for maintenance and repair. Or simply to answer your questions. We recently won a series of competitive situations where customers had a choice of who to hire to support their Stratasys systems. They chose PADT over other solutions for one simple reason: we know what we are doing and we really do care. Our team has driven through snow storms, stayed with machines late into the night, and personally shipped replacement parts just so they could get customer’s machines back online and running as quickly as possible.
Regardless of what systems you currently have, or if you don’t have any 3D Printing capability in-house, now is the time to talk to PADT. We have never had a better offering of solutions in terms of price, performance, and variety of capability. We are helping universities establish labs, Aerospace companies 3D Print hardware for launch vehicles, and consumer products companies shorten their design cycle. It may be time for you to upgrade or add a new material or technology. Or maybe you just need some accessories to get more out of the equipment you have. Regardless of where you are in your Additive Manufacturing journey, PADT is here to help you get more out of your investment.
If there is one service that most people connect PADT with it is our 3D Printing Services. We have been making prototypes for companies using this ever-advancing technology since we started the company in 1994. As 3D Printing has become more popular and entered the mainstream even beyond engineering, what 3D Printing means to people has changed as well. Along with that, people’s understanding of exactly what it is we do in this area has drifted a little from what goes on. In this month’s installment of our “Getting to Know PADT” series, we will work to provide insight into what 3D Printing Services are and how they can benefit your company.
To start, it should be called “Additive and Advanced Manufacturing and Prototyping Services, ” but people search for “3D Printing” so that is what we call it. 3D Printing is the common name for what is technically referred to as Additive Manufacturing, or AM. Most physical parts are made (manufactured) by casting or shaping material into a shape you want, removing material from stock to get the shapes you want, and/or combining physical parts you get by the other two methods. Instead of these well-proven methods, AM creates a part by building up material one layer at a time. That is why it is called additive – it adds layers of material to get a shape. Here is an older blog article showing the most common technologies used in AM.
The advantage of this approach is that you just need one machine to make a part, you can go straight from a computer model to that part, and you are not held back by the physical constraints of traditional processes. These features allow anyone to make a part and to make shapes we just could not create before. At first, we only used it for prototypes before parts were made. Then we started to make tools to make final products, and now 3D Printing is employed to manufacturing end-use parts.
In the world of mechanical engineering, where 3D Printing is heavily used, we call companies that use additive manufacturing to make parts for others 3D Printing Service Bureaus or 3D Printing Service Providers. Therefore, the full process of doing manufacturing using the technology is called: 3D Printing Services.
The critical word in that last sentence is “full.” Sending a computer model to a 3D Printer is just one of many steps involved in Additive Manufacturing. When the service is employed correctly, it includes identifying the right type of additive manufacturing to use, preparing the geometry, setting parameters on the machine, printing the parts, removing supports, cleaning the parts, sanding, applying a surface finish treatment, and then inspection and shipping. Anyone can send a part to a printer; the other steps are what make the difference between simply printing a part, and producing a great part.
Additive Manufacturing covers a wide range of technologies that create parts one layer at a time, using a variety of approaches. Some extrude, some harden, some use an inkjet print head, and still others melt material. What they have in common is creating solid geometry one layer at a time. Each technology has its own unique set of advantages, and that is why PADT offers so many different 3D Printing technologies for our customers. Each of these approaches has unique part preparations, machine parameters, and post-printing processes. Each with a unique set of advantages. The key to success is knowing which technology is best for each part and then executing it correctly.
Currently, PADT’s 3D Printing Services Group makes parts for customers using the following technologies. Each one listed has a brief description of its advantages. See our website for more details.
Reliability of systems
Broad material choice
Water soluble supports
Multiple materials in a single build
Broad material choices
Custom material choices
Multiple colors in single build
Water soluble supports
Fully dense metal parts
As a proud reseller for Stratasys systems, we feel strongly that the two primary technologies from Stratasys, FDM and Polyjet, are the best for customers who want to do Additive Manufacturing in-house or as a service provider. When customers need something different, they can come to PADT to take advantage of the unique capabilities found in each technology.
The difference is in what we know and how to execute the complete process. As a provider of 3D Printing services for over 23 years, very few people in the industry even come close to the amount of experience that we bring to the table. We also know product development and traditional manufacturing, so when a customer comes to us with a need, we understand what they are asking to do and why. That helps us make the right recommendation on process, material, and post-processing.
A few differentiators are:
In addition to all of these things, PADT also offers On-Demand Manufacturing as a Carbon Production Partner. We combine Carbon’s DLS technology with our existing and proven manufacturing processes to provide low volume manufacturing solutions for plastic components.
We are also always looking at the latest technologies and adding what our customers need. You can see this with the recent addition of systems from ConceptLaser, Carbon and Desktop Metal systems.
The very best way to learn more about PADT’s 3D Printing services is to have us print a part. The full experience and the final product will explain why, with so many choices, so many companies large and small count on us for their Additive Manufacturing. If you need to learn more, you can also contact us at 480.813.4884 or email@example.com.
Here are some links that you may find useful:
PADT is in the business of helping people who make products. So most people think of us as a provider of tools and services. What they do not know is that PADT actually has a few of its own products. The most successful of these is our line of Support Cleaning Apparatus systems, abbreviated as SCA. These devices are used to remove soluble support material from parts 3D printed in Stratasys Fused Deposition Modeling Systems. They are robust machines manufactured and serviced by PADT, but sold through the Stratasys worldwide sales channel. As of July of 2017, over 10,800 units have been delivered to Stratasys.
The Stratasys 3D Printing systems that use Fused Deposition Modeling extrude plastic through a heated nozzle to build parts one layer at a time. There are actually two nozzles. One puts down the building material and the other a support material that is dissolved in warm water that is slightly base. The best way to remove that support material is to put it into a warm bath where the part is gently tumbled so that the water can works its way evenly into the part. Stratasys tried several solutions for a companion washing system and eventually came to PADT and asked if we would try our hand at building a robust and efficient system.
The result was the SCA-1200. Launched at the end of 2008 it met the design requirements for reliability, part cleaning time, and noise. Over 7,000 of these systems were shipped and saw heavy usage. In fact, if you have a Stratasys FDM system there is a good chance you have an SCA-1200. It contained a unique shower head design that was optimized with simulation, and a modular assembly that could be repaired easily in the field.
Based upon the success and lessons learned from the SCA-1200, we released the SCA-1200HT in 2014. With the same basic form factor, this design replaced the off-the-shelf magnetically coupled pump with a simpler and more reliable custom design from PADT. The new unit also had a more pleasing visual design, several usability enhancements, and a greater temperature range. It has sold over 3,000 units and continues to be a popular system. The latest release includes a no-temperature setting that allows it to be used to clean Stratasys Polyjet parts.
The success of both system lead to a request to look at building a larger machine that could clean more parts at one time as well as larger parts. The SCA 3600 has three times the volume but shares many internal parts with the SCA-1200HT. Both of the new systems are doing well in the field with even better reliability and faster part cleaning times. They are also simpler to debug and repair.
The SCA systems are sold as stand alone devices or are bundled with key Stratasys FDM machines. You can learn more about them on our SCA page: www.padtinc.com/sca or you can contact whoever you buy your Stratasys equipment from.
Here is a video for the SCA-1200HT that talks all about what it does:
One of the most rewarding aspects of designing and manufacturing the SCA family of products was that it forced us to practice what we preach. We talk to companies every day about using simulation, 3D Printing, design for manufacturing, proper product development processes, and many more things needed to get a product right. With the SCA we were the customer. We had to Walk the Walk or stop talking the talk.
It has been a phenomenal experience that has made us even better at helping our customers produce their new products. We used CFD to optimize the gentle agitation design and shower head and worked closely with our vendors to minimize the cost of manufacturing. The worst part was that when the schedule slipped, we couldn’t blame the customer (only slightly joking). One of the best set of lessons came from doing the repair and refurbishment of systems that failed. Even though the failure rate was low, we learned a lot and were able to make improvements to future designs. Now when we sit across from a customer and talk about the design, test, and manufacture of their product, we can really say that we understand where they are coming from.
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 firstname.lastname@example.org 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.
Building on the worldwide success of previous products in the family, PADT has just released the new SCA 3600, a large capacity cleaning system for removing the support material from Stratasys FDM parts. This new system adds capacity and capability over the existing benchtop SCA-1200HT System.
A copy of the press release is below.
At the same time, we are also launching a new website for support removal: www.padtinc.com/supportremoval.
The SCA 3600 can dissolve support from all the SST-compatible materials you use – ABS, PC, and nylon. A “no heat” option provides agitation at room temperature for the removal of Polyjet SUP706 material as well. The SCA 3600’s versatility and efficient cleaning performance are built on the success of earlier models with all the features you have come to expect, in a larger and more capable model.
Since the launch of the original SCA-1200 in 2008, PADT has successfully manufactured and supported the SCA family of products for users worldwide. Common requests from desktop SCA users were for a larger system for bigger parts, the ability to clean many parts at the same time, and the option to remove supports from PolyJet parts. The SCA 3600 is the answer: Faster, larger, and more capable.
You can download our new brochure for both systems:
If you are interested in learning more or adding an SCA 3600 to your additive manufacturing lab, contact your Stratasys reseller.
A few months ago, I did a post on the Technology Trends in Laser-based Metal Additive Manufacturing where I identified 5 key directions that technology was moving in. In this post, I want to do the same, but for a different technology that we also use on a regular basis at PADT: Fused Deposition Modeling (FDM).
Many companies have released and are continuously developing composite materials for FDM. Most involve carbon fibers and are discussed in this review. Arevo Labs and Mark Forged are two of many companies that offer composite materials for higher performance, the table below lists their current offerings (CF = Carbon Fiber, CNT = Carbon Nano Tubes). Virtual Foundry are also working on developing a metal rich filament (with about 89% metal, 11% binder polymer), which they claim can be used to make mostly-metal parts for non-functional purposes using existing FDM printers and a heat treatment to vaporize the binder. In short, while ABS and PLA dominate the market, there is a wide range of materials commercially available and this list is growing each year.
|Arevo Labs||CF, CNT in PAEK|
|CF in PEEK|
|Fiberglass in PARA|
|Mark Forged||Micro-CF in Nylon|
|Fiberglass (High Strength High Temperature)|
Even with newer materials, a fundamental problem in FDM is the anisotropy of the parts and the fact that the build direction introduces weak interfaces. However, there are several efforts underway to improve the mechanical properties of FDM parts and this is an exciting space to follow with many approaches to this being taken. Some of these involve explicitly improving the interfacial strength: one of the ways this can be achieved is by pre-heating the base layer (as being investigated by Prof. Keng Hsu at the Arizona State University using lasers and presented at the RAPID 2016 conference). Another approach is being developed by a company called Essentium who combine microwave heating and CNT coated filaments as shown in the video below.
Taking a very different approach, Arevo labs has developed a 6-axis robotic FDM process that allows for conformal deposition of carbon fiber composites and uses an FEA solver to generate optimized toolpaths for improved properties.
A lot of press has centered around FDM printers that make bigger parts and at higher deposition rates: one article discusses 4 of these companies that showcased their technologies at an Amsterdam trade show. Among the companies that showcased their technologies at RAPID was 3D Platform, that showed a $27,000 3D printer for FDM with a 1m x 1m x 0.5m printing platform. Some of the key questions for large form factor printers is if and how they deal with geometries needing supports and enabling higher temperature materials. Also, while FDM is well suited among the additive technologies for high throughput, large size prints, it does have competition in this space: Massivit is one company that in the video below shows the printing of a structure 5.6 feet tall in a mere 5 hours using what they call “Gel Dispensed Printing” that reduces the need for supports.
Micro-extrusion through syringes or specialized nozzles is one of the key ways bioprinting systems operate – but this is technically not “fused” deposition in that it may not involve thermal modification of the material during deposition. However, FDM technology is being used for making scaffolds for bio-printing with synthetic, biodegradable or bio-compatible polymers such as PCL and PLGA. The idea is these scaffolds then form the structure for seeding cells (or in some cases the cells are bioprinted as well onto the scaffold). This technology is growing fast and something we are also investigating at PADT – watch this space for more updates.
Modeling FDM is an important part of being able to use simulation/analysis to design better processes and parts for functional use. This may not get a lot of press compared to the items above, but is a particular interest of mine and I believe is a critical piece of the puzzle going to true part production with FDM. I have written a few blog posts on the challenges, approaches and a micromechanics view of FDM printed structures and materials. The idea behind all of these is to represent FDM structures mathematically with valid and accurate models so that their behavior can be predicted and designs truly optimized. This space is also growing fast, the most recent paper I have come across in this space is from the University of Wisconsin-Madison that was published May 12, 2016.
Judging by media hype, metal 3D printing and 3D bioprinting are currently dominating the media spotlight – and for good reasons. But FDM has many things going for it: low cost of entry and manufacturing, user-friendliness and high market penetration. And the technology growth has no sign of abating: the most recent, 2016 Wohlers report assesses that there are over 300 manufacturers of FDM printers, though rumor on the street has it that there are over a thousand manufacturers coming up – in China alone. And as the 5 trends above show, FDM has a lot more to offer the world beyond being just the most rapidly scaling technology – and there are people working worldwide on these opportunities. When a process is as simple and elegant as extruding material from a hot nozzle, usable innovations will naturally follow.
Have you ever looked at the mechanical properties in an FDM material datasheet (one example shown below for Stratasys ULTEM-9085) and wondered why properties were prescribed in the non-traditional manner of XZ and ZX orientation? You may also have wondered, as I did, whatever happened to the XY orientation and why its values were not reported? The short (and unfortunate) answer is you may as well ignore the numbers in the datasheet. The longer answer follows in this blog post.
In the context of FDM, mesostructure is the term used to describe structural detail at the level of individual filaments. And as we show below, it is the most dominant effect in properties.
Consider this simple experiment we did a few months ago: we re-created the geometry used in the tensile test specimens reported in the datasheets and printed them on our Fortus 400mc 3D printer with ULTEM-9085. While we kept layer thickness identical throughout the experiment (0.010″), we modified the number of contours: from the default 1-contour to 10-contours, in 4 steps shown in the curves below. We used a 0.020″ value for both contour and raster widths. Each of these samples was tested mechanically on an INSTRON 8801 under tension at a displacement rate of 5mm/min.
As the figure below shows, the identical geometry had significantly different load-displacement response – as the number of contours grew, the sample grew stiffer. The calculated modulii were in the range of 180-240 kpsi. These values are lower than those reported in datasheets, but closer to published values in work done by Bagsik et al (211-303 kpsi); datasheets do not specify the meso-structure used to construct the part (number of contours, contour and raster widths etc.). Further, it is possible to modify process parameters to optimize for a certain outcome: for example, as suggested by the graph below, an all-contour design is likely to have the highest stiffness when loaded in tension.
The above result is not surprising – the more interesting question is, could we have predicted it? While this is not a composite material, I wondered if I could, in my model, separate the contours that run along the boundary from the raster, and identify each as it’s own “material” with unique properties (Er and Ec). Doing this allows us to apply the Rule of Mixtures and derive an effective property. For the figure below, the effective modulus Eeff becomes:
Eeff = f.Ec + (1-f).Er
where f represents the cross-sectional area fraction of the contours.
With four data points in the curve above, I was able to use two of those data points to solve the above equation simultaneously and derive Er and Ec as follows:
Er = 182596 psi
Ec = 305776 psi
Now the question became: how predictive are these values of experimentally observed stiffness for other combinations of raster and contours? In a preliminary evaluation for two other cases, the results look promising.
Below is a typical image showing the different orientations data are typically attributed to. From our micromechanics argument above, the orientation is not the correct way to look at this data. The more pertinent question is: what is the mesostructure of the load-bearing cross-section? And the answer to the question I posed at the start, as to why the XY values are not typically reported, is apparent if you look at the image below closely and imagine the XZ and XY samples being tested under tension. You will see that from the perspective of the load-bearing cross-section, XY and XZ effectively have the similar (not the same) mesostructure at the load-bearing cross-sectional area, but with a different distribution of contours and rasters – these are NOT different orientations in the conventional X-Y-Z sense that we as users of 3D printers are familiar with.
The point of this preliminary work is not to propose a new way to model FDM structures using the Rule of Mixtures, but to emphasize the significance of the role of the mesostructure on mechanical properties. FDM mesostructure determines properties, and is not just an annoying second order effect. While property numbers from datasheets may serve as useful insights for qualitative, comparative purposes, the numbers are not extendable beyond the specific process conditions and geometry used in the testing. As such, any attempts to model FDM structure that do not account for the mesostructure are not valid, and unlikely to be accurate. To be fair to the creators of FDM datasheets, it is worth noting that the disclaimers at the bottom of these datasheets typically do inform the user that these numbers “should not be used for design specifications or quality control purposes.”
If you would like to learn more and discuss this, and other ideas in the modeling of FDM, tune in to my webinar on June 28, 2016 at 11am Eastern using the link here, or read more of my posts on this subject below. If you are reading this post after that date, drop us a line at email@example.com and cite this post, or connect with me directly on LinkedIn.
Thanks for reading!
In part 1 of this two-part post, I reviewed the challenges in the constitutive modeling of 3D printed parts using the Fused Deposition Modeling (FDM) process. In this second part, I discuss some of the approaches that may be used to enable analyses of FDM parts even in presence of these challenges. I present them below in increasing order of the detail captured by the model.
Good agreement between numerical and experimental results can be achieved using orthotropic properties when the structures being modeled are simple rectangular structures with uniaxial loading states. In addition to require extensive testing to collect this data set (as shown in this 2007 Master’s thesis), this approach does have a few limitations. Like the isotropic assumption, it is only valid for the specific set of build parameters that were used to manufacture the test samples from which the data was initially obtained. Additionally, since the model has no explicit sense of layers and inter-layer effects, it is unlikely to perform well at stresses leading up to failure, especially for complex loading conditions. This was shown in a 2010 paper that demonstrated these limitations in the analysis of a bracket that itself was built in three different orientations. The authors concluded however that there was good agreement at low loads and deflections for all build directions, and that the margin of error as load increased varied across the three build orientations.
Discussion: At the present moment, the orthotropic approach is perhaps the most appropriate method for modeling parts since it is allows some level of build orientation optimization, as well as for meaningful design comparisons and comparison to bulk properties one may expect from alternative technologies such as injection molding. However, as the application of FDM in end-use parts increases, the demands on simulation are also likely to increase, one of which will involve representing these materials more accurately than continuum solids.
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.
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.
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.
GISHWHES is a huge international scavenger hunt. Every year teams around the globe comb through the list of 215 tasks and pick as many as possible that their team can do. Last year they introduced 3D Printing as a task, and we helped a team 3D Print a quill pen. That was a lot of fun, so when this year’s list included an item on 3D printing, we jumped at the chance to be involved.
The item was:
110: VIDEO. Use a cutting edge 3D printer to 3D print your representation of the 4th dimension.62 POINTS
Being engineers we said “4th Dimension? Time.” Then it became a choice between the way mass distorts the space-time continuum or some sort of clock’ish thing. The distortion thing seemed difficult so we focused on a clock. Being that we were constrained on budget and time we decided to do a sundial.
The result can be seen here in this YouTube video.
It was a fun project and the team spent a bit of time in the 112F sunshine trying it out. We can’t wait to see what we will get to do for the 2016 scavenger hunt.
A couple of people have asked if we downloaded the solid model for the sundial or if we made it. We actually made it. After a little bit of research we found that making a simple horizontal sundial like this one is very easy. Here are the steps we took:
So it turns out that the angle of each hour line is determined by the latitude of where the dial will go. The angle of the pointy thing, called a gnomon, is also the latitude. So for Tempe, AZ that is 33.4294°.That gets applied to the equation:
angle(h) = arctan(sin(L*tan(15° · h))
h = integer of the hour, 6 am to 6 pm
L = latitude
I plopped that into Excel:
and got the following:
The next step is to build the model. I used SolidEdge because I know it real well and was able to knock it out quickly. But all CAD tools would be the same:
And the final solid model looked like this: