3D Printing Polymer Parts with Electrostatic Dissipative (ESD) Properties

Getting zapped by static electricity at the personal level is merely annoying; having your sensitive electronic equipment buzzed is another, highly destructive story.

Much as you’d like to send these components out into the world wearing their own little anti-static wristbands, that’s just not practical (and actually, not good enough*). During build and use, advanced electronics applications need true charge-dissipative protection that is inherent to their design and easy to achieve. However, the typical steps of painting or coating, covering with conductive tape, or wrapping with carbon-filled/aluminum-coated films incur both time and cost.

Electrostatic dissipative (ESD) polymer materials instead provide this kind of protection on a built-in basis, offering a moderately conductive “exit path” that naturally dissipates the charge build-up that can occur during normal operations. It also prevents powders, dust or fine particles from sticking to the surface. Whether the task is protecting circuit boards during transport and testing, or ensuring that the final product works as designed throughout its lifetime, ESD materials present low electrical resistance while offering the required mechanical, and often thermal and/or chemically-resistant properties.

ESD-safe fixture for testing a printed-circuit board, produced by 3D printing with Stratasys ABS-ESD7 material. (Image courtesy of Stratasys)

Combining ESD Behavior with 3D Printing

All the features that are appealing with 3D printing carry over when printing with ESD-enabled thermoplastics. You can print trays custom-configured to hold circuit-boards for in-process testing, print conformal fixtures that speed up sorting, and produce end-use structures for projects where static build-up is simply not allowed (think mission-critical aerospace applications).

Acrylonitrile butadiene styrene (ABS), that work-horse of the plastics industry, has been available as 3D printing filament for decades. Along the way, Stratasys and other vendors started offering this filament in a version filled with carbon particles that decrease the plastic’s inherent electrical resistance. Stratasys ABS-ESD7 runs on the Fortus 380, 400, 450 and 900 industrial systems, and soon will be available on the office-friendly F370 printer.

What kind of performance does ABS-ESD7 offer? When evaluating materials for ESD performance, the most important property is usually the surface resistance, measured in ohms. (This is not the same as surface resistivity, plus there’s also volume resistivity – see Note at end). Conductive materials – typically metals – have a surface resistance generally less than 103 ohms, insulators such as most plastics are rated at greater than 1012 ohms, and ESD materials fall in the mid-range, at 106 to 109 ohms.

Compared to standard ABS filament, ABS-ESD7 offers more than five orders of magnitude lower resistance, converting it from an insulator to a material that provides an effective static-discharge path to the outside world. Due to the inherent layered structure of FDM parts, the differences in properties between flat (XY) and vertical (ZX) build orientations produces a range of resistance values, with a target of 107 ohms, reflected in the product name of ABS-ESD7. Stratasys offers an excellent, easy-to-read FAQ paper about ABS-ESD7.

Printed-circuit board production tool, custom 3D-printed in Stratasys ABS-ESD7 material for built-in protection from electrostatic discharge during test and handling. (Image courtesy of Stratasys)

When ABS isn’t strong enough or won’t hold up to temperature extremes, engineers can turn to Stratasys’ ESD-enhanced polyetherketoneketone (PEKK), termed Antero 840CN03. Developed in 2016 and slated for full release in October 2019, this new filament expands the company’s Antero line of  high-temperature, chemically resistant formulations. The PEKK base material offers a high glass transition temperature (Tg 149C, compared to 108C for ABS-ESD7) while meeting stringent outgassing and cleanroom requirements. As with ABS-ESD7, the carbon-nanotube loading lowers electrical resistance values of Antero 840CN03 parts to the desirable “ESD safe” range of 106 to 109 ohm.

Setting up Parts for Printing with ESD-Enhanced Filament                                                            

Support structures in contact with part walls/surfaces can disturb the surface resistance behavior. To counter-act this condition for filament printing with any type of ESD material, users should perform a special calibration that makes the printer lay down slightly thinner-than-usual layers of support material. In Stratasys Insight software, this is currently accomplished by setting the Support Offset Thickness to -0.003; this decreases the support layers from 0.010 inches to 0.007 inches. In addition, supports should be removed (in Insight software) from holes that are smaller in diameter than 0.25 inches (6.35mm).

As more of these materials are developed, the software will be updated to automatically create supports with this process in mind.

ESD Applications for 3D Printing

Avionics boxes, fixtures for holding and transporting circuit boards, storage containers for fuel, and production-line conveyor systems are just a few examples of end-use applications of ESD-enabled materials. Coupled with the geometric freedom offered by 3D printing, three categories of manufacturing and operations are improved:

  • Protecting electronics from ESD damage (static shock)
  • Preventing fire/explosion (static spark)
  • Preserving equipment/product performance (static cling)

If you’re exploring how 3D printing with ESD-enhanced materials can help with your industrial challenge, contact our PADT Manufacturing group: get your questions answered, have some sample parts printed, and discover what filament is right for you.

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

*Anti-static is a qualitative term and refers to something that prevents build-up of static, rather than dissipating what does occur


Surface Resistance, Surface Resistivity and Volume Resistivity

Surface resistance in ohms is a measurement to evaluate static-dissipative packaging materials.

Surface resistivity in ohms/square is used to evaluate insulative materials where high resistance characteristics are desirable. (Ref. https://www.evaluationengineering.com/home/article/13000514/the-difference-between-surface-resistance-and-surface-resistivity)

The standard for measuring surface resistance of ESD materials is EOS/ESD S11.11, released in 1993 by the ESD Association as an improvement over ASTM D-257 (the classic standard for evaluating insulators). Driving this need was the non-homogeneous structure of ESD materials (conductive material added to plastic), which had a different effect on testing parameters such as voltage or humidity,  than found with evaluating conductors.

Volume resistivity is yet a third possible measured electrical property, though again better suited for true conductors rather than ESD material. It depends on the area of the ohmeter’s electrodes and the thickness of the material sample. Units are ohm-cm or ohm-m.

             

Bring Your Most Imaginative Ideas to Life with Pantone Validation on the Stratasys J750 & J735

If seeing is believing, holding something this vivid is knowing for sure.

The Stratasys J735 and J750 deliver unrivaled aesthetics to your brightest ideas and boldest ambitions with true, full-color capability, texture mapping and color gradients.

3D print prototypes that look, feel and operate like the finished products in multiple materials and colors without sacrificing time for intricacy and complexity. Better communicate designs with vivid, realistic samples, and save on manual post-processing delays and costs.

Stratasys J735 and J750 printers are PANTONE Validated™

This validation makes the Pantone Matching System (PMS) Colors available for the first time in a 3D printing solution. It provides a universal language of color that enables color-critical decisions through every stage of the workflow for brands and manufacturers. It helps define, communicate and control color from inspiration to realization.

Color matching to Pantone Colors in a single click

GrabCAD Print software provides a quicker, more realistic expression of color in your models and prototypes, saving hours over traditional paint matching or iterative color matching processes.

  • Adding Pantone color selection increases the color gamut found within the GrabCAD Print Application and simplifies the color selection process
  • Designers can access the colors directly from GrabCAD Print, selecting Pantone within the Print Settings dialog box. From within this view the user can search for their desired Pantone color or select from the list.

Multiple material selections

This means  you can load up to six materials at once, including any combination of rigid, flexible, transparent or opaque materials and their components.

Double the number of print nozzles

More print heads means you can produce ultra-smooth surfaces and fine details with layer thickness as fine as 0.014 mm—about half the width of a human skin cell.

Discover how you can achieve stronger realism and color matching thanks to the Pantone Validation available on the Stratasys J750 & J735.

Contact the industry experts at PADT via the link below for more information:

Introducing the Stratasys V650 Flex – Stereolithography Upgraded

The result of over four years of testing, the Stratasys V650 Flex delivers high quality outputs unfailingly, time after time. More than 75,000 hours of collective run time have gone into the V650 Flex; producing more than 150,000 parts in its refinement.

Upgrade to the Stratasys V650 Flex 3D Stereolithography printer and you can add game-changing advances in speed, accuracy and reliability to the established capabilities of Stereolithography. Create smooth-surfaced prototypes, master patterns, large concept models and investment casting patterns more quickly and more precisely than ever.  

In partnership with DSM, Stratasys have configured, pre-qualified and fine-tuned a four-strong range of resins specifically to maximize the productivity, reliability and efficiency of the V650 Flex 3D printer. Create success with thermoplastic elastomers, polyethylene, polypropylene and ABS:

Next-generation stereolithography resins, ideal for investment casting patterns.

Stereolithography accuracy with the look, feel and performance of thermoplastic.

For applications needing strong, stiff, high-heat-resistant composites. Great detail resolution

A clear solution delivering ABS and PBT-like properties for stereolithography.

Thanks to reduced downtime and increased workflow, the Stratasys V650 Flex prints through short power outages, and if you ever need to re-start, you can pick up exactly where you left off. Years of testing have helped deliver not only the stamina to run and run, but also low maintenance needs and high efficiency. To make life even easier, the V650 Flex runs on 110V power, with no need to switch to a 220V power source.

For ease of use, every V650 Flex comes with a user-friendly, touch-enabled interface developed in parallel with SolidView build preparation software. This software contains smart power controls and an Adaptive Power Mode for automated adjustment of laser power, beam size and scan speeds for optimum build performance. 

The V650 Flex also comes equipped with adjustable beam spot sizes from 0.005” to 0.015” that enhance control, detail, smoothness and accuracy. With more precise printing comes better informed decision-making and better chances of success. You have twice the capacity and, to ease workflow further, this production-based machine provides a large VAT for maximum output (build volume 20”W x 20”D x 23”H) and interchangeable VATs.

Through partnering with Stratasys and Stereolithography now comes with an invaluable component: peace of mind. The V650 Flex is backed by the end-to-end and on-demand service and world-class support that is guaranteed with Stratasys. Any field issues get fixed fast, and their 30 years’ experience in 3D printing enable us to help you do more than ever, more efficiently.

Discover how you can work with advanced efficiency thanks to the all new Stratasys V650 Flex.

Contact the industry experts at PADT via the link below for more information:

Updates and Enhancements in ANSYS Mechanical 19.2 – Webinar

Don’t miss this informative presentation – Secure your spot today!

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

Updates and Enhancements in ANSYS Mechanical 19.1 – Webinar

Don’t miss this informative presentation – Secure your spot today!
Register Here

If this is your first time registering for one of our Bright Talk webinars, simply click the link and fill out the attached form. We promise that the information you provide will only be shared with those promoting the event (PADT).

You will only have to do this once! For all future webinars, you can simply click the link, add the reminder to your calendar and you’re good to go!

Stratasys – PolyJet Agilus 30 Webinar

Introducing New PolyJet Material: Agilus30

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

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

Agilus30 has applications in a number of areas, including:

  • Medical Models

  • Tooling needing rubber-like characteristics

  • Consumer Goods

  • Sporting Goods

  • General Prototyping

  • Overmolding & many more!

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

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

Importing Material Properties from Solidworks into ANSYS Mechanical…Finally!

Finally! One of the most common questions we get from our customers who use Solidworks is “Why can’t I transfer my materials from Solidworks? I have to type in the values all over again every time.”  Unfortunately, until now, ANSYS has not been able to access the Solidworks material library to access that information.

There is great news with ANSYS 18.  ANSYS is now able to import the material properties from Solidworks and use them in an analysis within Workbench.  Let’s see how it works.

I have a Solidworks assembly that I downloaded from Grabcad.  The creator had pre-defined all the materials for this model as you can see below.

Once you bring in the geometry into Workbench, just ensure that the Material Properties item is checked under the Geometry cell’s properties.  If you don’t see the panel, just right-click on the geometry cell and click on Properties.

Once you are in ANSYS Mechanical, for example you will see that the parts are already pre-defined with the material specified in Solidworks .

The trick now is to find out where this material is getting stored. If we go to Engineering Data, the only thing we will see is Structural Steel. However when we go to Engineering Data Sources that is where we see a new material library called CADMaterials.  That will show you a list of all the materials and their properties that were imported from a CAD tool such as Solidworks, Creo, NX, etc.

You can of course copy the material and store it for future use in ANSYS like any other material.  This will save you from having to manually define all the materials for a part or assembly from scratch within ANSYS.

Please let us know if you have any questions and we’ll be happy to answer them for you.

Technology Trends in Fused Deposition Modeling

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).

1. New Materials with Improved Properties

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.

Company Composition
Arevo Labs CF, CNT in PAEK
CF in PEEK
Fiberglass in PARA
Mark Forged Micro-CF in Nylon
CF
Fiberglass
Fiberglass (High Strength High Temperature)
Kevlar

2. Improved Properties through Process Enhancements

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.

3. Faster & Bigger

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.

 4. Bioprinting Applications

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.

5. Material Modeling Improvements

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.

Conclusion

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.

Checking Hyper-Elastic Material Models

non-linear-thumbWhen using hyper-elastic materials, analyst often have little material data to assist them. Fortunate engineers will have a tensile stress-strain curve; a lucky few will also have a simple shear stress-strain curve as well. Where do you start?

To gain confidence in the procedure which is typically used, a set of FEA models were run in a closed loop. The loop consists of assuming some material parameters, running FEA models based upon those parameters, and then using the FEA results to recover the material parameters using ANSYS’s built in hyper-elastic curve fitting.

To isolate the material model from boundary conditions effects, simple FEA models that are 3D but have 1D stress states are used. The figures below show tensile and shear models that can be used to verify material models.
cs1

For this article, a 2 Parameter Mooney-Rivlin material model with values consistent with typical Imperial units was selected. The figure below shows the data entry including a value of zero for d which indicates that the material is fully incompressible.
cs2

The tensile test FEA model was run with this 2 parameter MR model. The engineering stress-strain results were extracted from the results using /post26 APDL. The results are graphed and listed in the figure below. We use APDL because there are some calculations involved with getting engineering results. For example, the engineering stress was calculated by dividing the reaction force at node n1 by the original area like this:

RFORCE,2,n1,F,z,Fz_2
QUOT,3,2, , , , , ,-1/area_,1,

cs3This test data was then used in ANSYS’s curve fitting routine. The results of the curve fitting are shown below. The parameters from the curve fitting results are < 0.01% different than the assumed inputs. This is a reassuring result. Note that this is one instance in ANSYS that you are required to use engineering data (for hyper-elastic curve fitting only).
cs4

In recent versions of ANSYS, a hyper-elastic response function was introduced. This allows the user to enter the test data and use it without curve fitting. The figure below shows how uniaxial tension test data is entered and the response function activated to use it.
cs5

As expected, the response function matched the /post26 output exactly. This method offers a clear advantage in that the user doesn’t need to assume a material model.
cs6

The next step in this verification process was to run some simple shear FEA models to compare the curve fitting results. The plot below shows the engineering shear stress-strain curve using the 2 parameter MR model from above.
cs7

The data was curve fitted as shown in the figure below. This time both the uniaxial tension and simple shear data are entered. The resulting 2 parameter model differs (<2%) from the entered model.
cs8

These new values were used in the FEA models. As shown in the figures below, the change in material parameters (<2%) did not significantly change the tensile or shear stress-strain results (<1%). This raises some interesting questions regarding the 2 parameter MR model that will be explored at a later date.
cs9

Efficient Engineering Data, Part 2: Setting Default Materials and Assignments aka No, You’re Not Stuck with Structural Steel for the Rest of Your Life

Longer ago than I care to admit, I wrote an article about creating and using your own material libraries in Workbench. This is the long awaited follow-up, which concerns setting the default Engineering Data materials and default material assignments in Mechanical and other analysis editors.

imageNote:
Part of the reason it’s taken me this long is that I moved to New Mexico to help staff PADT’s new office there, and to shadow Walter White. It has been a hectic, exhausting endeavor but I’m here and I’m finally settled in. If you’re in New Mexico and are interested in ANSYS, engineering services, product development, or rapid prototyping (e.g. 3D printing), please feel free to contact me.

In order to make the best use of the procedures here, you will probably want to know how to create your own material libraries. Part 1 describes how to do this. This will also work with the material libraries that come with the ANSYS installation, though.

Pick Favorites

The first step is to get into Engineering Data and expose the material libraries by clicking on the book stack button ( image ). Then, drag the materials of your choice from the appropriate library(ies) to the Favorites Data Source. These can include materials you want to have available in Mechanical by default as well as materials that you would like to consolidate into a single location for quick access. At this point, the default material availability and assignments have not been altered. These will be handled in the next couple of steps.

image

Drag and Drop Materials to Favorites

Set Default Material Availability

To specify which materials will be immediately available for assignment in future analyses, go to the Favorites Data Source and check all applicable materials in column D. Though not assigned to the immediate set of engineering data, these will be on the default list of available materials in subsequent analyses, i.e. when you create a new analysis in the same project schematic or when you exit and reopen Workbench.

image

Check to Add to Default List of Available Materials

image

Materials Immediately Available Inside Mechanical

Set Default Material Assignment

Now our most commonly used materials are immediately available in our analysis editor. But Structural Steel still lingers. In many, if not most, cases, we would prefer our default assignment to be something else.

The fix is easy. Once again, go to the Favorites Data Source, right click the material you wish to have as your default material, and select Default Solid Material (and if you’re doing Emag or CFD, you can set your default fluid or field material with the right-click menu too). Your default solid material will now replace Structural Steel in subsequent analyses.

image

Example: Aluminum 6061-T651 Set as Default Material Assignment

image

Becomes Default Material Assignment in Analysis

Note that you can stop at any step in this process. If you want to consolidate favorite materials, but don’t want to have them immediately in your analysis editor, you can do that. If you want a default list of materials to select from without specifying a default material assignment, you can do that too. More than likely, though, you’ll want to do all three.