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Engineer's Toolbox: How to design the optimum hinge

Although many pin styles are available, Coiled Spring Pins are particularly well suited for use in both friction- and free-fit hinges. To achieve optimum long-term hinge performance, designers should observe these helpful design guidelines from SPIROL.
Read the full article.

Innovative new robo welding gun

Comau's newest N-WG welding gun is designed for high-speed spot welding for traditional, hybrid, and electric vehicles, in addition to general industry sectors. It features a patented, single-body architecture that enables rapid reconfiguration between welding types and forces, and it delivers consistent performance across a broad range of applications, including steel and (soon) aluminum welding. It supports both X and C standard gun configurations, has fast arm exchange, and universal mounting options. It is fully compatible with major robot brands and represents a significant advancement in spot welding performance and cost efficiency.
Learn more.

What's a SLIC Pin^®? Pin and cotter all in one!

The SLIC Pin (Self-Locking Implanted Cotter Pin) from Pivot Point is a pin and cotter all in one. This one-piece locking clevis pin is cost saving, fast, and secure. It functions as a quick locking pin wherever you need a fast-lock function. It features a spring-loaded plunger that functions as an easy insertion ramp. This revolutionary fastening pin is very popular and used successfully in a wide range of applications.
Learn more.

Engineering challenge: Which 3D-printed parts will fade?

How does prolonged exposure to intense UV light impact 3D-printed plastics? Will they fade? This is what Xometry's Director of Application Engineering, Greg Paulsen, set to find out. In this video, Paulsen performs comprehensive tests on samples manufactured using various additive processes, including FDM, SLS, SLA, PolyJet, DLS, and LSPc, to determine their UV resistance. Very informative. Some results may surprise you.
View the video.

Copper filament for 3D printing

Virtual Foundry, the company that brought us 3D-printable lunar regolith simulant, says its popular Copper Filamet™ (not a typo) is "back in stock and ready for your next project." This material is compatible with any open-architecture FDM/FFF 3D printer. After sintering, final parts are 100% pure copper. Also available as pellets. The company says this is one of the easiest materials to print and sinter. New Porcelain Filamet™ available too.
Learn more and get all the specs.

Copper foam -- so many advantages

Copper foam from Goodfellow combines the outstanding thermal conductivity of copper with the structural benefits of a metal foam. These features are of particular interest to design engineers working in the fields of medical products and devices, defense systems and manned flight, power generation, and the manufacture of semiconductor devices. This product has a true skeletal structure with no voids, inclusions, or entrapments. A perennial favorite of Designfax readers.
Learn more.

Full-color 3D-printing Design Guide from Xometry

With Xometry's PolyJet 3D-printing service, you can order full-color 3D prints easily. Their no-cost design guide will help you learn about different aspects of 3D printing colorful parts, how to create and add color to your models, and best practices to keep in mind when printing in full color. Learn how to take full advantage of the 600,000 unique colors available in this flexible additive process.
Get the Xometry guide.

Tech Tip: How to create high-quality STL files for 3D prints

Have you ever 3D printed a part that had flat spots or faceted surfaces where smooth curves were supposed to be? You are not alone, and it's not your 3D printer's fault. According to Markforged, the culprit is likely a lack of resolution in the STL file used to create the part.
Read this detailed and informative Markforged blog.

Test your knowledge: High-temp adhesives

Put your knowledge to the test by trying to answer these key questions on how to choose the right high-temperature-resistant adhesive. The technical experts from Master Bond cover critical information necessary for the selection process, including questions on glass transition temperature and service temperature range. Some of the answers may surprise even the savviest of engineers.
Take the quiz.

Engineer's Toolbox: How to pin a shaft and hub assembly properly

One of the primary benefits of using a coiled spring pin to affix a hub or gear to a shaft is the coiled pin's ability to prevent hole damage. Another is the coiled pin absorbs wider hole tolerances than any other press-fit pin. This translates to lower total manufacturing costs of the assembly. However, there are a few design guidelines that must be adhered to in order to achieve the maximum strength of the pinned system and prevent damage to the assembly.
Read this very informative SPIROL article.

What's new in Creo Parametric 11.0?

Creo Parametric 11.0 is packed with productivity-enhancing updates, and sometimes the smallest changes make the biggest impact in your daily workflows. Mark Potrzebowski, Technical Training Engineer, Rand 3D, runs through the newest functionality -- from improved surface modeling tools to smarter file management and model tree navigation. Videos provide extra instruction.
Read the full article.

What's so special about wave springs?

Don't settle for ordinary springs. Opt for Rotor Clip wave springs. A wave spring is a type of flat wire compression spring characterized by its unique waveform-like structure. Unlike traditional coil springs, wave springs offer an innovative solution to complex engineering challenges, producing forces from bending, not torsion. Their standout feature lies in their ability to compress and expand efficiently while occupying up to 50% less axial space than traditional compression springs. Experience the difference Rotor Clip wave springs can make in your applications today!
View the video.

New Standard Parts Handbook from JW Winco

JW Winco's printed Standard Parts Handbook is a comprehensive 2,184-page reference that supports designers and engineers with the largest selection of standard parts categorized into three main groups: operating, clamping, and machine parts. More than 75,000 standard parts can be found in this valuable resource, including toggle clamps, shaft collars, concealed multiple-joint hinges, and hygienically designed components.
Get your Standard Parts Handbook today.

Looking to save space in your designs?

Watch Smalley's quick explainer video to see how engineer Frank improved his product designs by switching from traditional coil springs to compact, efficient wave springs. Tasked with making his products smaller while keeping costs down, Frank found wave springs were the perfect solution.
View the video.

Top die casting design tips

You can improve the design and cost of your die cast parts with these top tips from Xometry's Joel Schadegg. Topics include: Fillets and Radii, Wall Thicknesses, Ribs and Metal Savers, Holes and Windows, Parting Lines, and more. Follow these recommendations so you have the highest chance of success with your project.
Read the full Xometry article.

Thin explosive films provide snapshot of how detonations start

An image from a test detonation at Sandia National Lab of a thin explosive film, about as thick as a few pieces of notebook paper, with a 3/8-in.-tall thunderbird-shaped barrier. The "shimmering" lines to the right of the thunderbird are the shock waves from the explosion detected by schlieren imaging, a technique that can detect differences in air density. [Photo courtesy of Eric Forrest]

 

 

 

 

Using thin films -- no more than a few pieces of notebook paper thick -- of a common explosive chemical, researchers from Sandia National Laboratories studied how small-scale explosions start and grow. Sandia is the only lab in the United States that can make such detonatable thin films.

These experiments advanced fundamental knowledge of detonations. The data were also used to improve a Sandia-developed computer-modeling program used by universities, private companies, and the Department of Defense to simulate how large-scale detonations initiate and propagate.

"It's neat. We're really pushing the limits on the scale at which you can detonate and what you can do with explosives in terms of changing various properties," said Eric Forrest, the lead researcher on the project. "Traditional explosives theory says that you shouldn't be able to detonate at these length scales, but we've been able to demonstrate that, in fact, you can."

Forrest and the rest of the research team shared their work studying the characteristics of these thin films and the explosions they produce in two recently published papers in ACS Applied Materials and Interfaces and Propellants, Explosives, Pyrotechnics.

For their studies, the team used PETN, also known as pentaerythritol tetranitrate, which is a bit more powerful than TNT, pound for pound. It is commonly used by the mining industry and by the military.

Typically, PETN is pressed into cylinders or pellets for use. The research team instead used a method called physical vapor deposition -- also used to make second-generation solar panels and to coat some jewelry -- to "grow" thin films of PETN.

Sandia is the only lab in the United States that has the skills and equipment to use this technique to make thin explosive films that can detonate, said Rob Knepper, a Sandia explosives expert involved in the project.

Growing and studying thin explosive films
Starting in late 2015, the team grew thin films of PETN on different types of surfaces to determine how that would affect the films' characteristics. They started with pieces of silicon about the size of a pinkie nail and grew films that were about one-tenth the thickness of a piece of paper, too thin to explode. Some of the silicon pieces were very clean, some were moderately clean, and some were straight-out-of-the-box and thus had a very thin layer of dirt -- 50,000 times thinner than a sheet of paper.

On the very clean silicon surfaces, the PETN films formed what appeared to be smooth plates by scanning-electron microscopy, yet had tiny cracks in between plates, somewhat like dried mud on a dried lakebed. On the dirty silicon surfaces, the surface of the PETN films appeared more like even hills.

Using an X-ray-based technique, the researchers determined this is because the PETN molecules orient themselves differently on dirty surfaces compared to very clean surfaces, and thus the film grows differently, Forrest said.

"This study in particular has shown that we can get not just novel, but very useful forms of traditional explosives that you would never be able to achieve via traditional means," Forrest said. "Finely controlling the film properties enables us to investigate theories to better understand explosive initiation, which will allow us to better predict reliability, performance, and safety of explosive systems through improved models."

Knepper, who served as Forrest's mentor on the project, agreed. "Developing a way that we can reproducibly control the microstructure of the films, just through the surface manipulation, is important. Right now, our focus is on using these films to further our understanding of explosive properties at small scales, such as the initiation and failure of explosives."

Small-scale tests to improve computer models
Once the characteristics and properties of the thin films were better understood, the research team grew thicker films -- this time about the thickness of two sheets of notebook paper -- on very clean pieces of plastic about the size of a pinkie finger.

Then, with a bang, they detonated the explosive films inside a specially designed safety enclosure called a "boombox," which was engineered to prevent a detonation from starting while the enclosure was open and to contain any debris from the detonation. Using an ultra-high-speed camera that can take up to a billion frames a second, they watched the shock wave rise up as the explosion raced across the thin film.

Video: The detonation of thin explosive films by Sandia National Laboratories researchers.

In collaboration with New Mexico Institute of Mining and Technology in Socorro, the research team developed a specialized setup to see the shock wave despite the smoke and debris from the test explosions using schlieren imaging, a technique that can detect differences in air density similar to the shimmering over a hot highway.

A mechanical engineering master's student from New Mexico Tech, Julio Peguero, used the data from these experiments to refine Sandia's explosives computer-modeling program. The program, called CTH, can be used for applications, such as to determine how to best shape explosive charges while drilling for oil, Knepper said.

Peguero plotted the velocity of the shock waves above the films with and without gaps and adapted the computer program to better match their experimental results on very thin films. The team engineered thin films with cracks in the middle of various sizes -- ranging from one-third the width of a human hair to 1 1/3 the width of a hair -- to better understand the reliability of thin films and how detonations can fail. The team found that gaps around the size of a hair could stop a detonation from continuing.

Forrest was particularly interested in the gap studies because the first study found thin cracks between the very smooth plates of some of the films. Although these cracks were far smaller than even one-tenth a hair's width, the data from the gap study provided insights into how these films would perform.

Peguero, who is now a Sandia employee, started working on the project in January 2018, first as a student and then later as a Sandia intern. "In addition to the excitement of doing explosives research, I gained an appreciation for measurement uncertainty and risks," Peguero said. "That is especially important for national security work to ensure that our confidence in our measurements is well understood."

Knepper agreed about the importance of the project. He said, "When you have experimental data at small scales, especially those that are relevant for the border between what can detonate and what can't, those data can be really helpful in calibrating computer models. Also, being able to have good characterization of the explosive microstructure to go into the models helps with having parameters that can successfully predict performance over a wider range of explosive behaviors."

Source: Sandia

Published April 2021

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