June 09, 2015 Volume 11 Issue 22

Mechanical News & Products

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SOLIDWORKS: FeatureManager tips for assemblies

Discover tools to make your SOLIDWORKS assembly Feature-Manager design tree display easier to view and use. Learn options to limit the amount of information in each component listing, combine multiple instances of a component into a single listing, and separate fasteners mates into a new folder. Lots more tips on the SOLIDWORKS YouTube channel.
View the video.


Top die casting design tips: Xometry

Optimize your die casting project's manufac-turability with these 23 top design tips from Xometry. Ensure your work is cost effective too, so you can hit the ground running and have the highest chance of success. Tips include: fillets and radii, wall thicknesses, ribs and metal savers, holes and windows, parting lines, finishes, and more.
Read the Xometry article.


8 top ways to wreck your coupling-driven system

Engineers at Ruland Manufacturing Co. have compiled the eight best ways to consistently sabotage or damage your coupling-driven system -- and how to avoid these pitfalls in the future. Misunderstanding performance criteria such as misalignment, torque, or rpm can be all it takes to cause a critical and costly failure.
Read the full article.


New washer tech for leak-free automotive sealing

Trelleborg Sealing Solutions has just launched the Rubore® Washer, a unique solution offering virtually leak-free sealing beneath screwheads to safeguard critical systems in vehicles, especially electric ones.
Read the full article.


How Reell electric wrap spring clutches work

Electric wrap spring clutches are ideally suited for critical timing applications requiring consistent, repeatable engagement and disengagement performance. Wrap spring technology used in Reell clutches provides the capability to transmit a large amount of torque in a small size -- package sizes smaller than other clutch technologies such as friction disk, tooth, or magnetic particle. Reell's technology has very positive engagement characteristics and also limits the effects of wear.
Read this informative Reell article.


New 'breathable' rupture disk tech provides overpressure and vacuum relief

To increase equipment safety and reliability, a new rupture disk technology activates at a set burst pressure, but it can also "breathe" to relieve minor pressure fluctuations. The patent-pending, dual-function device from BS&B Safety Systems is ideal for use on low-pressure vessels that are susceptible to ambient temperature changes.
Read the full article.


Engineer's Toolbox: 9 considerations for specifying a slewing ring bearing

In applications that require a bearing to support a structure while it rotates (e.g., cranes, radar, tank turrets), premature bearing failure can put people and equipment at risk. While slewing ring bearings have proven themselves countless times in such applications, designers must consider many factors when specifying them. According to engineers at Kaydon, the bearing's support structure, mounting (including bolt strength, tensioning, and hole patterns), installation, and even storage are all factors in a bearing's success or failure.
Read the full article.


ClampDisk micro fastener is new alternative for automotive and consumer electronics

Designed as a unique alternative in assemblies for the automotive and consumer electronics markets, the ClampDisk Press-on Fastener is a new offering from PennEngineering that delivers a fast, simple way to achieve sheet-to-sheet clamped fastening while replacing the use of standard screws, nuts, and adhesives. The most common challenges that can be eliminated or reduced by using ClampDisk include over installation, cross threading, stripped screw heads, broken screws, and damaged product. This fastener can be removed easily with a sharp-edged tool.
Learn more and see how ClampDisk works.


New nylon constant torque hinge

Southco has expanded its line of E6 Constant Torque Hinges with a compact, nylon version designed for small applications. The newest addition to the company's E6 50 Constant Torque Position Control Hinge series measures 45 mm with a torque range of 4 to 16 in./lb and is 65% lighter compared to the standard E6 50 Hinge. It provides constant resistance throughout the entire range of motion, enabling users to easily position doors, display screens, and other mounted components and hold them securely at any desired angle.
Learn more.


What injection molding material do I use?

How do you decide what type of plastic to use for your next injection molding project? Xometry can help you narrow your choices. Discover the different strengths and applications for materials that could be ideal for your application by learning about the most common plastic injection molding materials in detail.
Read this detailed Xometry article.


What are carbon composite bellows springs?

The Carbon Composite Bellows Spring (CCBS) from MW Components is a system of carbon fiber elements that combine to work as a high-performance, lightweight, and design-flexible compression spring meant to replace coil springs or metallic Belleville disc springs. A functional spring is made from several individual elements paired and joined to make a stack. The stack spring rate is determined by the number of elements, the base rate of each element, and their series or parallel orientation in the stack. Applications include motorsports, aerospace, and high-performance activities.
Learn more.


Conductive Brush Ring overcomes current leakage in EV powertrains

SKF's new Conductive Brush Ring paves the way to greater reliability and longer life in high-performance electric vehicle powertrain systems. Using pure carbon fiber bristles, it provides a reliable electrical connection between an EV eAxle rotor shaft and its housing. When used in combination with SKF Hybrid ceramic ball bearings, it helps to alleviate parasitic current effects that can lead to premature failure in bearings and other components. Available in different configurations for wet (oil-lubricated) motor designs -- and soon for dry (sealed) applications.
Learn more.


hyperMILL 2024 CAD/CAM software suite

OPEN MIND Technologies has introduced its latest hyperMILL 2024 CAD/CAM software suite, which includes a range of powerful enhancements to its core toolpath capabilities, as well as new functionality for increased NC programming efficiency in applications ranging from 2.5D machining to 5-axis milling. New and enhanced capabilities include: Optimized Deep Hole Drilling, a new algorithm for 3- and 5-axis Rest Machining, an enhanced path layout for the 3D Plane Machining cycle, better error detection, and much more.
Learn more.


One-part epoxy changes from red to clear under UV

Master Bond UV15RCL is a low-viscosity, cationic-type UV-curing system with a special color-changing feature. The red material changes to clear once exposed to UV light, indicating that there is UV light access across the adhesive material. Although this change in color from red to clear does not indicate a full cure, it does confirm that the UV light has reached the polymer. This epoxy is an excellent electrical insulator. UV15RCL adheres well to metals, glass, ceramics, and many plastics, including acrylics and polycarbonates.
Learn more.


SPIROL Press-N-Lok™ Pin for plastic housings

The Press-N-Lok™ Pin was designed to permanently retain two plastic components to each other. As the pin is inserted, the plastic backfills into the area around the two opposing barbs, resulting in maximum retention. Assembly time is quicker, and it requires lower assembly equipment costs compared to screws and adhesives -- just Press-N-Lok™!
Learn more about the new Press-N-Lok™ Pin.


Thin coating on condensers could make power plants way more efficient

Graphene layer one atom thick could quadruple rate of condensation heat transfer in generating plants.

By David L. Chandler, MIT

Most of the world's electricity-producing power plants -- whether powered by coal, natural gas, or nuclear fission -- make electricity by generating steam that turns a turbine. That steam then is condensed back to water, and the cycle begins again.

But the condensers that collect the steam are quite inefficient, and improving them could make a big difference in overall power plant efficiency.

An uncoated copper condenser tube (top left) is shown next to a similar tube coated with graphene (top right). When exposed to water vapor at 100 deg C, the uncoated tube produces an inefficient water film (bottom left), while the coated one shows the more desirable dropwise condensation (bottom right). [Image: MIT]

 

 

 

 

Now, a team of researchers at MIT has developed a way of coating these condenser surfaces with a layer of graphene, just one atom thick, and found that this can improve the rate of heat transfer by a factor of four -- and potentially even more than that, with further work. And unlike polymer coatings, the graphene coatings have proven to be highly durable in laboratory tests.

The findings are reported in the journal Nano Letters by MIT graduate student Daniel Preston, professors Evelyn Wang and Jing Kong, and two others. The improvement in condenser heat transfer, which is just one step in the power-production cycle, could lead to an overall improvement in power plant efficiency of 2 to 3 percent based on figures from the Electric Power Research Institute, Preston says -- enough to make a significant dent in global carbon emissions, since such plants represent the vast majority of the world's electricity generation. "That translates into millions of dollars per power plant per year," he explains.

There are two basic ways in which the condensers -- which may take the form of coiled metal tubes, often made of copper -- interact with the flow of steam. In some cases, the steam condenses to form a thin sheet of water that coats the surface; in others it forms water droplets that are pulled from the surface by gravity.

When the steam forms a film, Preston explains, that impedes heat transfer -- and thus reduces the efficiency -- of condensation. So the goal of much research has been to enhance droplet formation on these surfaces by making them water repelling.

Often this has been accomplished using polymer coatings, but these tend to degrade rapidly in the high heat and humidity of a power plant. And when the coatings are made thicker to reduce that degradation, the coatings themselves impede heat transfer.

"We thought graphene could be useful," Preston says, "since we know it is hydrophobic by nature." So he and his colleagues decided to test both graphene's ability to shed water, and its durability, under typical power plant conditions -- an environment of pure water vapor at 100 deg C.

They found that the single-atom-thick coating of graphene did indeed improve heat transfer fourfold compared with surfaces where the condensate forms sheets of water, such as bare metals. Further calculations showed that optimizing temperature differences could boost this improvement five to seven times. The researchers also showed that after two full weeks under such conditions, there was no measurable degradation in the graphene's performance.

By comparison, similar tests using a common water-repelling coating showed that the coating began to degrade within just three hours, Preston says, and failed completely within 12 hours.

Because the process used to coat the graphene on the copper surface -- called chemical vapor deposition -- has been tested extensively, the new method could be ready for testing under real-world conditions "in as little as a year," Preston says. And the process should be easily scalable to power plant-sized condenser coils.

"This work is extremely significant because, to my knowledge, it is the first report of durable dropwise condensation with a single-layer surface coating," says Jonathan Boreyko, an assistant professor of biomedical engineering and mechanics at Virginia Tech who has studied condensation on superhydrophobic surface. "These findings are somewhat surprising and very exciting."

Boreyko, who was not involved in the research, adds that this method, if proven through further testing, "could significantly improve the efficiency of power plants and other systems that utilize condensers."

The research team also included MIT postdoc Daniela Mafra and former postdoc Nenad Miljkovic, who is now an assistant professor at the University of Illinois at Urbana-Champaign. The work was supported by the Office of Naval Research and the National Science Foundation.

Published June 2015

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