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When you’re setting up a fluid control system, there are dozens of different types of valves you have to choose from. Each serves a specific purpose, but keeping them straight can get confusing. Many people have trouble with the difference between control valves and on-off valves.Control valves and on-off valves serve different purposes depending on the degree of control you need for your system. Control valves are more precise, whereas on-off valves are more all-or-nothing. Read on to learn more about these two different valves and how they’re used. Control Valves As you might guess from the name, a control valve is used to control the flow of fluid in a system. They can maintain different variables at specific set-points, including density, concentration, flow rate, pressure, temperature, and liquid levels. A control valve includes a valve body, actuator, and positioner, as well as body assembly and trim parts. The actuators on these valves can be pneumatic, hydraulic, or electrically powered, and they control how the valve opens and closes. The positioners monitor and control the actuator movements to maintain the desired set-point. On-Off Valves An on-off valve is a much less precise instrument than the control valve. It either allows for unimpeded flow or it shuts off flow completely. There are a couple of different styles of on-off valves, including ball, plug, butterfly, gate, and globe valves. A ball valve consists of a ball with a channel cut through it that can be turned so the channel aligns with the rest of the line, allowing flow, or so that it doesn’t, shutting off flow. Butterfly valves have a flat piece of metal that rotates to open or close the channel. Gate valves and plug valves use conical pieces that slide down through the channel, sealing it securely shut. Uses for Each Control valves are used in situations where you need specific control over a piece of a system. These are excellent for jobs where precision is crucial and there are a number of factors that have to be tightly controlled. Ball valves are good for more black-and-white situations. Because they’re all or nothing, they’re often used as emergency shutoff measures. You could even have a control valve and an on-off valve on the same system, with the on-off valve acting as a backup in case the control valve fails. Discover How to Use Different Valves On-off valves and control valves are similar in some senses, but the difference lies in their degrees of control. Where control valves can be very precise, on-off valves can do exactly what their name suggests: turn on or turn off. Each of the different valves has an important place in your system. CPV MANUFACTURING

valve is a device that controls, directs or regulates the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Various types of valves are available: gate, globe, diaphragm, pinch, pressure relief, plug, ball, butterfly, and check, control valves, etc. Each of these types has a number of models, each of which has different characteristics and functional capabilities. From many to pick from it can be hard to determine which valve is right for your application. We discuss the advantages of ball valves over globe valves in this article. Difference Between Ball and Globe Valves? The primary distinction between the ball and globe valves is how they close. Ball valves have a stem and ball that move horizontally and are generally called “rotational” valves. Globe valves, on the other side, have a stem and plug that strokes linearly, giving them their other name of “stroke” valves. Ball valves are ideally designed for systems that need on / off the power without reducing the pressure. While globe valves excel at regulating flow. How Does A Ball Valve Work? Ball valves are equipped for inside the valve with a ball. A ball valve is a type of a quarter-turn valve that regulates the flow through it using a hollow, perforated and pivoting ball (called a “floating ball”). It is open when the hole of the ball is in line with the flow and when the valve handle pivots it 90-degrees, it is closed. The handle is flat in alignment with the flow when it is opened and perpendicular to it when it is closed, making it easy to visually confirm the status of the valve. How Does A Globe Valve Work? Globe valves became the industry norm of control valves for many years. They’re known after their spherical body shape, with an internal baffle dividing the two halves of the body. It has an opening that creates a seat on which a movable plug (or disc) can be screwed to close the valve. Usually, automatic globe valves utilize smooth stems instead of threads and are opened and closed by the actuator assembly. Which Is Better: A Ball Valve or Globe Valve? Ball valves are robust, working well after several cycles, and stable, firmly closing even after long periods of disuse. Such characteristics make them an ideal alternative for shut-off applications, where they are sometimes favored to gates and globe valves. On the other hand, ball valves may not provide the finest control in the throttling applications provided by globe valves. VIRGIN ENGINEERS

How much energy can the sun provide in an hour? As anyone who’s ever fallen asleep while sunbathing can attest, it’s enough to leave a mark. The average solar power upon the Earth’s surface is 174.7 watts per square meter, according to a paper published by Sandia National Laboratories. Multiply that value by the Earth’s surface area (4πr2, where r is roughly 6378 km) and then again by 60 minutes (that’s 3600 seconds) and we have our answer: in one hour, the sun provides about 3.21 x 1020 joules of energy to Earth. That’s equivalent to 76,841 megatons of TNT. In less than two hours, the sun provides more energy than the entire planet used in all of 2017. In short, with efficiency improvements, solar power generation technology could have significant potential as an energy resource. The article discusses the emerging technologies in solar energy sources that could increase the technical and economical effectiveness of this source, thus boosting its popularity. The currently developing technologies have the potential to replace the dominant crystalline silicon (c-Si) technology in the future and significantly increase the efficiency of photovoltaic (PV) cells. In the past the solar technology has been expensive and relatively inefficient. Technological advances over the last twenty years have significantly increased its efficiency and decreased its costs. This resulted in the rapid growth of solar energy capacity. The solar energy system costs are less than half of what they were 20 years ago. However, solar energy still requires government support and incentives to be financially competitive with commercial energy sources. In addition to this, the efficiency of commonly used c-Si cells is already close to its theoretical maximum, which imposes a need for new technology. According to the IHS Markit global scenarios, only 5% of total generation capacity in the ranking top 10 countries came from solar (Figure 1). Generation capacity 2019 in GW, ranking top 10 countries (IHS Markit Autonomy scenario, July 2018). The new upcoming solar technologies promise growth in solar energy usage by decreasing its costs and increasing its efficiency. The most effective way of using solar energy is by distributing solar power generation, such as electricity produced by households with rooftop systems. Individual owners using distributed solar generation will produce electricity for their own use, with excess power production sold to a power company. The distributed solar power generation has numerous benefits such as: it is clean energy; it is cost effective; and it reduces the load on grid generation and reduces the infrastructure needed for transmission and distribution facilities, etc. However, many engineers working in the power generation industry will cringe when reading this, as distributed power generation has challenges in many areas due to the way many of today’s power grids are set up. Solar PV Cell Design Solar cells contain light energy absorbing materials and convert it into electrical energy. The cell semiconductor material is defined by the difference between two energy levels: the valence band and the conduction band. The lower-energy valence band contains negatively charged electrons, while the higher-energy conduction band is empty. When the electrons are hit by photons with energy greater than the bandgap, they can absorb enough energy to be excited from the valence band to the conduction band, producing an electron-hole pair. An internal electrochemical potential separates the electron-hole pairs, causing the flow of electrons and holes, which creates an electric current. The internal electrochemical potential is caused by semiconductor doping, where one part of the semiconductor interface is doped with electron donors (n-type doping) and another with electron acceptors (p-type doping) creating a p-n junction. Basic PV cell design. Image courtesy of Apricus. Efficiency The solar cell efficiency is limited because only one electron can be excited by one photon, regardless of the photon energy. Similar to the wind power plants’ limitations for maximum theoretical efficiency (which according to the Betz's law 16/27 (59.3%)), the solar PV cells also have limited maximum efficiency, known as Shockley–Queisser limit. The maximum solar conversion efficiency of a solar cell with a single p-n junction is approximately 33.7%, achieved at a bandgap of 1.34 eV. This limit (the peak of the graph from figure 3) is experimentally obtained by combining materials with different bandgaps into tandem solar cells. Figure 3 illustrates the dependance of cell efficiency on the bandgap. A high bandgap inhibits photons from causing the PV effect. In the case of a low bandgap, the photon energy is higher than the energy required to excite electrons across the bandgap, and the excess energy will be wasted. The commonly used semiconductors have bandgap values placed near the peak of the efficiency graph (for example silicon (1.1 eV) and CdTe (1.5 eV)). Solar cell efficiency vs material badgap for a single p-n junction cells. Image courtesy of Sbyrnes321 from Wikipedia The mentioned limitation applies only for a solar cell with a single p-n junction. The maximum efficiency can be increased by using tandem solar cells with multiple layers. Theoretically a tandem solar cell with an infinite number of layers could reach an efficiency of 86.8% while using concentrated sunlight. Multi-junction solar cells are made of different semiconductor materials which form multiple p-n junctions with multiple bandgaps. Different materials absorb different wavelengths of light, and they are optimized for each section of the spectrum. Emerging Technologies Can Increase the Cost-Effectiveness In order to impose a new technology on the market, economic and technical requirements must be met. The technology should be more efficient but still price-competitive with the currently available technologies. The new cutting-edge PV technologies that could replace c-Si include: concentrated photovoltaics, quantum-dot cells, perovskite, multi-junction cells, organic photovoltaics, cadmium telluride, copper indium gallium selenide (CIGS), and graphene. The first three technologies mentioned are the most promising ones. Concentrated Photovoltaics Concentrated PV (CPV) systems, similar to telescopes, contain lenses and curved mirrors which focus light on multi-junction solar cells. They also include solar tracking technology, providing more efficient sunlight absorbtion. CPV systems with a wide range of magnification ratio can be designed. They are grouped in three classes: low concentration (LCPV), magnification ratio is less than 10X, medium concentration (MCPV), magnification ratio between 10X and 150X; high concentration, magnification ratio above 150X, usually less than 1000X. According to the National Renewable Energy Laboratory (NREL), CPV has the best PV research-cell efficiency. In 2014, Fraunhofer Institute for Solar Energy Systems successfully developed a multi-junction CPV with 46% efficiency. The maximum efficiency of c-Si ever reached was 27.6% (with concentrated sunlight) and approximately 15% in commercial usage. Considering the cell efficiency, CPV has the potential to be the future technology. High cell efficiency provides a lower unit cost, because it requires less surface area to generate the same watt peak of electricity (Wp - the output power generated by a solar cell under a full solar radiation), thus decreasing the required number of cells. The maximum potential of the CPV technology can be achieved by using the nonconventional multi-junction solar cells. Multi-junction cells use several different materials arranged in multiple layers (conventional single-junction solar cells are built from one layer of a single type of material). Although the technology was tested in 1983, it has never achieved mass commercial usage. The CPV requires expensive components, such as the solar tracking modules that precisely orient the cells directly towards the sun, which ultimately increases the design complexity and the balance of system costs (BoS – including all components of a PV system). This PV system is suitable only in the regions with high direct solar radiation, which limits its potential market. However, its high efficiency is promising for the markets where direct normal irradiance is the highest, such as the Middle East, North Africa, and Australia. Quantum-dot Photovoltaics This PV solar cell design uses quantum dots (semiconductor nanocrystals) as the absorbing PV material instead of bulk materials such as silicon, copper indium gallium selenide (CIGS), or cadmium telluride (CdTe). The distinctive feature of this technology are the tunable bandgaps. While the conventional bulk materials have fixed bandgaps, quantum-dot cell bangaps are tunable across a wide range of energy levels by varying the size of the quantum dots. The bandgap can be changed without changing the material or the construction techniques. This property makes the quantum-dot technology attractive for multi-junction solar cells. The quantum dots can be used as one junction in a multi-junction cell, capturing additional solar energy that is usually lost as heat. Lower bandgaps are more suitable to generate electricity from photons with lower energy (and vice versa). Although this technology has been identified as a key future technology for the solar industry, quantum dot solar cells are not yet commercially viable on the mass scale, mostly because of the low efficiency, which can reach only 8%. However the efficiency is not the only parameter determining the cost efficiency. The quantum-dot design can be combined with important existing technologies, thus improving their efficiency. This feature opens the posibility for it to be a technology of the future. Perovskite The perovskite solar cell (PSC) type includes a perovskite structured compound (a hybrid organic-inorganic lead or tin halide-based material) as the light-harvesting active layer. The materials have high absorption coefficients, providing ultrathin films (approximately 500 nm) for complete visible solar spectrum absorption. Perovskite materials are cheap and simple to manufacture. When it comes to efficiency, PSC efficiencies have extremely increased - from 3.8% in 2009 to 25.2% in 2019 in a single-junction design source. When combined with silicon-based technology, an efficiency of 28.0% can be reached, higher than the maximum efficiency of single-junction silicon solar cells. Therefore, the perovskite solar technology is the fastest-advancing solar technology. Considering its efficiency, thin, lightweight design of modules, and low manufacturing costs, this cell type is commercially attractive as the future technology. Currently the main challenge for peroskite is its sensitivity to moisture. It degrades quickly and needs to be protected by a watertight seal. Summary Although the c-Si is the dominant solar PV technology for the time being, it does not have the potential to remain so forever. The presented emerging technologies have the potential to replace the c-Si in the long term. The most promising emerging technologies are provided in the table below. However, the leading countries should make an effort to develop the emerging PV technologies to their full potential. ENGINEERING.COM

To anyone who's ever flown a quadcopter, dictionary definitions of a "drone" just don't do them justice, especially when the standard definition of the word is "a male bee…which does no work but can fertilize a queen." The recent addition of "unmanned aircraft or ship guided by remote control or onboard computers" is too sparse, so below we offer some positive linguistic ballast to the current dreary characterizations: A drone is an unmanned vehicle that performs tasks while either traveling from its launch point to a specified destination and back or loitering in a designated area, with or without human intervention while avoiding collisions with other objects. When operating autonomously such a vehicle is called an Unmanned Autonomous Vehicle (UAV) or Unmanned Autonomous System (UAS). These unusual combinations of aeronautic and electronic technology are made possible by advances and cost reductions in sensors, processors, communications, and other technologies, are taking the world. Together, all this low-cost technical wizardry makes it possible for virtually anyone to own one, even if it is just a toy commonly offered at mall kiosks in the holiday season. There are several quadcopter solutions on the Mouser Electronics website. Infineon has a portfolio of products meant for multicopters as shown on the Infineon multicopter solutions page, Cypress Semiconductor has a complete quadcopter solution that was created at Maker Faire, and the Intel Aero platform for UAVs includes a Aero Ready-to-Fly Drone, Aero Compute Board, Vision Accessory Kit and Enclosure Kit. Quadcopter kits can help students to better understand physics, control systems, programming, mathematics, and engineering. Quadcopters, or drones, are not your father's radio controlled (RC) Cessna. Figure 1: Multicopter system block diagram by Infineon. (Source: Infineon) The drone business is poised to quickly reach new heights according to Grand View Research (Figure 2) and in 2015 manufacturers of commercial drones racked up global sales of $356 million (including multi-rotor, nano, hybrid, fixed-wing, and other types) with projections of a tenfold increase to $1 billion by 2022. Figure 2: The drone market through 2022. (Source: Grand View Research.)Some might consider quadcopters to be a mere addendum to the "RC" market that today includes replicas of the Hindenburg. In fact, radio-control was first demonstrated in the late 1800s by Nicola Tesla, who demonstrated an RC boat in 1898. Tesla was followed by his associate and 1963 IEEE Medal of Honor winner John Hays Hammond Jr., the "father of remote-control," who among more than 400 other things, invented pitch propellers and single-dial radio tuning. Figure 3: Tesla demonstrated this radio-controlled boat in 1898 for which he was awarded a patent. (Source: Nikola Tesla, 1898 - Nikola Tesla Museum, Belgrad.) RC vehicles have over the years been powered by rubber bands, gasoline, electric motors, "nitro" glow fuel consisting of methanol, castor oil, and nitromethane (the latter also powers dragsters), and rocket engines. They range in price from a few hundred dollars to tens of thousands of dollars for huge homebrew RC aircraft. Applications Unlimited The supremely nimble capabilities of quadcopters along with their relatively low cost are making quadcopters the go-to aircraft for dozens of applications ranging from simply taking high-resolution photos and video from above for personal use, to photojournalism and filmmaking, search and rescue, monitoring utilities, border patrol, surveying, law enforcement and crowd monitoring, wildlife and land management (including counting wildlife and detecting forest fires, illegal hunting, and many more applications. Drones have been used to film the 2014 Winter Olympics, and the United Parcel Service (UPS) recently completed tests using a 42-inch, eight-rotor quadcopter to simulate delivery of medical supplies.1 DHL Express earlier conducted similar tests for the same purpose. Last but far from least is Amazon Prime Air, the company's proposed package delivery system whose goal is to deliver packages up to 55 pounds within 30 minutes. Amazon may or may not be able to make this a reality, but one cannot underestimate this company, which confidently states that "it looks like science fiction, but it's real. One day, seeing Prime Air vehicles will be as normal as seeing mail trucks on the road." 2 The Quadcopter Defined A quadcopter is considerably more complex than four sets of electric-motor-powered rotors operated by remote control. A typical First Person View (FPV)-type quadcopter allows the "pilot" to view real-time images from the drone's camera on a video display, smartphone, or with goggles. A hand-held remote unit controls all flight functions as well as others, depending on what sensors it carries. The control unit contains a transceiver operating on up to nine channels within the unlicensed Industrial Scientific and Medical (ISM) bands at 2450MHz and 5.8GHz and in some cases Wi-Fi. One frequency, usually 2450MHz, is used for control and the higher frequency for video transmission. Operating the controls sends a signal to drone's receiver and then to the drone's control board, which commands the motors to spin either clockwise or counterclockwise and at speeds that alter the flight direction of the drone. Flying any aircraft requires the ability to balance its weight by generating lift and balance moments around its center of gravity, which is accomplished by creating opposite moments. To understand how quadcopters work, see Figure 5. In a quadcopter, both lift and balance are accomplished by the four rotors, the most difficult challenge being generating the moments required to stabilize it while simultaneously producing control forces that allow it to move. Figure 5: How rotors allow drones to fly. (Source: Barry Manz.) Each quadcopter rotor produces both thrust and torque as well as a drag force opposite to the vehicle's direction of flight. When all rotors spin at the same velocity with two rotors spinning clockwise and two rotors spinning counterclockwise (left in Figure 5), the aircraft remains in place while providing lift for maintaining altitude. When two rotors deliver more thrust and two less, the aircraft turns (center diagram.) Finally, to induce pitch and roll, one rotor gets more thrust, two get much less, and the remaining rotor gets the least (far right, Figure 5.) In this way, quadcopters, unlike helicopters, require no tail rotor, a significant benefit. Quadcopters can achieve greater stability by using two sets of rotors in what's called a coaxial configuration, with one set of rotors mounted above the other on a concentric shaft with the same axis of rotation but spinning in the opposite direction. This approach, which is used on some commercial and military helicopters, is also available on some of the most expensive commercial and consumer quadcopters. However, like helicopters (but not fixed-wing aircraft), quadcopters have no inherent aerodynamic stability, so they need an onboard computer to fly, without which they fall like a rock. They also need a battery-operated power supply, rotor speed controllers, and software, and to be fully autonomous they have to combine information from their onboard three-axis gyroscope, magnetometer, and accelerometer with data from GPS and a barometer; all to determine orientation and location. All of the resulting data, as well as inputs from sensors (including cameras) must also be processed, transmitted, and received using an onboard radio transceiver and antennas. This requires prodigious amounts of processing power, high-speed memory, and multiple forms of connectivity in a very small package. Fortunately, all this is currently achievable. DIY Redefined Not surprisingly, the quadcopter DIY community is growing rapidly, and numerous websites can help in building a quadcopter either from scratch or a semi-assembled kit. The community builds on open-source hardware and software such as the Beagleboard, Orocos-Robot Operating System, and DDS-ROS 2.0. A typical "flight stack" consists of firmware such as ArduCopter-v1.px4, middleware such as Cleanflight, ArduPilot, and an operating system such as Linux or several others. Like all hobbyist communities, drones have a large number of suppliers that give drone builders the ability to highly customize their aircraft, and hundreds of different rotors, modules, controllers, and other components are available. For the most technically astute and handy, it is possible to create a drone that can fly beyond the line of sight, miles from the pilot, using lower-frequency transceivers that have greater range. If the drone has the payload capacity and the developer is well versed in electronics, applications are limited only by the imagination. Unfortunately, one use that got U.S. national media attention was a video that shows a drone carrying a semi-automatic handgun firing live rounds when commanded by its creator, an 18-year-old engineering student named Austin Haughwout. He later posted another video of a drone with a remote-controlled flamethrower. Not surprisingly, his activities also got attention from local and federal law enforcement, who (incredibly enough) had a hard time determining if Haughwout actually violated any laws. Situations like this conjure up nightmarish visions at the FAA and Department of Homeland Security, but regulations for commercial drone use and registration of all drones weighing over half a pound have been put into place fairly recently, and more regulation will come. What's to Come Even though quadcopters can already achieve astonishing feats, there's little doubt that they will achieve much more in the years ahead. For example, artificial intelligence and machine learning could allow a quadcopter to make intelligent decisions based on various types of sensor input. Although both AI and machine learning require formidable processing power, this could be provided by data centers (that is, the cloud), eliminating the need for extensive processing to be performed in the drone itself. Package delivery services are obviously immensely attractive to Amazon, UPS, FedEx, and national postal services, but the day when drones will be buzzing around neighborhoods is probably years away. One thing is sure: quadcopters are here to stay, and the potential for novel and useful applications is magnificent. ENGINEERING.COM

The electric vehicle (EV) as a green energy solution has already become a popular and accepted replacement for the internal combustion engine (ICE) vehicle. Their use is increasing daily because of rising awareness of carbon emissions, government incentives like providing privileges EV drivers, and, of course, increasing oil prices and decreasing reserves. According to the Bloomberg NEF (BNEF) 2019 Electric Vehicle Outlook , EVs will account for 55 percent of all new passenger cars worldwide by 2040. In addition, compared to the ICE vehicles, EV motors are more efficient and react quickly with high torque. They are also cost-efficient because of their lower fuel and maintenance costs. Today, there are different commercially successful models of EVs, from economical models to the powerful sports models. Annual global vehicle sales. (Image courtesy of BNEF.) The performance of the EV is closely related to the design of the battery pack that powers the vehicle’s engine and must be able to provide enough current for the motor over an extended time. Since one battery cell provides quite low voltage and capacity, in an EV, hundreds of cells are connected in series and in parallel to provide the required voltage and amp hours (Ah). For example, a powerful EV like the Tesla Model S has 7,104 battery cells. It is wellknown that lithium-ion (Li-Ion) batteries are the most commonly used battery type in EVs. However, several different battery types have also been used in EVs. This article will present the different battery technologies used in EVs and explore their advantages and disadvantages. Important Battery Parameters There is specific information available about each battery, but two common ratings are battery voltage and capacity Ah. The nominal voltage of lead-acid batteries is 2V or 12V, while Li-Ion batteries can be in the range of 3.3-3.7V. Nickel-metal hydride (NiMH) batteries have a nominal voltage of 1.2V. Nominal capacity (Ah) rating represents the current value that can be provided by the battery in one hour. This indicates the amount of energy stored in the battery. Additional important information are battery type and the number of cells in the battery string. In order to select the most suitable battery type for an EV application, the following battery parameters should be considered: Life span—The battery life cycle is influenced by different factors, such as the purpose the battery will be used for, operating conditions, and the depth of battery discharge, but you can generally estimate EV battery life as 8 years or 160,000 km (100,000 miles). Safety—It takes a lot of power to drive an EV, which must be managed properly. A safe operation is assured by a carefully designed battery management system (BMS). Cost—This is a major problem for EVs (compared to ICE vehicles) because an EV’s battery system costs as much as a small ICE vehicle. Performance—This depends mostly on battery operating temperature. High temperature reduces the battery’s life span, while low temperature decreases a battery’s performance. Specific energy—Energy density represents battery capacity in weight (Wh/kg) and the amount of energy stored per unit mass (or by volume). Since the battery system is a significant part of an EV’s weight, the specific energy value is one of the most important parameters for EV batteries. High specific energy is required in applications where a long runtime is required at moderate load. Specific power—Power density represents loading capability. EVs have much better torque than ICE vehicles, and therefore have better acceleration. Battery Types Used in EVs EVs are powered by rechargeable batteries. This battery type provides a reversible chemical reaction, allowing both their discharging and charging process. During the battery discharging process, the electrical current flows from cathode (+) to anode (-), while the reverse process occurs during charging. Battery configuration. Since an ideal universal battery does not exist, different types of batteries are suitable for different applications. The main kinds of rechargeable batteries are lead acid, nickelcadmium (NiCd), nickel-metal hydride (NiMH) and Li-Ion. NiCd batteries are being replaced by more efficient and environmentally friendly batteries such as NiMH and Li-Ion. Although NiCd batteries are robust, less prone to damage and longer lasting, they are an outdated technology and are highly toxic. Lead-Acid Batteries Lead-acid battery technology is mature and reliable, but is considered obsolete. Two common lead-acid battery types are the engine starter batteries and deep cycle batteries used in EVs (these days in forkl ifts or golf carts). This battery type requires inspection of electrolyte level and has a short life span, at approximately three years. These batteries have poor specific energy rate (34 Wh/kg). Because they are heavy (remember, it’s made from lead) in order to provide sufficient energy, in an EV application these batteries could represent 25 to 50 percent of the vehicle’s total mass. They also have a negative environmental impact, generate harmful gases, are toxic, and contain concentrated sulfuric acid. This type of battery was used in the early EVs (e.g., General Motors EV1). Taking into consideration all the mentioned disadvantages and the new developments available in other battery types, lead-acid batteries are not used in any new EV designs. Golf cart batteries. (Image courtesy of bernasjogja.co.) NiMH Batteries Considering the specific energy, NiMH batteries are superior to lead-acid ones in that they have double the value of 68 Wh/kg (with range of 60 to 120 Wh/kg). This feature allows for lower battery weight and reduces the space required for storing the batteries. However, this is still significantly lower compared to the Li-Ion batteries, which have a 40 percent higher value of specific energy. The main advantage of NiMH batteries is their durability. Nickel batteries are well-proven for use in EVs. Many cars with these batteries have been on the road for more than 100,000 miles and have been operating successfully for over 7 years. Basically, this is the only battery type proven to belong lasting (Li-Ion batteries promise a long life, but we’ll have to see if that’s the case after they have had years of real use). In terms of their use with EVs, NiMH batteries’ disadvantages include low charging efficiency, self-discharge (up to 12.5 percent per day at room temperature, with deteriorating performance at higher temperature). Advantages of this type of battery include that they contain little toxic material and are recyclable. Another disadvantage of NiMH batteries is also their heat generation rate during fast charging and discharging. This requires a cooling system that consequently increases the weight of the battery, costs and limits the number of batteries that can be used. A number of legal disputes (patent encumbrance) have limited the use of NiMH batteries in EVs, shifting the focus to Li-ion technology. Li-Ion Batteries Today, Li-Ion batteries are the most commonly used battery in EVs. According to the Financial Times, Li-Ion batteries will take up to a 90 percent share of the EV battery market by 2025. The cathode of the traditional Li-Ion battery is made of lithium cobalt oxide and the anode involves graphite. This technology provides properties to overcome some of the shortcomings of other battery types. The Li-Ion batteries are lightweight, have a good charge cycle rate (meaning they are capable of being recharged many times), higher energy density, higher cell voltage, and a better self-discharge rate (at only 5 percent per month). An amazing specific energy rate of 140+ Wh/kg is definitely the Li-Ion battery’s main advantage. High energy density allows for a lighter battery weight, which increases an EV’s range and performance. Compared to the lead-acid batteries, the Li-Ion is one-third of the weight, is three times more powerful, and has three times the cycle life. Li-Ion batteries have a high price, which is their biggest disadvantage. Their production costs can be 40 percent higher than nickel batteries. However, intensive research on Li-ion technology has led to decreased production costs. According to McKinsey, from 2010. to 2016, the cost of Li-Ion batteries decreased by 80 percent. Safety remains a big concern with these batteries, however, as thermal runaway can cause EVs to catch fire or explode if the battery is overcharging and the heat is not dissipated. Also, fluctuating battery charging can be dangerous. Because of this, an advanced battery management system (BMS) is required, which monitors each cell’s voltage and temperature, the state of charge (SoC) and the state of health (SoH), helping to ensure safe and reliable operation, balanced cells for long battery life and an optimized EV performance. Li-Ion battery pack for a Tesla Model S. (Image courtesy of qnovo.com.) Many types of Li batteries are available, such us lithium nickel cobalt aluminum oxide (NCA), lithiummanganese oxide (LMO), lithiumnickel manganese cobalt (NMC), lithium titanate (LTO) and lithium-iron phosphate (LFP). The increasing popularity of EVs has brought battery technology into focus. Studies of new advanced battery types abound. Recent EV battery designers are focusing on providing features like fire resistance, environmental friendliness, fast charging, and long life span. At times, competing requirements have sacrificed specific energy and power properties. Despite the public perception, the metals in Li-Ion batteries: cobalt, copper, nickel and iron are considered safe for landfills or incinerators. Materials in batteries are nontoxic, including lithium carbonate (e.g., used in ovenware), cobalt oxide (e.g., used in pottery glaze), nontoxic graphite (used in pencils), and a polymer (plastic) membrane. The toxic parts of the battery are the electrolyte and lithium cobalt oxide, which are being replaced by more benign compounds. According to Kate Krebs of the U.S. National Recycling Coalition, “Lithium Ion batteries are classified by the federal (U.S.) government as nonhazardous waste and are safe for disposal in the normal municipal waste stream.” The recycling technology of Li-Ion batteries is constantly under development. Since the availability of the battery material is limited, the recycling not only makes sense environmentally, but also economically. As mentioned before, EVs primarily use Li-Ion batteries, but other types of batteries are also in use. The battery types of some popular EV models are presented here: *Batteries of a plug-in hybrid electric vehicle (PHEV) can be charged by using an external source of electric power, as well by the vehicle’s onboard engine: The PHEV Toyota Prius uses 4.4 kWh Li-Ion batteries, which provide 11 miles of driving with a charging time of 3 hours (115VAC 15A) and 1.5 hours (230VAC 15A). The Chevy Volt uses 16 kWh Li-manganese/NMC batteries, which weigh 400 lb and provide 40 miles of driving with a charging time of 10 hours (115VAC 15A) and 4 hours (230VAC 15A). *Pure electric vehicles include: The Nissan Leaf has 30 kWh Li-Manganese batteries with 192 cells, and weigh of 600 lb, with a driving range of 156 miles and a charging time of 8 hours at 230VAC, 15A, and 4h 30A. The BMW i3 uses 42 kWh LMO/NMC batteries that weigh 595 lb, with a driving range of up to 215 miles and charging time of 4 hours with an 11kW onboard AC charger and 30 minutes with a 50kW DC charger. The Tesla Model S uses a 75kWh battery, has a driving range of 310 miles, with a charging time 9 hours with a 10kW charger and 30 minutes with a 120kW supercharger. Conclusion The battery system is a significant and important part of an EV. The different varieties of Li-Ion batteries are currently the most dominant battery type used in EVs. As a result of increasing demand, there is a requirement for better performance of batteries in terms of reduced weight, better cycling ability, the use of recyclable materials, and general battery performance and better driving range. The next generation of EV batteries will be solid-state batteries where the liquid electrolyte is replaced with a solid, conductive material. This technology provides a high specific energy rate that will provide an improvement over today’s Li-ion batteries. BMW and Solid Power havealready partnered to develop a new solid-state battery for EVs. In addition, Nexeon is researching new materials based on silicon to replace carbon in the anode, which could double the range of EVs. The combination of silicon and binder significantly increases the battery’s energy density. ENGINEERING.COM

Bifacial modules and tracking systems can both increase the production of a photovoltaic (PV) farm, but they also drive up the initial cost of the array, leaving designers wondering whether the added cost is worth the investment. A group of researchers decided to analyze the yield potential and cost-effectiveness of bifacial modules, fixed-tilt mounts, single-axis trackers, and dual-axis trackers to see which, if any, provides the most bang for the buck. In the electric utility world, the technical term for “bang for the buck” is “levelized cost of electricity (LCOE),” and in this context, it’s actually “bucks for the bang”—lower numbers are better. The researchers developed models of the various systems using actual data from a variety of locations, cross-referenced a multitude of factors to validate the models, and ran a slew of simulations. Tracking Systems. (Image courtesy of Rodrıguez-Gallegos et al.) The results, which were reported in the energy journal Joule, show that a combination of bifacial modules and dual-axis tracking delivers the most total energy. That’s not surprising, but it doesn’t take into account the added cost of the bifacial modules or the tracking systems. When those costs were factored in, the researchers discovered that for more than 90 percent of the analyzed land area (i.e., regions within 60 degrees of the equator), bifacial modules with single-axis tracking deliver the lowest LCOE. (In regions close to the equator, single-axis tracking with horizontal tilt is the best. Farther from the equator, single-axis tracking with the rows tilted toward the equator is preferable.) Tracking is the single largest factor that affects yield, but in most cases, bifaciality makes a contribution as well. The following table shows the comparison between any two factors: LCOE comparison (lower numbers are better). (Image courtesy of Rodrıguez-Gallegos et al.) To interpret the table, note that each cell represents the ratio of the column (the “experimental” factor) with the row (the “comparison” factor). Looking at the Bifacial-1T column and the Monofacial-1T row, we see that the bifacial LCOE is 97 percent of the monofacial. In other words, for every million dollars spent per unit of energy from a monofacial system, you’ll only spend $970,000 to get the same amount of energy from the bifacial system. While not nearly as dramatic as the difference between tracking and fixed, it does offer an advantage worth considering. Note, however, that while the researchers had access to each site’s albedo (ground reflectivity) and did factor that into their energy calculations for each site, the table above shows overall averages. Albedo is the strongest influencer of bifacial gain, so a site with a high albedo may outperform the averages in the table, while one with low albedo won’t fare as well. Engineering a 500-Watt Solar Panel Trina Solar is known for its high-power photovoltaic (PV) panels. Ever wonder how they manage to eke out as much efficiency as they can from those modules? Well, you’re in luck, because the company released a white paper that sheds some light on the technology of its 500-watt Vertex solar panels. You can read the paper for all the details, but I’ll discuss one feature that lowers the cost and another that increases performance. High-performance solar module. (Image courtesy of Trina Solar.) Silicon PV cells are made from the same material as the semiconductor chips found in nearly every electronic device, including the one you’re using to read this article. Purified silicon is rolled into a cylinder shape and sliced into ultrathin wafers. The larger the wafer diameter, the lower the cost per unit of area, since it takes the same number of steps to process a big wafer as it does to handle a small one. The industry is moving to wafers that are 210 mm (8.27 in) in diameter. Wafers are then split into individual cells. The cutting process can cause defects in the silicon, which affects each cell’s mechanical strength as well as its electrical properties, so you might think larger cells are preferable. However, since the cell current is proportional to area, larger cells would produce high currents, resulting in the panels getting hotter and losing more power due to resistance in the wires. The ideal panel should produce high voltages and low currents. In order to reduce cell current, PV cells are often cut in half (known as half-cell technology), which decreases power loss and reduces the required wire size. With even bigger wafers, Trina decided to go a step further: one-third cell technology. Why not one-fourth or even smaller? According to the white paper, “Trina Solar’s engineering team calculated the theoretical module power based on the different busbar numbers in combination with the different options to cut the cells in smaller pieces.” The results are shown in the following image: (Image courtesy of Trina Solar.) As you can see, cells cut into fourths and fifths performed incrementally better, but after cells are cut into thirds, the law of diminishing returns makes it not worth pursuing at this time. But there’s a trade-off: the more cuts made to a cell, the greater the potential for cell defects. Again, the white paper explains, “In order to overcome the risk, Trina Solar has adopted a non-destructive low-temperature cutting technology based on the principle of thermal expansion and contraction. Under heat stress, the wafer separates by itself. The cutting surface is very smooth without any micro-cracks. A [non-destructive cutting] NDC cell has a similar strength and mechanical robustness as a full cell and greatly surpasses that of the traditionally cut ones.” A few other innovations include multi-busbar (MBB) technology, optimized cell layout, high-density cell interconnect technology, and hot-spot prevention. (See the white paper for details.) Company white papers are generally used to plug their products, and this one does its share of corporate cheerleading. But regardless of that, I found it to be very informative about PV technology itself, independent of the brand. This paper would be great as a classroom/textbook supplement to discuss the pros and cons of modern PV technologies. Water Splitting with Near-Perfect Efficiency Hydrogen is nature’s near-perfect energy carrier and energy storage system—it’s light, clean-burning, and abundant. Unfortunately, the ability to extract pure hydrogen in a sustainable, efficient, and cost-effective manner has been “10 years away” for many decades. Researchers at Shinshu University recently made a breakthrough that could stop the perpetual shifting of that 10-year mark. Using a method called photocatalysis—employing light to split water molecules—the researchers experimented with the various arrangements of catalysts and found a combination that isolated hydrogen with 96 percent efficiency. Their work was published in Nature. The study was limited to using a narrow UV portion of the solar spectrum, so more work needs to be done on using a bigger part of the solar resource, but the research lays a solid foundation for selecting and arranging materials that can absorb more of the solar spectrum. ENGINEERING.COM

Electric vehicle (EV) customers are always concerned with both battery range and charging rate. Today, EV charging still takes much longer than refueling gas-powered vehicles. This is one of the crucial issues that must be addressed. Battery company Enevate has developed new anode technology that could enable inexpensive lithium-ion batteries to increase EV range by 30 percent. The anodes, which are covered by a porous pure silicon film, could allow the batteries to be charged in only five minutes and deliver 400km of range. All About the Anode In standard Li-ion batteries, lithium ions move from the anode to the cathode when discharging. Consequently, during charging, lithium ions are stored in the anode, and the number of stored ions determines the battery capacity. For years, battery developers have been working to replace graphite anodes with silicon. Lithium ions, when combined with silicon, create Li15Si4, providing a high 15:4 ratio, which means more lithium can be stored in a smaller anode. Thus, silicon anodes could provide higher battery capacity. Furthermore, silicon is a cheaper material than graphite and could be charged up to 75 percent of its capacity in only five minutes. Designing Silicon Anodes Making silicon anodes batteries is a real design challenge. Silicon reacts with lithium during charging to expand 300 percent. During discharging, it shrinks again. Over time, silicon anodes disintegrate due to these changes. This leads to a chemical reaction between the anode and electrolyte that damages the battery, which is why silicon anodes have not been able to last long so far. To overcome this issue, EV battery manufacturers have used a small amount of silicon and combined it with graphite powder using plastic binders. Still, lithium ions react with silicon before graphite, which again leads to the anode disintegration issue. Now, Enevate’s researchers have started using an engineered porous pure silicon film. Unlike the commercial approach, it does not use plastic binders but makes a porous thick silicon film (10 to 60µm) directly on a copper foil. It is covered with a protective coating that prevents the silicon from reacting with the electrolyte. Double-sided finished anode with copper foil in the middle. (Image courtesy of Enevate.) As it does not require high-quality silicon, these anodes are more cost-effective than those with graphite elements. In addition, lithium ions slip in and out quicker in the silicon anode, charging the battery to 75 percent of its capacity in five minutes. Enevate founder and CTO Benjamin Park predicts this will result in EVs with 30 percent more range on one charge. Enevate is now working with multiple EV manufacturers to develop standard-size battery cells for EVs models to be manufactured in 2024 or 2025. ENGINEERING.COM

Pins are widely used within manufacturing machinery and other plants, especially to fix collars and pulleys to shafts. There is a confusing array of choices such as dowels, grooved pins, spiral pins, coil pins and cotters. In this article, I’ll look at what each of these pins is, why it exists and its specific advantages. Pins have an unthreaded, approximately cylindrical shaft, which is inserted into a hole. Many types of pins rely purely on the friction of this shaft within the hole to remain securely in place. Some types of pins also have other features, such as a head or bent tines, which provide a positive lock to prevent removal from the whole. This article will consider pins in these two categories. Pins that rely purely on friction within the hole involve an inherent compromise between high forces and secure fastening. On the other hand, pins with some form of positive lock preventing removal can be held securely without requiring high insertion forces and without inducing a high preload stress on the hole. Pins that Rely on Friction within the Hole to Remain in Position dowel pinThere are many types of pins that rely on friction to hold them in a hole. They can be considered as ranging from completely solid dowel pins to much more compliant roll pins. The more solid the pin, the more precisely it can locate components and greater the shear force it can withstand. A solid pin may be able to provide a secure connection, provided the components it is fitted into have the correct dimensioned holes and are strong enough to resist the insertion force. Conversely, a more compliant pin will be easier to insert, more tolerant of dimensional variation in the hole size and will reduce fatigue loading when there is relative movement between the components being fastened together. The most solid type of pin is a dowel pin. This is simply a solid cylinder of material. These are normally used with an interference fit. Elastic deformation of the pin and hole results in a radial surface normal force, leading to friction that holds the pin in place. Most dowel pins are chamfered at each end to aid insertion. However, because they offer little compliance, dowel pins usually require precise reamed holes that are well-aligned. This type of pin provides the most precise location for concentric holes in jigs and precision machinery. It is also able to transmit the highest shear forces. grooved pin A grooved pin is also a solid pin, similar to a dowel pin. However, a grooved pin has three grooves swaged along all or part of its length. Because the grooves are swaged, the displaced material increases the diameter of the pin along the length with the grooves. When the pin is forced into a hole, the grooves close, giving grooved pins considerably more elasticity than dowel pins and enabling insertion into holes that aren’t as tightly toleranced. They can often be inserted into simple drilled holes with deviations in diameter and circulatory that would not be suitable for dowel pins. It is also often possible to remove and reuse them. These pins are typically driven into interference fit holes to provide strong semi-permanent connections that are robust and resistant to vibrations. They are almost as strong as dowel pins. Typically, there are three grooves at equal spacing around the circumference of the pin, and there are smooth pilot sections at the ends, before the grooves start, to enable alignment before driving the pin into the hole. The grooves may have parallel or tapered sides, with parallel grooves providing a tighter fit that requires higher insertion forces but is better able to resist vibration and remain in position. Half-length and third-length grooved pins have grooves along only part of their length. This enables them to grip along part of their length while providing a smooth clearance pin along another part. Components may be drilled through with a single diameter, and the grooved pin inserted through the stack of components. The pin will firmly locate into one component while allowing the other component to freely rotate. Knurled pins are similar to grooved pins but instead of having grooves swaged longitudinally, they have a knurled pattern swaged into their surface. Grooved pins may have higher pullout forces. CotterCotters are solid pins with a tapered flat face. This enables them to be driven securely into holes with a range of diameters. The flat face may also be used to prevent rotation of the pin, allowing a nut to be attached to a threaded end section. In this case, they are no longer relying entirely on friction within the hole to remain in position. Simple wedges that have no cylindrical faces, but which are also used to secure components by driving into a hole, may also be referred to as cotters. Spring pins, also known as roll pins, are considerably more compliant than grooved pins. They are produced from a thin sheet of material, usually steel, rolled into a cylindrical shell with the outer diameter of the pin. This enables elastic deformation over a range of hole diameters. They can, therefore, be easily inserted into holes and typically have chamfered ends to make it even easier. There are two types of spring pins, or roll pins: slotted spring pin *Slotted pins have the sheet material coiled by less than one revolution, leaving a slot along the length into which the pin can compress. They are generally used for light-duty applications or where a slightly more accurate and rigid location is required. *Coiled or spiral roll pins coil the sheet material by more than one complete revolution, typically about two full revolutions, so that the sheet coils toward the center. This enables them to be made from thinner, more flexible material while achieving a greater overall strength. This means that they are able to withstand a greater shear force than a slotted pin while also being more flexible. The increased flexibility helps reduce stress concentrations and the cyclic loading that can lead to fatigue, particularly around the edges of a hole. Coiled pins are, therefore, well-suited to heavy-duty applications. For example, they are used to pin joints on earth-moving equipment. Pins with Some Form of Positive Locking Pins that do not solely rely on friction to remain in a hole can be fitted much more loosely into the hole but still provide a secure fastening. This can enable rapid assembly and disassembly by hand, often without any tools. It also minimizes the insertion and removal forces, which might pose a risk of damaging some delicate components. split pins A split pin is produced from a malleable material with a half-circular profile. It is bent back on itself so that the two ends together form an approximately circular profile. The bent end is formed into an enlarged circular head. At the other end, the two tines can be initially inserted through a hole and then bent over to prevent removal. R-clip An R-clip is a type of pin produced from a sprung material that can be easily inserted by hand. It has two ends. One is straight and intended to be inserted through a hole in a shaft. The other end is curved so that it can deform outward to fit around the shaft as the other end is being inserted into the hole. It then grips around the shaft, remaining in place despite high vibrations. It allows rapid and repeated assembly and disassembly by hand without any tools. Lynch pin A lynch pin is used in similar applications to R-clips, but it uses a sprung ring attached to a pin. While an R-clip can be used at any position along a shaft, a lynch pin can only be used at an end, for example, to retain a wheel on an axle. There are a range of different pins available, but they all have specific advantages and disadvantages in different applications. If you have a good knowledge of the different options, you should always be able to select the right pin for a particular job. ENGINEERING.COM

Brakes in gear motors are accessories that let the motor maintain a correction position in electric transmission systems. Nowadays, its use has been divided into two major groups: conventional gear motors with brake and the new brakes which use electromagnetic systems. Speed reducers with brakes may be used in several systems. Their use is safety equipment is quite interesting. For example, in automatic garage doors, the brake could lock the door at the top of its run to prevent it from falling due to gravity. How do conventional gear motors with brake work, basically? In regard to their operation, we can find two main options: open brake and closed brake. The difference between both models lies in the way in which the brake works. In some cases, it will be engaged when powered down, while in others, it will only work as long as it is powered up. On the other hand, we can find other braking systems that employ ratchets as a mechanical brake. More specifically, the ratchet prevents it from turning in one direction, and allows it to turn in the other one. What are the main features of brake control units? – Start-up reaction time Brake control systems enable the connection of the starter coil, to then activate the stopping coil. Response times of the brakes during start-up are a key aspect. The sooner a brake is activated, the lesser the heat and wear of a motor during start-up, and the greater the energy savings. – Reaction times on disconnection Reaction times when the flow of direct and alternating current stop are another important factor when designing gear motors with brakes. The faster the magnetic field is eliminated and the sooner the braking effect takes place, the sooner it will provide the motion we seek, and the safer the entire system will be. On the other hand, thanks to a high response speed, the braking precision required for braking improves, as well as the positioning during ungoverned service. – Safety The safety of these systems when a power shortage takes place is also an important factor. Likewise, another key factor for safety is offering a precise response to all nominal loads that affect the system. – Noise levels For any indoor application that requires low decibel levels, noise levels will have to be kept well in mind for these systems. – Stopping precision This is a key factor for positioning systems. Dispersion values in the braking run have to be kept in mind. This mechanical property may be limited if we shorten reaction times. In this manner, we achieve a greater stopping precision. *Gear motors with magnetic brakesThese brakes can exert a greater force than mechanical ones, without resulting in greater shaft wear. Generally, they are more precise, since they can be controlled by electronic means and programming. In addition, these brakes have a greater brake torque, high load grip and significant heat dissipation capabilities. *Gear motors with double disc brake Another common solution in actuator braking systems is the application of 2 parallel motors with individual brakes. This is not a recommended solution, since its application results in greater costs and use of space. To address this issue, the use of double disc brakes offers the possibility of designing a safe braking system with 2 partial brakes acting on a single actuator.CLR

On every electromechanical engineering project, it is of utmost importance to think about how each actuation is to be performed. In order to accomplish them, there are different types of gear motors on the market, but the best choice will depend on the movement we want to accomplish, the power, or the space that is available. In this article we introduce you to an actuation system that may be very useful for certain applications: the parallel shaft gear motors. Do you want to learn about its applications and advantages? Keep reading! Parallel shaft gear motors are a type of gear motor which uses gears to accomplish the speed reduction. They are called “parallel shaft” since the motor shaft and the speed reducer shaft are on parallel planes. It is precisely this disposition that enables for quite flat gearboxes, which are ideal for applications where space is limited, such as stirrers for liquid mixing processes. The parallel shaft gear motor may use three types of gears to accomplish the transmission. Choosing one or the other will depend on the final application and the characteristics we need to obtain within the speed reducer: Spur gears: they are the most widespread. The teeth on their toothed wheels are straight and parallel to the driveshaft of the speed reducer. Helical gears,: their teeth are oblique to the axis of rotation. They transfer greater power and speed. They are likewise more silent and enduring. Double helical gears: used to eliminate the axial thrust; in other words, the rotation elicited by the shaft itself. What are the advantages of the parallel shaft gear motors? Compact design, which translates into less space and weight when compared to coaxial shaft gear motors. Parallel shaft gear motors may reach a power rating of up to 200 kW and a nominal torque for the speed reducer of up to 20,000 Nm. They withstand a high torque and great radial forces. Low vibration, and therefore, low noise levels. CLR

Products are getting more complex, with organic shapes increasingly being specified to achieve the required strength while minimizing material use. There is also a trend for reshoring and producing goods closer to the market where they are sold. The usual business case for close-to-market manufacturing is being able to respond quickly to increasingly dynamic markets. Reducing the carbon footprint involved in transporting goods and making supply chains more resilient are also important drivers. The current need for an urgent ramp-up in ventilator production has sharply brought into focus the need to respond rapidly to increasing demand with a resilient supply chain. Additive manufacturing (AM) plays into both trends. It is making people believe that products can be any shape we like and that they can be locally produced. In reality, AM has little scope to replace conventional production in the foreseeable future. Issues with material properties, feedstock costs, machine costs and build speeds mean that AM will remain a relatively niche process. This article gives a detailed overview of another highly automated manufacturing process that can produce complex shapes in high-strength alloys. Die-casting may not be a new technology, but it is very well-suited to many modern products. I recently reported on how European bicycle manufacturers are reshoring production as demand for high-quality e-bikes ramps up rapidly. These are sophisticated machines that use aerospace-grade materials with correspondingly high prices. In that article, I noted the importance of automation when reshoring production into high-wage economies and identified high-pressure die casting as the most highly-automated process for high-quality bicycle frames. High-pressure die casting is a highly automated process that can economically produce parts with very complex shapes. It is typically suited to high-volume production. This article explores the process in detail, looking at tooling requirements, breakeven volumes, material properties and surface finish. Die Casting Process Basics The die-casting process uses a permanent metal mold, or die. Molten metal is forced into the die cavity at a pressure of between 0.7 MPa and 700 MPa. Die casting is essentially the same process as injection molding. The term injection molding refers to the production of plastic parts while die casting involves production in metals. Die casting is most suited to softer alloys. In the past, tin and lead were popular materials for die-cast parts, such as toy soldiers. Today, zinc, aluminum and magnesium-based alloys are most common. High-strength structural automotive and aerospace components are produced, as well as many consumer goods. Each injection, is known as a shot. A shot may be made up of more than one casting or part, as well as the scrap material that is produced during the casting process. Scrap includes the sprue, where the material enters the die; the runners, which distribute material to multiple part cavities; and the gates, where the material flows into individual part cavities. Sprues, runners and gates are found in other types of casting as well as in injection molding. If you’ve ever made an Airfix model, you will remember receiving the parts still attached to the shot. You may have also sometimes had to trim away flash, a thin layer of material that has leaked into the interface between the two halves of the mold. The parts are attached to the gates and joined together by the runners. In industrial casting processes, the individual parts must be separated from the scrap. This process is known as shakeout and may be carried out using a trim die in a press. The die is made in two halves so that the shot can be removed. One half of the die is fixed and contains a hole through which the molten metal is injected. The other half is closed with a press that must be able to resist the pressure of the metal being injected. This pressure can be considerable, resulting in die casting machines being very large and heavy. Molten metal enters an injection cylinder, known as a shot chamber, and a piston then injects it through a nozzle into the die. Die casting is normally categorized into two basic types, depending on whether the shot chamber is heated: In Hot-Chamber die casting, the shot chamber is located within a large crucible containing molten metal, and it is ejected through a gooseneck that rises up out of the molten metal and into the nozzle. This is suited to lower pressures, of up to 35 MPa, and low melting temperature alloys of zinc and magnesium. Cycle times are typically 200 to 300 shots per hour, although very small mass-produced parts, such as zipper teeth, can be cast at 18,000 shots per hour—five every second! In Cold-Chamber die casting, the shot chamber is not heated, and the molten metal is poured into it. Pressures can be as high as 150 MPa. This process is suited to higher melting point alloys of aluminum, magnesium and copper. It is even possible, although unusual, to cast steel using this process. Process Considerations Die casting machines are rated by the clamping force used to keep the die closed, typically between 25 tons and 3,000 tons. Other machine specifications include the die size, piston stroke and shot pressure. Higher pressures allow rapid cycle times, thin walls and fine features. Dies typically weigh 1,000 times the weight of the part being produced, so a 3kg part will require a 3,000kg die. Dies often include additional cooling channels, which must be machined and hardened. Ejector pins are also required to remove the part after it has been cast. Dies must be able to withstand the thermal shock of repeated thermal cycling and should not soften at the shot temperature. Hardened tool steel is normally used. These considerations mean that dies represent a considerable capital expense. Surfaces running in the direction of die separation must be designed with tapered faces, known as draft angles, to enable removal from the die. If overhangs are required, moveable cores or slides must be included in the die, which can greatly increase complexity and cost. Despite their high initial cost, correctly operated dies can perform over 500,000 shots before showing significant signs of wear. Long die life, combined with a high level of automation, makes die casting very economical for high-volume production. Thin walls of just 0.4mm are possible. In fact, thinner walls generally improve material properties as the more rapid cooling reduces the size of crystals in the solidifying metal, resulting in a fine grain structure. Dimensional accuracy and surface finish are also excellent for a casting method. For small parts, accuracies of 0.1mm are possible and surface roughness can be as low as one micrometer. It is also possible to include inserts such as steel bearing housings and threads during the casting process. Highly Scalable Production Although dies represent a significant cost, the greatest capital investment is in the die-casting machine itself. The time required for die changes varies between a few days and a few hours. Many foundries focus on high-volume production, but die-casting can be economical with batches of 500-2,000 parts. Some parts are even produced in volumes as small as a few hundred a year. Once the die is available, it becomes easy to rapidly ramp-up production. This ability to suddenly increase production rate has been dramatically demonstrated in the challenge to produce ventilators for the Covid-19 pandemic. One die-casting company I spoke to recently, MRT Castings, produces 21 parts for an existing ventilator design. Normally, these are produced in small batches. Because they already have the tooling, they were able to perform die changes on their casting machines and focus their production on ventilators in just a few hours. This meant that the production rate was immediately increased five fold. Achieving Structural Material Properties The two classes of material typically used for structural die-cast parts are aluminum and magnesium alloys. Thin-walled parts and optimized casting processes are often able to achieve fine-grain structures. However, a major challenge for achieving high-strength cast parts is porosity caused by tiny air bubbles becoming trapped in the molten metal. High pressures are required to squeeze metal into intricate molds, especially if rapid cycle times are required. However, this also causes turbulence that traps air and increases porosity. This has two negative effects. First, the voids themselves weaken the material, especially in terms of fatigue performance, by acting as crack initiation sites. Second, the presence of small air bubbles can prevent heat treatment being carried out, which is particularly important for aluminum alloys. Optimizing mold design and casting parameters can reduce turbulence. Most foundries now use flow simulation during mold design, which can reduce turbulence and optimize cooling. Real-time shot control can further improve the properties of cast parts. Applying a vacuum to the mold can help prevent porosity forming while injecting oxygen can cause rapid oxidation in pores, filling them with metallic material. Semi-Solid Casting Semi-solid die casting is another variation on die-casting suitable for producing high-strength parts. Instead of fully melting the metal, it is heated to just below its melting temperature. It, therefore, shares some properties with forging as well as casting. Porosity can be virtually eliminated, which means that excellent ductility and fatigue resistance can be achieved. It also enables full heat treatment and welding. A major challenge for semi-solid casting is the process control of temperature and mixing required to maintain the semi-solid state. Although research demonstrated that semi-solid casting was possible in the early 1970s, these difficulties meant it took some time to become an industrial reality. There are now a few practical semi-solid casting processes. Thixocasting was the first to become a commercial process in the 1990s. It is usually used for aluminum alloys and uses a pre-cast billet that allows the process to be controlled but makes it considerably more expensive. Rheocasting was developed a little later, which is also for aluminum alloys. It reduces cost by avoiding the need for pre-case billets. Rheocasting allows both primary and secondary metal sources to be used, even scrap of the right composition, and offal can be easily recycled. Thixomolding is another semi-solid casting process that produces parts in magnesium alloys. Machines are fed with chipped material from a hopper into a heated barrel containing a screw conveyor. This feeds the magnesium chips while mixing them to create a globular semi-solid state. Thixomolding machines resemble the injection molding machines used for plastics, and they can operate in fully automated cells. Materials Aluminum, magnesium and zinc are the most common types of metallic alloys used in the die casting process. Traditionally, tin and lead were also popular. For many years, the FAA refused to allow magnesium alloy in aircraft interiors due to flammability concerns. However, extensive flammability testing has now largely proven these materials to be safe, resulting in a relaxing of certification requirements. Compared to aluminum, it has a far higher damage tolerance. Its major advantage over carbon composites is that it is fully recyclable. Magnesium alloys are designated using the ASTM and SAE system, in which the first part denotes the two main alloying elements in the alloy and the second part represents their percentages. Elektron 43 is one magnesium alloy that has obtained AMS specification and is now included in the aerospace Metallic Materials Properties Development and Standardization (MMPDS) handbook. Allite Super Magnesium is a leading proprietary alloy with extremely good structural properties for high-strength, low-weight applications. It has been in use within aerospace and defense since 2006 and is now becoming more widely available. Materials like aluminum alloys and carbon-fiber may have excellent mechanical properties, but their sustainability is not so great. They take a lot of energy to produce and, in the case of carbon fiber, is virtually impossible to recycle. Magnesium alloys are fully recyclable and have low embodied energy. The Future of High-Performance Die-Cast Components The transition to a low-carbon economy is now driving widespread industrialization of semi-solid casting processes. Electric vehicles require low-weight and high-strength components with performance close to that required in aerospace. However, this must be achieved in high-volume production using highly automated processes with costs comparable to traditional automotive production. Processes such as Rheocasting and Thixomolding offer a way to achieve this. ENGINEERING.COM

Most of us savor spaghetti. The word that describes the long, thin staple of Italian cuisine, however, is best avoided in the world of additive manufacturing. Typically used to describe the tangled mess of stringy plastic that often results from a failed print, the term gives 3D printers sleepless nights. For 3D hobbyists, an open-source software like Spaghetti Detective can monitor prints and notify users if it detects a possible print failure. But that won’t cut ice with big manufacturing companies where the failure of a single critical part during an industrial 3D printing process can pose a very serious problem. Not only does it lead to a colossal waste of material and time but it also lowers productivity and adds to the cost of manufacturing a part. Artificial intelligence (AI)-powered 3D printing promises to effectively bridge this gap. Armed Forces Prove Early Movers Almost two years back, global security and aerospace company Lockheed Martin and the Office of Naval Research said they were jointly exploring how to apply AI to train robots to independently oversee and optimize the 3D printing of complex parts. The researchers said they would apply machine learning techniques to monitor variables and control the robot during fabrication. These are critical considerations since aerospace-grade metals, including several recipes of titanium alloy, are supplied by foundries. They come with guaranteed strength, porosity and thermal tolerance characteristics. 3D-printed metals, on the other hand, may look identical to traditionally manufactured pieces but may not fit the bill on close inspection. Lockheed Martin’s research was aimed at helping machines make decisions about how to optimize structures based on previously verified analysis. That verified analysis and integration into a 3D printing robotic system was core to the $5.8 million contract signed in October 2018. Last month, army researchers said they discovered how to detect and monitor the wear and tear of 3D-printed maraging steel through sensor measurement. Maraging steels—a portmanteau of martensitic and aging, referring to an extended heat-treatment process—are steels that possess superior strength and toughness while remaining ductile. “3D printed parts display certain attributes, due to the manufacturing process itself, which, unchecked, may cause these parts to degrade in manners not observed in traditionally machined parts,” explained Jaret C. Riddick, director of the Vehicle Technology Directorate at the U.S. Army’s Combat Capabilities Development Command’s Army Research Laboratory. Army researchers study the performance of 3D-printed metal parts and how they degrade as part of ongoing research in vehicle technology. The CCDC Army Research Laboratory at Aberdeen Proving Ground, Md., prints metal parts from powder. (Image courtesy of the U.S. Army.) The study was recently published in the International Journal of Advanced Manufacturing Technology. Todd C. Henry, a mechanical engineer at the laboratory who coauthored the study, says the sensor technology he is developing offers a way to track individual parts, predict failure points, and replace them a few cycles before they break. An experimental validation set was done to assess the real-time fatigue behavior of metallic 3D-printed maraging steel structures. These findings are now being applied to the 3D printing of stainless steel parts and using machine learning (ML) techniques, instead of sensors, to characterize the life of parts, according to Henry. How AI Systems Help Machine and deep learning, subsets of AI, can sift through mountains of data and make very good predictions. Of course, all this is subject to the data being good. ML is broadly about teaching a computer how to spot patterns and use mountains of data to make connections to accomplish specific tasks. A recommendation engine is a good example. Deep learning, an advanced ML technique, uses layered (hence “deep”) neural networks that are loosely modeled on the human brain. Neural nets enable image recognition, speech recognition, self-driving cars and smart home automation devices, among other things. Driving Home the Point In August 2018, researchers from Kansas State University’s Department of Industrial and Manufacturing Systems Engineering (IMSE) integrated supervised machine learning, a camera, and image processing software to create a production-quality monitoring system for assessing 3D-printed parts in realtime. They used a LulzBot Mini 3D printer for this purpose. The researchers used the Support Vector Machine (SVM), which is a supervised machine learning model. SVM applications are typically found in bioinformatics, image and text recognition, among other applications. The images calculated at checkpoints were loaded as inputs to the vectors of the training models. Two categories of training models were loaded into the system: good (identical to the ideal parts) and bad (defective parts). The SVM training algorithm built a model that classified any new model loaded into the system as either a ‘good’ or a ‘bad’ print. If a model was classified as ‘bad’ during the initial stages of printing, a corrective measure was employed to stop the printing process to prevent further wastage, and the part was reprinted. A production-quality monitoring system for assessing 3D-printed parts in realtime, featured was in “Automated Process Monitoring in 3D Printing Using Supervised Machine Learning.”(Image courtesy of Delli et al.) The researchers noted that the main drawback of the proposed method is that the printing process needs to be paused while the images of a semifinished part are taken. Another drawback is that since only top view images are taken, the proposed method might not be able to detect the defects on the vertical plane. Researchers believe that they can overcome these drawbacks by incorporating cameras on the sides of the printer as well to detect defects on both the horizontal and vertical planes. Geometric Accuracy Control Researchers at Purdue University and the University of Southern California are using ML to ensure among other things that the pieces of an aircraft fit together more precisely and can be assembled with less testing and time. The technology allows a user to run the software component locally within their current network, exposing an application programming interface (API). The software uses ML to analyze the product data and create plans to manufacture the needed pieces with greater accuracy. The researchers have developed a new model-building algorithm and computer application for geometric accuracy control in additive manufacturing systems. They claim the improved accuracy ensures that the produced parts are within the needed tolerances and that every part produced is consistent and will perform the same way, whether it was created on a different machine or 12 months later. Layer-By-Layer Scanning In June 2019, Inkbit, a startup out of MIT, announced that it had paired its multi-material inkjet 3D printer with machine vision and machine learning systems. Inkbit uses a proprietary 3D scanning system to generate a topographical map of each layer after deposition. Any discrepancy is corrected in subsequent layers. The data are also used to train a machine learning algorithm that enables the printer to learn the properties of each material and anticipate its behavior. This ensures that parts are built quickly and accurately every time. The layer-by-layer scanning also allows Inkbit to generate a full 3D reconstruction of each part as it was printed, providing a complete digital record of every print. (Image courtesy of Inkbit.) Machine vision (MV) comprises methods used to provide imaging-based automatic inspection and analysis for applications such as automatic inspection, process control, and robot guidance, usually in industry. A machine vision system uses a camera to view an image. Computer vision algorithms then process and interpret the image before instructing other components in the system to act upon that data. “The company was born out of the idea of endowing a 3-D printer with eyes and brains,” Inkbit cofounder and CEO Davide Marini said back in June 2019. Autonomous Decisions on the Fly Similarly, London-based Ai Build develops AI and robotic technologies for large-scale additive manufacturing. It has developed an automated AI-based 3D printing technology with a smart extruder. Its AiMaker attaches itself to industrial robotic arms and is able to 3D print large objects at high speed with great accuracy. Combining advanced AI algorithms with real-time manufacturing data from its sensors and cameras, AiMaker detects problems and makes autonomous decisions on the fly in a bid to achieve the best possible print quality. IoT Control ML is currently also being used to solve the accurate quality of the 3D printing problem by using generative design and testing in the prototyping or prefabrication stage. Bengaluru-headquartered HyCube Works, for instance, has an AI-based smart extruder that can detect problems such as clogging while 3D printing. The Indian startup also uses the Internet of Things (IoT) technology to control its 3D printers remotely. “3D printing involves numerous and complex parameters to be controlled and monitored in the process to achieve an acceptable level of accuracy. Trial and error methods for finding the correct lattice positions or design of appropriate support structures, are not a sustainable or speedy solution,”explained cofounder Reethan Doijode. HyCube Works, according to Doijode, plans to “integrate supervised algorithms for defect detection in real-time build control of the 3D-printed part in the machine, and any disorientation of printing layers or failures in the part would be monitored. The vision system comprehensively scans each layer of the object as it is being printed to correct errors in realtime.” Peek into the Future Big companies like GE, with their massive R&D budgets, are taking further steps. In January 2019, GE Research and GE Additive integrated edge computing with 3D printers to give the latter “‘digital eyes’ to track each layer of every build” in a bid to help manufacturers know in real time whether a part build is good or has to be scrapped. Edge computers sit directly on machines—in this case, 3D printers. Edge systems equipped with machine-learning algorithms can run instant analysis and supply insights to operators, and eventually to the printers themselves. GE believes that while the system can transform the 3Dprinting process by monitoring the building of parts in real time, the Holy Grail is controlling the process at the speed and precision required to prevent or fix minute defects on the fly. Meanwhile, researchers believe that additive manufacturing can get a further boost if AI-powered 3D printers collaborate as teams. A multidisciplinary robotics team at the New York University (NYU) Tandon School of Engineering, hosted by NYU’s Center for Urban Science and Progress (CUSP) and supported by a $1.2 million grant from the National Science Foundation (NSF), is working on one such concept. It is designing autonomous systems for 3D printers on robotic arms attached to mobile, roving platforms. Functioning in teams—a concept called collective additive manufacturing—these printers are equipped with ML and other AI capabilities and could repair bridges, tunnels and other civic structures; work in ocean depths and disaster zones; or even head to space to work on the Moon, Mars, and beyond. Roving printers could repair civic structures, work in ocean depths and disaster zones, or even head to space to work on the Moon, Mars, and beyond. (Image courtesy of NYU Tandon.) The team plans to demonstrate the effectiveness of the algorithms by 3D printing new concretes using mobile printers at NYU Tandon. 3D printers already churn out plane parts and even houses. This AI boost will only take the technology to another level of manufacturing. ENGINEERING.COM