Directed energy deposition (DED), which leverages commercial robotic welding systems, is an agile and economical large-scale additive manufacturing (AM) process. DED AM is low risk since it leverages existing welding process equipment, consumables, procedures, and standards – which all have decades of proven performance. Using DED “digital” computer-aided manufacturing (CAM) software, component structures can be additively manufactured, welded, cladded, or repaired utilizing solvers that automate robotic path plans. Robotic CAM software makes high-mix/low-volume applications affordable. It also enables multi-process digital manufacturing in which welding, AM, and metalworking (milling, grinding) can be combined into “lights-out” applications. To achieve this manufacturing advantage, a “digital twin” must be set up of the robotic system and carefully calibrated to the physical system for robust operations. Once the digital twin is developed, most DED AM equipment suppliers will offer a “pre-engineered” system to recover their system development costs over many units and provide better value to industry.

Due to the complexity of existing DED software, the range of commercial robotic DED systems available has been limited. EWI’s arc welding & DED processes team has been busy over the last two years transforming EWI’s robotic welding laboratory into a “digital” robotic manufacturing laboratory. Six commercial robotic systems have been modeled in Autodesk PowerMill CAM software, and new equipment like Cloos Robotics’ multi-process system are in progress. Each robotic system has a digital twin and post-processor that have been calibrated to ensure precise CAD-to-path deposition performance. These range from 7- and 8- axis systems for single and double-sided builds to a duel-robot 14-axis system for multi-process applications to our new Navus robotic gantry DED system which offers the largest metal DED-build capacity available in North America for application development. 

As an example, the Motoman 7-axis DED system (Figure 1) is equipped with a Fronius TPS 500i welding package. It is used for both single-sided and double-sided build platform builds using a head and tail stock positioner. The Motoman DED system was used in a National Shipbuilding Research Program (NSRP) project to make a commercial ASME steel pipe coupler and nickel-aluminum-bronze high-pitch propeller blade.

EWI’s robotic DED lab also includes two OTC Daihen 8-axis systems, a 6-axis Fanuc system, a 14-axis Genesis duel-arm Fanuc system, and the Navus multi-process 11-axis ABB robotic gantry system (Figure 3).  This gantry system offers an extra-large build volume of 8-10’ high (depending on ceiling conditions) x 14’ wide x 30’ long. Other features include a 60-kg arm capacity, an ATI tool changer, and a diverse sensor package for quality, thermal, and dimensional management. The ATI tool changer can be used to switch between deposition apparatus (arc to laser to hybrid laser arc equipment) and metalworking apparatus (a 5-hp spindle with grinding, brushing, and burring capabilities). The system offers a 2-axis 1-ton tilt/turn positioner for single- and double-sided builds, as well as a Binzel neck-changer and maintenance station to support lights-out build conditions.

EWI is focused on improving the economics of robotic DED systems for large-scale structures.  This technology can be used to replace large-scale castings, build complex structures and much more. Please contact Dennis Harwig at [email protected] or Michael Carney at [email protected] to explore the potential for your structure manufacturing needs.

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For a more detailed look at EWI’s recent arc DED research, click here.

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EWI is pleased to present several live events in the month of October:

• The EWI Additive Manufacturing Automotive Workshop — Join EWI and Additive Manufacturing Consortium experts to learn about recent advances in AM technology. Tuesday, October 5, 2021 in Troy, Michigan.

• Fundamentals of Welding Engineering Course — This week-long class offers engineers and technicians a comprehensive introduction to welding processes, metallurgy and weldability, design and testing, and qualifications and procedure review. October 11-15, 2021 at EWI Headquarters in Columbus, Ohio.

• Robotics Integration Course — Through both classroom and hands-on instruction, this 5-day training gives students an understanding of robotic concepts that can be applied in a variety of production settings. The course culminates with each participant wiring and assembling their own fully functioning robotics cell. October 8-12, 2021 at EWI/Buffalo Manufacturing Works in Buffalo, New York.

• EWI Fall Member Day will be held as a live, virtual program on October 26, 2021. To learn more about this event, click here. For information about EWI membership, visit ewi.org/services/membership-services.

To learn more about upcoming EWI classes, workshops, conference presentations, and special programs, visit ewi.org/events/ today.

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By Henry Cialone
President & CEO, EWI

The existence of a manufacturing workforce shortage is old news. I wrote about it in a December 2019 blog, and it wasn’t new news even then! But what we’re hearing now from the manufacturing community echoes what we’re all hearing, reading, and seeing more broadly — the pandemic has exacerbated workforce shortages across most sectors of the United States economy.

• People have been retiring both earlier and in greater numbers in response to the pandemic. This is especially challenging when you add it to the “gray wave” manufacturing was already experiencing before the pandemic.
• Further, some people have been pivoting to other kinds of work, sometimes to be able to work from home. Others have been moving to new geographic locations. In both cases, more people have been leaving their jobs. 
• Additionally, many people have been rethinking their ideas about work, and that has translated into an increased desire for more interesting, fulfilling, and/or balanced jobs and career paths.

The impact on small to medium-sized manufacturers (SMMs) is an acute workforce crisis. Experienced workers are leaving in droves, and it’s hard to get new workers in the door — even with the promise of training. When new workers do come on board, there’s a significant risk of them leaving because they find the job uninteresting or being lured away after six months because competitors can offer higher wages for already-trained labor.

Being shy a few workers is one thing. Operating without 25% of the employees you need to run your operation is another thing altogether.

Here’s what we’re doing about it…

To read the full article, click here.

The post One Piece of the Manufacturing Workforce Challenge Puzzle appeared first on EWI.

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Want to contact an EWI expert about a project? Call 614.688.5152 or click here.

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A standard electric vehicle (EV) automotive battery can be decomposed into cell level, module level, and pack level. A cell mainly includes the anodes and cathodes, a module includes multiple cells, and a pack includes multiple modules.

The three most common metal-to-metal joints in a lithium-ion battery pack are foil-to-tab, tab-to-tab, and tab-to-bus. All three joints pose joining challenges, but of the three, welding multiple layers of foil to a tab is the most challenging. The joint is often made up of dissimilar metals, and the metal thicknesses are mismatched. The tab is relatively thick (e.g., 0.2 mm) while the multiple foils are extremely thin (e.g., 0.025 mm). The image below shows a schematic of a large format lithium-ion pouch style cell.

The foil-to-tab weld is needed to gather all the anode and cathode foils inside the cell and join them to tabs which exit the cell casing allowing the cell’s energy to be transferred to an external source. There are two foil-to-tab welds in each cell, and hundreds of cells in a typical large format lithium-ion battery pack. Because of the series and parallel connections, one failure in a foil-to-tab joint will compromise the output of the entire pack. Therefore, a robust joining process is required to meet the joint requirements, such as satisfactory joint strength, low electrical resistance joint, and minimum intermetallic layers in joining dissimilar materials.

Ultrasonic metal welding (UMW) was evaluated for this particular application. A schematic of the process is shown below. Ultrasonic metal welding is capable of welding similar and dissimilar combinations of battery-related materials such as copper, aluminum, and nickel. Ultrasonic vibrations, typically 20 to 40 thousand Hz, are used to rub two parts together under pressure. The scrubbing action breaks off oxide and contamination on the surface and breaks down surface asperities creating two smooth, clean metal surfaces. Once these contact under moderate heat and pressure, a weld is formed.

The process has several advantages. Since it is a solid-state process, it can be adapted to dissimilar materials combinations and avoids most concerns about formation of intermetallic compounds. It is ideally suited to welding the highly conductive materials used in batteries including plated copper and aluminum. It does not require high power, and weld cycles are very short, fractions of a second. It also joins multiple layers of thin materials in one operation and provides a high strength joint with low resistance.

Other joining processes including soldering, magnetic pulse welding (MPW), resistance spot welding (RSW) and laser beam welding (LBW) were also considered, but they lacked certain attributes that make UMW a more desirable joining process for multi-layer foil to tab application.

• Soldering can be used for joining pouch cell tabs. It is especially desirable for joining dissimilar materials, but the use of flux can increase the chance of corrosion which can directly affect the strength of the joint.
• MPW can provide high strength joints, but the process can create large distortion and the induced current might damage the internal components of the cell. Note that the application of MPW for battery components is under research, therefore, this technology is not ready yet to be used by the battery manufacturer.
• RSW relies on the resistance of a material to generate heat for joining. However, the aluminum and copper foils typically used in the battery industry have extremely low resistance. In addition, aluminum alloys form a tough surface oxide layer which inhibits RSW and is further compounded by the fact that the oxide layer is present on both sides of each foil layer.
• LBW is very sensitive to gaps between material layers in the weld joint. As a general rule, the gap should be less than 10% of the material thickness. Joining a 12 µm foil would require a 1.2 µm, or less, gap which is very difficult to achieve and requires excessive fixturing. An additional issue with LBW is sensitivity in the use of reflective material.

UMW does not rely on bulk resistance and inherently scrubs away oxide layers as part of the process.  Because UMW is self-clamping, gaps are not an issue. In addition, the UMW process is not sensitive to reflective material.

A typical large format lithium-ion cell uses copper foil as the anode current collector and aluminum as the cathode current collector; therefore, both copper and aluminum were evaluated with the UMW process. The experimental joints, as shown in the image above, were limited to similar material stacks only, meaning aluminum foils were joined to aluminum tabs and copper foils to copper tabs. The tab thicknesses were held constant at 0.127 mm. Two foil thicknesses, 0.012 and 0.025 mm, and two foil stack heights, 20 and 60 layers, were evaluated to prove feasibility and to study the effects on joint properties as the foil thickness and number of foil layers varies.

Analysis of the above cross sections provided a closer look at foil compression, foil damage, and the final state of the weld joint. The samples with thinner and fewer layers of foil show an increase in foil movement directly adjacent to the weld zone.  In contrast, the samples with thicker and more foil layers showed a consolidation of the foils adjacent to the weld zone often resulting in a larger bond region. The consolidation and increase in bond region occurred because the thicker foil stacks bottomed out on the weld tool causing compression in the area adjacent to the weld zone.

Conclusions:

Joining multiple layers of thin foils to a tab in a single ultrasonic metal weld operation is feasible. The welds are achievable without fracturing the delicate foil layers. Bonding occurs at the foil to tab interface as well as at each foil-to-foil interface which results in a strong, highly conductive electro-mechanical joint. This process which is considered a low energy consumption process can be used for joining dissimilar materials in fractions of a second.

Infrared (IR) videography shows that all joints, except the copper sample made from 60 layers of 0.025 mm foil, stayed under 60 ºC during the weld cycle indicating the process will not harm nearby heat sensitive components. Below is IR videography of a 60-layer foil stack being welded to a tab. The segment of the video showing the weld cycle is slowed down dramatically to illustrate the heat generation in a large foil stack.

If you would like further information on this topic, please contact Amin Moghaddas at 614.688.5188, or by email at [email protected].

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Does your company want to incorporate robotics into its production line? Do you feel like you staff needs more familiarity and training in robotic processes before you get started? EWI can help!

The EWI Skillform Center offers three levels of robotics competency courses to bring your employees up to speed in the technology before you make decisions and investment to implement robotics on your factory floor. EWI’s Mike Garman, Senior Automation Engineer and Robotics Training Director, describes the course offerings in this brief video:

To find about upcoming classes or to register, click here.

If you have questions about these or other training courses offered by EWI, contact Susan Witt, Manager of Industrial Training, at [email protected]ewi.org.

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