Archives For Corporate Blog

A Sense of Adventure

Elaine Pelz —  September 16, 2014 — 1 Comment

It is amazing what a little drive, ambition, and perhaps fear can do…

EWI engineer Marc Purslow completed his epic cross-country bicycle journey late last month. It started with a desire to do something big that mattered. Back in August 2013, he decided to ride his bicycle across the country – all the way from Maine to California. His goal was to raise money for the After School All-Stars program and use the experience to teach kids that with motivation, determination, and a plan you can conquer just about anything.

Marc left Bar Harbor and the Atlantic Ocean on July 5th, and reached San Diego on August 23rd. All in all he racked up some impressive stats, including:

Purslow - Route 66 -2Raising over $13,000 for kids
Pedaling 3,645 miles in 43 days
Burning 304,700 calories – give or take a few
Sweating through a high temperature of 105F
Riding over hundreds of miles of gravel and mud,
Surviving a hurricane, endless headwinds, and a haboob (look it up!)
And, he’s here to talk and laugh about his 12 flat tires, 5 broken spokes, 1 broken wheel, and yes, 1 complete bike smash-up 18 miles shy of the Pacific.
Yet he still pedaled on!

What helped make it actually happen, Marc said, was talking about it. Telling every single person he knew about the trip made him keep his commitment, and turn a challenge into an inspirational journey. And it kept him going on the toughest of days, when his depleted energy hit the wall of unfriendly terrain and endless obstacles.

Marc met some incredible people, traversed our country’s byways and small towns, learned a lot about himself, and inspired us to seek out our own goals and ambitions. One noteworthy life lesson; due to his continual exposure to an expansive horizon, Marc now finds himself looking up at the sky and the vistas around him more often, instead of always at the narrow path directly in front of his feet. If that’s not the definition of uplifting, I don’t know what is.

The Pacific!

The Pacific!

 

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, the metal thickness is mismatched, and one side (the tab) is relatively thick (e.g. 0.2 mm) while the other is made up of multiple, extremely thin, layers. The image below shows a schematic of a large format lithium-ion battery pack cell.  The foil to tab weld is needed to gather all the current collector plates (foils) inside the cell and join them to a tab which exits the cell casing and allows 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 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.

 

Lithium-ion Cell Cutaway

Lithium-ion Cell Cutaway

 

Ultrasonic metal welding (UMW) was evaluated for this particular application. A schematic of the process is shown below. Ultrasonic metal welding is very capable of welding similar and dissimilar combinations of battery related materials such as copper, aluminum, and nickel. Ultrasonic vibrations, typically 20 to 40 thousand Hertz, 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.

 

UMW-process-schematic

UMW-process-schematic

 

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. 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.

Both resistance spot welding (RSW) and laser beam welding (LBW) were also considered, but lack certain attributes that make UMW a more desirable joining process for the lithium-ion battery application. 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. UMW does not rely on bulk resistance and inherently scrubs away oxide layers as part of the process. LBW is very sensitive to gaps between material layers in the weld joint. As a general rule of thumb, 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. Because UMW is self-clamping, gaps are not an issue.

 

Joint Configuration Used For Testing

Joint Configuration Used For Testing

 

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 have been 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 0.005-inch. Two foil thicknesses, 12 and 25 µm, 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.

Cross Section - 20 Layers Of Thin Copper Foils to Copper Tab

Cross Section – 20 Layers Of Thin Copper Foils to Copper Tab

 

Cross Section - 60 Layers Of Thick Aluminum Foils To Aluminum Tab

Cross Section – 60 Layers Of Thick Aluminum Foils To Aluminum Tab

 

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.

IR videography shows that all joints, with the exception of the copper sample made from 60 layers of 25 µm 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, feel free to contact Mitch Matheny at 614.688.5000, or by email at mmatheny@ewi.org.

 

 

 

rig_w_helicopterEWI associates have the best training in the world.  But they don’t train JUST in their fields of expertise.  Earlier this month, Sam Lewis and I completed training far outside our comfort zones.  We spent three days on the Louisiana Gulf Coast learning what life is like on the oil rigs where EWI’s expertise is utilized.  The first requirement to set foot on a rig anywhere in the world is certified completion of Basic Offshore Safety Induction Emergency Training (BOSIET).  The three-day course ensures the ability to operate safely offshore, which includes more than might be expected.  We trained in safety “induction” (basic offshore safety standards), survival skills in the open ocean, and how to handle emergency situations.

First, we reviewed usage of different types of extinguishers before actually putting out fires in the training center in Houma.  (Louisiana’s 95-degree heat and 95% humidity effectively duplicate the conditions of a platform fire.)  Then it got exciting.  After reviewing emergency procedure, we donned coveralls and life jackets, proceeded to the facility’s lifeboat and launch mechanism for lifeboat muster, boarded the TEMPSC (Totally Enclosed Motor Propelled Survival Craft—like you might have seen in the movie Captain Phillips), and actually launched from platform height to a purpose-built water tank below.

In preparation for transport to the platform, we had trained in safe travel aboard a helicopter, and correct emergency procedures in the event of a forced landing.  Because of the risk of an emergency water landing, much of the training focuses on escape from a capsized sinking helicopter.   A simulator lowers a helicopter mockup big enough to hold five people into a swimming pool and turns it upside-down.  Trainees, strapped inside in full gear, then have to make their escape to the surface.

All of us exited the “helicopter” UNDERWATER AND UPSIDE-DOWN.  It sounds terrifying, but once you’ve been through it, you might even describe it as “fun.”

So remember, EWI associates are willing to go the extra mile to ensure that those skills can be applied wherever you need them—even on an oil rig hundreds of miles from shore.

Sheet Metal Welding Conference XVI, sponsored by the American Welding Society – Detroit Section in cooperation with EWI and the Advanced Laser Applications Workshop (ALAW), will be held in Livonia, Michigan, October 22-24. EWI Technology Leader Jerry Gould is co-chair for this year’s technical program, and Technology Leader Ian Harris is chairing a session titled “Arc Welding: Lightweight Materials.”

EWI Associates George Ritter, Warren Peterson, and Jerry Gould will also be making presentations during the 3-day conference.

SMWC XVI is an excellent opportunity to get up-to-date on the most recent technical breakthroughs in nearly every aspect of sheet metal joining. The biennial conference includes information of importance to anyone welding sheet metal plus access to the leading technical and equipment experts.

For program and registration information, click here.

shutterstock_150401579Is your work related to the oil & gas industry? If so, we need to hear from you!

In an effort to identify and address the issues and needs of the Exploration and Production (E&P) sector of the oil & gas industry, EWI is conducting an E&P Technology Survey.  The results of this survey will be reviewed and considered by industry stakeholders at the first-ever Global Oil and Gas Technology Workshop hosted by EWI, September 15-16, in Houston, TX.

The future of E&P depends on input from those involved in the industry. If you would like to add your input to this important conversation, Please complete this survey by Friday, September 12.

 

 

Motion System

Single-Mode Fiber Laser Welding with a Scanner on EWI’s High Speed Motion System

I was setting up a demonstration of high-speed fiber laser welding using a scanner in EWI’s laser lab. I mounted a ScanLab scanner to EWI’s high speed motion system to manipulate and focus the laser beam. The laser used was a 600-watt IPG single mode fiber laser. I programmed the motion system to move the scanner in long straight lines to create long straight welds across a piece of sheet metal. The scanner was then programmed to make four circular welds at several locations. The purpose of the program was to show the work envelope of the motion system.

During this high-speed fiber laser welding, a small plume is created where the focused laser beam melts the surface. However, sometimes this plume varied in intensity as the scanner was moved through the work envelope. There are a few reasons that the plume can quit during a weld. It can happen if the laser stops working or varies its output power. A less intense plume could also be caused by something blocking the beam or debris on mirrors or lenses. A third possibility is shown in the video below. The sheet metal, is not secured well and can distort or move up or down. This will cause the laser beam to be out of focus at that location. When this happens, the focused laser spot size increases in diameter, the power density drops, and the laser beam stops melting the surface.

Video: When the Laser Beam goes Out of Focus during a High Speed Fiber Laser Weld

This video demonstrates the importance of maintaining the focus position of the laser beam all across the work envelope. How much the laser beam can be out of focus, its “depth of focus”, should be determined experimentally for different situations. Something else to observe is the distortion of the sheet metal. The laser welds shrink as they cool causing residual stress. This causes the sheet metal to lift-up or otherwise move. Watch the front edge of the sheet lift.

For more information on high-speed fiber laser welding please contact Jay Eastman at jeastman@ewi.org.

EWI-TWI 2The 7th International Seminar on Joining Aerospace Materials will be held September 17-18, 2014, Organized by EWI and TWI, the biennial event is attended by leading technologists and engineers involved in state-of-the-art aerospace manufacturing and assembly of aircraft structures. The upcoming event will be hosted by Boeing at the Boeing Longacres Customer Center outside of Seattle, Washington.

Topics will focus on improved or recently developed technologies for welding, joining,
additive manufacturing, and allied technologies for a variety of materials (aluminum,
titanium, nickel-based alloys, and composites). Manufacturing and repair needs will also be addressed.

Interested in attending? The deadline for registration is August 29, so hurry! To learn more, click here.

To sign up now, click here.

PrintEWI will hold its inaugural oil and gas industry-focused workshop this September 15-16, at the Houston Marriott Energy Corridor in Houston, TX.

The Global Oil and Gas Technology Workshop, sponsored by the EWI Strategic Technology Committee (STC) for Oil & Gas, will bring together leaders across the oil and gas industry in an open forum in which they may network, share insights and discuss industry challenges. EWI membership is not required to attend.

To register for the workshop, click here. For more information on how to join the EWI STC for Oil & Gas, please contact Jon Jennings, Business Development Director, at jjennings@ewi.org.

Buffalo’s brand new advanced manufacturing institute, now officially named Buffalo Manufacturing Works, has been established as a regional collaboration between industry and academic partners with EWI in the lead.

Details of the center’s launch plans were reported in The Buffalo News late last week. To read the article, click here. To visit the Buffalo Manufacturing Works website, click here.

- – - – - – - – - – - – - – - – - – -

AMIisBMW

 

Congratulations to EWI associate Miranda Marcus on her recently published article in Assembly (magazine): “Comparing Methods for Plastics Assembly.” Reading this article is a great way to learn more about plastics assembly. Explore the options for welding plastic parts — such as ultrasonics, laser, hot plate, and radio frequency — as well as factors to consider when deciding on a joining process.

The full article is found in the August 5, 2014 online edition of Assembly.

marcus

Author: Miranda Marcus, Applications Engineer, EWI.

The article is freely available online at http://www.assemblymag.com/digitaleditionsased. EWI Members may request a copy of the article by contacting the EWI Library.