Adjusting Winding and Stacking Machines

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Emerald Bridges
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1 Dreamweaver International Document Number: AN0001 Application Note Rev. 1.0, 03/2015 Adjusting Winding and Stacking Machines 1 Introduction Dreamweaver International separator is designed to be used in existing cell assembly line equipment successfully with appropriate settings. Dreamweaver material is, however, different in its material properties from polyolefin based materials. This application note highlights potential areas of adjustment in winding and stacking machines for successful use of Dreamweaver separators. 2 Background There are two general types of separator operations in cell or capacitor production, stacked and rolled. Each type of operation has its own considerations, but both share characteristics in the handling of separators. Of paramount importance is the result of adding separator between the anode and cathode of a cell without introducing wrinkles, torn, stretched, or otherwise damaged components. Both polyolefin and Dreamweaver separators arrive on rolls slit appropriately for the process they are intended. Dreamweaver separators have had excellent results in replacing polyolefin on assembly lines. One of the differences between the materials is the amount of stretch the Dreamweaver International Adjusting Winding and Stacking Machines Page 1

2 material may be put under during the process. There are two helpful parameters to consider, constant tension, and instantaneous tension. Winding and stacking machines generally allow adjustment of separator tension as one of their setup parameters. These settings can vary from production environment to production environment due to overall process setup and can, in practice, be set to different values on identical machines running in different factories. Due to this variation in settings a trial run paying attention to areas as outlined below is key to successfully using Dreamweaver separator on any given assembly line. 3 Recommendations In switching a winding or stacking machine to DWI separator, the key areas for evaluation are: 1. Roll to roll squareness or tracking 2. Tension in both steady state and instantaneous operations 3. Cutting operations Each of these areas should be evaluated and adjusted as necessary for successful Dreamweaver separator usage. 3.1 Roll to Roll Squareness / Tracking Winding or stacking machines have a good number of rollers over which separator travels to deliver the separator in smooth form to the stacking head or winding roll. The squareness or tracking from roller to roller should be kept within close tolerances to prevent tearing of the separator. Dreamweaver separator stretches very little to accommodate such variances. Figure 1 is a graphic showing the basic misalignment and the uneven forces introduced into the separator should this condition exist. Dreamweaver International Adjusting Winding and Stacking Machines Page 2

Figure 1 - Roll to Roll Squareness As can be seen in Figure 1, the roller on the right is misaligned with the roller on the left. In this case, it is displaced in two axes.

3 Figure 1 - Roll to Roll Squareness As can be seen in Figure 1, the roller on the right is misaligned with the roller on the left. In this case, it is displaced in two axes. Any displacement from normal will result in the path length from roller/separator contact point to differ across the width of the separator. This places one edge of the separator in tension and the other edge in slack or lower tension. This difference in tension is conducive to ripping the material when the tension exceeds the materials ability to withstand the difference either in long time constant form or instantaneous spikes. Besides the separator ripping in the roller area, other clues that this is happening to a lesser degree may be visible sag along one edge of the separator between rollers, tracking problems keeping the separator on the path, or wrinkles being folded into one side of the separator. This type of out of square condition may be masked somewhat if a polyolefin separator is being used. That material's stretch may be able to accommodate some amount of this, although material properties may be altered in virtually imperceptible ways. Using a Dreamweaver separator may bring out-of-squareness conditions to light. Solution A typical failure is torn Dreamweaver separator which can be observed when the machine tension is brought up to operating levels after a threading operation. Tension reduction and tracking adjustment have proven to eliminate this issue. Adjust the machine to bring all rollers into alignment. Please consult machine documentation for instructions on tracking adjustments. Dreamweaver International Adjusting Winding and Stacking Machines Page 3

4 3.2 Tension In stacking and rolling operations, tension should be carefully monitored to not exceed material specifications in either static / long time constant values or short instantaneous tension spikes Z-Fold or Similar Processes A very common operation in the assembly of prismatic or pouch cells is a Z-fold. This involves placing an electrode, pulling a continuous separator over the electrode, pressing or holding the separator down over the electrode, placing another electrode in the stack and repeating the operation until the desired number of electrodes is stacked. As far as the separator is concerned, the tension profile has roughly a periodic appearance as seen below in figure 2: Tension Peak at each fold Tension profile at start of new stack Material safe limit Figure 2 - Typical Stacking Operation Tension vs. Time Time As seen in Figure 2, each electrode that is placed down then has a machine operation to lay the separator over the electrode and hold it down so the next electrode can be placed. These periodic operations can introduce a spike of tension to the separator. The figure shows a case where the peak tension exceeds the material specification limit the result of which is a likely tear in the separator. Typical polyolefin z fold processes may rely on a tension peak implemented as a stretch or snap to promote wrinkle free z folding. This tension peak is absorbed by the stretch in polyolefin and serves the purpose of preventing, or pulling out, any wrinkles. From experience, this may be an Dreamweaver International Adjusting Winding and Stacking Machines Page 4

5 area where the instantaneous tensions from the machine exceed the strength of Dreamweaver separators and tearing can occur. Examples of torn separator during z-folding: Photographic examples will be added when received and permission from owners secured. If you would like to contribute a photo for the benefit of the community, please contact Dreamweaver International through the contacts listed below. Solution Dreamweaver separator differs from polyolefin in that it does not stretch as much but is also more robust against wrinkling. A machine setting reducing the peak tension should be tried, as Dreamweaver separator does not typically require the tension peak to prevent wrinkles. On some machines, this is achieved by reducing the tension on the in-feed section of the machine. Other machines may have adjustable peak tension settings that need to be appropriately set. Please consult the machine instructions or work with the machine manufacturer for adjustments Winding Processes Cell winding processes run at very high speeds and can introduce tension spikes to the separator material during the start or end of the winding operation. Care should be exercised to not exceed material strength limits in a fashion similar to the scenario and techniques described above. A variation of cylindrical cell winding is jelly roll construction of flat or pouch cells where a wound cell assembly is placed in a pouch or box enclosure. Depending on the construction technique used an area to watch for material stressing is in the packaging of the jelly roll to the enclosure. Some squeezing of the jelly roll is not unusual and this can result in stretching the already rolled materials at the short radius areas of the roll (see Figure 3 below). Please note that while Dreamweaver separator has less stretch than polyolefin, it has more stretch than the foils used for electrodes. Dreamweaver International Adjusting Winding and Stacking Machines Page 5

Examples of torn separators during winding: Figure 3 Flattened Jelly Roll Separator Stress Photographic examples will be added when received and permission from owners secured.

6 Examples of torn separators during winding: Figure 3 Flattened Jelly Roll Separator Stress Photographic examples will be added when received and permission from owners secured. If you would like to contribute a photo for the benefit of the community, please contact Dreamweaver International through the contacts listed below. Solution Experimentation with rolling tension can affect the stresses seen by the separator during roll squeezing. Reduction of separator tension during this process may allow for more material to be available in the jelly roll accommodating the squeezing operation. Please adjust the machine according to its instructions or work with the machine manufacturer to reduce separator tension as necessary. 3.3 Cutting Operations At the beginning or end of each cell stacking or winding operation, the separator must be cut to allow the next cell operation to begin. In addition to the tension observations above, Dreamweaver separator may behave differently with the cutting apparatus. Our experience is that cutting operations that use a continuous blade (like a guillotine or paper cutter) will perform acceptably with Dreamweaver separators. The behavior of the cut end of the separator, or loose scrap if any, may have different characteristics than polyolefin. Some adjustments may be necessary to the separator handling mechanism to accommodate the loose end behavior of Dreamweaver separator. Dreamweaver International Adjusting Winding and Stacking Machines Page 6

Examples of cutting blades: Figure 4 - Preferred straight blade cutters Solution Figure 5 - Perforation style cutters Please work with

7 Some machines will use a comb like blade to cut polyolefin under tension, essentially perforating the separator which then tears. Dreamweaver separators may not perform similarly. Examples of cutting blades: Figure 4 - Preferred straight blade cutters Solution Figure 5 - Perforation style cutters Please work with the machine manufacturer to switch to a straight blade style cutter. If already using a blade style cutter, please adjust and sharpen the blades as necessary. Dreamweaver International Adjusting Winding and Stacking Machines Page 7

8 4 Material Specifications Please refer to specific Dreamweaver product data sheets for specifications on material strength. 5 Specific Machine Settings The following machine settings will be updated as information becomes available. It is provided as a guide only. Please refer to the machine manufacturers' information for the most up to date information Manufacturer: XYZ Co. Model # XXXX For DWI separator type ABC: Setting 1: Setting 2: Setting 3: Specific setup examples will be added when received and permission from owners secured. If you would like to contribute a successful machine setup for the benefit of the community, please contact Dreamweaver International through the contacts listed below. Dreamweaver International Adjusting Winding and Stacking Machines Page 8

9 To contact us: USA Dreamweaver International, Inc.- USA 2 Parkway Commons Way Greer, SC Brian.Morin@Dreamweaverintl.com Jim.Schaeffer@Dreamweaverintl.com Laura.Bruce@Dreamweaverintl.com Europe Dreamweaver International, Inc- Europe Sionsweg CR Groesbeek The Netherlands Jan.Averes@Dreamweaverintl.com Asia Dreamweaver International - China No Zhenhau building Rongui, Shunde, Foshan Guangdong China Daniel.Chang@dreamweaverintl.com Revision log: 4/30/2015 Pre release ver /4/15 Added "solution" sects /8/ added note, release 1.0 Information in this document is provided solely to enable implementers to use Dreamweaver International, Inc. products. There are no express or implied copyright licenses granted hereunder to design or fabricate any separator products based on the information in this document. Dreamweaver International, Inc. reserves the right to make changes without further notice to any products herein. Dreamweaver International, Inc. makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Dreamweaver International, Inc. assume any liability arising out of the application or use of any product and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Typical parameters that may be provided in Dreamweaver International, Inc. data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including Typicals", must be validated for each customer application by customer s technical experts. Dreamweaver International, Inc. does not convey any license under its patent rights nor the rights of others. Should Buyer purchase or use Dreamweaver International, Inc. products for any unintended or unauthorized application, Buyer shall indemnify and hold Dreamweaver International, Inc. and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Dreamweaver International, Inc. was negligent regarding the design or manufacture of the product. Dreamweaver and the Dreamweaver logo are trademarks of Dreamweaver International, Inc. All other product or service names are the property of their respective owners. Dreamweaver International, Inc., All rights reserved. Dreamweaver International Adjusting Winding and Stacking Machines Page 9

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