AGILE SHEET METAL FORMING: BASIC CONCEPTS AND THE ROLE OF ELECTROMAGNETIC METAL FORMING

Glenn S. Daehn Department of Materials Science and Engineering

The Ohio State University 2041College Road, Columbus, OH 4320

E-mail: Daehn.1@osu.edu, web page: http://www.osu.edu/hyperplasticity

Key words: agile metal forming, electromagnetic metal forming, embossing, short-run manufacture

Summary: While it is becoming increasingly difficult for high-wage countries to compete in commodity sheet metal forming, another model based on agile sheet metal forming is introduced where the value is in rapid development, modification, and change of high quality products. The case is also made that impulse-based methods such as electromagnetic metal forming has a central role in agile sheet metal manufacturing. 1. INTRODUCTION: WHAT IS AGILE MANUFACTURING

The term agile sheet metal forming here indicates the ability to rapidly respond to customer needs by being able to quickly move from a specified design to producing a number of high-quality, dimensionally-acceptable items. In this paper, the focus will be on sheet metal. The most challenging issue related to making the first run of parts is related to the design, tryout, and finishing of production tooling. In later production runs, the changeover between one toolset to another often becomes the most time-consuming and expensive issue. All of this is thematically similar to lean manufacturing, however there the emphasis is on management procedures and the choosing new systems that are more re-configurable, that are often based on automation and vision systems, etc.

Here, the focus remains on sheet metal that still requires some ‘hard’ tools to provide acceptable dimensional tolerance and reproducibility. However, the focus will be on shifting manufacturing methods to reduce lead time, by reducing the need for matched tool sets and precision alignment between tools, and reducing the need for ‘tuning’ the system by modifying tool shapes. In summary for our present purpose agile sheet metal forming is defined as: using a minimum set of easily changed hard tools to accomplish sheet metal forming that meets conventional dimensional and property specifications. 2. MARKET PULL FOR AGILE SHEET METAL FORMING

The manufacturing world is clearly shifting. Mass production work that involves significant labor and is most cost sensitive is increasingly going to low-wage environments. There seem to be few ways to stop this trend. However, it is also clear that all types of customers are willing to pay for distinctive products that have high design content and are less common. Such limited edition, personalized or customized products have rapid design cycles from conception to the end of the run. However, here the consumer decision is not dominated by price, but instead on design, customization, and availability. This ability to respond positively to local customer demand gives local manufacturers a great advantage over far-away low-cost manufacturers. The local producer can discuss requirements and desires in detail and can deliver the product virtually immediately after production. Also, the local agile manufacturer can also produce rapid modifications to his product to keep it ‘fresh’ or to respond to shifting needs.

Examples of demand for agile-produced goods are all around us. Affluent consumers are fueling a growing demand in custom items in businesses such as: designer-clothing boutiques, shops for custom golf clubs, and providers of custom motorcycles. Such businesses are becoming more numerous. Elements within the department of defense also procure items for special missions and forces in this way, for example many military vehicles (land and air) are built in fleets of less than 500. There is much evidence that there are more and more needs for implements for high-value missions and from affluent consumers worldwide who are demanding these distinctive customized products. This basic postulate seems rather obvious;

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however detailed analysis of this is outside the scope of the present paper. The agile manufacturing methods being discussed presently have the common emphasis

on meeting customer demands quickly with high quality products. However, the basic methods that are described can also be intrinsically low-cost. They are particularly cost-effective when considering modest production volumes on the order of 1000 units or less. However, there is no reason to believe that the methods presented here cannot be competitive with traditional fixed-tool sheet forming methods even on a mass-production basis. 3. ELEMENTS OF AGILE SHEET METAL FORMING

Here a tentative set of some of the essential elements of agile sheet metal forming is presented. These are not all required to be present at one time, but they represent the basic technical goals and directions in developing an agile sheet metal forming production method:

1) One sided dies — The elimination of the punch in a traditional matched tool system immediately eliminates half the tooling that must be manufactured. However the savings can be much bigger, yet. The precision in metal forming tools is often not dictated by the required precision of the component to be manufactured, but instead it is due to providing the proper tolerance between punch and die. Also in tuning the toolset (i.e., making more robust by grinding or welding), the punch usually also must be modified. Savings can also result from the elimination or simplification of blank holders. Superplastic metal forming uses one-sided tools and is enjoying rapid growth in automotive, aerospace and architectural metal forming because of its agile nature. Hydroforming or rubber pad forming, with one-sided tools, is also the standard in aluminum aircraft manufacturing, because production volumes are not large enough to justify matched tool sets.

2) Minimal Static Forces — In order to react large static forces, large presses are required, as are heavy tooling sets. Often for coining, pressures in excess of 500 MPa are required. For this reason coined or embossed areas are usually minimized in sheet forming and when they are present, the coined areas are small (like in coins!). Dynamic or impulse forces do not require large press frames. The blacksmith can produce large intricate components using just a hammer. He has two advantages working for him. His impulses are relatively short in time and can be absorbed by the mass of the hammer and anvil. Also, he is only trying to work a small region of the component at one time. Both these allow him to use a very light and agile forming tool (the hammer).

3) Rapidly Produced Tools — Often it can take months to produce a toolset for sheet metal forming. This is unacceptable in the agile metal forming paradigm. Wherever possible it is desirable to create tools rapidly, even if they are not sufficient for long-run production, due to wear constraints. Tools made from machined polymers, cast ceramics or deposited metals can offer rapid solutions. Often inserts can be used in high wear areas or cutting surfaces. This coupling is a natural fit, if one is to focus on runs on the order of 1000 parts or so. Another of the benefits of superplastic forming is that it can often be carried out with dies made from castable ceramics that are shaped by casting over molds that can be as simple and light as those made from polymer.

4) Reduced Process Steps — The manufacturing of sheet metal articles is progressive in nature. For example, in deeply formed components it is common to use multiple operations where one stretches the metal rather uniformly to thin it and create surface area and the next step produces the required shape. Or, one step may provide a shape, the next a cut, and another flange. Agile manufacture seeks to combine these operations into a smaller number of discrete steps. Later, methods are demonstrated that accomplish this reduction in process steps, often by carrying out multiple operations with a single toolset. The ability to embed electromagnetic actuators in otherwise traditional tooling makes this possible.

5) Increased Degrees of Freedom — Traditional stamping has very few degrees of freedom. Once punch and die geometries are set, about the only adjustments one can make are to change binder pressure (possibly as a function of press stroke) or change lubrication conditions. This causes problems when there are significant variations in the properties of incoming materials and, for example, springback characteristics change. To the other extreme, the blacksmith has almost infinite discretion to modify his process to accommodate

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new materials or modified customer needs. 6) Late Stage Product Differentiation — Processes that can be used to add a feature to

a product (embossment, cutout, feature line, etc.), after it has been nominally finished are agile processes. In many existing processes adding features late in the game will produce unacceptable part distortion. Impulse-based methods have the ability to produce local features without gross product distortion. 4. ELECTROMAGNETIC FORMING: A TOOL FOR AGILE SHEET METAL FORMING

There are many new and existing metal forming methods that largely conform to the agile sheet metal forming principles listed previously. They include: Superplastic forming, spinning, flow forming, hydroforming, peen forming, and progressive sheet metal forming (Descriptions and discussions of each of these can be found in ASM Handbook Vol 14B, [1]). Also, the ultimate agile metal forming methods are those practiced by blacksmiths.

Electromagnetic forming is a method that has many similarities with the impact of the blacksmith’s hammer. Electromagnetic forming is a method where an impulse can be imparted on to a piece of sheet metal in a highly controlled and reproducible manner. In brief, the configuration of the electromagnetic actuator controls the spatial distribution of the force and the stored discharged energy controls the magnitude of the impulse.

A complete description of how electromagnetic metal forming is accomplished and how a process might be designed is beyond the scope of this report, however a brief description follows and the interested reader is directed elsewhere [2-5]. The key to electromagnetic metal forming is the production of an intense transient magnetic field. This is done by charging a capacitor bank to store a significant energy (typically 1 - 100 kJ) at a high voltage (typically 2kV to 20 kV). Fast acting switches allow this energy to discharge through a ‘coil’ or ‘actuator’ that is in close proximity to the workpiece that will be deformed. The primary current creates a magnetic field and induces currents in the nearby workpiece, much in the manner of how a transformer works. These currents generally run in opposed directions and this provides a mutual electromagnetic repulsion between the actuator and workpiece. The magnetic pressure can reach values exceeding 250 MPa, but they usually only persist over a period of less than 30µs. This pressure can act to deform or accelerate the workpiece. It is relatively easy to accelerate conductive metals such as aluminum or copper to velocities in excess of 200 m/s over distances of a few mm. Very high pressures can be obtained if this high velocity workpiece impacts a hard tool. The basic equipment and procedures for electromagnetic forming are fairly well established and the method has been in commercial use since the late 1950’s. Ohio State maintains a website on this technical area as well [6].

The key in using electromagnetic forming as a tool in an agile sheet metal forming process is designing an actuator and process that suit the needs of the desired part. At this point there is not a unified theory or design method as how to best use electromagnetic forming, so instead, examples of useful and agile methods of electromagnetic forming follows. So rather than explaining the detailed theory of electromagnetic metal forming its use will become clear in the following examples.

5. EXAMPLES OF AGILE ELECTROMAGNETIC SHEET METAL FORMING Principles are demonstrated in the following examples. They are organized to build upon

one another. These examples are presented very briefly and details can be found in more detailed papers that have been published previously or are forthcoming. 5.1. The Path Coil and Punchless Electromagnetic Shearing

One of the simplest ways to use electromagnetic forming is simply by having the discharge current run along a pre-defined path in close proximity to a piece of conductive sheet metal. The path can take on virtually any nearly closed path that does not cross itself. A large primary current is provided by the capacitor bank. This induces a secondary current, similar in magnitude and opposite in direction in the nearby sheet. An example of this is shown in Figure 1 where the path is a simple circle made from an aluminum tube that is

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backed in an insulating G-10 Phenolic. On top of this is a thin electrically insulating layer of Kapton Tape, then the sheet to be formed, and the form die sits atop that. In the case shown a 3.2 kJ discharge produces a primary current in the form of a damped sine wave with a peak current of about 150 kA rising in a period of about 12µs. The induced current can be used to deform metal as shown in Figure 1. In this present case the cut channel in the form die is wider than the coil and sits approximately centered over the coil. This arrangement encourages forming, and as will be shown later, this action can also be used to conventional press stamping.

Figure 1. This example shows how a very simple coil made from aluminum tube (center) that is cut and has electrodes added can be embedded in a matching insulating support and used as a metal forming tool. The assembled tool is shown right; the form die is on the left and 1mm thick aluminum formed at modest energy is shown in the center, beneath the coil. Waterjet or laser cutting methods can be used to create such tooling very quickly.

There are a couple important degrees of freedom on the path coil. First, the magnitude

of the force can be controlled both by the capacitor bank discharge energy and the width of the coil. As the coil becomes narrower, the local pressure will scale with the inverse of coil width squared (so long as the distance between the coil and sheet is relatively small). Second, the coil position can be chosen with respect to forming features. In Figure 1 the center of force is in the center of the channel. The force could also be centered over a cutting edge. The cutting edge and coil both can take on complex configurations. With sufficient electromagnetic pressure the electromagnetic coil can shear the metal past the shearing edge. There are many features of this mode of forming that are consistent with the agile forming model. First, as shown in Figure 2, even without a punch, edges can be created that do not have burrs, normally tight clearance between punch and die with sharp edges are required for this. Second, cutouts made in this way can have excellent dimensional tolerance. This is set by the size of the cutout die that would be placed over the sheet and coil. This method is considerably simpler and more agile than traditional shearing with fixed tools and dies, and it produces parts with high edge quality and high dimensional tolerance. Work in this area is active at Ohio State and will be the focus of forthcoming papers [7].

Figure 2. Conventional press shearing causes burr and rollover as schematically illustrated on the left, and photographed in the center. In order to avoid burrs and slivers tight tolerance between the punch and die is typically required. The results of many Punchless ElectroMagnetic Shearing (PEMS) experiments on copper, aluminum and steel alloys have robustly shown a cut profile as shown on the right. Modest rollover is present, but no burr. The tolerance is set by the single tool that sits on top of the sheet and path coil.

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5.2. The Uniform Pressure Actuator for Forming, Coining, Embossing and Micro-Embossing The following section demonstrates the use of an electromagnetic actuator known as the

Uniform Pressure Actuator (UPA). This device has been developed and analyzed in the PhD thesis of Manish Kamal [8], and elsewhere [9]. The UPA is a tool for agile sheet metal forming in at least three ways. First, it uses one-sided tools. Second, it uses very light tooling. Third, it provides opportunities to perform multiple functions in a single operation. Summarized here is the use of UPA to form a fuel cell bipolar plate and micro surface embossed features. More detail on these operations can be found elsewhere [10,11].

Presently there are many possible candidate materials and designs for fuel cell bipolar plates but it is widely believed the use of stamped metal plates will minimize cost and mass and be the standard when fuel cells are in widespread use in portable electronics or transportation applications. Key problems are that the plates need significant mechanical strength to maintain clamping loads without leaking, serpentine channels on the face of the plate should be deep and narrow to optimize efficiency and the plates should be relatively thin but strong to minimize mass. All of this points to the need for a forming technology that can produce very complex shapes from high strength metal sheets.

Here we present a relatively new way of making such a component and through this example we will also demonstrate the overall utility of high velocity forming. Figure 3 schematically presents the Uniform Pressure Actuator (UPA). This device, when coupled to a commercial capacitor bank can accelerate a sheet of metal (typical thicknesses are between 0.1 to 2 mm) to a velocity above 250 m/s (560 mph) over a distance of a few mm. Forming (or cutting, or embossing, or microembossing) is done when the material impacts the form die at this high velocity. Also, impact between the die and sheet from such velocity can produce transient pressures on the order of 10 GPa. Also rates of strain hardening and strain rate sensitivity may be greater at high strain rates (beyond about 103 s-1), and strain rates in these forming operations can be on the order of 105 – 106 s-1, high enough to significantly increase strain hardening rates.

The very high pressure developed at impact provides a number of useful characteristics: 1. The net hydrostatic compressive stress (and possibly the high strain rate) can dramatically improve the formability of the material. For example ordinary magnesium can be formed at room temperature to complex shapes with use of an impact velocity of about 300 m/s [12]. 2. The high interface pressure also permits very fine surface detail to be transferred from the die surface to the workpiece (see Figure 4, detailed later). 3. Because only single-sided tooling is used and the pressures are all very transient, tooling systems are very light and die change is trivial, enabling small lot manufacture at low cost.

The example in Figure 5 shows how the UPA can be used to form a fuel cell bipolar plate in a manner that is competitive with conventional stamping.

Figure 3. Schematic diagram of the uniform pressure actuator. The coil has many turns going into the plane of the paper. The metal sheet and conductive channel provide a secondary circuit that develops a current in response to the primary current.

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Figure 4. Examples of micro-embossing onto sheet from a coin with a holographic optical diffraction grating image (about 2.5 cm across) into 0.13 mm thick copper sheet (left) and 0.25 mm thick 5052-H32 sheet. Both experiments had rough (several torr) vacuum on both sides of the sheet and a standoff of 2.32 mm. The copper was formed at 2.4 kJ; the aluminum was formed at 4.0 kJ. SEM images compare the original holographic surface (electroformed nickel) and the pattern embossed in the copper (right). In both cases the entire area formed was about 100 x 75 mm.

In impact forming the impact pressure can exceed the yield stress of the material by several times. In much the same manner such overpressures can cause material to conform to a hardness indenter, such impacts can cause a relatively soft material to conform to a hard die on a minute scale. An example of this is shown in Figure 4, where an optical diffraction grating in a nickel die (formed by electroless nickel deposition) that has micron-level features is reproduced by plastic deformation on impact between both copper and aluminum sheets (at velocities estimated near 200 m/s) with a diffraction grating. This example shows how impact forming can be used to replicate minute features over the surface of a macroscopic body. This allows forming of features over a range of length scales simultaneously. This may be an enabling technology for micro-forming. One-sided tools have obvious advantages at these short length scales.

5.3. Example: Electromagnetically Assisted Stamping This section focuses on how electromagnetic forming can be used in conjunction with

traditional stamping to make stamping more agile. In this case the basic agility principles of adding additional degrees of freedom and control to the process, and by adding multiple functions in a single operation (such as forming a part and dimensionally calibrating it, or cutting out features).

Figure 5. A stainless steel prototype subscale fuel cell plate (left) and the single sided tool it was formed against using a uniform pressure actuator. Other work has shown these to have good dimensional precision and reproducibility [11].

Traditional, displacement controlled, forming is very commonly used because these methods are well developed, understood, and except springback. The part shape is definitely determined by forced conformation with a hard tool. Impulse based methods can offer improved strain distribution, improved formability, the ability to add crisper part detail, and as detailed in the next section, springback can also be controlled. In many instances, it may be best to use impulse-based techniques only in regions where these special advantages are required. Here methods are described to make modest modifications to the stamping process to improve control, allow ‘tuning’ or adjustment without machining the tool, and to perform

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multiple operations in a single press station. Conversely, the basic procedures proposed here can be used in another toolset to provide new features, late in the production process for product differentiation.

Electromagnetic forming coils can be rather simply embedded into traditional stamping tools, or in the blankholder regions of a toolset [13]. The path coil shown earlier is particularly useful in the blankholder surface. Figure 6 shows two different approaches as to how electromagnetic forming tools can be integrated with stamping systems. Figure 6 (a) shows a system where traditional tooling is used to make the bulk of the shape, but discrete features and corner radii for example require greater formability than the material can offer. These features can be created using a single electromagnetic pulse that can be applied at the end of the forming cycle. This will create the relatively small, but difficult, feature. This eliminates the need for a second operation. This basic approach has been demonstrated in the context of forming an automotive door inner from aluminum [14]. Typically aluminum does not have sufficient formability to form a door inner, and an electromagnetic actuator was used to put a sharp corner in a panel that had a large radius of curvature put in by traditional forming.

The approach of using a single electromagnetic discharge to form a feature (6 (a)) has two drawbacks. First, quite high magnetic flux densities are required to give sufficient electromagnetic force to create the feature in a single discharge. This makes the development of long-life actuators a challenging issue. Second, in making features by a single high velocity impulse, die bounce-off at areas of high strike velocity can make it difficult to maintain dimensional tolerance. These drawbacks can be avoided by using a number of electromagnetic pulses in a hybrid tool of the type shown in Figure 6 (b). The key idea here is that the capacitor bank is optimized for quickly producing a large number of small electromagnetic pulses, and it is coupled to coils in regions of the tool where increased strains are required in order to make a part. The setup is shown schematically in Figure 6 (b). Typically in forming such a part the sheet will neck and tear just outside the punch perimeter. The sheet can be stretched in regions 2 and 3 to add strains that can provide increased line length to provide further punch displacement. Also, actuators 1b and 1a can be sequentially discharged in order to facilitate sheet draw-in into the die. This can be efficiently carried out by using many (5-50) small discharges to strain the sheet just a few percent with each discharge and moving the tool with each cycle to re-establish contact between the sheet and actuator. This avoids the challenging issues associated with handling the large and potentially destructive energies associated with forming with a single discharge designed to developing large strains. The hard die set controls part shape and the relatively small pulses required to produce only a few percent strain with each impulse are not damaging on the coils.

Figure 6. Two concepts of how electromagnetic forming coils can be used profitably in press systems. (a) shows how a single significant discharges can be used to sharpen or add features that would cause failure of the part if they were produced in the initial stamping operation. Increases in formability and improved strain distributions both aid the situation. (b) schematically demonstrates a press where a large number of small discharges can be used to aid draw-in (in region 1) and produce strain in desirable areas (in region 2). After strain or displacement the punch is moved to re-establish close proximity between the sheet and coil.

The concept of using a series of small electromagnetic discharges to alter the strain distribution in sheet metal parts has been tested [13, 15]. Figure 7 shows a series of images related to this. Figure 7 (a) shows a coil path that was inserted into a die. An electromagnetic pressure acts along this line when the actuator is energized by a capacitor bank discharge. During the stamping process, the clamp load is fixed and the punch is advanced a prescribed amount between discharges. This is repeated with each discharge until failure. A result of

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hybrid incremental forming is shown in Figure 7(b). It shows that the draw depth of the parts can be dramatically increased without any reliance on lubricants. The draw depth increased by 44% (from 4.4cm to 6.35cm). This experiment shows that the approach of placing forming energy where required, can significantly increase the ability to make aggressive sheet metal parts. The effect of the embedded electromagnetic coil is to produce tensile strain across the top surface of the part, and the tooling defines the part shape in the usual way. Figure 7 (c) shows the punch force versus stroke profile for the standard process and the electromagnetically assisted bump forming process. With the electromagnetically assisted process, with each cycle the strain across the top reduces the punch force. This reduction in punch force ultimately is responsible for the delay in tearing. Figure 7 represents one of the first experiments of this kind to be carried out. It simply shows that formability can be significantly enhanced and electromagnetic actuators can be embedded in forming dies. Better results will certainly follow as this type of process is further developed and improved.

There are also methods where these basic concepts can be made still more agile and used in single-sided tooling operations such as hydroforming, which dominates aircraft production and is used in other low-volume processes such as prototyping. In both cases the general goal is to get the best from established methods, while treating difficult part features by using impulse-based metal forming methods where needed.

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Figure 7. Illustrations of the bump forming process. (a) shows an actuator path in an electromagnetically augmented stamping punch, (b) shows the increase in draw depth available using such a hybrid process and (c) shows the force-displacement trace for the traditional forming process as well as when periodic electromagnetic impulses are used.

5.4. Precision Calibration and Electromagnetic Springback Control A very different capability that has recently been demonstrated for electromagnetic

forming is the ability to overcome springback by using what is effectively an advanced electromagnetic hammer that can uniformly give a component an impulse against a precise net-shape die. Electromagnetic forming has long been known for its ability to cause one body to collapse in a net-shape manner against another to make slop-free crimp joints. It has recently been demonstrated that this ability to precisely calibrate items can also be applied to large items of fairly arbitrary shape. The results of a recent collaboration between Aerojet Corp. of Sacramento, CA and OSU are summarized in Figure 8. Aerojet developed a process for creating liquid-fueled rocket nozzles by first photo etching paths in copper alloy plates, next laminating and diffusion bonding them together and then stamping them to shape and joining the segments by e-beam welding. A limiting problem with this process was the springback after stamping was too large to permit joining of the segments to a whole. Hot sizing after stamping was attempted but had marginal effectiveness. It caused some delamination and proved to be very slow and expensive.

The figure caption briefly describes the process and the results, and a fuller description

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is available elsewhere [16]. What is significant here is that outside of hot-sizing, this method is unique in that it permits one to precisely calibrate a 3-D item to a tooling form without any compensation for springback. The other industrially common solutions to this problem are using rubber hammers and check-gages to calibrate the part or using combinations of simulations and trial and error to guide the development of tools that properly overbend the part to compensate for springback. These methods are only partially satisfying in that if the properties of the material to be formed change the amount of overbend required also changes. Other advantages of EM sized panels in comparison to hot sized panels are: 1) Evidence of less channel deformation, resulting in more uniform flow in the channels, less pressure drop, greater and more uniform flow admittance, 2) Dramatic cost and schedule improvements: calibration cost is reduced by 98% and operation time is reduced by 95%. EM resizing is now part of the standard procedure for Aerojet’s stamped nozzle process. This approach to calibration and springback control has been effectively used on high strength steel stampings as well [17].

Figure 8. From top to bottom photos on the left show (top) the Aerojet stamped rocket nozzle, (middle) the electromagnetic actuator used in electromagnetic calibration of the liner, (bottom) shows the urethane-potted liner with the nozzle segment above it and the form die to be calibrated to on the top. In the process, several modest electromagnetic impulses are used to provide the nozzle with an impulse that throws it against the die. If the impulse is too small, there are no changes in dimension. If it is too large, it can cause collapse of the cooling channels. The best results are obtained when several modest impulses are used. The graph on the right shows the dimensional error along the minor radii of curvature moving from the nozzle (station 1) to barrel end (station 2 being at the throat). Dimensional error is always less than .0015” after EM resizing, considerably better and more reproducible than those hot resized. EM calibrated panels have been welded together and test fired successfully.

6. CONCLUDING REMARKS This paper has introduced agile sheet metal forming as: using a minimum set of easily

changed hard tools to accomplish sheet metal forming meeting conventional dimensional and property specifications. Also, a number of principles of agile sheet metal forming are introduced. Established but growing processes such as superplastic forming and hydroforming conform to the agile model. Lastly it is suggested that impulse-based electromagnetic metal forming can be a great enabler of agile metal forming. Several examples of this are shown and it is postulated that with some further work in this area a number of other agile impulse-based methods await discovery.

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7. ACKNOWLEDGMENTS: Crystallization of the motives for agile metal forming, and the desire to try to provide a framework is based on numerous conversations with Steve Hatkevich of American Trim Corporation of Lima, Ohio and his co-workers. The work in each of the examples is based on the work of collaborators at Ohio State. In particular, Scott Golowin is working on shearing and the path coil, Manish Kamal, Jianhui Shang and Kristin Banik have been active with the Uniform Pressure Actuator, and John Bradley of GM has been instrumental in its application to fuel cells, and Steve Hatkevich and Allen Jones of American Trim have assisted greatly in the development of robust UP actuators. Jianhui Shang and Vincent Vohnout have greatly developed the Electromagnetic Assisted Stamping methods and concepts. Lastly work on calibration has been performed by Vincent Vohnout, Jianhui Shang, Scott Golowin and Edurne Irondo, of Labein, Bilbao Spain and the rocket nozzle work was done in collaboration with Bill Hayes of Aerojet of Sacremento, CA. Financial support has been provided by General Motors, American Trim, EWI and other sources. References: [1] ASM Handbook, Volume 14 B, “Metalworking: Sheet Forming” (2006). [2] G. S. Daehn, “High Velocity Metal Forming” in ASM Handbook, Volume 14 B,

“Metalworking: Sheet Forming (2006). [3] Moon, F.C., Magneto-Solid Mechanics.1984: John Wiley and Sons. [4] ASTME, American Society of Tool and Manufacturing Engineers: High Velocity

Forming of Metals, ed. E.J. Bruno. 1968, New Jersey: Prentice Hall, Inc. [5] Jablonski, J., Winkler, R., Analysis of the Electromagnetic Forming Process.

International Journal of Mechanical Sciences, 1978. 20: p. 315-325. [6] See www.osu.edu/hyperplasticity. [7] S. Golowin and G. S. Daehn, Work in progress, Ohio State University, 2007. [8] M. Kamal, A Uniform Pressure Electromagnetic Actuator for Forming Flat Sheets, Ph.D.

Thesis, Ohio State University, 2005. [9] M. Kamal and G.S. Daehn, “A Uniform Pressure Electromagnetic Actuator for Forming

Flat Sheets” Journal of Manufacturing Science and Engineering accepted, (2006). [10] M. Kamal, V. Cheng, T.K. Sue, J. Shang and G.S. Daehn, “Replication of Microfeatures

by Electromagnetic Launch and Impact” Proceeding from International Conference on Micromanufacturing 2006, Urbana, IL September 13-15, accepted (2006).

[11] S. Golowin, M. Kamal, J. Shang, J. Portier, A. Din, J. Bradley, S. Hatkevich, G.S. Daehn, "Development and Use of the Uniform Pressure Electromagnetic Actuator for Forming Sheet Metal over a Range of Length Scales, in press, Journal of Materials Engineering and Performance (2006).

[12] A. J. Turner, Spot Impact Welding of Aluminum Sheet, M. S. Thesis, Ohio State University, 2002.

[13] Daehn, G.S., Shang, J., Vohnout, V.J. Electromagnetically Assisted Sheet Forming: Enabling Difficult Shapes and Materials by Controlled Energy Distribution, in The MPMD Fourth Global Innovation Symposium. 2003.

[14] Vohnout, V.J., A Hybrid Quasi-Static Dynamic Process for Forming Large Sheet Metal Parts from Aluminum Alloys, in Materials Science and Engineering. 1998, Ohio State University: Columbus.

[15] J. Shang, Electromagnetically Assisted Sheet Metal Stamping, PhD Thesis, Ohio State University, 2006.

[16] E. Iriondo, B. Gonzalez, M. Gutierrez, V. Vonhout, G. Daehn, B. Hayes, “Electromagnetic Springback Reshaping”, Proceedings from 2nd Annual ICHSF 2006: Dortmund, Germany March 20-21, accepted (2006).

[17] See E. Iriondo, B. Gonzalez, M. Gutierrez, I. Eguia and G.S. Daehn, “New approach for HSS Springback correction: Electromagnetic pulses”, Proceedings from the International Conference New Developments in Sheet Metal Forming, Stuttgart, Germany May 10-12, accepted (2006). And additional work is in progress.

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