Editing Electromagnetic forming

{{Citation style|date=November 2019}}
[[Image:aluminium-can-pinched.jpg|thumb|150px|A pinched aluminium can, produced from a pulsed magnetic field created by rapidly discharging 2 kilojoules from a high-voltage capacitor bank into a 3-turn coil of heavy gauge wire.]]

'''Electromagnetic forming''' ('''EM forming''' or '''magneforming''') is a type of high-velocity, cold [[:Category:Metal forming|forming]] process for electrically conductive metals, most commonly [[copper]] and [[aluminium]]. The workpiece is reshaped by high-intensity [[Pulse (signal processing)|pulsed]] [[magnetic field]]s that induce a current in the workpiece and a corresponding repulsive magnetic field, rapidly repelling portions of the workpiece. The workpiece can be reshaped without any contact from a tool, although in some instances the piece may be pressed against a die or former. The technique is sometimes called ''high-velocity forming'' or ''electromagnetic pulse technology''.

== Explanation ==
A special coil is placed near the metallic workpiece, replacing the pusher in traditional forming. When the system releases its intense magnetic pulse, the coil generates a magnetic field which in turn accelerates the workpiece to hyper speed {{quantify|date=January 2016}} and onto the die.
The magnetic pulse and the extreme deformation speed transforms the metal into a visco-plastic state – increasing formability without affecting the native strength of the material. See the [http://www.bmax.com/technology/magnetic-pulse-forming/ magnetic pulse forming illustration] for a visualization.

A rapidly changing magnetic field induces a circulating [[electric current]] within a nearby [[conductor (material)|conductor]] through [[electromagnetic induction]]. The induced current creates a corresponding magnetic field around the conductor (see [[Pinch (plasma physics)]]). Because of [[Lenz's Law]], the magnetic fields created within the conductor and work coil strongly repel each other.

[[Image:Electromagnetic Forming 01.png|thumb|right|When the switch is closed, electrical energy stored in the ''capacitor bank'' (left) is discharged through the ''forming coil'' (orange) producing a rapidly changing magnetic field which induces a current to flow in the metallic ''workpiece'' (pink). The current flowing the workpiece produces a corresponding opposite magnetic field which rapidly repels the workpiece from the forming coil, reshaping the workpiece — in this case, compressing the diameter of the cylindrical tube. The reciprocal forces acting against the forming coil are resisted by the '''supportive coil casing'' (green).]]

In practice the metal workpiece to be fabricated is placed in proximity to a heavily constructed coil of wire (called the ''work coil''). A huge pulse of current is forced through the work coil by rapidly discharging a high-voltage [[capacitor]] bank using an [[ignitron]] or a [[spark gap]] as a [[switch]]. This creates a rapidly oscillating, ultra strong [[electromagnetic field]] around the work coil.

The high work coil current (typically tens or hundreds of thousands of [[amperes]]) creates ultra strong magnetic forces that easily overcome the [[yield strength]] of the metal work piece, causing permanent deformation. The metal forming process occurs extremely quickly (typically tens of [[microsecond]]s) and, because of the large forces, portions of the workpiece undergo high [[acceleration]] reaching velocities of up to 300&nbsp;m/s.

== Applications ==

The forming process is most often used to shrink or expand cylindrical tubing, but it can also form sheet metal by repelling the work piece onto a shaped [[Die (manufacturing)|die]] at a high [[velocity]]. High-quality joints can be formed, either by electromagnetic pulse crimping with a mechanical interlock or by [[magnetic pulse welding|electromagnetic pulse welding]] with a true metallurgical weld. Since the forming operation involves high [[accelerate|acceleration]] and deceleration, mass of the work piece plays a critical role during the forming process. The process works best with good [[electrical conductor]]s such as copper or [[aluminum]], but it can be adapted to work with poorer conductors such as [[steel]].

==Comparison with mechanical forming==
Electromagnetic forming has a number of advantages and disadvantages compared to conventional mechanical forming techniques.

Some of the advantages are;
*Improved formability (the amount of stretch available without tearing)
*Wrinkling can be greatly suppressed
*Forming can be combined with joining and assembling with dissimilar components including glass, plastic, composites and other metals. 
*Close tolerances are possible as [[springback]] can be significantly reduced.
*Single-sided dies are sufficient, which can reduce tooling costs
*Lubricants are reduced or are unnecessary, so forming can be used in [[clean room|clean-room]] conditions
*Mechanical contact with the workpiece is not required; this avoids surface contamination and tooling marks. As a result, a surface finish can be applied to the workpiece before forming.

The principle disadvantages are;
*Non-conductive materials cannot be formed directly, but can be formed using a conductive drive plate
*The high voltages and currents involved require careful safety considerations

==References==
{{Reflist}}
* {{cite web|title=Materials and Manufacturing: Electromagnetic Forming of Aluminum Sheet |work=Pacific Northwest National Laboratory |url=http://natt.pnl.gov/tech/electro_alum.pdf |access-date=2006-06-09 |archive-url=https://web.archive.org/web/20051218171044/http://natt.pnl.gov/tech/electro_alum.pdf |archive-date=2005-12-18 |url-status=dead }}
* {{cite web|title=Electromagnetic Hemming Machine And Method For Joining Sheet Metal Layers |work=US Patent and Trademark Office |url=http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220050109769%22.PGNR.&OS=DN/20050109769&RS=DN/20050109769 |archive-url=https://web.archive.org/web/20180518200817/http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&s1=%2220050109769%22.PGNR.&OS=DN/20050109769&RS=DN/20050109769 |url-status=dead |archive-date=2018-05-18 |access-date=2005-09-02 }}
* {{cite web |title=Resources on Electromagnetic and High Velocity Forming |work=Department of Materials Science and Engineering, Ohio State University |url=http://www.ecr6.ohio-state.edu/%7Edaehn/hyperplasticity.html |access-date=2006-04-06 |url-status=dead |archive-url=https://web.archive.org/web/20051219085116/http://www.ecr6.ohio-state.edu/~daehn/hyperplasticity.html |archive-date=2005-12-19 }}
* {{cite web |title=Electromagnetic Metal Forming Handbook |work=An English translation of the Russian book by Belyy, Fertik, and Khimenko |url=http://www.mse.eng.ohio-state.edu/%7EDaehn/metalforminghb/index.html |access-date=2006-08-06 |url-status=dead |archive-url=https://web.archive.org/web/20060905155116/http://www.mse.eng.ohio-state.edu/~Daehn/metalforminghb/index.html |archive-date=2006-09-05 }}
* {{cite web |title=FEA of electromagnetic forming using a new coupling algorithm |work=Ali M. Abdelhafeez, M.M. Nemat-Alla and M.G. El-Sebaie |url=https://www.researchgate.net/publication/237196984 |access-date=2013-01-15 }}<ref>{{Cite journal |last=Abdelhafeez |first=Ali M. |last2=Nemat-Alla |first2=M.M. |last3=El-Sebaie |first3=M.G. |date=2013-03-05 |title=FEA of electromagnetic forming using a new coupling algorithm |url=https://www.medra.org/servlet/aliasResolver?alias=iospress&doi=10.3233/JAE-131653 |journal=International Journal of Applied Electromagnetics and Mechanics |volume=42 |issue=2 |pages=157–169 |doi=10.3233/JAE-131653|url-access=subscription }}</ref>

==External links==
* {{cite web | title=Industrial Application of the Electromagnetic Pulse Technology | work=PSTproducts GmbH | url=http://www.english.pstproducts.com/index_htm_files/English%20White%20Paper%20by%20PSTproducts.pdf | access-date=2010-08-01 | url-status=dead | archive-url=https://web.archive.org/web/20110715125631/http://www.english.pstproducts.com/index_htm_files/English%20White%20Paper%20by%20PSTproducts.pdf | archive-date=2011-07-15 }}
* {{cite web|title=Electromagnetic Forming of Cylindrical Components |work=Magnet-Physik |url=http://www.magnet-physik.de/st_magnetopuls.html |access-date=2006-06-06 |archive-url=https://web.archive.org/web/20051214213911/http://magnet-physik.de/st_magnetopuls.html |archive-date=2005-12-14 |url-status=dead }}

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[[Category:Electromagnetic radiation]]
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[[Category:Pulsed power]]