Electroforming

Electroforming is a metal forming process that forms parts through electrodeposition on a model, known in the industry as a mandrel. Conductive (metallic) mandrels are passivated (chemically) to preclude 'plating' and thereby to allow subsequent separation of the finished electroform. Non-conductive (glass, silicon, plastic) mandrels require the deposition of a conductive layer prior to electrodeposition. Conductive layers can be deposited chemically, or using vacuum deposition techniques (e.g., gold sputtering). The outer surface of the mandrel forms the inner surface of the form.

The process involves high current through very clean water, having no more than about 5 parts per million organic contamination. The 'thrown' ions find their missing electrons on the mandrel, which is in electrical contact with the cathode of the electroforming tank. The ions deposit as neutral metal atoms, which bind to each other. Metal is electrodeposited until it is strong enough to be self-supporting. The mandrel is most often separated intact or dissolved away after forming, but occasionally (as in the case in decorative electroforming) left in place.

The surface of the finished part that was in intimate contact with the mandrel is rendered in fine detail with respect to the original, and is not subject to the shrinkage that would normally be experienced in a foundry cast metal object, or the tool marks of a milled part. The side of the part that was in contact with the electroforming solution is less well defined, and that loss of definition increases with thickness of the deposit. In extreme cases, where a thickness of several millimetres is required, there is preferential build-up of material on sharp outside edges and corners. This tendency can be reduced by a process known as periodic reverse,[1] where the electroforming current is reversed for short periods and the excess is preferentially etched away. The finished form can either be the finished part, or can be used in a subsequent process to produce a positive of the original mandrel shape, such as with vinyl record-stamper manufacture.

In recent years, due to its ability to replicate a mandrel surface very precisely with practically no loss of fidelity, electroforming has taken on new importance in the fabrication of micro and nano-scale metallic devices and in producing precision injection moulds with micro- and nano-scale features for production of non-metallic micro-moulded objects.

Eformschematic
Electroforming process

Process

Electroforming process
Electroforming process detail

In the basic electroforming process, an electrolytic bath is used to deposit nickel or other electroformable metals onto a conductive patterned surface, such as stainless steel. Once the deposited material has been built up to the desired thickness, the master electroform is parted from the substrate. This process allows high-quality duplication of the mandrel and, therefore, permits quality production — at low unit costs with high repeatability and excellent process control.

If the mandrel is made of a non-conductive material it can be covered with a conductive coating.

The object being electroformed can be a permanent part of the end product or can be temporary (as in the case of wax), and removed later, leaving only the metal form, the “electroform”. New technologies have made it possible for mandrels to be very complex. In order to facilitate the removal of the electroform from the mandrel, a mandrel is often made of aluminum. Because aluminum can easily be chemically dissolved, a complex electroform can be produced with near exactness.

Advantages and disadvantages

The main advantage of electroforming is that it reproduces the external shape of the mandrel within one micrometer. Generally, forming an internal cavity accurately is more difficult than forming an external shape, however the opposite holds true for electroforming because the mandrel's exterior can be accurately machined.[2]

Compared to other basic metal forming processes (casting, forging, stamping, deep drawing, machining and fabricating) electroforming is very effective when requirements call for extreme tolerances, complexity or light weight. The precision and resolution inherent in the photographically produced conductive patterned substrate, allows finer geometries to be produced to tighter tolerances while maintaining superior edge definition with a near optical finish. Electroformed metal is extremely pure, with superior properties over wrought metal due to its refined crystal structure. Multiple layers of electroformed metal can be molecularly bonded together, or to different substrate materials to produce complex structures with "grown-on" flanges and bosses.

Tolerances of 1.5 to 3 nanometres have been reported.

A wide variety of shapes and sizes can be made by electroforming, the principal limitation being the need to part the product from the mandrel. Since the fabrication of a product requires only a single pattern or mandrel, low production quantities can be made economically.

See also

References

  1. ^ Journal of Applied Electrochemistry 1979 407-410 Periodic reverse current electroplating and surface finishing. M.I. Ismail
  2. ^ The electroforming process, archived from the original on 2010-02-02, retrieved 2010-02-02.

Further reading

  • Spiro, P. Electroforming: A comprehensive survey of theory, practice and commercial applications, London, 1971.

External links

Acetate disc

An acetate disc is a type of phonograph (gramophone) record, a mechanical sound storage medium, widely used from the 1930s to the late 1950s for recording and broadcast purposes and still in limited use today.They are also known as a test acetate, dubplate (a term from Jamaican reggae culture, now also applied to individually recorded discs of solid plastic), lacquer (a technically correct term preferred by engineers in the recording industry), transcription disc (a special recording intended for, or made from, a radio broadcast) or instantaneous disc (because it can be played immediately after recording without any further processing),

Unlike ordinary vinyl records, which are quickly formed from lumps of plastic by a mass-production molding process, a so-called acetate disc is created by using a recording lathe to cut an audio-signal-modulated groove into the surface of a special lacquer-coated blank disc, a real-time operation requiring expensive, delicate equipment and expert skill for good results. They are made for special purposes, almost never for sale to the general public. They can be played on any normal record player but will suffer from wear more quickly than vinyl. Some acetates are highly prized for their rarity, especially when they contain unpublished material.

Acetates are usually made by dubbing from a master recording in another medium, such as magnetic tape. In the vinyl record manufacturing process, an acetate master disc is cut and electroforming is used to make negative metal molds from it; each mold, known as a stamper, can be used to press thousands of vinyl copies of the master. Within the vinyl record industry, acetates are also used for evaluating the quality of the tape-to-disc transfer. They were once a favored medium for comparing different takes or mixes of a recording, and if pressed vinyl copies of an impending new release were not yet available, acetates were used for getting preview copies into the hands of important radio disc jockeys.

Acetates were produced in very small quantities using elementary cutting machines. Majority of discs found on the market were not labelled or marked, as distributing studios would only at most have their name and address written on the disc. It was generally up to the recipients to scribble on the song title or artist by hand.

Cold shield

A cold shield is a device to protect an object from unwanted heating by thermal radiation or light. Usually it is a cooled object with low absorption and high reflectivity.

It can be found in molecular beam epitaxy chambers to protect the growth areas from thermal radiation from hot sources. In cryostats, a radiation shield protects a sample from infrared radiation. An infrared detector is protected from thermal background radiation outside its optical field of view. These devices are usually cooled to the same temperature as the detector.

Cold shields are typically used in IR optical devices for military, scientific and industrial applications to protect IR sensors from stray IR radiation (lowering noise figures). Most cold shield applications require near instantaneous cooling, making low mass of the structure very important. Therefore, electroforming is the preferred method of fabricating cold shields.

Compact Disc manufacturing

Compact disc manufacturing is the process by which commercial compact discs (CDs) are replicated in mass quantities using a master version created from a source recording. This may be either in audio form (CD-Audio) or data form (CD-ROM). This process is used in the mastering of read-only compact discs; CD-Rs, CD-RWs, and DVDs are made somewhat differently, though the methods are broadly similar.

A CD can be used to store audio, video, and data in various standardized formats defined in the Rainbow Books. CDs are usually manufactured in a class 100 (ISO 5) or better clean room; they can usually be manufactured to quite strict manufacturing tolerances for only a few US cents per disk.

CD mastering differs from burning, as the pits and lands of a mastered CD are moulded into a CD blank, rather than being 'burn marks' in a dye layer (in CD-Rs) or areas with changed physical characteristics (in CD-RWs). In addition, CD burners write data sequentially, while a CD pressing plant 'writes' the entire disk in one physical stamping operation.

Coronet of Charles, Prince of Wales

The Coronet of Charles, Prince of Wales is a small crown that is part of the Honours of Wales. The gold coronet, with diamonds set in platinum, was made for and used by Prince Charles at his investiture as Prince of Wales in 1969. Designed by the artist Louis Osman, the coronet was a gift from the Worshipful Company of Goldsmiths to the Prince's mother, Queen Elizabeth II. It has been described as modern but its form is traditional. The coronet is in storage along with the other Welsh regalia at St James's Palace, London.

Direct metal mastering

Direct metal mastering (DMM) is an analog audio disc mastering technique jointly developed by two German companies, Telefunken-Decca (Teldec) and Georg Neumann GmbH, toward the end of the 20th century after having seen the same technology used by RCA Princeton Labs for its SelectaVision videodiscs in the late-1970s.

Records manufactured with this technology are often marked by a "DMM" logo on the outer record sleeve. Many current production high quality pressings, as well as standard production LPs from the 1990s, only indicate its use by inscribing "DMM" in the lead-out groove area of the disc.

Neumann was responsible for manufacturing the actual DMM cutting equipment as part of its VMS80 series lathes. Unlike conventional disc mastering, where the mechanical audio modulation is cut onto a lacquer-coated aluminum disc, DMM cuts straight into metal (copper), utilizing a high frequency carrier system and specialized diamond styli, vibrating at more than 40 kHz (i.e. 60 kHz) to facilitate the cutting.

Eleanor Moty

Eleanor Moty (born 1945), is an American metalsmith and jewelry artist. Her experimentation with industrial processes, such as photoetching and electroforming, was revolutionary in the field of American art jewelry in the 1960s and 1970s.

Electrometallurgy

Electrometallurgy is the field concerned with the processes of metal electrodeposition There are four categories of these processes:

Electrowinning, the extraction of metal from ores

Electrorefining, the purification of metals. Metal powder production by electrodeposition is included in this category, or sometimes electrowinning, or a separate category depending on application.

Electroplating, the deposition of a layer of one metal on another

Electroforming, the manufacture of, usually thin, metal parts through electroplating

Electroplating

Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. The term is also used for electrical oxidation of anions on to a solid substrate, as in the formation of silver chloride on silver wire to make silver/silver-chloride electrodes. Electroplating is primarily used to change the surface properties of an object (such as abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities), but may also be used to build up thickness on undersized parts or to form objects by electroforming.

The process used in electroplating is called electrodeposition. It is analogous to a concentration cell acting in reverse. The part to be plated is the cathode of the circuit. In one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called an electrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that it comprises and allowing them to dissolve in the solution. At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they "plate out" onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated and thus the ions in the electrolyte bath are continuously replenished by the anode.Other electroplating processes may use a non-consumable anode such as lead or carbon. In these techniques, ions of the metal to be plated must be periodically replenished in the bath as they are drawn out of the solution. The most common form of electroplating is used for creating coins, such as US pennies, which are made of zinc covered in a layer of copper.

Electrotyping

Electrotyping (also galvanoplasty) is a chemical method for forming metal parts that exactly reproduce a model. The method was invented by Moritz von Jacobi in Russia in 1838, and was immediately adopted for applications in printing and several other fields. As described in an 1890 treatise, electrotyping produces "an exact facsimile of any object having an irregular surface, whether it be an engraved steel- or copper-plate, a wood-cut, or a form of set-up type, to be used for printing; or a medal, medallion, statue, bust, or even a natural object, for art purposes." In art, several important "bronze" sculptures created in the 19th century are actually electrotyped copper, and not bronze at all; sculptures were executed using electrotyping at least into the 1930s. In printing, electrotyping had become a standard method for producing plates for letterpress printing by the late 1800s. It complemented the older technology of stereotyping, which involved metal casting. By 1901, stereotypers and electrotypers in several countries had formed labor unions around these crafts. The unions persisted into the 1970s, but by the late 20th century, after more than a century in widespread use for preparing plates, the two technologies had been bypassed by the transitions to offset printing and to new techniques for the preparation of printing plates.

Europafilm

Europafilm was an influential Swedish film company established in 1929 by Schamyl Bauman and Gustaf Scheutz.

The office was located at Kungsgatan in central Stockholm, while the film studio was located in Mariehäll, Bromma, northwest of Stockholm city. It was acquired by Bonnier in 1984 and merged with Svensk Filmindustri in 1985. It was best known for the films starring Edvard Persson.

Aside from its film activities Europafilm also manufactured electroforming equipment for the vinyl record manufacturing industry. This division was later sold to the now defunct Alpha Toolex AB of Sundyberg, Sweden manufacturers of vinyl record pressing machinery. Both Europafilm plating equipment and Alpha Toolex pressing equipment is still considered to be the finest engineered equipment in their respective categories.

Florence Resnikoff

Florence Resnikoff was an artist and educator in the fields of metals and jewelry.

George Macdonald Reid

George MacDonald Reid (1907–1969) was a Canadian sculptor who worked in London during the 1960s.

MacDonald Reid was born in Winnipeg in 1907. He developed a new approach to portrait sculpture using photography, a revolving dentist’s chair, and a machine he built himself that outlined the contours of the human face, for which he was awarded the US patent. This speeded up the early stages of the sculpting process, which he then rendered into an exact likeness using traditional artistic skills. He used electroforming to cut the price of bronze sculptures.MacDonald Reid was stationed in Madagascar during World War II and got the idea for his automated method making sculptures from the techniques used to make contoured terrain maps. His basement studio was in Alford House, Park Street, just off Park Lane. Macdonald Reid's portrait busts included Prime Ministers Harold Wilson (UK), John Diefenbaker (Canada); and President Jomo Kenyatta of Kenya. Other busts included Gerald Nabarro MP, actor Jon Pertwee, racing driver Stirling Moss, Yama Saki, Madame Pandit, High Commissioner for India, and the Lord Mayor of London, Sir Edmund Stockdale. The Royal Automobile Association commissioned a portrait bust of HRH The Duke of Edinburgh for their head office.

Macdonald Reid died in January 1969.

Jamie Bennett (artist)

Jamie Bennett (born 1948) is an American artist and educator known for his enamel jewelry. Over his forty-year career, Bennett has experimented with the centuries-old process of enameling, discovered new techniques of setting, and created new colors of enamel and a matte surfaces. This has led him to be referred to as “one of the most innovative and accomplished enamellers of our time” by Ursula Ilse-Neuman, historian and former curator at the Museum of Art and Design in New York City.

Bennett is closely associated with the State University of New York at New Paltz, where he studied himself as a student, and taught in the Metal department for many years. Bennett retired from teaching in 2014, after thirty years at SUNY New Paltz.

Joseph McGeough

Joseph Anthony McGeough FREng FRSE is a former Regius Professor of Engineering, and now an Honorary Professorial Fellow, in the School of Engineering at the University of Edinburgh.

McGeough was born in Kilwinning, Scotland, on 29 May 1940. A graduate of Glasgow (BSc, 1963; PhD, 1967) and Aberdeen (DSc, 1982) Universities, he gained industrial training as an undergraduate vacation apprentice for a firm of electrical contractors at ICI Nobel Division, and with Cossor Radar and Electronics, Harlow. Following graduation he worked for International Research and Development Ltd, Newcastle, as a research metallurgist. He then held research appointments as a Demonstrator and Senior Research Fellow at respectively Leicester, and Queensland and Strathclyde universities.

He was a Lecturer (1972–1977), then Senior Lecturer (1977–1980) and Reader (1980-1983) in engineering at Aberdeen University, before being appointed in 1983 to the Regius Chair of Engineering at the University of Edinburgh. While Regius Professor he also served for eight years as the Head of the Department of Mechanical Engineering.

His main field of research is manufacturing; his research outcomes are published in journals including the Proceedings of the Institution of Mechanical Engineers, Proceedings of the Royal Society, the Journal of the Institute for Mathematics and its Applications, and, latterly, in the Journal of Bone and Joint Surgery. McGeough's books include Principles of Electrochemical Machining (1974), Advanced Methods of Machining (1988), Micromachining of Engineering Materials (editor, 2001) and The Engineering of Human Joint Replacements (2013). He is the author of the entry on Electroforming for the Encyclopaedia of Production Engineering (2013), and a volume editor for Comprehensive Materials Processing (2014). The IMechE and the Society for Underwater Technology have awarded him prizes for his researches. He held a Royal Society/SERC (now EPSRC) Industrial Fellowship between 1987–89, and has been the director of three spin-off companies.

McGeough is a Fellow of the Institution of Mechanical Engineers, the Royal Society of Edinburgh, the International Academy for Production Engineering, and the Royal Academy of Engineering. He is a member of the Royal Institution of Great Britain. He has served as vice-president of the IMechE and chair of its Professional Publishing Board, and of its International Strategy Board. He has held visiting appointments at the University of Naples "Federico 2", Monash University, Tokyo University of Agriculture and Technology, and Dublin City University. He is an Honorary Professor of Nanjing Aeronautical and Astronautical University.

When he was a student he gained a number of county, universities and national athletics championship awards, and was the winner of an Australian Universities’ soccer championship medal. He was Secretary and Vice-Captain of Glasgow University Athletics, and became an Honorary Vice-President of Aberdeen University Athletics Association.

More recently he served as Chairman for Aberdeen Dyce Academy College council, and President for Edinburgh Colinton Literary Society (including its centenary year). He gives lectures on science to the community, including the National Trust for Scotland, and the Royal Society of Edinburgh.

He has been married for more than 40 years, with three children and six grandchildren.

LIGA

LIGA is a German acronym for Lithographie, Galvanoformung, Abformung (Lithography, Electroplating, and Molding) that describes a fabrication technology used to create high-aspect-ratio microstructures.

Linda Threadgill

Linda Threadgill (born 1947) is an American artist whose primary emphasis is metalsmithing. Born in Corpus Christi, TX, her early interests in art explored both ceramics and painting. She became interested in working with metal while an undergraduate, and received a Bachelor of Fine Arts degree from the University of Georgia in 1970, where she studied with noted American metalsmith Robert Ebendorf. A portfolio of work based on her experimentation with photo-etching and electroforming led her to study with innovative metalsmith Stanley Lechtzin at the Tyler School of Art in Philadelphia, where she was awarded the Teaching Assistantship in the Metals Department, and earned a Master of Fine Arts degree in 1978. In 1979, she was awarded a Florida Fine Arts Council Individual Artist Fellowship based on her studio work. Later this same year, she was invited to join the faculty of the Art Department at the University of Wisconsin-Whitewater. In 1983 she was named a Distinguished Member of the Society of North American Goldsmiths, and in 1984, received a National Endowment for the Arts Visual Arts Fellowship. In 1994, she received the University of Wisconsin-Whitewater Chancellor's Award for Outstanding Research. During her tenure on the faculty of the University of Wisconsin, she also received 11 University of Wisconsin Faculty Research Grants, and was awarded the University of Wisconsin Outstanding Research Award in 1987, 1995 and 1999. She served as a Craftsman Trustee to the American Craft Council from 1996-1999, and in 2000, she was designated Trustee Emerita. In 2001, she was named an Artisan Member of the Society of American Silversmiths. She headed the Metals Program at the University of Wisconsin-Whitewater from 1979-2003, and is Professor Emerita. In 2005 she was named a Fellow of the American Craft Council.

In 1984, she developed a small-scale portable spray etching machine based on technology used for the etching of printed circuit boards in the electronics industry. This etching machine's simple yet functional design led to its adoption by many university metals programs as well as by numerous private studio artists, enabling them to rapidly and accurately etch and pattern non-ferrous metals for jewelry and small sculpture. Threadgill has shared the technology, techniques and practices associated with her etching machine in over 80 workshops and technical presentations in the United States, Canada, England and Korea. Her work and process are also included in the 1996 ENCYCLOPEDIA OF JEWELRY TECHNIQUES. She now lives and maintains a studio in Santa Fe, New Mexico.

In 2015, she was named Master Metalsmith by the National Ornamental Metal Museum, Memphis, TN, who mounted a major retrospective exhibition of her work in late 2015.

This exhibition is illustrated in the catalogue "Cultivating Ornament", ISBN 978-1-943092-51-2Her artistic metalwork is included in the collections of The Victoria and Albert Museum, London, England, The Swiss National Museum, Zürich, Switzerland, The National Museum of American Arts of the Smithsonian Institution, Washington, DC, The Museum of Arts and Design, New York, NY, The Museum of Fine Arts, Boston, MA, The Walker Hill Art Center, Seoul, Korea, The Racine Arts Museum, Racine, WI, the deYoung Museum, San Francisco, CA, The George and Dorothy Saxe Contemporary Craft Collection, Palo Alto, CA and many others. ...

List of manufacturing processes

This tree lists various manufacturing processes arranged by similarity of function.

Matrix (printing)

In the manufacture of metal type used in letterpress printing, a matrix, from the Latin meaning womb or a female breeding animal, is the mould used to cast a letter, known as a sort. Matrices for printing types were made of copper.However, in printmaking the matrix is whatever is used, with ink, to hold the image that makes up the print, whether a plate in etching and engraving or a woodblock in woodcut.

Stanley Lechtzin

Stanley Lechtzin is an American Jewelry and metals artist noted for his work in electroforming and Computer Aided Design and Computer Aided Manufacture.

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