Electroforming is a metal forming process in which parts are fabricated through electrodeposition on a model, known in the industry as a mandrel. Conductive (metallic) mandrels are treated to create a mechanical parting layer, or are chemically passivated to limit electroform adhesion to the mandrel and thereby allow its subsequent separation. Non-conductive (glass, silicon, plastic) mandrels require the deposition of a conductive layer prior to electrodeposition. Such 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.
Electroforming process
The process involves passing direct current through an electrolyte containing salts of the metal being electroformed. The anode is the solid metal being electroformed, and the cathode is the mandrel, onto which the electroform gets plated (deposited). The process continues until the required electroform thickness is achieved. The mandrel is then either separated intact, melted away, or chemically dissolved.
The surface of the finished part that was in intimate contact with the mandrel is replicated 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 solution side of the part 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 shielding, or a process known as periodic reverse,[1] where the electroforming current is reversed for short periods and the excess is preferentially dissolved electrochemically. 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 records or CD and DVD stamper manufacture.
In recent years, due to its ability to replicate a mandrel surface 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 molds with micro- and nano-scale features for production of non-metallic micro-molded objects.
In the basic electroforming process, an electrolytic bath is used to deposit nickel or other electroformable metal onto a conductive surface of a model (mandrel). Once the deposited material has been built up to the desired thickness, the electroform is parted from the substrate. This process allows precise replication of the mandrel surface texture and geometry at low unit cost with high repeatability and excellent process control.
If the mandrel is made of a non-conductive material it can be coated with a thin conductive layer.
Advantages and disadvantagesEdit
The main advantage of electroforming is that it accurately replicates the external shape of the mandrel. Generally, machining a cavity accurately is more challenging than machining a convex shape, however the opposite holds true for electroforming because the mandrel's exterior can be accurately machined and then used to electroform a precision cavity.[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 photo-lithographically 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 can be extremely pure, with superior properties over wrought metal due to its refined crystal structure. Multiple layers of electroformed metals can be bonded together, or to different substrate materials to produce complex structures with "grown-on" flanges and bosses.
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 model or mandrel, low production quantities can be made economically.
^Journal of Applied Electrochemistry 1979 407-410 Periodic reverse current electroplating and surface finishing. M.I. Ismail
^, archived from the original on 2010-02-12, retrieved 2010-02-02.
Further readingEdit
Spiro, P. Electroforming: A comprehensive survey of theory, practice and commercial applications, London, 1971.
External linksEdit
. Opti-Forms, Inc. Archived from the original on 2014-03-11. Retrieved 2015-08-28.
NiCoForm, Inc. "Net-shape Electroforming". www.nicoform.com. Retrieved 2020-05-24.
October 19, 2023
electroforming, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, february, 2. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Electroforming news newspapers books scholar JSTOR February 2010 Learn how and when to remove this template message Electroforming is a metal forming process in which parts are fabricated through electrodeposition on a model known in the industry as a mandrel Conductive metallic mandrels are treated to create a mechanical parting layer or are chemically passivated to limit electroform adhesion to the mandrel and thereby allow its subsequent separation Non conductive glass silicon plastic mandrels require the deposition of a conductive layer prior to electrodeposition Such 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 Electroforming processThe process involves passing direct current through an electrolyte containing salts of the metal being electroformed The anode is the solid metal being electroformed and the cathode is the mandrel onto which the electroform gets plated deposited The process continues until the required electroform thickness is achieved The mandrel is then either separated intact melted away or chemically dissolved The surface of the finished part that was in intimate contact with the mandrel is replicated 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 solution side of the part 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 shielding or a process known as periodic reverse 1 where the electroforming current is reversed for short periods and the excess is preferentially dissolved electrochemically 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 records or CD and DVD stamper manufacture In recent years due to its ability to replicate a mandrel surface 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 molds with micro and nano scale features for production of non metallic micro molded objects Contents 1 Process 2 Advantages and disadvantages 3 See also 4 References 5 Further reading 6 External linksProcess Edit nbsp Electroforming process detailIn the basic electroforming process an electrolytic bath is used to deposit nickel or other electroformable metal onto a conductive surface of a model mandrel Once the deposited material has been built up to the desired thickness the electroform is parted from the substrate This process allows precise replication of the mandrel surface texture and geometry at low unit cost with high repeatability and excellent process control If the mandrel is made of a non conductive material it can be coated with a thin conductive layer Advantages and disadvantages EditThe main advantage of electroforming is that it accurately replicates the external shape of the mandrel Generally machining a cavity accurately is more challenging than machining a convex shape however the opposite holds true for electroforming because the mandrel s exterior can be accurately machined and then used to electroform a precision cavity 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 photo lithographically 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 can be extremely pure with superior properties over wrought metal due to its refined crystal structure Multiple layers of electroformed metals can be 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 citation needed 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 model or mandrel low production quantities can be made economically See also EditLIGA Electrotyping Electroplating Electrochemical engineeringReferences Edit Journal of Applied Electrochemistry 1979 407 410 Periodic reverse current electroplating and surface finishing M I Ismail The electroforming process archived from the original on 2010 02 12 retrieved 2010 02 02 Further reading EditSpiro P Electroforming A comprehensive survey of theory practice and commercial applications London 1971 External links Edit Opti Forms Inc Optical Coatings Electroformed Reflectors Cold Shields Opti Forms Inc Archived from the original on 2014 03 11 Retrieved 2015 08 28 NiCoForm Inc Net shape Electroforming www nicoform com Retrieved 2020 05 24 Retrieved from https en wikipedia org w index php title Electroforming amp oldid 1147286221, wikipedia, wiki, book, books, library,
