Electroforming Technology: An Advanced Manufacturing Process For Metal Fabrication

By Dr Thoguluva Raghavan Vijayaram PhD

Senior Lecturer, Department of Manufacturing Process and System,
Faculty of Manufacturing Engineering,
UTeM Universiti Teknikal Malaysia, Melaka Ayer Keroh, 75450 Melaka Malaysia.
Email: thoguluva@utem.edu.my

Electroforming technology is a highly specialized process for fabricating a metal part by electro deposition in a plating bath over a base form or mandrel which is subsequently removed. Metal is electrodeposited on a mandrel, also called as a mold or matrix, which is the removed. Thus, the coating itself becomes the product. The electroforming process is particularly suitable to produce intricate parts such as molds, dies, waveguides, nozzles, and bellows made of nickel, copper, gold, and silver. This article discusses about the process description of electroforming technology, advantages, and its major engineering applications.

A variation of electroplating process is electroforming technology, which actually is a metal fabrication process. Both simple and complex shapes can be produced by electroforming, with wall thicknesses as small as 0.025 mm. Parts may weigh from a few grams to as much as 270 kg. Production rates can be increased through the use of multiple mandrels. Mandrels are made from a variety of materials like metallic zinc or aluminium or non metallic, which can be made electrically conductive with the proper coatings. It should be able to be physically removed without damaging the electroformed part. They may also be made of low-melting alloys, wax, or plastics, which can be melted away or dissolved with suitable chemicals.
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.

Figure-1 Electroforming process

Figure-1 shown above explains the principle of electroforming process. The positively charged electroformed metal source (anode) at the left is broken down (ionized) in the copper electrolyte solution and is attracted to the negative charged mandrel (cathode). Build-up is achieved over all mandrel surfaces at an approximate deposition rate of .001 inch per hour.

Electroforming is economical for making parts with special features that are difficult to produce by more common methods. It is advantageous for complex shapes, inside and outside, with thin walls, for laminating metals without heat or pressure, for producing fine and precise details and openings like small holes, and for incorporating inserts and flanges made of metallic and non metallic materials, difficult to attach otherwise. Walls can be made as thin as a few micrometers to 50 mm but seldom are over 15 mm. Tolerances have been held to a fraction of the wavelength of light in electroforming diffraction gratings, and those of the order of 25 mm are common place, with surface finishes, Ra, of 51 to 203 nm.

Electroforming process is compared with other fabrication methods and some of the advantages are highlighted below.

Electroforming process is insensitive to temperature or humidity.
Electroformed parts have excellent light transmission when used in optical application, such as encoders, aperture plates, and slits.
Electroformed parts have very low mass (weight and inertia).
Electroformed parts are electrically conductive and unbreakable.

Electroforming technology is applied to fabricate complex 2D and 3D microstructures. One can fabricate micron size features in nickel, nickel-cobalt alloy, gold, and copper. Some of the application examples of the microstructures that have been fabricated with the aid of electroforming technology are shown below in Figure-2.

COMPONENT NUMBER: 1 Technical Features: The component to the right is fabricated in nickel-cobalt alloy, over plated with gold, and has a length of 2.7 mm and width of 3.0 mm. Its thickness is 250 microns. The narrowest section has a width of 100 microns and the same overall part thickness of 250 microns for an aspect ratio of 2.5:1. Depending upon specific feature geometry and material, higher aspect ratios are achievable. These dimensions can be held to +/- 3 microns.
COMPONENT NUMBER:2 Technical Features: The spring component to the right is fabricated in nickel-cobalt alloy, overplated with gold, and has a length of 6.1 mm and width of 1 mm. The overall part thickness is 250 microns. The spring has a width of 100 microns and thickness of 250 microns for a 2.5:1 aspect ratio. Higher aspect ratios are achievable depending upon specific feature geometry. The depth of the teeth on the ends is 100 microns. These dimensions can be held to +/- 3 microns.
COMPONENT NUMBER:3 Technical Features: The part to the right is a contact spring fabricated in nickel-cobalt alloy. It has an overall length of 0.173 inch and width of 0.1 inch. Its thickness is 50 microns. The width of the tip is 50 microns. Dimensional tolerance of +/- 3 microns can be held.
COMPONENT NUMBER:4 Technical Features: One can fabricate more complex apertures as shown in the image to the right. This aperture has a diameter of 75 microns and is surrounded by a circular ring that has an in inside diameter of 635 microns, an outside diameter of 1270 microns and a depth of 125 microns. These tolerances can be held to +/- 2 microns.
COMPONENT NUMBER:5 Technical Features: Below is an example of a complex 3D mechanical structure fabricated in nickel-cobalt alloy. The overall size of this part is 0.300 inch X 0.450 inch. The elements of the three springs have a cross-section of 50 microns by 50 microns. The spaces between the spring elements are also 50 microns. A second electroformed layer of nickel-cobalt alloy, 200 microns thick, has been deposited over the non-spring areas to add structural integrity. Total thickness of the two combined layers is 250 microns.
Figure-2 Application of electroforming process to fabricate micron size parts

Electroforming process faithfully reproduces the form or mandrel exactly, to within one micron, without shrinkage and distortion associated with other metal forming techniques such as casting, stamping or drawing. And, since the mandrel is machined as an outside surface, close dimensional tolerances and high surface finishes can be held and maintained on complex interior configurations. It is also suitable for aerospace, electronics, and electro optics applications. It is concluded that electroforming process is an efficient metal fabrication technology than other forming methods.

About the author
Dr.Thoguluva Raghavan Vijayaram, currently working as Senior Lecturer in the Faculty of Manufacturing Engineering at UTeM, Universiti Teknikal Malaysia Melaka, Malaysia. He hails from India and he has completed his PhD Research Degree in Mechanical Engineering (Metal Matrix Composites: Materials Engineering) from the Faculty of engineering, Universiti Putra Malaysia. He has published quality research papers in reputed International journals, National journals, International conference proceedings and in the Malaysian broadsheet. He has a wide range of work experience, both in academics and as well as in industry, consultancy, and teaching and especially in research and development work. His areas of expertise include: Metallurgical Engineering, Mechanical Engineering and Manufacturing Engineering and his special areas of research interests are in the field of advanced casting technology and techniques, composite materials and processing, powder metallurgy, Ferrous and Non-Ferrous foundry metallurgy, solidification science and technology, solidification processing of metals, alloys and composites, microgravity solidification, squeeze casting, die casting die design, heat treatment, Metallography, microstructure-property correlation ship, new materials and process development, aerospace engineering materials, computer simulation of casting solidification, FEM analysis and advanced engineering mathematics. Besides, he is a prominent writer and possesses wider experience in editing technical papers, theses and dissertations.

Advances In Diamond Coating Technology
Rubber: An Effective And Suitable Elastomer
Titanium and Titanium Alloys: Key Engineering Materials for Aerospace Applications