What is Electroforming?
Electroforming is a space age technology used effectively to produce shapes and accuracies in metal products unmatched by any other fabrication method. Electrochemistry, and additives in plating baths, permit close control of electroformed parts. Results are now as reproducible as those obtained with welding, casting, forging, and other conventional techniques.
In electroforming, as in plating, metal ions are transferred electrochemically through an electrolyte from an anode to a surface where they are deposited as atoms of plated metal. But in electroforming, the surface that is to receive the plated metal, called a mandrel, is conditioned so that the plating does not adhere. Instead, the plated metal, or electroform, is lifted away and retains its as-deposited shape as a discrete component.
A part formed by this process has several unusual characteristics:
- It can have extremely thin walls – less than one mil. In fact, minimum thickness is generally limited only by the fact that a part requires a certain amount of sturdiness to avoid being bent or broken by normal handling.
- Surface features of the mandrel are reproduced with extreme fidelity on the surface of the electroform. High surface finish and intricate detail are easily obtained.
- Complex contours are produced quite easily.
- Dimensional tolerances can be held to high accuracy. Accuracies of +/- 0.0001 in. are not unusual.
- Maximum size is limited only by the size of the available plating tank. Parts over 7 ft. long have been successfully electroformed.
Probably the most interesting aspect of electroforming is the ease with which complex shapes are produced. The mandrel and electroform bear the same geometric relationship that exists between a mold and a cast metal. Internal features of the electroform, therefore, are simply machined as negative-image external features on the mandrel.
Two types of mandrels are used: permanent and disposable. Permanent mandrels are used where the electroform has no undercut surfaces and can thus be lifted directly from the mandrel. Where undercuts are required on the electroform, the mandrel must be dissolved or melted away, or in some other way destroyed to be removed.
GAR Electroforming Division products need not be made entirely from deposited metal. Other materials, even non-conductors, can be incorporated into the component by plating onto, over, or around separate pieces attached to the mandrel. Threaded inserts, bearing surfaces, shafts, and other such inserts – called grow-ons – are often incorporated in electroforms by this technique, a patented process. The non-deposited metal, in fact, often constitutes a larger portion of the final part than the electroformed metal. Some waveguides are comprised primarily of machined wrought pieces, joined by a relatively small amount of electrodeposited metal.
The joining aspect of electroforming is an important feature. Two parts of an assembly can be formed separately by electroforming, machined to mate with the proper degree of precision, then joined in a second electroforming step.