Electro forming process in detail
Electro forming is a process of producing precision metal parts, that is usually thin in section, by electro-deposition on to a form (variously called mandrel mold, matrices, or die), which is shaped exactly to the interior form of the product and which is subsequently removed. In the process, a slab or plate of the material of the product is immersed into the electrolyte (an aqueous solution of a salt of the same metal) and is connected to the positive terminal of a low voltage, high current d.c. power. So, it becomes an anode.
A correctly prepared master mandrel or pattern of correct shape and size is immersed at some distance from the anode and is connected to the negative terminal (cathode). The mandrels are made from a variety of materials, both metallic or non – metallic. If the material is non-conducting, a conductive coating must first be applied in order to perform electroplating. The mandrel should possess a mirror-like finish.
When the circuit is closed, metal ions are removed from the anode, transported through the electrolyte towards the cathode (master), and deposited there. After the deposition, the master is removed or destroyed. A metal shell is left, which conforms exactly to the contours of the master. It may take hours or days to get a deposit of sufficient thickness. The thickness of electro – forms ranges from 0 25 to 25 mm. The process is very much similar to electroplating, with the difference that whereas in electroplating, the deposit stays in place (on the cathode), in electroforming, it is stripped from the form. The electro-formed products are typically made from Nickel, Iron, Copper, or Silver, and more recently from copper-tin, nickel – cobalt and nickel – manganese alloys.
- Low plant cost, cheap tooling, and the absence of heavy equipment.
- Low labor operating costs.
- The process can be designed to operate continuously throughout day and night.
- Electrodeposition can produce good dense deposits, and compared with castings electroforming offers high purity, freedom from porosity with a homogeneous structure. These important qualities are seldom obtained to such a degree in machined parts, stampings, or forgings.
- There is no restriction on the internal complexity of electro- forms, and this advantage eliminates in many instances, the costly joining processes.
- The process has no equal for the reproduction of fine or complex details.
- The use of inserts has widened the application of the process. Metal inserts are attached to or are embedded in wax or fusible alloy master, and, when the master is melted, the inserts remain attached to the electroformed.
- A high-quality surface finish is obtained on both the internal and external surfaces of the electro-forms. Accuracies as close as 0.005 min with surface finishes up to 0.125 p.m can be produced.
- Complex thin-walled parts can be produced with improved electrical properties.
- Shell-like parts can be produced quickly and economically.
There is a wide range of applications of electroforming process:
- Molds and dies feature high on the list. Molds for the production of artificial teeth, rubber and glass products, and high -strength thermosetting plastics are now commonplace. The molds can be made with undulating parting lines which have made a considerable impact upon the production of thermoplastic toys and novelties.
- Radar and electronic industry Radar waveguides, probes, complicated grids, screens, and meshes can be produced much more easily, to find accuracies and at a lesser cost.
- Spline, thread, and other types of form gauges.
- Cathodes for ECM arid electrodes for. EDM.
- Electro-formed core boxes with inbuilt heating elements. Electro-formed molds for the wax patterns.
- Electro-formed precision tubing, parallel and tapered, formed to different shapes to eliminate the need for bending which distorts the bore.
- Electrotypes floats, bellows, venturi tubes, fountain pen caps, reflectors, heat exchanger parts, honeycomb sandwich, parts for gas appliances and musical instruments, radio parts, spraying masks and stencils, seamless screen cylinders for textile printing, filters and dies for stamping of high-fidelity records.
Electro-forming is particularly useful for:
- High-cost metals.
- Low production quantities
- Quantity of identical parts, for example, a multi- impression mold.
- The possibility of using a single master for the production of a number of electro forms.
- Whereas intricate female impression is required, so that is would be much easier to produce a male form, that is, the master.
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