Conductor Material for Enamelled Wire

Copper is the standard used conductor material for enamelled wire with excellent conductivity and very good windability. For low weight and larger diameters, Aluminium sometimes can be used as a conductor material for enamelled wire. Because of the difficult contacting of Aluminium wire with problems of oxidation, Copper Clad Aluminium can help to compromise between Copper and Aluminium. For special applications a wide variety of conductor materials for enamelled wire is offered, such as Brass, Silver, Nickel, Gold, Stainless Steel, or alloys of copper for special characteristics like higher mechanical strength or bending performance. In addition, the core conductors can be plated with different materials such as Silver or Nickel.

Bare Wire Diameter Range

Elektrisola specializes in fine enamelled wire diameters, starting with 0.008 mm (8 microns), and going up to a diameter of 0.50 mm. Beside the standardized diameters a big variety of special diameters is produced according to customer’s specification. Bare wire tolerances are very important in enamelled wire as they have direct impact on the resistance what again determines the variance of the final coil resistance.

Outer Diameter of Enamelled Wire

International standards like IEC group enamelled wires according to ranges of specific outer diameters. IEC standard for enamelled wire groups the insulation in Grade 1, 2, or 3, NEMA in single, heavy, or triple, and JIS in class 0, 1, 2, or 3. The tolerances in these enamelled wire standards can be further restricted if necessary to design and optimize the wound coils and final products.

Selfbonding Layer

In addition to the base coat insulations described separately, a selfbonding layer can be applied to the enamelled wire, by which the wire will be bonded together for example for bobbinless coils, such as voice coils.

Spool Types for Enamelled Wire

Spool types have to fit to the wire size. Finer enamelled wire sizes are wound on smaller spools, while for heavy sizes of enamelled wire, very large spools can be used. They are important for productivity as larger spools require less spool changes on the winding machines.

The wire length on one spool can be very long:

0.018 mm on spool 99L: up to 417 km of enamelled wire
0.05 mm on spool 199L: up to 1143 km of enamelled wire
0.30 mm on spool 400/630: up to 277 km of enamelled wire

Insulation Types for Enamelled Wire

Elektrisola offers a wide range of different insulations. Polyurethane has the advantage of easy direct contacting by soldering, while Polyester insulations are more resistant against higher temperatures. Thin top coats as Nylon or Polyamidimide may improve certain desired characteristics like mechanical or chemical strength of the enamelled wire.

Enamelled Wire Colors

Colors may be used to differentiate enamelled wire types or enamelled wire diameters, but have the disadvantage of lower technical properties and higher costs.

Lubrication for Enamelled Wire

A defined very low amount of lubrication – mostly special types of paraffin – is applied to achieve excellent windability of the enamelled wire in all winding processes without wire breaks.

For copper wires an 8 mm copper rod (5/16″ in USA) is used as raw material, which is drawn through drawing dies to the required bare wire dimension in several stages. The copper rod has to be of high purity (copper content 99.99 %) and consistenly high quality to manufacture fine and ultrafine wires of sizes below 10 µm. ELEKTRISOLA uses only pure electrolytic copper ETP1 (copper content min. 99.99 %) from pre-approved high quality vendors.

The drawing process is carried out sequentially through several groups of machines producing specific diameter ranges. The wire is elongated in several stages through dies, so that the larger wire is permanently becoming thinner and longer during the drawing process while the volume by weight remains unchanged.

The quality of the copper, the fine tuning between the different drawing stages, and especially the quality of the drawing dies, are all of high importance to achieve a high quality final bare wire. The bearing surfxes of the wire drawing dies consist of natural or artificial diamonds or, for heavy wire production, of carbide.

Enamelling Process for Enamelled Wire

All enamelled wires are enamelled on special enamelling machines which are developed and produced by ELEKTRISOLA for our exclusive use. Enamelling of enamelled wire is a continuous process, mainly consisting of the annealing process, enamel application, curing process, lubricant application, tension control and spooling.

1. Annealing Process
During the drawing process the bare wire’s grain structure has been changed through cold deformation. Annealing will re-crystalize the copper and make it soft again. This thermal stress relief process is carried out under protective atmosphere in order to avoid oxidizing the wire surface, which would interfere with good adherence of the initial coating of insulation later in the process. Softness of the enamelled wire is an important criteria for good windability, in particular significantly reducing the number of wire breaks.

2. Enamel Application
There are 2 main application systems for enamelling of winding enamelled wires, i.e felt application and die application, whereas felt application is mainly used in fine Enamelled wire production, while die application is mainly used in heavy enamelled wire production. The enamel coating should always be applied in as many single layers as possible rather than fewer and thicker layers to achieve better mechanical and electrical properties of the enamelled wire.

3. Curing Oven
Solvents contained in the liquid enamel are driven out in the curing oven at high Temperature and then are burnt catalytically by using the thermal energy in an environmentally friendly way. Temperature control is very important: if the temperature is too low, too many solvent residues will be left in the enamel layer, leading to poor adhesion and reduced mechanical and electrical properties of the enamelled wire. If the temperature is too high, the enamel coating will be hard and brittle, leading to cracks in the insulation coating of the Enamelled wire resulting from mechanical stress.

4. Lubrication
A defined amount of lubricant is precisely applied to the insulated enamelled wires surface. Lubrication is necessary to achieve consistent winding properties and failure-free winding of the wire even at high winding speeds.

5. Diameter Control
ELEKTRISOLA continuously monitors the Outer Diameter of all enamelled wires after the final pass by laser.

6. Tension Control
A continuous wire tension control during the enamelling process results in a consistently uniform spooling onto the spool. With effective tension control, elongation of the enamelled wire is avoided and thus a change in resistance. Furthermore, good de-reeling properties of enamelled wire for customer can be guaranteed.

7. Spooling
The wire pitch and the spool’s rotational speed are spooling process variables closely to be controlled. This results in consistently good enamelled wire de-reeling performance and minimizes other problems like trapped and tangled wires.

8. Monitor
The monitor informs the operator about all important parameters of the process.