Copper Profile Extrusion
Copper profiles for electrical purposes can be produced by the Meltech-Confex extruder. Although the same machine can be used to extrude both aluminium and copper, there are various process and line equipment differences that require consideration when extruding one metal or the other.
Copper Rod – pre processing
Copper rod as standard is manufactured and supplied with a wax protection that is applied to prevent oxidisation during transportation and storage. This wax can cause defects in the extruded product so must be removed prior to use in the continuous rotary extrusion. Suitable cleaning systems can be provided.
There are two alternative copper rod production systems. The ideal copper feed rod is that which has been vertically cast directly to the desired diameter (for example as in the Rautomead process) – this is Oxygen Free Copper rod (OFHC) – and provided no wax protection has been used it can be used as a feed rod with no surface cleaning required.
The other systems is to cast a bar and roll to final size (for example via the Properzi or Southwire type processes) and this can also be used subject to any wax removal. However, there are other potential problems with this rod due to the manufacturing process. After casting the copper bar, small cracks radiating inwards over a short distance occur as it cools and contracts. Subsequent rolling using emulsions can result in oil becoming entrapped in these cracks and during processing through the extruder, these residuals volatilise leaving gasses and carbon behind which form a defect known as a blister on the surface of the extruded product. These defects can be avoided by using suitable cleaning systems.
However, cleaning is expensive when taking into account the capital cost of the equipment and the operating costs, so the ideal solution is to avoid cleaning altogether by using vertically upward cast copper rod without waxing. Several extruded copper manufacturers have installed casting equipment alongside the extruder - the best solution - and guarantees that there will be minimum quality problems.
Copper Extrusion
As noted earlier, copper products are extruded almost without exception for the electrical industry. The most common use being for the extrusion of rectangular sections for use in transformers or bus bars. When used in transformers the product is required in the ‘as extruded’ condition which is soft. For busbars, the required temper is hard and this has to be achieved by subsequent mechanical working.
Until the continuous rotary extrusion process was available the other methods of producing bus bar was either by conventional billet extrusion or rolling and intermediate annealing. There is an obvious distinct advantage over the rolling route in that a product can be extruded to a size that requires the minimum amount of mechanical work to achieve the required temper without annealing, giving beneficial energy reductions.
Moreover, compared with conventional extrusion there are further advantages. A billet is a discreet length and the maximum weight is relatively small, for example 400kgs. The extruded section is then pointed and passed through drawing processes to final size and temper. Pointing the larger sections is a time consuming and labour intensive processes which results in poor utilisation of equipment. With the continuous rotary extrusion process it is possible to make very long lengths limited only by the size of the take-up (and tooling life). Product weights of up to six tonnes (and larger, take-up dependant) are made which means only one pointing is required instead of fifteen for the same amount of product by the conventional extrusion process. There has been much development work over the past years relating to the continuous extrusion of copper profiles, and Meltech-Confex continues to innovate in this area and is the only company to offer automated coiling systems enabling true continuous production of copper profiles.
For more information on the Meltech-Confex Continuous Rotary Extrusion lines call Meltech-Confex Ltd on +44 (0)1254 691488, e-mail sales@meltechconfex.com