Tinned copper braiding operations
In process testing
Quality assurance documentation
Pink extruded cable
The first process step of cable manufacture is wire drawing. Copper wire is drawn down to the required size. Wire drawing is a stretching process. The wire is pulled through a die or a series of dies until the required diameter is achieved.
By pulling the wire through a smaller hole then it's original diameter, the cross sectional area of the wire shrinks. As the wire is pulled through the die, its volume remains the same, and as the diameter decreases the length increases.
The smaller the die in relation to the diameter of the starting wire, the more force is required to pull the wire through the die. That is why several dies are arranged in series, the wire is drawn through each die succesively until the it reaches the desired cross sectional area.
Heat treatment (Annealing)
During the drawing process the metallic wire experiences a great deal of stresses and strains. The external forces applied change the physical properties of the metal wire. The wire loses flexibility and becomes brittle and harder to bend. At this point in the process the wire is described as hard drawn. Hard drawn wire is less likely to stretch than annealed wire.
To overcome these physical changes in the metal the wire is heat treated. Heat treating (also known as annealing) increases the grain size of the wire and therefore improves the flexibility and workability of the wire. Annealed wire is also referred to as soft drawn.
Electrical cables normally have stranded or multistranded conductors. Stranded conductors are typically utilised in building wires and multistranded conductors are used in flexible cables. Sometimes solid conductors are required for practical reasons or for cost effectiveness. Cables with a solid conductor are not as flexible as cables with bunched conductors. Multiple conductive wires are bunched together by a machine that twists them together. Insulated bunched metal wire is called a core. In addition to bunching bare metal wires together we can also bunch multiple cores together. The group of bunched cores can then go through numerous other processes such as having a braid screen applied, an aluminium foil screen applied a strength member applied prior to extrusion of the outer sheath. The ultimate cable design depends on the final application of the cable.
Core sizes are determined by the application of the cable, the electrical limitations of the conductor and of the insulating material. The more wire strands that are bunched together the larger the cross sectional area. The larger the cross sectional area, the lower the electrical resistance is to the flow of electrons passing through the conductor.
A cable braid is a cylindrical sheath made of strands of metal placed around a cable cores. It is formed by laying a number of strands of metal, usually copper, diagonally in such a way that the strands pass alternately over and under strands laid up in the opposite direction. This acts as a shield against electromagnetic interference. Cables usually have a sheath applied over the braid. The braid is grounded while the central conductor(s) carry the signal. Braiding is a slow process, as the wire ends needs to be interwoven. Braiding also assists the cable to be flexed during use and provides additional mechanical strength.
The extrusion process involves heating and mixing a polymer compound and then forcing it through a die to cover and insulate a bunched conductor or a cable. The polymer compound is the insulating layer that physically separates the electricity carrying conductor from its surroundings. Different polymer compounds have different physical and electrically insulating properties. The type of compound and the size of the insulating layer is determined by the application of the cable. Compounds can be made from polymers that do not emit toxic gases and black smoke in a fire situation. Other features of these and other compounds can be oil resistance, submersibility and resistance to heat and cold. Colour additives can be mixed with the polymer to produce different colours. Other additives can be added for ultraviolet stability and vermin resistance.
Cable manufacture is quite flexible and can be easily tailored to suit electrical and environmental applications. For more information or if you would like a tour of our Sydney based production facility please contact our friendly sales team.
Bambach employs a “right from me” approach to quality where operators are trained to identify and act upon defects at the point at which they first occur. In addition to the continual screening for defective items Bambach have in place a final testing production step to catch any quality occurrences before the products are dispatched to the customer. Bambach have an exceptionally high quality record, due to the internal quality management processes securely in place.
As an AS/NZS ISO 9001:2008 certified company, you have the assurance of professionalism and expertise in the development and manufacture of the highest quality specialist industrial cables. Bambach Wires & Cables are dedicated to quality, customer service and the continual improvement of our business. We are constantly reviewing our products and services and welcome your suggestions for improvement.