Modern Machines Turning Copper Into Cables

Press, Volume CI, Issue 29754, 22 February 1962, Page 19

Modern Machines Turning Copper Into Cables

From the basic raw materials of copper rod, imported from Australia, jute, paper and polythene, imported from Britain, banks of intricate machinery at the Austral Standard Cables factory produces modem telecommunications cable.

The machinery ranges from delicate equipment with parts revolving at tremendous speeds, to slow-moving drums of three-inch lead-covered cable coils. Telephone cable may consist of any number of pairs of fine copper conductor wires up to 1800. Each individual wire is separately insulated and must be easily identifiable to facilitate location of pairs for testng, jointing and fault-finding.

The first stage of manufacture is the conversion of 5 l«in copper rod to medium fire wires W’hich vary from .016 m (41b a mile) to .050 in (4OIb a mile). This is done on equipment as up-to-date as anything in the world. First, the copper rod in 2501 b coils is "pickled” to remove rolling scale, and it finishes on wire spools of 250 to 3001 b, each containing 225 miles of wire.

The insulating stage of manufacture is done on 10 head insulating machines, where a very thin, speciallyprepared cable kraft paper in strips as narrow as 3/16in is helically wrapped around a single wire conductor to form an insulated "single.” Paper Prepared In preparation for this, the paper is slit from bulk rolls and simultaneously marked with identification, which consists of either one, two. three or four lines grouped in red, blue, orange and green. The marking is arranged so that when the paper-wrapping operation is completed on the insulating machines the identification mark appears as a series of rings around the conductor.

“Single” is provided on spools of about 12in diameter for movement to the next operation, which comprises "twinning” two wires of a pair to form basic telephone cirr

A nigh-speed twinning machine is used. Two wires are laid together with a predetermined twist length so arranged as to reduce to a minimum “cross-talk” between adjacent insulated pairs in the finished cable. After twinning, the finished spools are available in unit loads, the number of pairs required depending upon the finished cable size. Most of the cable manufactured at Hornby is made up from 102 pair units, each consisting of 100 separate telephone circuits, with two spare wires.

The laying-up process is carried out on a standing machine, where pairs are laid up to a pre-determined pattern in concentric layers. The formation at this stage also follows a specified identification arrangement.

Finally the unit is wrapped in a multiple-end cotton binder over a single wrapping paper identified with a numeral.

Under pressure of up to two tons and a half to the square inch, the alloy, which has been allowed to cool to a plastic state, is extruded through an annular ring formed by a core and die. forming a continuous tube of sheathing alloy.

The cable now goes off the straining machine in set lengths and is contained on 25in unit drums.

Multiples of these units, the number depending upon cable size, are then laid up in cable form from the unit flier of the stranding machine. A final double wrapping of cable kraft paper is laid over all to form a final binding for the finished cable “core.”

The core and the die have been, pre-selected for requisite dimensions and the setting and adjustments in the die block of the press determine the over-all diameter, radial thickness and concentricity of the finished tube. Once a short test run has cheeked the specification tolerance, the dried cable is fed through the back of the die block of the extrusion press, and emerges in the front as a finished leadsheathed article. The lead-covered cable is reeled on to a wooden takeup drum, which can be up to Bft in diameter and contain up to four or five tons of cable. It is then ready for a range of tests. Armouring

By this stage, because of the increasing diameter of the cable, the "take-off” drum has increaserd to approximately 4ft 6in.

Drying Process Known in the industry as “green” cable, the paperwrapped product contains a high degree of moisture as the insulating paper is hygroscopic. Before lead sheathing it must be thoroughly dried to obtain the necessary insulation resistance characteristics.

If the cable has to be armoured, there is pne further process before dispatch. For armouring either steel tape or steel wire is used.

For this process, a drum of lead-sheathed cable is placed behind the armouring machine, which is approximately 130 ft long and various coatings of impregnated paper, bitumen, jute bedding and serving as well as the steel tape or steel wire armouring is applied. The steel tape, which may vary from lin to l|in in width, is applied helically in two layers so that the outer tape covers the gap in the inner, and the result is a continuous sheath of steel.

The drying takes place in one of the series of massive 6ft diameter vacuum ovens, in which the drum of cable is subjected to a temperature of up to 240 degrees Fahrenheit.

After a pre-heat period the hot air is evacuated from the oven by a vacuum pump and chemically-dried air is fed into the oven. This process is repeated through an exhaustive drying cycle which varies in accordance with the type and size of cable being processed. Sheathing The nexj step is to give the cable a lead alloy protective sheathing. For this it goes to a steam-heated supply oven behind one of the two (another is on order from overseas) lead extrusion presses. Alloy in nearby furnaces is melted and run off through a “launder” or chute into the container in a hydrau-lically-actuated press.

The jute serving is laid helically over the steel tape, and the “bedding” is beneath to provide a cushion between the armouring steel and the softer lead sheath.

The process for wire armouring is much the same, the main difference being that the galvanised steel

wire is laid on as a single layer, still helically, to form a continuous section. The cable, whether in leadsheathed or armoured form, is then ready for the final stage. The drum is closed in with wooden battens to protect the cable in transit, the identification destination stencilling is done in the company’s colours of yellow lettering on a deep blue base and the cable leaves for delivery to any point in New Zealand from the company’s rail siding at the factory.