WCA January 2011

The object is to present profiled material to the strander. The round wire is re-shaped into the optimum format for the desired strand con- struction and finished cable size. This roll form system can be as simple as a two-layer (1+6) construction or as intricate as a five-layer (1+6+12+18+24) construction. The scope of the strand design determines the application confi- guration; there are many different designs available for each layer. (a) Roll forming of the input wires. This is achieved with a driven roll stand shaping each wire in a layer to a precisely designed shape. (b) Round wire layers where a number of round wires are closed without any change in section. Depending on the strand design, up to four layers of roll forming strand may be produced. Each roll strand is driven individually, allowing slight changes in speed to be made at each position to compensate for the variances in the spiral length.

Figure 1 ❍ ❍ : Close up of roll formers

Figure 2 ❍ ❍ : Roll form unit and closing point

Single input wire schedules

Compact

Six wire sizes required using a conventional system One wire size required using SIW system

Figure 3 ❍ ❍

It further allows more precise distribution of wire tension in each layer, optimising the straightness of the resulting conductor. The shaped conductors are formed into a compact unilay strand using a high-speed double twist strander. The machine is a side-loading unit equipped with a standard floor loader, designed to load and unload the take-up reel with minimum operator effort.

The scope of products that can be manufactured includes: Copper and aluminium stranded conductors between • 8AWG and 600kcmil or 10mm 2 and 300mm 2 Bunched conductors to compact strand with fill factors • between 76% and 97% Aluminium conductors steel reinforced (ACSR) using • a single steel wire core All aluminium and aluminium alloy conductors (AAC • & AAAC) Cabling of insulated conductors •

Figure 4 ❍ ❍ : Process cost/twist comparison

$ Planetary Strander Planetary Strander

$ Rigid Strander Rigid Strander

$ Drum Twister

Capital cost/ Twist

$ Tubular Strander

$

Double twist Strander Double Twist Strander

Tubular Strander

Drum Twister

Factors

Capital cost/twist

1

3-5

7-16

9-12

16-24

“Working factor”

Significant (rigid)

Almost none (planetary)

Significant (rigid)

Significant (rigid)

Almost none (planetary)

Lay limitations

Unilay only

Not applicable

None

None

None

Layer limitations

Up to 4 layers

2 layers

None

None

None

Typical payoff package

Stem

Bobbin

Stem

Bobbin

Bobbin

Required loading cycle

Required loading cycle

Required loading cycle

Continuous

Payoff mode

Continuous

64

Wire & Cable ASIA – September/October 2007 January/February 2011