WCA January 2011

Wire & Cable ASIA – September/October 2007

Wire & Cable ASIA – January/February 11

Ceeco Bartell believes its roll form strander is the only

process to fully utilise the advantages of single input

wire (SIW) diameter. SIW represents a strand and design

mentality, with a manufacturing methodology that

effectively reduces the conversion cost from rod to strand

without compromising conductor performance.

This concept replaces the traditional stranding of wires

using different wire diameters with the stranding of wires

using the same wire diameter for a wide range of cross

sections. SIW diameter meets major conductor standards

such as IEC 60228, HD 383 and the ASTM standards. By

incorporating a single input wire diameter program into the

strand design, significant savings can be achieved in wire

drawing, stranding and the insulation processes.

Traditionally a finished stranded conductor requires its

own drawn wire diameter. Each wire diameter typically

requires a new string-up in the wire drawing machine.

Some conductor designs require more than one drawn wire

size. The set up time taken on the drawing, combined with

inventory levels that are necessary to manage the number

of wire diameters, represent unnecessary activities that

add to the cost of conversion from rod to strand.

The SIW approach, using the same input wire diameter to

finish a range of stranded conductors, eliminates much of

the unnecessary activity associated with the traditional set

up.

This leads to increased efficiency in the wire drawing

process. Instead of having to produce a large number of

different wire sizes only one or two are required using the

SIW system.

The improvements can be seen in the following areas:

Higher productivity in wire drawing

•

Lower drawn wire scrap

•

Quicker set-up

•

Reduced work in process

•

Shorter cycle times

•

Smaller input wire storage area

•

Reduced drawing die inventories

•

The single input wire method can

save between 15% and 20% on

wire drawing costs, including the

elimination of re-strings for size

changes, lower die inventory and

reduced in-process wire.

Double twist stranding has always

been among the most productive

methods of producing strand. Its

incorporation into the roll form

strander, with the application of the

individual shaping of the wire, has

further extended its performance

range.

Figure 4

its performance can

clearly be seen. Each machine type

works the wire differently, and this

impacts on the strand design that

can be used for that process.

Figure 4

highlights some of the

advantages and disadvantages of

each machine type as they relate

to product capability and relative

cost. It is important to recognise that if the roll formed or

die shaped wire is used in the strand construction a ‘rigid’

machine, or a machine that puts a twist in the wire for each

lay length, is a prerequisite for manufacture.

Capital cost per twist

Determining the range of equipment to cover the strand

designs is an important consideration in achieving the

lowest conversion cost.

For example, the double twist machine offers the lowest

cost per twist but is the most limiting in terms of the

construction possibilities. By its incorporation into the roll

form strander this range of construction possibilities has

been greatly expanded. The planetary machine, at the

other end of the spectrum, has the highest cost per twist

but the greatest construction possibilities, which is why it

is used for special purpose products.

Material limitations

Each machine type works the wire differently. For this

reason alone it is necessary to identify the differences to

be able to use the same drawn wire size for the multitude

of stranding possibilities.

This applies not only to the principle of the machine

but also to the area reduction that can be expected

from different machine types. Keep in mind that in most

cases the area reduction through the machine varies at

different speeds and, to some extent, all machines used

to manufacture strand require that the stress in the wire

during the stranding point exceed the yield point of that

material.

For example, the double twist, single twist and rigid

strander put a twist into each input wire along the axis

of the wire for each lay length; the tubular and planetary

machines are more forgiving and put almost no twist into

each wire, which is important when stranding steel wire.

Lay and layer limitations

Both the double twist and single twist machines currently

can manufacture up to four layers (typically a 37-wire

Figure 5

❍

: Line speed comparisons

Conductor size (mm

)

Line speed comparison aluminium

Single twist

Line speed (metre per minute)

RC double twist

Ceeco Bartell