Current-carrying conductor (CCC) manufacturing

Depending on the purpose and operating conditions of cable products, it’s used CCC with different designs.

What materials are used in the CCC manufacturing?

The main materials for CCC manufacturing are copper or aluminum wire.

Cu. The use of copper is due to its high electrical conductivity, the bending resistance and cable stretching and good fabricability in the cable manufacturing process. Using copper wire, manufacture CCC from 1st to 6th flexibility class according to GOST 22483-2012 “Current-carrying conductor for cables, wires and cords”.

For cables used in aggressive environments (marine cables, cables for rolling stock, etc.), it’s used inert metals coatings (tin, zinc, silver, nickel)/ These metals are applied to the surface of copper wire and significantly increase its corrosion resistance.

Al. The widespread use of aluminum is due to its relatively high electrical conductivity and low cost compared to copper. Aluminum wire has worse mechanical characteristics and fabricability compared to copper, it is usually used in the production of cables for fixed installation. These cables are not bent during operation. CCC made of aluminum wire usually has 1-2 flexibility classes according to GOST 22483-2012.

How made wire for CCC?

The main method of producing copper and aluminum wire is the drawing method. It is that during the drawing process, a rolled wire (or a heavy-gage wire) is stretched through the conforming section (channel) of the drawing tool - dies. Dies have a special configuration channel that facilitates the stretching process. Dies are made of hard alloy, synthetic polycrystalline diamond and even natural technical diamonds. By repeatedly a workpiece stretching through dies with a gradually decreasing diameter of the outlet, it is obtained the required diameter of wire. The number of drawing steps and, accordingly, dies are usually in the range from 9 to 27 pieces.

While copper wire drawing process for lubricate dies channel, it’s used wire-drawing fluid for the cooling of the drawing lines and traction bandages of the drawing machine, and washing of the dies channel from the metal chips. The fluid is usually made by mixing the fluid concentrate with water in a certain ratio. The fluid concentrate is a mixture of natural and synthetic lubricating mineral oil, surfactants, plant oil and other special additives.

While aluminum wire drawing process, it’s used multicomponent mixtures of natural and synthetic lubricating mineral oils with special additives (without adding water).

In the wire drawing process, wire plastic properties is changing, therefore formed "wear hardening" effect. The wire becomes less flexible and more brittle when bent, all this worsens the fabricability of the wire during cable production, increases breakage and reduces the physical characteristics of the finished cable. To eliminate this problem, the wire is subjected to annealing. In modern drawing machines, the drawing process is combined with the annealing process, i.e. annealing occurs continuously and in “one direction welding". The annealing key point is wire heating and curing to a temperature at which the metal structure and its original characteristics are restored and then cooled to room temperature. The annealing temperature for copper wire is 480-600C, for aluminum wire is 400-480C. The wire is heated by passing an electric current through it, that supplied through the contact rollers.

While annealing copper wire process, copper is oxidized by its heating, the surface of the wire darkens by the formation of an oxide film. Therefore, annealing is performed in an inert environment. Commonly , this is water steam, that produced by using an electric steam generator, or nitrogen, that produced in a special machine.

Classification of drawing machines.

Depending on the diameter of the manufactured wire, drawing machines are distinguished:

• coarse wire drawing machine– Ø 3,5 -1,2 mm;
• medium drawing machine – Ø 1,2 -0,2 mm;
• fine drawing machine – Ø 0,9 – 0,1.

Depending on the method of multiple drawing (when several longways are used sequentially), are distinguished:

• no-slip drawing (The wire, after leaving the next die, is wound onto the next sheave. The machines, that are complex in design and difficult to operate, have large dimensions and lower productivity, and are used more often for drawing aluminum wire);
• slip drawing (The wire, after leaving the next die, is wound onto the draft wheel tread (2-3 turns) and has the ability to slip over the surface of the tread. The machines are more productivity.)

Depending on the number of wires, that are simultaneously, in a "single pass" drawing on one machine, are distinguished:

• single-thread machines (have low productivity)
• multithread machines (multi-wire drawing line) - (The machines have high productivity and take up less space compared to a similar number of single-thread machines. They provide greater productivity In CCC stranding, require fewer maintenance engineers).

How to choose a drawing machine for the manufacture of CCC for fixed wiring (cable with solid conductor)?

Step-by-step actions:

1. Making a decision about the nomenclature and volume of cable products intended for production.
2. CCC structural calculations, the volume of wire production for the manufacture of cable products (wire material, wire diameter, the production volume of each wire size).
3. Receiving commercial offers from potential equipment suppliers.
4. The choice of supplier and type of coarse wire drawing machine, based on: the core material used, the range of wire produced, the required production volumes, the presence/absence of an integrated continuous annealing attachment and the equipment price.
5. Checking the compliance of the required productivity of the drawing machine and the nameplate capacity (the commercial offer information). At the same time, the operating capacity shouldn’t be more than 0.8 of the nameplate capacity.
6. Taking a decision upon equipping the drawing machine with wire take-up machines (single-seat automatic take-up machines for steel drums / dual automatic take-up machines for steel drums / take-up machines for receiving wire into a barrel-shaped container/basket). This decision will impact on the set of equipment for the next technological operation – CCC insulating
7. Estimation of the amount of necessary auxiliary equipment and materials, their purchase:

• Tanks and their working volume for fluid/oil cooling (in the case of aluminum wire manufacturing). Fluid/oil cooling system.
• A fluid cleaning unit.
• Technological take-up drums or barrel-shaped container.
• Push pointer for restringing
• Welding machine (contact / cold welding).
• Steam generator / nitrogen production plant for creating an inert medium in a continuous annealing attachment.
• Tensile-testing machine for controlling the finished wire elongation.
• Wire-drawing fluid concentrate / drawing oil (for aluminum).
• The set (route) of dies is based on the wire production of the required diameters.

8. Conclusion of a suppling contract on coarse wire drawing machine
9. Installation and configure and adjustment operations (if possible, it’s necessary participation of the equipment manufacturer's maintenance engineers).
10. Coarse wire drawing machine operators training.

How to choose a set of drawing machines for flexible cables,that are bending, torsion and movement from place to place (cables and wires with a multi-wire core)?

The production of cables and wires with flexible CCC involves manufacturing of CCC, that consist of a large number of twisted wires.

Different sets of drawing equipment can be used for manufacturing the required diameter wire:

• For small production volumes.
• For large production volumes.

For small production volumes, you can use a complete set or reduced set of drawing equipment. While using the reduced set, for the medium drawing machine operation, the workpiece (supporter) is purchased from an external supplier, but required diameter of the wire drawing is produced on single-thread medium and fine drawing machines.

While using a complete set of drawing machine, it’s used the following algorithm of equipment selection:

1. The coarse wire drawing machine is selected as described in the section above. This machine will produce rough workpiece for medium/fine drawing machines.
2. Making a decision about the nomenclature and volume of cable products intended for production.
3. CCC structural calculations, the volume of wire production for the manufacture of cable products (wire material, wire diameter, the production volume of each wire size).
4. Receiving commercial offers from potential suppliers of single-thread medium or fine drawing machines.
5. The choice of supplier and number of medium drawing machine or fine drawing machine, based on: the core material used, the range of wire produced, the required production volumes, the presence of an integrated continuous annealing attachment and the equipment price.
6. Checking the compliance of the required productivity of drawing machines and the nameplate capacity (the commercial offer information). At the same time, the operating capacity shouldn’t be more than 0.8 of the nameplate capacity.
7. Taking a decision upon equipping the drawing machine with a pay-off machine for the workpiece, that compatible with take-up machines of the coarse wire drawing machine. Taking a decision upon a wire take-up machine is compatible with the pay-off machine for CCC stranding .
8. Estimation of the amount of necessary auxiliary equipment and materials, their purchase:

• Tanks and their working volume for the cooling fluid. Fluid cooling system.
• To assess the need for a fluid cleaning unit.
• Technological taking-up drums or coils.
• Hand-operated cold welding machine
• Steam generator / nitrogen production plant for creating an inert medium in a continuous annealing attachment.
• Wire-drawing fluid concentrate.
• The set (route) of dies is based on the wire production of the required diameters.

9. Conclusion of a contract for the supply of single-thread medium or fine drawing machines.
10. Installation and configure and adjustment operations (if possible, it’s necessary participation of the equipment manufacturer's maintenance engineers). Training of drawing machines operators.

For large production volumes, it is used a set of drawing equipment, that consisting of the coarse wire drawing machine and a multithread drawing machine (multi-wire drawing line).

Step-by-step actions:

1. The coarse wire drawing machine is selected as described in the section above. This machine will produce a rough workpiece for a multi-wire drawing line
2. Making a decision about the nomenclature and cable products volume of cable products, that ntended for use in production.
3. CCC structural calculations (including the number and diameter of wires in the CCC), the volume of wire production for the manufacture of cable products (wire material, wire diameter, the production volume of each wire size).
4. Estimation of the optimal wires amount of multi-wire drawing line (8, 14, 16, 24, ets.), based on the amount of wires in the CCC.
5. Receiving commercial offers from potential suppliers of multi-wire drawing lines.
6. The choice of a multi-wire drawing line supplier based on: wires amount, the range of wire produced, the required production volumes and the price of the equipment.
7. Checking the compliance of the required productivity of multi-wire drawing lines and the nameplate capacity (the commercial offer information). At the same time, the operating capacity shouldn’t be more than 0.8 of the nameplate capacity.
8. Taking a decision upon equipping the multi-wire machine with a pay-off machine for the workpiece, that compatible with take-up machines of the coarse wire drawing machine. Taking a decision upon a wire take-up machines is compatible with the pay-off machines for CCC stranding.
9. Estimation of the amount of necessary auxiliary equipment and materials, their purchase:

• Tanks and their working volume for the cooling fluid. Fluid cooling system. A fluid cleaning unit.
• Technological taking-up drums or multi-wire drawing lines.
• Hand-operated cold welding machine
• Steam generator / nitrogen production plant for creating an inert medium in a continuous annealing attachment.
• Wire-drawing fluid concentrate.
• The set (route) of dies is based on the wire production of the required diameters.

10. The conclusion of a contract for the supply of a multi-wire drawing line.
11. Installation and configure and adjustment operations (if possible, it’s necessary participation of the equipment manufacturer's maintenance engineers). Training of drawing machines operators.

Multiwire CCC. Types of core stranding equipment. Equipment selection.

The technological process of current-carrying conductor ensures the stability of the conductor structure during cable manufacture and operation.

CCC stranding is the process of twisting individual wires or wires groups (strands) around the core axis (one or more wires/strands).

Strand kinds. According to the stranding direction，there are:

• Unidirectional stranding In this case, all the core elements are twisted in one direction. There are “left" and "right" stranding. The "left" stranding is obtained when the core elements are twisting in the counterclockwise direction, and the "right" stranding, when they are twisting in the clockwise direction.
• Multidirectional stranding In this case, each lay changes the twisting direction to the opposite direction.

According to the organization of the wire placement in the CCC, there are:

• Proper (concentric-lay) stranding. The CCC has more correct geometric shape in the sectional view. The wires are twisted by one or more layes around the central wire. The direction of each lay changes in relation to the previous one.
• Bunchy (bunch-stranded) stranding. The CCC has less correct geometric shape in the sectional view. In this case, all the wires are twisted together in one direction.

The main types of machines used in the CCC stranding.

Depending on the CCC requirements, its wire sections use different types of stranding machines. For products with strict requirements to the CCC geometry (for example: coaxial cables, products with a thin radial thickness of insulation (automotive wires), products with large wire section, products with sector-shaped conductors), machines are usually used to ensure proper stranding:

• Lantern-type (cage-type) machines provide "unscrewing" stranding, i.e. during the twisting process, the lantern of the machine twists in one direction, and pay-off coils in the other direction, which allows to get a core with minimal internal voltage.
• Rigid stranding machine. This is a type of lantern machine in which pay-off drums are rigidly placed on the lantern frame and don’t have the counter-rotation ability in relation to the direction of lantern rotation. The CCC, that obtained on machines of this type, is more rigid.
• Tubular machines. This type of machine has a torsion frame in the form of a long cylinder with holes in which "chairs" with pay-off coils are placed, that remain in a horizontal position when the frame (cigar body) is rotating. The productivity of tubular machines is slightly higher than lantern-type machines have.
• Bow-type machines. These machines can be considered a kind of tubular machines, in which, instead of a metal cylinder frame, it’s used curves: each one rotates around its own pay-off drum.

For CCC with reduced geometrical specification, frame-type bunchy stranding machines are used:

• Single stranding machines. In this type of machine, the frame rotates around the pay-off device. The machine provides the rather high quality of twisting and productivity.
• Double stranding machines. In this type of machine, the frame rotates around the take-up and pay-off device, which ensures that the core is twisted in 2 steps per turn of the frame. Because the frame weight in comparison with proper stranding machines lanterns or frames has a small weight, the productivity of these machines is the highest, and therefore they are widely used in CCC twisting operation with a maximum sectional view up to 95 mm².

How to choose a double stranding machine for the production of flexible CCC with the wire section from 0.5 mm² to 6.0 mm²?

Step-by-step actions:

1. Making a decision about the nomenclature and cable products volume of cable products, that intended for use in production.
2. Determination of the flexibility class of the CCC and the maximum wire diameter based on the requirements of the reference documentation for the cable product.
3. CCC structural calculations (including the number and diameter of wires in the CCC, optimization of wire number, that a multiwire drawing machine can provide), the production volume of each CCC size.

For example, we need to make CCC with 0.75 mm² sectional view. Supposing that, in accordance with requirements of the reference documentation for the CCC cable product must comply with the 5th flexibility class under Table 7 of GOST 22483-2012 “Current-carrying conductor for cables, wires and cords”. For 0.75 mm² sectional view, it is specified that the wire size for this wire section cannot be greater than 0.21 mm. Based on your availability of the 16th wires drawing machine (multi-wire drawing line), we choose 24 × 0.20 CCC design, i.e. for the manufacture of this core, it is necessary to make rough workpiece set by using multi-wire drawing line. This set is consisting of a drum with 16 wires with 0.20 mm diameter and a drum with 8 wires with 0.20 mm diameter. As a result, after 16+ 8 wires twisting, we will get 24 × 0.20 CCC.

4. Receiving commercial offers from potential suppliers of double stranding machines.
5. Estimation of the most preferred variant of the stranding machine based on: the range of stranding sections, productivity, amount and size of the pay-off coils / drums with wire, the size of the taking-up drum, the dimensions of the machine with consideration to pay-off devices, price and other important parameters for you.
6. Productivity calculation of a double stranding machine.

The formula for determining the machine linear speed:

• Vl = 2h × N of frames, where
• Vl - linear speed of stranding, m/min;
• h – stranding length, meters;
• N of frames - rotations of the torsion frame, rpm.

The formula for machine productivity calculation:

• Р = Vl×T×К, where
• P - machine productivity, m/shift;
• Vl - linear speed of stranding, m/min;
• Т – machine operating time (shift duration), minutes;
• K – the machine loading factor (approximately 0.8).

7. Calculation of the required number of machines based on the monthly product production program, machine productivity and working time.
8. Estimation of the amount of necessary auxiliary equipment and materials, their purchase:

• Taking up drums of stranding machines.
• Contact welding machine
• A set of hardalloyed dies, based on twisted core nomenclature (diameters) .

9. The conclusion of a contract for the supply of stranding machines.
10. Installation and configure and adjustment operations (if possible, it’s necessary participation of the equipment manufacturer's maintenance engineers). Training of drawing machines operators.