The application of polymer insulation and sheathing. Selection of extrusion lines for the application of polymer insulation and sheathing.

The manufacture of insulated and sheathed cable products made of thermoplastic polymers with using extrusion lines is the most common manufacturing method. The extrusion process is that molten thermoplastic polymer under the action of the extrusion force created by the stock screw flows through a narrow hole (forming tool) and then, after cooling or vulcanization, retains its newly acquired shape. The following materials are widely used as raw materials for the extrusion process: Plasticized PVC, polyethylene, polypropylene, extrudable fluoroplast, rubber compounds and some others.

The extruder is the main technological unit of the extrusion line. The extruder consists of the following parts:

1. The cylinder is made of special wear-resistant steel.
2. The screw is made of special wear-resistant steel.
3. The heating and temperature control system of the cylinder zones consists of electric heaters and an air (liquid) cooling system.
4. Extruder die with a set of forming tools.
5. Reduction gear
6. The main engine.
7. Charging hopper with the plastics granulates feeding system.
8. Command terminal

Extruders are classified according to the screw diameter. For example: 23, 32(35), 45(50), 60(63), 70, 80, 90, 100, 120(125), 150 mm,.etc.

What components does the extrusion line consist of?

The composition of the extrusion line, depending on its purpose, includes the following elements:

1. Pay-off machines.
2. Straightening device.
3. Core cable heater
4. Talc spreader.
5. Main extruder.
6. Auxiliary extruders (co-extruder).
7. Vacuum device for plastics granulates loading.
8. Color metering device
9. Coolant bath.
10. Haul-off unit
11. Horizontal storage or compensator.
12. Insulation and sheathing dehumidification device.
13. A high-frequency device for testing a product by "one direction welding” high voltage .
14. Diameter gauge
15. Extensiometer
16. Stigmator
17. Take-up machine.
18. Electricity closet and line control terminal.

How to choose an extrusion line?

Step-by-step actions:

1. Making a decision about the nomenclature and volume of cable products intended for production.
2. Calculation of cable products structures, the volume of elements production of cable products and finished cables (according wire sections, number of cores, colors, kilometrage).
3. The choice of materials, which will be processed on this line and, accordingly, the choice of a set of screws with different cutting configurations (if necessary).
4. The choice of specialization of this line (insulation, sheathing, universal use).
5. Preliminary calculation of the line performance based on the constructive consumption of material for this cable, the extruder productivity, the duration of the work shift. Rlin. = Re./m ×T × K , where Rlin. – line productivity, km/shift; Re. – extruder productivity, kg/h: m – constructive consumption of the extruded material, kg / km; Т – the duration of the work shift, h.; К – operation factor, К = 0,8.

6. Estimation of the required set of line equipment:

• Estimation of the required set of line equipment:
• the range of sizes of the expected production output;
• the number and size of the pay-off machines (active, passive, dual flyer type, etc.), the dimensions tie-in of pay-off drums of the extrusion line with the drums dimensions for workpiece (drums with сurrent-carrying conductor (CCC) or with an isolated core / a rolling up workpiece);
• the necessity for a talcating workpiece mashine;
• the screw diameter of the main extruder, which materials will be used during extrusion;
• the necessity for co-extruder and its number (striping on insulation / sheat, surface dyeing)
• the extrusion die type (manually adjustable, self-centering, with surface and stripe coloring);
• the volume of the charging hopper, productivity of the granulates vacuum loader;
• the necessity for a dye dispenser on the main and co-extruder;
• the necessity for "hot" diameter gauge;
• coolant bath (single-level or double level)
• haul-off unit (type, maximum linear speed);
• horizontal storage or compensator.
• Insulation and sheathing dehumidification device.
• the necessity for "cool" diameter gauge;
• countdown device;
• Stigmator (by pressing, jet printing or laser printing);
• a high-frequency device for testing products by "one direction welding” high voltage;
• Take-up machines (single and their number, dual automatic, the size of the take-up drums, a device for receiving products into the hank). The dimensions tie-in of taking-up drums with the manufacturing machinery in subsequent cable manufacturing operations.

7. Receiving commercial offers from potential suppliers of extrusion lines.
8. Estimation of the most preferred option of the extrusion line based on: the range of manufactured products, productivity, line dimensions, price and other important parameters for you.
9. Calculation of the required number of lines based on the monthly product production program, line productivity and working time.
10. Estimation of the amount of necessary auxiliary equipment, tools and materials, their purchase:

• Take-up and pay-off drums.
• Contact welding machine / cold welding machine.
• A set of forming tools (tube spindles and moulds), based on the product range.

11. The conclusion of a contract for the supply of an extrusion line.
12. Installation and configure and adjustment operations (if possible, it’s necessary participation of the equipment manufacturer's maintenance engineers). Extrusion line operators training.