A wire and cable extruder is a type of equipment primarily used for extruding the cores of power cords, power cables, and other types of wires and cables. Proper and rational operation of the extruder can maximize its performance, maintain optimal operating conditions, and extend the machine’s service life. So, how should a wire and cable extruder be operated?

Operating Procedures for Wire and Cable Extruders

The operating procedures for extruding different plastic products vary, yet they also share certain commonalities. Below, we briefly outline the standard operational steps applicable to the extrusion of various products, along with key considerations to keep in mind during the process.

I. Preparations Before Powering On

1. Plastics used for extrusion molding: The raw materials must meet the required drying specifications and, if necessary, undergo additional drying. Furthermore, the materials should be screened to remove agglomerates, lumps, and mechanical impurities.

2. Inspect the water, electricity, and gas systems of the equipment to ensure they are functioning properly; verify that water and gas lines are unobstructed and leak-free, that the electrical system is operating normally, and that the heating system, temperature control, and all instruments are working reliably. Conduct a no‑load, low‑speed trial run of the auxiliary machinery to confirm normal operation, then start the vacuum pump on the shaping table and check its performance. Lubricate all designated lubrication points on the equipment. If any malfunctions are detected, address them promptly.

3. Mount the die head and sizing sleeve. Select the appropriate die head specifications based on the product type and dimensions, and install the die head in the following sequence.

3.1 The die head shall be assembled as a single unit and installed integrally on the extruder.

3.2 Before assembling the machine head, remove the grease applied during storage, carefully inspect the cavity surface for dents, scratches, or rust spots, perform any necessary polishing, and then apply a thin layer of silicone oil to the runner surfaces.

3.3 Assemble the head’s individual plates in sequence, apply high-temperature grease to the bolt threads, and then tighten the bolts and flanges.

3.4 Place the porous plate between the head flanges to ensure tight clamping without material overflow.

3.5 Before tightening the fastening bolts that connect the die head to the extruder flange, the die’s horizontal position must be adjusted. For square die heads, use a level to ensure horizontality; for round die heads, use the bottom surface of the shaping mold’s adhesive base as a reference and adjust the die head’s bottom surface to achieve levelness.

3.6 Tighten the flange bolts, secure the machine head with its mounting bolts, and install the heating ring and thermocouple, ensuring that the heating ring is firmly bonded to the outer surface of the machine head.

3.7 Install the shaping sleeve and adjust it into position; verify that the centerlines of the main machine and the shaping sleeve align with those of the traction machine. After adjustment, tighten the mounting bolts and connect all water and vacuum lines to the shaping sleeve.

3.8 Turn on the heating power supply to uniformly heat and raise the temperature of the die head and barrel. At the same time, open the cooling water valves at the bottom of the hopper and in the gearbox, as well as the inlet valve for the venting vacuum system. During the heating process, first set the temperature to 140°C; once it reaches 140°C, maintain this temperature for 30–40 minutes, then increase it to the normal operating temperature. After reaching the required operating temperature, hold it for approximately 10 minutes to allow the temperatures of all machine components to stabilize before starting production. The duration of the holding period varies depending on the extruder model and the type of plastic resin being processed. This holding period ensures that the internal and external temperatures of the machine are uniform, preventing a situation where the instrument reading indicates the desired temperature while the actual temperature remains too low. If material is fed into the extruder under such conditions, the excessively high melt viscosity caused by the low temperature can lead to excessive axial forces, potentially damaging the equipment.

3.9 Feed the raw materials required for startup into the hopper for subsequent use.

II. Power On

1. After reaching the set temperature, the machine may be started. Prior to startup, re‑tighten the head and extruder flange bolts to compensate for differential thermal expansion between the bolts and the head. Tighten the head bolts in a diagonal sequence, applying even torque. When tightening the head flange nuts, ensure uniform tension around all four sides; otherwise, material leakage may occur.

2. Power on the machine, select and press the “Ready to Start” knob, then press the “Start” knob. Next, slowly turn the screw speed adjustment knob to initiate a gradual start-up of the screw speed. Subsequently, increase the speed progressively while adding material in small quantities. During feeding, closely monitor the changes indicated by the main motor ammeter and various other gauges. The screw torque must not exceed the red‑marked limit (typically 65%–75% of the full‑scale reading on the torque meter). Before the plastic profile is extruded, no one shall stand directly in front of the die head to prevent injury caused by bolt breakage or foaming due to moist raw materials. Once the plastic exits the die head, promptly cool the extrudate, guide it onto the traction device and the sizing mold, and activate these units. Then, based on the readings from the control instruments and the requirements for the extruded product, make appropriate adjustments to all system components to ensure normal operating conditions, and replenish the material as needed. For twin‑screw extruders, use a metering feeder to supply material uniformly at a constant rate.

3. When the die discharge is uniform and the plasticization is good, proceed with traction and sizing. Assessing the degree of plasticization relies on experience; generally, it can be judged by the extrudate’s appearance—its surface should be glossy, free of impurities, bubbles, scorch marks, and discoloration. Extrude a sample to a specified diameter; if no burrs or cracks appear and the material exhibits adequate elasticity, this indicates proper plasticization. If plasticization is inadequate, adjust the screw speed, barrel temperature, and die head temperature as needed until the desired conditions are achieved.

4. During the extrusion process, verify that various process parameters are within specified limits in accordance with process requirements, and complete the process record form. Inspect the quality of extruded profiles according to quality inspection standards, and take timely corrective actions upon identifying any issues.

III. Shutdown

1. Stop feeding material, extrude all the plastic remaining in the extruder until the screw is exposed, then turn off the barrel and die heaters and halt further material feed.

2. Turn off the extruder and auxiliary equipment power supplies to stop the screw and auxiliary machines.

3. Open the die head connection flange and remove the die head. Clean the porous plate and all components of the die head. To prevent damage to the inner surfaces of the die head during cleaning, use steel rods and steel blades to remove residual material, then sand off any plastic adhering inside with sandpaper, polish the surface, and apply machine oil or silicone oil to prevent rust.

4. Cleaning the screw and barrel: After removing the die head, restart the extruder and feed in stop‑material (or recycled material) to clean the screw and barrel. During this process, operate the screw at a low speed (rev/min) to minimize wear. Once the stop‑material has been fully extruded into a powdery form, use compressed air to repeatedly blow out any remaining pellets and powder through the feed port and vent ports until no residual material remains inside the barrel. Then reduce the screw speed to zero, stop the extruder, and shut off the main power supply and the main cooling‑water valve.

5. Safety precautions during extrusion include electrical hazards, heat, rotating machinery, and the handling of heavy components. The extrusion workshop must be equipped with tools for dismantling and installing the die head, screws, and other heavy parts to ensure safe production.