Robot Cable Extrusion Line

Robot Cable Extrusion Line

Robot cables, as the name implies, are cables specifically designed for industrial robots and their automation systems. They are not ordinary wires but high-tech composite products that need to withstand extreme mechanical stresses such as continuous bending, torsion, tension, and friction generated by the robot (especially at the joints) during high-speed motion.

Main Characteristics

Compared to ordinary cables, the core characteristics of robot cables lie in their exceptional mechanical durability and reliability. This is specifically reflected in the following aspects:
High Flexibility: This is the most basic requirement. The cable must be very flexible to follow the frequent, small-radius bending movements of the robot arm.
Torsion Resistance: This is the most crucial distinction between robot cables and ordinary high-flex cables. Cables at the robot's joints not only bend but also endure significant rotational torque. High-quality robot cables are designed to withstand millions of torsion cycles within a certain positive and negative angle (e.g., ±180°/m or higher).
Bending Endurance: The cable needs to withstand long-term, high-frequency bending cycles, with a service life typically calculated in millions of cycles.
Anti-interference Capability: Robot systems often integrate power lines, encoder lines, data lines, etc. To prevent signal interference, the cables usually require good shielding performance (such as tinned copper braided shielding) to ensure stable and accurate signal transmission.
Compact Design: To reduce the robot's volume and motion inertia, the cable's outer diameter is typically designed to be small, while the internal structure is compact, integrating multiple functions (such as power, signals, feedback, and gas/liquid transmission into one).
Environmental Resistance: Depending on the application scenario, the cable may need properties such as oil resistance, chemical corrosion resistance, high and low-temperature resistance, and flame retardancy.

Common Structure

A typical robot cable features a "softness overcomes hardness" structure, usually employing a layered design:
Conductor: Made of finely stranded extra-fine oxygen-free copper wires, typically Class 6 or 7 conductors, which form the basis for high flexibility.
Insulation Layer: Uses special high-elasticity materials (such as TPE, PUR, etc.) that protect the conductor without cracking due to frequent movement.
Inner Sheath/Filling: Fillers are used between the stranded cores to create a round structure, secured by an inner sheath to prevent internal structure slippage and mutual friction.
Shielding Layer: A high-density braided tinned copper mesh is used to provide excellent electromagnetic shielding protection, while itself possessing good flexibility and bend resistance.
Outer Sheath: This is the outermost layer of protection, usually made of extremely wear-resistant materials (such as PUR), often in black or orange. It must withstand friction against machinery or other cables, as well as potential exposure to oil, coolant, etc.

Robot Cable Extrusion Line

The robot cable extrusion production line is a complete set of equipment specifically used for manufacturing the core stages of robot cables—the insulation layer and the sheath layer. Due to the extremely high requirements for flexibility, wear resistance, and torsion resistance of robot cables, its extrusion production line, compared to ordinary cable extrusion equipment, features high precision, high stability, and a high degree of synergy. This production line uses processes such as melting, extrusion, and cooling to uniformly coat the conductor or cable core with special elastic materials (such as PUR, TPE, etc.), forming high-performance insulation layers and protective outer sheaths.

Core Components

A complete robot cable extrusion production line usually consists of the following major systems, arranged according to the process flow:
Pay-off System
Function: To smoothly release the conductor (e.g., copper wires) or the cable core that has been stranded or assembled.
Characteristics: For robot cable production, the pay-off system must possess precise tension control capability. Excessive tension will thin the conductor, while insufficient tension will cause the cable to be slack, affecting structural stability. Active pay-off or magnetic powder brakes are typically used to maintain constant tension.
Preheating System
Function: To preheat the conductor before it enters the extruder head.
Purpose:
Remove moisture from the conductor surface to prevent bubble formation in subsequent steps.
Increase the conductor temperature, allowing the molten insulation material to bond more tightly with the conductor, reducing internal stress and improving adhesion. This is crucial for the cable's bending and torsion resistance.
Extruder System
Extruder:
Screw: Typically uses a deep-channel, low-compression ratio screw, specifically designed for processing soft materials like thermoplastic elastomers, ensuring uniform plasticization and lower shear heat to prevent material degradation.
Temperature Control: The temperature of each zone of the barrel requires precise control with minimal error range, ensuring the material melts under optimal conditions.
Head and Die:
Structure: Often uses a crosshead or semi-crosshead design, allowing the molten material to uniformly surround the conductor from all sides, avoiding eccentricity.
Die: The precision requirements for the die are extremely high. The smoothness of its inner hole directly affects the smoothness of the extruded surface. The die design is critical for eliminating internal stress and ensuring the roundness of the cable.
Cooling System
Function: To gradually cool and set the high-temperature cable just exiting the die.
Form: Usually a stepped cooling water tank, divided into multiple sections with water temperature decreasing from high to low.
Importance: Slow and gradual cooling is key to producing highly flexible cables. Rapid cooling causes uneven shrinkage between the inside and outside of the sheath, generating significant internal stress, which can lead to wrinkling and cracking when the cable is bent or twisted. Warm water cooling and a sufficiently long water tank are essential requirements.
Diameter Gauge and Eccentricity Gauge
Function: To perform online real-time detection of the outer diameter of the extruded cable and the uniformity of the insulation/sheath thickness (i.e., eccentricity).
Importance: This is the "eyes" for ensuring consistent product quality. Any eccentricity or fluctuation in outer diameter can seriously affect the cable's electrical performance and mechanical lifespan. Data is fed back to the control system for fine-tuning.
Spark Tester
Function: To perform online detection of the continuity of the insulation layer, checking for defects such as broken skin or pinholes.
Principle: By applying high voltage, any defect point will cause a spark discharge, which is recorded by the equipment, triggering an immediate alarm.
Caterpillar Haul-off / Puller
Function: To provide stable pulling force, drawing the cable through the entire production line at a constant speed.
Characteristics: Uses a dual-wheel belt-type puller or a caterpillar track puller to grip the cable with even pressure, avoiding crushing the soft core. The haul-off speed must be synchronized with the extruder's output to ensure stable cable diameter.
Take-up System
Function: To wind the finished cable neatly onto a reel.
Characteristics: Uses active take-up or a torque motor, synchronized with the haul-off, to maintain constant and gentle take-up tension, preventing the cable from being over-stretched or damaged.
Central Control System
Function: Integrates PLC and touchscreen interfaces to centrally set, monitor, and record parameters such as speed, temperature, and tension for the entire production line.
Importance: It enables automation, precision, and traceability of the production process, serving as the "brain" for producing high-quality, consistent robot cables.

Robot Cable Extrusion Line Datasheet

Model	30	40	50	60	70	80	90	100	120	150
Screw Diameter (mm)	φ30	φ40	φ50	φ60	φ70	φ80	φ90	φ100	φ120	φ150
Screw L/D Ratio	25:1	25:1	26:1	26:1	26:1	26:1	26:1	25:1	25:1	25:1
Extrusion Amount (kg/hr)	25	40	70	100	140	200	250	320	450	650
Outlet Wire (mm)	0.2-1	0.4-3	0.8-5	1-8	2-15	3-25	5-35	8-60	10-80	15-120
Total Power (KW)	18	20	25	33	40	55	63	120	165	220
Traction Power (KW)	2.2	2.2	4	4	4	5.5	5.5	11	11	15
Production Speed (m/min (Max.))	600	600	600	500	500	300	300	100	80	60
Take-up Spool (mm)	φ200-400	φ300-500	φ400-630	φ400-630	φ500-630	φ800-1000	φ800-1250	φ1000-2000	φ2000-2500	φ2500-3150

Robot Cable Extrusion Line Application

The robot cable extrusion production line is a technology-intensive, high-end cable manufacturing equipment. It is not simply about extruding plastic onto wires, but rather a systematic engineering project involving precision machinery, materials science, automatic control, and other disciplines. It is mainly applied in the following scenarios:
Robot body cables: particularly the internal cables of joints that require torsion resistance.
High-flexible drag chain cables: used for the seventh axis of robots, moving parts of automated equipment, etc.
Special cables such as servo motor cables and encoder cables, which have high requirements for flexibility and durability.

Process Characteristics

"Slow work yields fine products": The production speed is relatively slow to ensure sufficient plasticization and gradual cooling, eliminating internal stress.
Material handling is crucial: Materials like PUR and TPE used are prone to moisture absorption and must undergo strict drying treatment before production.
Precision is paramount: Requirements for temperature control, tension control, and mold precision are far higher than those of ordinary production lines.
Cooling process is the soul: The unique warm water gradient cooling process is one of the core secrets to ensuring cable flexibility and durability.