Tungsten wire tendon ropes are mainly used in precision transmission applications such as humanoid robot dexterity hands and medical surgical robots. They are made of multiple strands of ultra-fine tungsten wire twisted or braided. The number of braiding layers, or the strand structure and multi-strand configuration, mainly affects the performance of tungsten wire tendon ropes in terms of strength, flexibility, fatigue life, roundness, torsional resistance, creep, and compatibility with pulleys.
1. Common Structures and Layer Number Concepts of Tungsten Wire Tendon Ropes
Typical structures of tungsten wire tendon ropes include 1×7, 7×7, 7×19, 19×19, 7×7×7, 1×37, 49 strands and above. Multi-strand configurations such as 8×19+7×7 represent more complex multi-strand braiding or twisting configurations. The number of braided layers typically refers to the number of strands (including core and outer layers), the number of strands, or the overall number of twisted layers. Increasing the number of layers or strands results in a more complex multi-layered structure. Key aspects of the braiding process include tension control, pitch optimization, and fill factor.
2. Positive Impacts of Increased Braided Layers on Tungsten Wire Tendon Cord Performance
Increased Strength and Load Capacity: Multi-strand or multi-layered structures distribute loads evenly, preventing single-filament breakage and overall cord failure, thus increasing overall breaking load and tensile strength.
Improved Flexibility and Smaller Bending Radius: More fine filaments and multi-layered configurations enhance bending adaptability, making them suitable for multi-degree-of-freedom robot joint movements and small-radius pulleys, reducing wire skipping and strand unraveling.
Enhanced Fatigue Resistance and Durability: Multi-layered structures disperse stress, improving cyclic bending and tensile life, especially in long-term operation scenarios.
Increased Non-rotational Performance and Stability: Multi-layered non-rotational braiding reduces torsion and internal stress, improving transmission accuracy and dimensional stability.
Other: Better roundness, improved pulley compatibility, and optimized wear/fatigue resistance.
3. Negative Impacts of Increased Braiding Layers on Tungsten Wire Tendon Cord Performance
Conflict Between Flexibility and Tightness: Tight tendon cords with excessive layers, strands, or high filler coefficients exhibit greater rigidity but insufficient flexibility; looser cords are more flexible but may have slightly lower strength. Pitch and structure need to be customized based on load and bending direction.
Increased Manufacturing Difficulty: Multi-layer braiding places extremely high demands on equipment, tension control, and monofilament consistency (diameter tolerance, strength deviation). Ordinary equipment struggles to fabricate complex structures, easily leading to uneven stress, residual internal stress, creep, or terminal failure.
Increased Creep Risk: Internal stress introduced by braiding needs to be eliminated through pre-stretching and heat treatment; otherwise, increasing the number of layers may amplify the creep risk. Optimization can control the stress relaxation rate to within 5%.
Increased Manufacturing and Cost: More complex structures improve performance but require higher standards for surface finish, strength consistency, monofilament quality, and braiding precision, impacting mass production difficulty and cost.
4. Selection of the number of braided layers for tungsten wire tendon cords
For specific usage scenarios, please contact CTIA GROUP (sales@chinatungsten.com) for customization.
