High-tension low-relaxation tungsten tendon rope for dexterous hand and preparation process of high-tension low-relaxation tungsten tendon rope

Abstract

The invention relates to a high-tension low-relaxation tungsten tendon rope for a dexterous hand and a preparation process of the high-tension low-relaxation tungsten tendon rope for the dexterous hand. The process comprises the following steps: a) mixing high-purity tungsten powder and nano lanthanum oxide powder, and sintering after cold isostatic pressing to obtain a compact blank strip; b) carrying out hot rotary swaging on the blank strip to obtain a rod material, and repeatedly carrying out single-pass drawing at 800-1000 DEG C until the wire diameter is 0.5 mm; then multi-pass drawing is conducted at the temperature of 600-800 DEG C to obtain thin wires with the required diameter; c) according to the designed monofilament specification combination, differential pretension is applied to the different-diameter filaments, and the pretension is the filament diameter D * 30 (+ / -0.2) N; d) stranding and rope combining: adopting a 7 * 7 composite structure; e) heat setting; and f) drying the tendon rope after ultrasonic cleaning. According to the tendon rope, the lanthanum oxide doped tungsten filaments serve as the monofilaments, the 7 * 7 composite structure is adopted, and the prepared tendon rope has the high breaking force, the low stress relaxation rate and the good bending fatigue life by precisely regulating and controlling technological parameters.

Description

Technical Field

[0001] This invention belongs to the field of high-performance metal wire processing technology, specifically relating to a high-tensile, low-relaxation tungsten tendon rope for dexterity hands and its preparation process. Background Technology

[0002] In recent years, the humanoid robot industry has developed rapidly, with major domestic and international technology giants investing heavily in research and development, providing new direction for the future technology market. Among these technologies, "tendon cords," acting as the "tendons" of robots, are primarily used in the dexterous hands and joints of humanoid robots. They drive movement by mimicking the traction methods of human tendons, and their performance directly determines the dexterous hand's flexibility, load capacity, precision, and lifespan. An ideal dexterous hand drive tendon cord needs to simultaneously meet the following key requirements: first, high breaking tensile strength to provide sufficient gripping force; second, low relaxation rate to ensure long-term postural stability; third, excellent flexural fatigue life to withstand repeated pulley movements; and fourth, a small diameter to accommodate the compact space of the finger bones.

[0003] Currently, the mainstream materials for tendon chords are ultra-high molecular weight polyethylene fiber (UHMWPE), stainless steel wire, and pure tungsten wire, but all of these materials have obvious defects: (1) Ultra-high molecular weight polyethylene fiber (UHMWPE): Although it has high specific strength and light weight, its inherent viscoelasticity leads to severe creep relaxation. Under long-term load, the elongation of the tendon ligaments can cause dexterity hand positional drift, requiring frequent calibration. In addition, its low elastic modulus affects the response speed of force control.

[0004] (2) Stainless steel wire: It has a high elastic modulus and relatively good anti-relaxation performance, but its specific strength is limited and its breaking tensile strength is insufficient under the same diameter. More seriously, stainless steel wire rope has poor fatigue performance under small bending radius and usually fails after tens of thousands of bending cycles.

[0005] (3) Pure tungsten wire: Although it has the potential for high density, high elastic modulus and high strength, its inherent low-temperature brittleness and high recrystallization brittleness make it extremely easy to break during processing and rope making. Traditional tungsten wire rope production processes are difficult to precisely control internal stress, resulting in poor toughness, high relaxation rate and unsatisfactory bending fatigue life of the finished rope. Summary of the Invention

[0006] The purpose of this invention is to provide a manufacturing process for high-tensile, low-relaxation tungsten tendon ropes for dexterous hands. By doping traditional tungsten materials with La2O3 and precisely controlling the temperature, tension, twist pitch, and twist direction of the heat treatment, the technical problem that existing tendon ropes cannot simultaneously achieve high load-bearing capacity, long-term dimensional stability, and excellent fatigue resistance is solved. This invention is suitable for high-end robot dexterous hand drive systems with stringent requirements for precision, load, and lifespan.

[0007] The technical solution adopted by this invention to solve the above problems is as follows: a process for preparing high-tensile, low-relaxation tungsten tendon ropes for dexterity hands, comprising the following steps: a) Selection of tungsten wire composition and preparation of billet: High-purity tungsten powder and nano lanthanum oxide powder are mixed, cold isostatically pressed, and then sintered under a hydrogen protective atmosphere to obtain a dense billet.

[0008] b) Multi-pass hot spinning forging and temperature-controlled drawing: The dense billet is hot-spinned to obtain a rod with a diameter of 2.0 mm. Then, it is repeatedly drawn in single passes at 800-1000℃ to a wire diameter of 0.5 mm, with a diameter reduction rate of 15-20% per pass. After that, it is continuously drawn in multiple passes at 600-800℃ to a fine wire of the required diameter, with the surface area reduction rate controlled at 12% to 16% per pass.

[0009] c) Wire distribution and differentiated tension configuration: According to the designed combination of monofilament specifications, differentiated pretension is applied to the different diameter wires, where the pretension is D×30 (±0.2) N. In this way, through differentiated pretension, the monofilaments of different specifications can achieve the best state of synergistic work in the composite material.

[0010] d) Precision control of twisting and rope bonding: carried out at room temperature. Twisting of 1×7 strands: left-hand (S twist) with a twist pitch of 1.47mm to 1.78mm, and maintaining a tension of 2.7N to 2.9N during the process; final 7×7 rope bonding: right-hand (Z twist) with a pitch of 4.23mm to 4.96mm, and maintaining a tension of 3.9N to 4.1N during the process. e) Heat treatment and shaping: The tendon rope after being combined is heat-shaped in situ online under an argon protective atmosphere to achieve stress relief, making the rope less prone to loosening and straight. f) Ultrasonic cleaning: The tendon ligaments are cleaned in an ultrasonic cleaning tank and then dried.

[0011] Preferably, the mass of the nano-lanthanum oxide powder in step a) is 0.5% to 1.2% of the total mass of high-purity tungsten powder and nano-lanthanum oxide powder, and the sintering temperature is 2000℃ to 2200℃.

[0012] Preferably, the multi-pass drawing in step b) requires the use of a drawing lubricant, which is a graphite emulsion.

[0013] Preferably, the initial forging temperature of the hot rotary forging in step b) is 1500℃~1700℃, and the final forging temperature is not lower than 1000℃.

[0014] Preferably, in step d), the 1×7 strands of twisted monofilaments contain two different diameter specifications and adopt a symmetrical structure of "1 thicker filament + 6 thinner filaments".

[0015] More preferably, the two different diameter specifications are a combination of diameters of 0.06 mm and 0.05 mm, or a combination of diameters of 0.07 mm and 0.052 mm.

[0016] Preferably, the online in-situ heat setting temperature in step e) is 950℃~1050℃, and the time is 30~60 seconds.

[0017] Preferably, the ultrasonic cleaning in step f) specifically involves cleaning in a 40kHz±2kHz ultrasonic cleaning tank for 9 to 12 seconds.

[0018] Another objective of this invention is to provide a high-tensile, low-relaxation tungsten tendon cord for dexterity hands, wherein the high-tensile, low-relaxation tungsten tendon cord is prepared using a dexterity hand high-tensile, low-relaxation tungsten tendon cord manufacturing process, and the diameter of the high-tensile, low-relaxation tungsten tendon cord is 0.48mm ± 0.01mm.

[0019] Compared with the prior art, the advantages of the present invention are as follows: The tendon rope of this invention uses lanthanum oxide-doped tungsten wire as the monofilament and adopts a 7×7 composite structure. By precisely controlling the heat treatment temperature, tension, twist pitch and twist direction, the prepared tendon rope can work for a long time under a load of up to 70% breaking tensile force, with a relaxation rate that remains stable at an extremely low level. At the same time, it has excellent bending fatigue resistance and is suitable for high-end robot dexterity hand drive systems with stringent requirements for precision, load and life. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0021] A process for manufacturing high-tensile, low-relaxation tungsten tendon ropes for dexterity hands includes the following steps: 1. Material preparation and filament preparation High-purity tungsten powder and nano-lanthanum oxide powder were mixed at a mass ratio of 0.86% La2O3, and then cold isostatically pressed and sintered at 2100℃ under a hydrogen protective atmosphere to obtain a dense billet. The billet was then subjected to multiple hot rotary forgings at an initial forging temperature of 1550℃ and a final forging temperature of 1050℃ to process it into a rod with a diameter of 2.0mm.

[0022] 2. Temperature-controlled drawing process A 2.0mm rod was repeatedly drawn in single passes at 800-1000℃ to a wire diameter of 0.5mm. During this process, the temperature decreased as the diameter decreased (the initial pass temperature was 1000℃, and the temperature of each single pass was different and decreased linearly by 25℃, with the final pass temperature being 800℃). The diameter reduction rate per pass was 18%. Then, multiple consecutive passes were drawn at 700℃ to obtain monofilaments with diameters of 0.06mm and 0.05mm, respectively, with the surface area reduction rate controlled at 14%. The drawing lubricant used in the drawing process was graphite emulsion. The tensile strength of both types of monofilaments could reach over 4250MPa.

[0023] 3. Rope-making process parameters Wire configuration: A combination of 0.06mm and 0.05mm diameter wires is used, with each 1×7 strand consisting of a central 0.06mm wire and an outer 6 0.05mm wires.

[0024] Tension control: 1.8 N pretension for 0.06 mm diameter wire, 1.5 N pretension for 0.05 mm diameter wire.

[0025] Twisting parameters: 1×7 strand twist: left-hand (S twist), twist pitch 1.65mm, strand tension 2.8N.

[0026] Final 7×7 rope: right-hand (Z-twist), twist pitch 4.77mm, overall rope tension 4.0N.

[0027] 4. Heat treatment and shaping: After the tendon rope is combined, it is heat-shaped online at 1000℃ for 45 seconds under an argon protective atmosphere to achieve stress relief, making the rope less prone to loosening and straight. 5. Ultrasonic cleaning: The tendon ligament is cleaned with 40kHz ultrasonic waves for 25 seconds and then dried by compressed air blowing. Example 2

[0028] A process for manufacturing high-tensile, low-relaxation tungsten tendon ropes for dexterity hands includes the following steps: 1. Material preparation and filament preparation High-purity tungsten powder and nano-lanthanum oxide powder were mixed at a mass ratio of 0.92% La2O3, and then cold isostatically pressed and sintered at 2100℃ under a hydrogen protective atmosphere to obtain a dense billet. The billet was then subjected to multiple hot rotary forgings at an initial forging temperature of 1550℃ and a final forging temperature of 1050℃ to process it into a rod with a diameter of 2.0mm.

[0029] 2. Temperature-controlled drawing process A 2.0mm rod was repeatedly drawn in single passes at 800-1000℃ to a wire diameter of 0.5mm, with a diameter reduction rate of 17% per pass. The initial pass temperature was 1000℃, and the drawing temperature for each pass was different and decreased linearly by 20℃, with the final pass temperature at 820℃. Subsequently, multiple passes were drawn at 700℃ to obtain monofilaments with diameters of 0.07mm and 0.052mm, respectively, with a face area reduction rate controlled at 13% per pass. The drawing lubricant used in the drawing process was graphite emulsion. The tensile strength of both types of monofilaments reached 4310MPa.

[0030] 3. Rope-making process parameters Wire configuration: A combination of wires with diameters of 0.07mm and 0.052mm is used. The center strand consists of one 0.07mm wire in the center and six 0.052mm wires on the periphery. The center and surface strands of the face strands are both 0.052mm.

[0031] Tension control: 2.1N pretension for 0.07mm diameter wire, 1.6N pretension for 0.052mm diameter wire. Twisting parameters: 1×7 strand twist: left-hand (S twist), twist pitch 1.65mm, strand tension 2.9N Final 7x7 rope configuration: right-hand (Z-twist), lay length 4.77mm, total rope tension 4.0N. 4. Heat treatment and shaping: After the tendon rope is combined, it is heat-shaped online at 1000℃ for 45 seconds under an argon protective atmosphere to achieve stress relief, making the rope less prone to loosening and straight. 5. Ultrasonic cleaning: The tendon ligament is cleaned with 40kHz ultrasonic waves for 25 seconds and then dried by compressed air blowing.

[0032] Comparative Example 1 (304 stainless steel wire rope) The only difference from Example 1 is that stainless steel wires with diameters of 0.06 and 0.05 mm are used to twist into stainless steel wire ropes, i.e. steps 1 and 2 are omitted.

[0033] Comparative Example 2 (UHMWPE fiber rope) UHMWPE fiber rope is obtained by using 0.04mm diameter polyethylene fiber as a single strand and employing a 12-strand braiding structure.

[0034] Comparative Example 3 (Conventional Tungsten Tendon Rosette) The only difference from Example 1 is that no nano-lanthanum oxide powder is added; instead, high-purity tungsten powder is added.

[0035] Comparative Example 4 The only difference from Example 1 is that in step 2, the 2.0mm rod is repeatedly drawn in a single pass at a temperature of 900℃ to a wire diameter of 0.5mm, and the diameter reduction rate for each pass is 18%. Comparative Example 5 The only difference from Example 1 is that precise tension control is not performed; the tension of the filament is simply maintained, excluding the step of pre-tensioning 1.8 N for 0.06 mm diameter filament and 1.5 N for 0.05 mm diameter filament.

[0036] The performance of the examples and comparative examples is shown in the table below. The breaking tensile strength test refers to GB / T 8358, the isothermal relaxation test refers to GB / T 10120, and the uniaxial bending fatigue test refers to GB / T 12347.

[0037] The comparison between the above embodiments and comparative examples shows that: The tendon rope of this invention achieves the best balance between high breaking tensile strength, low stress relaxation rate, and good bending fatigue life (≥5 million cycles). Although Comparative Example 1 has a low relaxation rate under load, its breaking tensile strength is limited and its bending fatigue life is short, which cannot meet the requirements of long-term use of dexterous hands. Comparative Example 2 has a long bending fatigue life, but its stress relaxation rate is too high, which cannot guarantee the positional accuracy for long-term use, and its breaking tensile strength is insufficient. In Comparative Example 3, the conventional material tendon rope is not doped with lanthanum oxide, and in Comparative Example 4, the temperature-controlled drawing process is carried out at the same temperature. In Comparative Example 5, no pre-tension treatment is performed, so its breaking tensile strength, relaxation rate, and fatigue performance are all lower than those of Example 1.

[0038] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A process for manufacturing high-tensile, low-relaxation tungsten tendon ropes for dexterity hands, characterized in that: Includes the following steps: a) Selection of tungsten wire composition and preparation of billet: High-purity tungsten powder and nano lanthanum oxide powder are mixed, cold isostatically pressed, and then sintered under a hydrogen protective atmosphere to obtain a dense billet. b) Multi-pass hot spinning forging and temperature-controlled drawing: Dense billets are hot-spinned to obtain rods with a diameter of 2.0 mm, and then repeatedly drawn in single passes at 800-1000℃ to a wire diameter of 0.5 mm, with a diameter reduction rate of 15-20% per pass; subsequently, continuous multi-pass drawing is performed at 600-800℃ to obtain fine wires of the desired diameter, with a controlled surface area reduction rate of 12% to 16% per pass; c) Wire distribution and differentiated tension configuration: According to the designed combination of monofilament specifications, apply differentiated pretension to the different diameter wires, where the pretension is D × 30 (±0.2) N. d) Precision control of twisting and rope bonding: carried out at room temperature. Twisting of 1×7 strands: left-hand (S twist) with a twist pitch of 1.47mm to 1.78mm, and maintaining a tension of 2.7N to 2.9N during the process; final 7×7 rope bonding: right-hand (Z twist) with a pitch of 4.23mm to 4.96mm, and maintaining a tension of 3.9N to 4.1N during the process. e) Heat treatment and shaping: The tendon rope after being combined is heat-shaped in situ online under an argon protective atmosphere to achieve stress relief, making the rope less prone to loosening and straight. f) Ultrasonic cleaning: The tendon ligaments are cleaned in an ultrasonic cleaning tank and then dried.

2. The manufacturing process of the high-tensile, low-relaxation tungsten tendon rope for dexterity hands according to claim 1, characterized in that: The mass of the nano-lanthanum oxide powder mentioned in step a) is 0.5% to 1.2% of the total mass of high-purity tungsten powder and nano-lanthanum oxide powder, and the sintering temperature is 2000℃ to 2200℃.

3. The manufacturing process of high-tensile, low-relaxation tungsten tendon rope for dexterity hands according to claim 1, characterized in that: The multi-pass drawing process described in step b) requires the use of a drawing lubricant, which is a graphite emulsion.

4. The manufacturing process of the high-tensile, low-relaxation tungsten tendon rope for dexterity hands according to claim 1, characterized in that: The initial forging temperature of the hot rotary forging described in step b) is 1500℃~1700℃, and the final forging temperature is not lower than 1000℃.

5. The manufacturing process of the high-tensile, low-relaxation tungsten tendon rope for dexterity hands according to claim 1, characterized in that: The online in-situ heat setting temperature described in step e) is 950℃~1050℃, and the time is 30~60 seconds.

6. The manufacturing process of the high-tensile, low-relaxation tungsten tendon rope for dexterity hands according to claim 1, characterized in that: The ultrasonic cleaning described in step f) specifically involves cleaning in a 40kHz±2kHz ultrasonic cleaning tank for 9 to 12 seconds.

7. A high-tensile, low-slack tungsten tendon rope for dexterity hands, characterized in that: The high-tensile, low-relaxation tungsten tendon rope is prepared according to the manufacturing process of the high-tensile, low-relaxation tungsten tendon rope for dexterity hands as described in any one of claims 1-6.

8. The high-tensile, low-slack tungsten tendon rope for dexterity hands according to claim 7, characterized in that: The diameter of the high-tensile, low-relaxation tungsten tendon rope is 0.48mm ± 0.01mm.

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