Tube Drawing Machine

In the jewelry sector, tubular structures are the core form for chains, components, and shaped ornaments (e.g., the tubular links of a snake chain, the fine needle of an earring post, or the hollow frame of a pendant). The Tube Drawing Machine (TDM) is the essential equipment that executes the transformation from “precious metal blank” to “precision tube.” Its status and value are manifested in three dimensions:

1.1, Irreplaceable Association: Supporting the Mass Production of Tubular Jewelry

Traditional manual methods cannot achieve uniform forming of fine-diameter ($0.3\text{mm}-5\text{mm}$)  and thin-wall ($0.05\text{mm}-0.5\text{mm}$) precious metal tubes, often resulting in high raw material loss (manual processing loss can exceed 20%). TDM uses precise matching of dies and pulling force to consistently produce fine tubes that meet jewelry requirements. TDM’s capability for efficient production and material saving makes it a cost-effective method for high-volume production.³ This capability is the prerequisite for scaling up tubular jewelry from “small-batch customization” to “mass production,” especially critical for high-value processing of gold, silver, and platinum.

1.2, Core Value Manifestation: Precisely Addressing Three Major Industry Pain Points

• Optimizing Precious Metal Utilization: Raw materials like gold, silver, and platinum are costly. TDM, through micron-level dimensional control, increases material utilization from the traditional 70% to over 90%, with some precision models achieving up to 95%. Only the small percentage of scrap (below 5%) needs to be recycled, significantly reducing material waste.

• Ensuring Jewelry Refinement: Jewelry demands extremely high standards for tube roundness, straightness, and surface finish (e.g., a $0.5\text{mm}$ fine tube link requires a roundness deviation $\le 0.01\text{mm}$ and surface roughness $Ra \le 0.4 \mu\text{m}$). TDM ensures stable compliance with these metrics through multi-pass drawing and high-precision dies, preventing issues like chain jamming or loose component assembly caused by dimensional variance. High-spec industries, such as medical manufacturing, aim for an $Ra$ below $0.1$ microns , setting the benchmark for premium jewelry finish.

• Optimizing Production Efficiency: Small precision TDM units can produce hundreds of meters of precious metal tubing per day, while multi-die continuous models can exceed thousands of meters, vastly surpassing manual output (which is typically tens of meters daily). Furthermore, mold changeover time can be controlled to within 1 hour, adapting well to the “small batch, multi-specification” nature of jewelry orders.

1.3, Adapted Jewelry Types: Covering Mainstream Tubular Scenarios

• Chain Components: Basic tube stock for snake chains, bamboo chains, O-chains, and other tubular link styles, requiring uniform tubes with diameters of $1\text{mm}-3\text{mm}$ and wall thicknesses of $0.1\text{mm}-0.3\text{mm}$. For example, snake chain machines require input materials to produce finished chains with a minimum round diameter .

• Accessory Components: Fine components like earring posts , pendant bails, and bracelet clasps ($2\text{mm}-5\text{mm}$ diameter), requiring high strength and dimensional accuracy.

• Special-Shaped Jewelry: Square, rhombic, or oval cross-section tubes used for geometric pendants and personalized bangles, requiring customized dies to achieve special shapes via the TDM

TDM selection in the jewelry industry must combine material characteristics, tube specifications, and production scale to ensure precise matching.

2.1, Mainstream Machine Types and Characteristics

2.2, Core Selection Criteria: Four Steps to Identify the Right Model

(1) Selection by Precious Metal Type

• Stable Precious Metals (Gold, Platinum): Standard small precision or multi-die continuous TDM can be chosen, with no extra anti-oxidation design needed.

• Easily Oxidized Precious Metals (Silver, Palladium): Prioritize Vacuum TDM to prevent the formation of an oxide layer during drawing, which could cause uneven plating or surface blackening later.

• Alloys (K Gold, Silver-Copper Alloys): Must select machines with an “intermediate annealing” function, as alloys harden easily during drawing, requiring regular softening (e.g., K Gold requires annealing every 2–3 passes).

(2) Selection by Tube Specification

• Fine Diameter Tubes ($\le 1\text{mm}$, e.g., earring posts): Must select small precision TDM, paired with natural diamond dies for high precision and low wear, ensuring diameter tolerance $\le \pm 0.01\text{mm}$.

• Mid-Spec Tubes ($1\text{mm}-3\text{mm}$, e.g., standard chain stock): Multi-die continuous TDM can be chosen to balance precision and capacity.

• Coarse Diameter Tubes ($3\text{mm}-5\text{mm}$, e.g., bangle frames): Enhanced small TDM models can be used, focusing on uniform wall thickness rather than continuous production features.

(3) Selection by Production Scale

• Customization Studios (Monthly Capacity $\le 100$ meters): Select 1–2 Small Precision TDM units to meet multi-spec, small-batch needs, avoiding idle equipment.

• Medium Jewelry Factories (Monthly Capacity $1,000\text{m}-5,000\text{m}$): Configure 1 Multi-Die Continuous TDM (for regular orders) + 1 Small Precision TDM (for custom orders).

• Large Brand Factories (Monthly Capacity $\ge 10,000$ meters): Multiple Multi-Die Continuous TDM units linked together, featuring automated loading/unloading systems for continuous production.

(4) Selection Pitfalls to Avoid

• Avoiding “Capacity-Only” Mindset: Small studios choosing high-capacity multi-die machines may face complex changeovers and high equipment costs, increasing the burden.

• Do Not Neglect “After-Sales Service”: Prioritize manufacturers who offer mold customization and equipment calibration services, which are crucial for the jewelry industry’s frequent need for custom and special-shaped dies.

• Focusing on “Energy Consumption and Space”: Small studios should choose energy-efficient models

TDM operation directly impacts the quality of precious metal tubes and raw material loss. Strict adherence to the “Pre-Operation – Core Operation – Post-Operation” three-stage process is necessary, with each step adapted to the refined demands of the jewelry industry.

3.1, Pre-Operation Phase: Laying the Foundation for Quality

(1) Differentiated Drawing Parameters for Precious Metals

3.2, Core Operation Phase: Precise Control at Every Step

2) Vacuum Drawing Technology for Easily Oxidized Precious Metals

• Vacuum Level Control: Vacuum TDM must operate with a stable vacuum level . The system should feature a real-time pressure monitoring and alarm device to notify the operator if the vacuum deviates by more than , ensuring continuous oxidation protection.

• Atmosphere Protection: Inert gases (Argon or Nitrogen) can be introduced into the vacuum chamber to create a positive pressure layer. Argon protection is recommended for high-purity silver or palladium tubes to prevent surface yellowing or oxide film formation.

• Cooling Method: Vacuum TDM requires a circulating water-cooling + air-cooling combination to dissipate heat while maintaining vacuum integrity, preventing high temperatures from causing silver discoloration or grain coarsening.

• Vacuum Environment Lubricants: Specialized vacuum-compatible lubricants (low volatility, high lubricity), such as synthetic ester-based vacuum oils, should be used, with viscosity controlled

(3) Maintenance of Vacuum TDM

• Vacuum System Maintenance: Check the vacuum pump oil cleanliness and replace the filter core every 100 hours of operation. Inspect and replace chamber seals every 500 hours to maintain air tightness.

• Sensor Calibration: Calibrate the vacuum pressure sensor, temperature controller, and tension sensor quarterly to ensure precision monitoring.

1. Dimensional Precision Control: The Pursuit of Micron-Level Excellence

(1) Diameter and Wall Thickness Deviation Control

• Mold Wear Compensation: Tungsten carbide molds should be checked for bore wear every 200 meters of use. If wear exceeds $0.005\text{mm}$, the mold should be replaced or drawing parameters should be adjusted.

• Environmental Temperature Control: Maintain workshop temperature at $18^\circ\text{C}-25^\circ\text{C}$ to prevent thermal expansion/contraction of equipment parts from affecting drawing precision.

(2) Roundness and Straightness Assurance

• Straightness Control: Drawn tubes must pass through a straightening mechanism (such as rotating anti-bending rollers).² The straightening pressure is adjusted based on the tube specification. After straightening, the deviation should be $\le 0.1\text{mm/m}$.

• Roundness Control: Ensure the concentricity between the die and the traction mechanism is $\le 0.01\text{mm}$ and drawing speed stability is $\le \pm 5\%$ fluctuation.

2. Surface Quality Assurance: The Leap from “Standard” to “Premium”

(1) Prevention of Scratches and Drawing Marks

• Die Entrance Treatment: Die entrances must be rounded (radius $0.1\text{mm}-0.2\text{mm}$) to prevent sharp edges from scratching the tube.

• Sufficient Lubricant Supply: Ensure a constant supply of drawing oil at the die entrance to avoid “dry drawing,” which causes friction damage.

(2) Anti-Oxidation and Discoloration Control

• Material-Specific Equipment: Easily oxidized materials like silver and palladium must use Vacuum TDM. The vacuum level needs to be $\ge 0.001\text{Pa}$ to completely isolate the atmosphere.

• Rapid Post-Processing: Drawn tubes must be cleaned, dried, and sealed within 30 minutes, or temporarily stored in an inert gas protection box.

(3) Surface Finish Enhancement

• Die Polishing: Before using new dies, polish the inner surface with diamond abrasive paste to reduce surface roughness.

• Multi-Pass Fine Drawing: The final 1–2 passes should use a small deformation rate (10%–15% reduction) to achieve the final size, which effectively enhances the final surface finish.

3. Precious Metal Specific Technology: Addressing Material Challenges

(1) Differentiated Drawing Parameters for Precious Metals

(2) Vacuum Drawing Technology for Easily Oxidized Precious Metals

• Vacuum Level Control: Vacuum TDM must operate with a stable vacuum level of $0.001\text{Pa}-0.005\text{Pa}$. The system should feature a real-time pressure monitoring and alarm device to notify the operator if the vacuum deviates by more than $\pm 0.002\text{Pa}$, ensuring continuous oxidation protection.

• Atmosphere Protection: Inert gases (Argon or Nitrogen) can be introduced into the vacuum chamber to create a positive pressure layer. Argon protection is recommended for high-purity silver or palladium tubes to prevent surface yellowing or oxide film formation.

• Cooling Method: Vacuum TDM requires a circulating water-cooling + air-cooling combination to dissipate heat while maintaining vacuum integrity, preventing high temperatures from causing silver discoloration or grain coarsening.

• Vacuum Environment Lubricants: Specialized vacuum-compatible lubricants (low volatility, high lubricity), such as synthetic ester-based vacuum oils, should be used, with viscosity controlled at $40\text{cSt}-60\text{cSt}$.

(3) Maintenance of Vacuum TDM

• Vacuum System Maintenance: Check the vacuum pump oil cleanliness and replace the filter core every 100 hours of operation. Inspect and replace chamber seals every 500 hours to maintain air tightness.

• Sensor Calibration: Calibrate the vacuum pressure sensor, temperature controller, and tension sensor quarterly to ensure precision monitoring.

As demand for micro-tube structures, special shapes, and automated precision processing in the jewelry industry increases, the TDM is evolving toward intelligent, energy-efficient, and highly integrated systems.

• Intelligent Monitoring and Adaptive Control: Future TDM units will integrate AI temperature control and self-learning algorithms to realize “human-free, constant-quality output” by automatically adjusting drawing speed and pulling force.¹⁵ High-end models already feature online dimensional inspection (laser diameter gauge) and automated compensation systems, which automatically adjust parameters upon detecting a deviation.

• Micro-Machining and Special-Shaped Tube Technology: To address micro-tube ($\le 0.3\text{mm}$) and special cross-section demands, TDM is introducing micro-servo systems and multi-axis linkage drawing mechanisms to support the integrated forming of various geometric shapes (oval, square, wavy).

• Green Manufacturing and Energy Optimization: Modern TDM uses variable frequency energy-saving motors and low-viscosity biodegradable lubricants, reducing energy consumption by 20%–30% compared to traditional models.

• Digital Quality Traceability System: Advanced TDM will feature MES (Manufacturing Execution System) interfaces to record the process parameters (speed, vacuum level, mold number) of every tube. This full-process data traceability, often achieved through barcode and data matrix marking systems , provides verifiable production records for high-end brand jewelry, meeting compliance and quality verification needs.

The Tube Drawing Machine (TDM) is not just a piece of production equipment; it is the critical process core connecting precious metal raw materials to high-end jewelry products. Through the synergistic operation of precision molds, stable vacuum environments, and intelligent control systems, it achieves the combination of micron-level precision, high material utilization, and sustainable manufacturing.   

Moving forward, with the widespread adoption of digital manufacturing and smart factory concepts, the TDM will serve as a strategic fulcrum for the jewelry industry to realize “high-precision + customization + efficient production,” providing a solid foundation for the innovative design and global mass production of gold, silver, and platinum jewelry.