CNC Gold Bangles Machine

1.1 Material Characteristics of Gold Bangle Processing (Compared with Silver and Platinum)

Gold bangle processing mainly uses pure gold (999 gold) and K gold (18K, 22K). The material’s characteristics directly determine the technical requirements of the CNC machine:

• • Ductility and Hardness: Pure gold has a hardness of only 2.5–3HV and extremely high ductility (1g of gold can be stretched into a 3,000m wire). During machining, excessive tool pressure easily causes plastic deformation (e.g., edge collapse of bangles). 18K gold contains 25% other metals, increasing hardness to 4–5HV, but cutting force control is still essential. The CNC Gold Bangles Machine must support low-pressure cutting, with spindle feed pressure adjustable to 0.1–0.3N to prevent material deformation.

  • Density and Value: Gold’s density reaches 19.3g/cm³—1.8× silver and 1.05× platinum—with a price exceeding $55 per gram. Thus, loss control is critical. Traditional manual processing causes a 3–5% gold loss, whereas specialized CNC machines must keep loss below 0.5%, relying on high-precision chip recovery and optimized cutting parameters.

  • Surface Finish and Color: Finished gold bangles require a mirror-like shine (polished bangles) or fine matte texture (ancient-style matte bangles). The surface roughness must be ≤Ra0.1μm; otherwise, the surface may trap dirt or appear dull. CNC tools should use diamond-coated or ultra-fine tungsten carbide cutters (grain size 0.1–0.5μm) to avoid tool marks transferring onto the surface.

1.2 Exclusive Technical Configurations of the CNC Gold Bangles Machine

To meet gold bangle machining needs, the CNC machine must include:

• • High-Precision 4-Axis Linkage System: Gold bangles often have circular surfaces with 3D patterns (e.g., twisted or push bangles). The 4-axis system (X/Y/Z linear + A rotary) enables full 360° processing, with A-axis rotation accuracy of ±0.001° and circular error ≤0.02mm, ensuring consistent fit.

  • Dynamic Pressure Compensation: The system automatically adjusts cutting pressure for different gold hardness—0.1N for pure gold, 0.3N for 18K gold—to prevent tool sticking (pure gold) or tool chipping (18K gold).

  • Closed-Loop Gold Chip Recovery System: Uses negative-pressure suction + centrifugal separation + electrostatic collection. Negative pressure ≥ -0.095MPa, separation speed 5000rpm, and electrostatic voltage 8000V ensure a gold recovery rate ≥99.8%.

  • Specialized Gold Bangle Fixtures: Uses curved soft-alloy fixtures with silicone pads for >95% surface contact, avoiding pressure marks. Supports adaptive clamping for 50–70mm diameters without frequent fixture changes.

2.1 Polished / Matte Basic Bangles (e.g., Round or Flat Bangles)
These bangles focus on curved surface precision and surface finish:

• Processing Flow and Parameters:

  • Gold Material Preparation: Roll gold into 5–8mm thick strips, rough-machine into ring blanks (with 0.2mm finishing allowance).

  • Finishing: Use φ6mm diamond-coated ball-end cutter, spindle speed 12,000–15,000rpm, feed rate 60–80mm/min, spiral toolpath (80% overlap) to achieve surface roughness ≤Ra0.08μm.

  • Matte Treatment: Use φ3mm sandblasting tool, pressure 0.2MPa, with 1500-grit diamond sand for even texture.

• Key Control Point: Calibrate A- and Z-axis perpendicularity (≤0.005mm/m) to prevent elliptical distortion affecting fit.

2.2 3D Pattern Bangles (e.g., Twisted or Filigree Bangles)

• Twisted Bangle:
  Use a 4-axis CNC. The A-axis rotates 10° per stop. Use φ2mm ultra-fine tungsten carbide end mill (0.1mm edge radius) to cut spiral grooves 2–3mm deep, depth error ≤0.01mm. Clean grooves with 0.5mm soft wool brush to remove residual chips.

• Filigree Bangle:
  CNC-mill gold into 0.3mm-thick filigree strips (1–1.5mm wide), fix them on the blank with multi-station fixtures. Use φ1mm diamond cutter for spot-weld-style cutting fixation (every 2mm), reducing material loss to ≤0.1% (vs. 1–2% for traditional welding).

2.3 Custom Bangles (e.g., Engraved or Gem-Set Bangles)

• Engraved Bangles:
  Import custom fonts, generate arc engraving paths matching bangle curvature. Use φ0.5mm tungsten cutter, spindle 18,000rpm, depth 0.1–0.2mm, width tolerance ≤0.05mm for clear engraving.

• Gem-Set Bangles:
  Use φ1mm ball-end cutter to machine inlay slots. For a 0.5ct diamond, slot depth 2mm and width 1.8mm, with wall perpendicularity ≤0.005mm. Use optical inspection to ensure perfect fit and prevent looseness or deformation.

3.1 Pain Point 1: Bangle Deformation (Especially Pure Gold)

Symptoms: Flattening (ellipticity >0.03mm) or edge collapse.

• • Solutions:

    • Fixture Optimization: Use three-point even clamping (120° apart), each applying 0.2N.

    • Processing Sequence: Machine inner surface → outer surface → edges to minimize stress.

    • Cooling Control: Use low-temperature oil mist cooling (15–20°C) to prevent softening (>100°C).

3.2 Pain Point 2: Excessive Gold Loss

Symptoms: Loss exceeding 0.5g per 100g bangle (worth over $27).

• Solutions:

  • Recovery Upgrade: Add magnetic plates to separate impurities; combined system yields 99.9% recovery.

  • Tool Optimization: Use super-lubricated coated tools (e.g., DLC diamond coating); maintain feed rate 60–80mm/min.

  • Material Reuse: Melt recovered chips into small gold blocks for accessory parts to achieve zero waste.

3.3 Pain Point 3: Insufficient Pattern Precision

• Symptoms: Uneven twists or inconsistent filigree gaps.

• Solutions:

  • Path Optimization: Use adaptive toolpaths—0.05mm step for complex patterns, 0.1mm for simple ones.

  • Real-Time Compensation: Laser probe checks every 5mm, auto-adjusting for tool wear.

  • Gold Annealing: Preprocess at 300°C for 2h with slow cooling to release internal stress.

Whether for personalized customization of gold jewelry or mass production, SuperbMelt can achieve efficient and precise processing through its integrated functions while controlling material loss.

4.1 Small Gold Workshops (50–100 Bangles/Month)

• Needs: Low cost, easy operation, small footprint.

• Recommendations:

  • Model: Desktop 4-axis CNC (≤0.6㎡), single-station.

  • Functions: Built-in design library (≥500 templates), one-click operation, basic recovery ≥99.5%.

  • Specs: Spindle 5000–18,000rpm, positioning ±0.005mm, daily output ≥10 pieces.

4.2 Medium Factories (500–1000 Bangles/Month)

• Needs: Efficient batch production, multi-type adaptability, low loss.

• Recommendations:

  • Model: Vertical dual-station 4-axis CNC (two bangles simultaneously).

  • Functions: Dynamic pressure compensation, triple recovery system, optical inspection, MES monitoring.

  • Specs: Spindle 8000–20,000rpm, repeatability ±0.003mm, output ≥50/day, loss ≤0.3%.

4.3, Ensuring Purity and Polishing Support After Gold Processing