How long does it take to CNC a part?

Answer

Extended Response

I. Part Complexity: Decisive Impact of Structure and Precision

1. Dimensional and Shape Complexity
   • Simple structures: Regular parts like cubes or cylindrical pins, where processing time depends on material removal.
     Example: Machining a 100mm×50mm×20mm aluminum block (5mm allowance removal) takes ~20 min for roughing and 10 min for finishing on a 3-axis mill, totaling <30 min.
   • Complex structures: Deep cavities, thin walls, or free-form surfaces (e.g., automotive panel molds) requiring multi-axis and layered machining.
     Example: 5-axis milling of an impeller (200mm diameter, 2mm blade thickness) takes 4 hours for roughing (removing 90% material) and 6 hours for finishing (Ra≤1.6μm), totaling ~10 hours.
2. Precision and Surface Requirements
   • General precision (±0.1mm): Single-pass machining (e.g., one drilling for holes), accounting for ~30% of time.
   • High precision (±0.01mm): Requires multi-stage processes (roughing→semi-finishing→finishing).
     Example: Machining a precision bearing hole (Φ50H7) via drilling→reaming→honing takes 2-3x longer than general hole machining.

II. Material Properties: Core of Machinability and Efficiency

1. Hardness and Toughness
   • Easy-to-cut materials: Aluminum (6061), brass, allowing high-speed machining.
     Example: Milling a Φ100mm aluminum disc at 3000rpm spindle speed and 800mm/min feed takes ~15 min.
   • Difficult materials: Titanium (TC4), stainless steel (316L), requiring reduced parameters due to high cutting heat and tool wear.
     Example: Same-sized TC4 disc needs spindle speed down to 1000rpm and feed to 300mm/min, extending time to 45 min with mid-process tool changes.
2. Material Removal Rate (MRR)
   • Formula: MRR = depth of cut × feed rate × cutting speed, directly impacting process time.
     Example: Machining 45# steel (600MPa tensile strength) with a Φ16mm end mill at ap=3mm, F=500mm/min:
     MRR ≈ 3×500×16 = 24,000mm³/min, removing 100cm³ takes ~4.2 min.

III. Equipment and Process: Dual Constraints of Hardware and Flow

1. Machine Type and Axes
   • 3-axis machines: Suitable for planar/simple contouring, lower efficiency.
     Example: Machining a 100×80×50mm cuboid on a 3-axis mill takes ~1 hour with multi-face processing.
   • 5-axis machines: Complete complex surfaces in one setup, reducing clamping time.
     Example: 5-axis machining of aerospace blades saves 40% time (from 8h to 4.8h) vs. 3-axis step-by-step processing.
2. Process Route Planning
   • Rational process splitting: E.g., drilling→tapping in separate steps requires tool changes and re-calibration (+5-10 min), while combined drill-tap tools reduce to 2 min.
   • Cutting strategy: Climb milling is 30% more efficient than conventional milling (better surface finish, fewer finishing passes), and helical ramping reduces tool wear, enabling 10-20% higher feed rates.

IV. Programming and Simulation: Digital Time Costs

1. CAM Programming Efficiency
   • Auto-programming: 5-10 min for simple parts in Mastercam, 2-4 hours for complex molds (including toolpath optimization).
   • Manual programming: 1-2 min for simple contours (e.g., linear interpolation G-code), but double time for complex curves (e.g., ellipses).
2. Simulation and Debugging Time
   • Software simulation (e.g., VERICUT) takes 5-30 min for collision/over-cut checks; machine debugging (tool setting, test cuts) may account for 20% of total time (e.g., 1-2 hours for complex parts).

V. Auxiliary Time: Invisible but Critical

1. Clamping and Tool Changes
   • Standard clamping: 5-10 min for vise clamping, 15-30 min for special fixtures (e.g., 4-jaw chucks).
   • Tool change frequency: 5-10 sec per change on machining centers, but 3-5 changes for multi-process parts (+1-2 min total).
2. Inspection and Post-Processing
   • On-machine inspection: 3-5 min per key dimension check with built-in probes.
   • Off-line CMM inspection: >30 min for complex parts, plus 1-3 hours for rework if unqualified.

VI. Batch Production and Optimization Strategies

1. Time Compression in Batch Processing
   • Example: Machining 100 identical parts: 2-hour setup for the first piece, then 20 min per part afterward, totaling ~35 hours—30% more efficient than single-piece production.
2. Efficiency Optimization Methods
   • High-Speed Cutting (HSC): Spindle speeds ≥10,000rpm boost aluminum machining efficiency by 50%, though equipment costs are high.
   • Automation integration: Robot loading/unloading reduces manual clamping time, ideal for batches (e.g., saving 2 hours per batch in phone case machining).
   • DFM (Design for Manufacturability): Simplifying structures (e.g., avoiding deep slots) shortens processing time by 20-40%.

VII. Case Studies: Time Comparison for Different Parts

Extended: Impact of Intelligent Technologies

• AI parameter optimization: FANUC’s AI spindle load control automatically adjusts speeds/feeds, reducing cycle time by 15-20%.
• Digital twin simulation: Virtual machine pre-processing predicts bottlenecks, cutting debugging time by >50%.
• Adaptive machining: Real-time cutting force monitoring dynamically adjusts parameters, avoiding rework and saving 10-30% time.