3. Material Selection and Heat Treatment

3.1 Mold Material Selection

Cavity and Core Materials
  • P20 (3Cr2Mo): Hardness 30-35HRC, life 100,000-500,000 cycles, suitable for small to medium batches
  • 718H (3Cr2NiMo): Hardness 35-40HRC, life 500,000-1,000,000 cycles, suitable for mass production
  • NAK80: Hardness 40-42HRC, excellent mirror polishing performance, suitable for high requirement products
Molding Insert Materials
  • Cr12MoV: Hardness 58-62HRC, good wear resistance, suitable for complex molding parts
  • SKD61: Hardness 48-52HRC, good toughness, suitable for high stress areas
Standard Component Materials
  • Guide pillars and bushes: 20 steel + T10A steel
  • Ejector pins and return pins: T8A steel
  • Springs: 65Mn steel

3.2 Heat Treatment Processes

P20 Mold Steel
  • Pre-hardening treatment: 30-35HRC
  • Nitriding treatment: 520-540℃×20-30h, layer depth 0.15-0.25mm
718H Mold Steel
  • Pre-hardening treatment: 35-40HRC
  • Nitriding treatment: 520-540℃×20-30h, layer depth 0.15-0.25mm
Cr12MoV Mold Steel
  • Annealing treatment: 830-860℃×2-4h, slow cooling
  • Quenching treatment: 950-1050℃×0.5-1h, oil cooling
  • Tempering treatment: 180-200℃×2-3h, hardness 58-62HRC

3.3 Surface Treatments

Polishing Treatment
  • Rough polishing: #400-#800 sandpaper
  • Fine polishing: #1000-#2000 sandpaper
  • Mirror polishing: #3000-#8000 sandpaper + diamond paste
Coating Treatments
  • Hard chrome plating: Thickness 5-10μm, hardness 800-1000HV
  • Nitriding treatment: Improve surface hardness and wear resistance
  • DLC coating: Suitable for high requirement molds

4. Manufacturing Process Technology

Plastic Water Cup Mold Technical Guide

4.1 Processing Technology Route

Cavity and Core Processing
  1. Material cutting → Annealing → Rough machining → Semi-finishing → Heat treatment → Finishing → Polishing → Assembly
Template Processing
  1. Material cutting → Plane processing → Hole processing → Surface treatment → Assembly

4.2 Processing Equipment Selection

Rough Machining Equipment
  • CNC milling machine: Machining accuracy ±0.01mm
  • Machining center: Multi-axis linkage, suitable for complex shapes
Finish Machining Equipment
  • High-speed machining center: Speed 10,000-20,000rpm, accuracy ±0.005mm
  • EDM machine: Machining accuracy ±0.01mm
  • Wire-cut EDM: Machining accuracy ±0.003mm
Measurement Equipment
  • Coordinate measuring machine: Measurement accuracy ±0.002mm
  • Profile projector: Measurement accuracy ±0.005mm
  • Surface roughness tester: Measurement range Ra0.01-10μm

4.3 Processing Parameters

CNC Milling
  • Cutting speed: 100-300m/min
  • Feed rate: 500-2000mm/min
  • Cutting depth: 0.1-0.5mm
  • Tooling: Carbide or coated tools
EDM Machining
  • Discharge current: 1-50A
  • Pulse width: 1-100μs
  • Machining speed: 10-50mm³/min
  • Surface roughness: Ra0.4-1.6μm
Wire-cut EDM
  • Wire diameter: 0.1-0.3mm
  • Cutting speed: 50-200mm²/min
  • Surface roughness: Ra0.8-1.6μm
  • Perpendicularity: ≤0.005mm/100mm

4.4 Assembly Process

Assembly Preparation
  • Component cleaning: Remove oil, impurities
  • Component inspection: Dimensional accuracy, surface quality
  • Tool preparation: Torque wrench, feeler gauge, dial indicator
Assembly Sequence
  1. Fixed mold part: Fixed mold base → Fixed template → Cavity → Gating system
  1. Moving mold part: Moving mold base → Moving template → Core → Ejection mechanism
  1. Guidance system: Guide pillars → Guide bushes → Locating pins
  1. Hydraulic system: Cylinders → Pipes → Fittings
Assembly Accuracy Requirements
  • Parting surface gap: ≤0.02mm
  • Guide pillar and bush gap: 0.01-0.02mm
  • Core and cavity fit: 0.03-0.05mm
  • Movement smoothness: No jamming, no abnormal noise
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