Injection Mold Design & Manufacturing: Automotive Dashboard Component
This showcase presents a comprehensive injection mold design project for an automotive dashboard air vent component. The project demonstrates the complete workflow from part analysis to mold fabrication, including cooling system optimization, flow simulation, and multi-cavity mold design.
🎯 Project Objectives
- Design 4-cavity injection mold for high-volume production (500,000 units/year)
- Optimize cooling system to achieve cycle time ≤ 35 seconds
- Ensure part quality: warpage < 0.5mm, sink marks < 0.2mm
- Design ejection system for consistent part removal without damage
- Minimize manufacturing cost through efficient cavity layout
Part Specifications & Design Constraints
| Parameter |
Specification |
Design Challenge |
| Part Dimensions |
120mm × 80mm × 65mm |
Complex internal louver geometry |
| Wall Thickness |
2.0 - 2.5 mm (nominal 2.2mm) |
Uniform cooling required |
| Material |
ABS + PC blend (Bayblend T65) |
High shrinkage rate (0.5-0.7%) |
| Surface Finish |
VDI 3400 Grade 24 (matte) |
Class A surface on visible face |
| Tolerance |
±0.15 mm (general), ±0.05 mm (critical features) |
Tight tolerance on mounting bosses |
| Production Volume |
500,000 parts/year |
4-cavity mold for cost efficiency |
| Target Cycle Time |
≤ 35 seconds |
Optimized cooling channels required |
Mold Design Workflow
Phase 1: Part Analysis & DFM (Design for Manufacturability)
Analyzed plastic part for moldability issues:
- Draft Angle Check:
- Minimum draft: 1.5° on all vertical walls
- Louver blades: 3° draft for easy ejection
- Internal ribs: 0.5° draft (acceptable for shallow ribs)
- Undercut Analysis:
- Side louvers require 2 slide cores (left/right)
- Internal snap-fit features need lifter mechanisms
- Bottom mounting holes: straight-pull design (no action)
- Gate Location Study:
- Evaluated 5 gate positions using Moldflow simulation
- Selected edge gate on non-visible side (hidden by assembly)
- Gate size: 2.5mm × 1.5mm (rectangular cross-section)
- Parting Line Design:
- Main parting line: horizontal plane at mid-height
- Secondary parting: slide core interfaces at 30° angle
- Parting line flash risk: minimized through precision machining (±0.01mm)
Phase 2: Mold Flow Simulation (Autodesk Moldflow Insight 2024)
Performed comprehensive injection molding simulation:
🔧 Simulation Parameters
- Material Database: Bayblend T65 XF (ABS+PC, 20% glass fiber reinforced)
- Melt Temperature: 260°C (recommended: 250-280°C)
- Mold Temperature: 70°C (cavity), 65°C (core)
- Injection Pressure: 85 MPa (max available: 180 MPa - good safety margin)
- Injection Speed: 50 cm³/s
- Packing Pressure: 60 MPa for 8 seconds
- Cooling Time: 22 seconds (to reach ejection temperature 110°C)
📊 Simulation Results:
- Fill Time: 2.8 seconds - even flow front progression ✓
- Weld Lines: 3 locations identified (all in non-critical areas) ✓
- Air Traps: 2 potential traps - addressed with 0.02mm venting ✓
- Warpage: Maximum 0.38mm (within 0.5mm tolerance) ✓
- Sink Marks: 0.15mm at thick rib junctions (acceptable) ✓
- Volumetric Shrinkage: 0.58% (compensated in mold design) ✓
- Clamp Force Required: 280 tons (using 350-ton machine) ✓
Phase 3: Cooling System Design
Designed optimized cooling channels using conformal cooling principles:
- Core Cooling Channels:
- 8 × Φ10mm drilled channels following part contour
- Channel spacing: 25-30mm (3× wall thickness rule)
- Distance to cavity surface: 12-15mm
- Series connection with baffle plates for even flow distribution
- Coolant: water at 20°C inlet, 28°C outlet (ΔT = 8°C)
- Cavity Cooling Channels:
- 6 × Φ12mm channels in cavity block
- Conformal cooling around deep louver pockets (CNC milled)
- Bubble cooling inserts for hard-to-reach corners
- Flow rate: 8 liters/min per circuit
- Slide Core Cooling:
- 2 × Φ8mm channels in each slide (4 total)
- Quick-disconnect couplings for slide movement
- Cooling time optimization: reduced from 28s to 22s (-21%) 🎯
Mold Structure & Components
Mold Base Configuration:
- Mold Base Type: Standard HASCO K series (650mm × 550mm)
- Cavity Layout: 2×2 balanced cavity arrangement (4 cavities)
- Stack Height: 480mm (fits 350-500 ton injection machines)
- Runner System:
- Hot runner manifold (4-drop Mold-Masters system)
- Valve gate nozzles (Φ16mm tip diameter)
- Heated to 280°C, independent zone control
- Eliminates runner scrap - 100% material utilization ✓
Core & Cavity Materials:
| Component |
Material |
Hardness |
Reason |
| Cavity Insert |
P20 Steel (pre-hardened) |
30-32 HRC |
Good machinability, polishable to VDI 24 |
| Core Insert |
H13 Tool Steel |
48-50 HRC (hardened) |
High wear resistance, thin features |
| Slide Cores (2×) |
S7 Tool Steel |
52-54 HRC |
Impact resistance, frequent motion |
| Ejector Pins |
Nitrided Steel |
62-65 HRC (surface) |
Wear resistance, long life |
Action Mechanisms:
- Slide Core System (Angled Lifters):
- 2 slide cores for left/right louver undercuts
- Cam angle: 20° (gentle actuation, low wear)
- Slide travel: 45mm (hydraulic cylinder actuation)
- Wear plates: hardened steel (60 HRC) for long life
- Ejection System:
- 18 × Φ6mm ejector pins (distributed across part)
- 4 × Φ10mm ejector pins at thick rib sections
- 2 × sleeve ejectors around mounting bosses
- Ejection stroke: 80mm (sufficient for 65mm part depth)
- Return pins: 4 × Φ12mm with springs (auto-reset)
- Venting System:
- Parting line vents: 0.02mm × 6mm wide (12 locations)
- Ejector pin vents: 0.01mm clearance (auto-venting)
- Air trap vents: 0.03mm × 3mm (2 locations identified by simulation)
Manufacturing Process
Mold Fabrication Workflow:
- Rough Machining (CNC Milling):
- Machine: 5-axis Makino a61nx (high-speed machining center)
- Roughing: Φ20mm carbide end mill, 8,000 RPM, 2,500 mm/min feed
- Leave 0.5mm stock for semi-finishing
- Time: 12 hours for cavity block, 10 hours for core
- Heat Treatment:
- H13 core: Hardened to 48-50 HRC (austenitize at 1,030°C, oil quench, triple temper)
- S7 slides: Hardened to 52-54 HRC (air quench, double temper)
- Stress relief to prevent warping (<0.01mm distortion)
- Semi-Finishing (CNC Milling):
- Φ12mm ball end mill, 12,000 RPM, 1,500 mm/min
- Leave 0.1mm for final grinding/EDM
- Surface roughness: Ra 1.6 µm
- EDM (Electrical Discharge Machining):
- Thin ribs and deep pockets: CNC wire EDM (Φ0.25mm wire)
- Complex 3D contours: Graphite electrode EDM
- Surface finish: Ra 0.8 µm (ready for polishing)
- Time: 18 hours (EDM is slowest process)
- Surface Finishing (Polishing):
- Cavity surface: Hand polished to VDI 24 (matte texture)
- Core surface: VDI 33 (as-machined, slight texture acceptable)
- Parting line: Stoned to 0.01mm fit (no flash)
- Time: 24 hours (skilled craftsman)
- Assembly & Fitting:
- Slide cores fitted with 0.02mm clearance
- Ejector pins: running fit (H7/f7 tolerance)
- Hot runner manifold alignment: ±0.05mm concentricity
- Leak test: Cooling channels pressure tested at 10 bar
Mold Trial & Validation
First Mold Trial Results:
- Cycle Time Achieved: 33 seconds (target: ≤35s) ✅
- Part Weight: 68.5g (spec: 68±2g) ✅
- Dimensional Accuracy:
- Overall dimensions: ±0.12mm (spec: ±0.15mm) ✅
- Mounting boss position: ±0.04mm (spec: ±0.05mm) ✅
- Surface Quality: No sink marks, weld lines barely visible ✅
- Warpage Measurement: 0.42mm (spec: <0.5mm) ✅
Minor Adjustments Required:
- Gate vestige polishing: Reduced gate mark from 0.3mm to <0.1mm
- Ejection pin marks: Relocated 2 pins to non-visible areas
- Cooling balance: Adjusted flow rate to equalize cavity temperatures (ΔT < 3°C)
Production Validation (PPAP - Production Part Approval Process):
- 100 parts measured: Cpk = 1.45 (target: ≥1.33) ✅
- Drop test: 30 parts - no cracking or deformation ✅
- Thermal cycling: -40°C to +85°C (50 cycles) - no warping ✅
- UV resistance test: 500 hours xenon arc lamp - no color shift ✅
Project Outcomes & Economics
| Metric |
Target |
Achieved |
Status |
| Cycle Time |
≤ 35 seconds |
33 seconds |
✅ Exceeded |
| Part Quality (Cpk) |
≥ 1.33 |
1.45 |
✅ Exceeded |
| Annual Production |
500,000 units |
530,000 units |
✅ +6% |
| Mold Life |
1,000,000 shots |
Projected: 1,200,000 |
✅ +20% |
| Material Scrap Rate |
< 2% |
0.8% |
✅ Excellent |
Cost Analysis:
- Mold Development Cost: $58,000 (4-cavity hot runner mold)
- Part Cost: $1.85 per unit (material: $0.95, labor: $0.45, overhead: $0.45)
- Break-Even Point: 185,000 units (amortize mold cost at $0.31/part)
- ROI at 500k units: Mold paid off in 11 months ✓
Lessons Learned & Best Practices
✅ Key Achievements
- Moldflow simulation accurately predicted warpage (0.38mm sim vs 0.42mm actual - only 10% error)
- Conformal cooling reduced cycle time by 21% compared to conventional straight-drilled channels
- Hot runner system eliminated runner scrap - saved $45,000/year in material costs
- 4-cavity design balanced production efficiency with mold cost
🎓 Engineering Insights
- Gate Location: Edge gate on non-visible surface eliminated vestige polishing - saved $0.15/part
- Slide Core Design: 20° cam angle provided smooth actuation - no wear after 100k cycles
- Venting Strategy: Air trap venting critical - eliminated burn marks that caused 5% scrap in first trial
- Cooling Balance: Temperature differential <3°C between cavities ensured consistent part quality
- Material Selection: P20 pre-hardened steel saved 2 weeks vs hardening after machining
🔄 Continuous Improvement
- Implement mold monitoring sensors (cavity pressure, temperature) for predictive maintenance
- Explore 3D printed conformal cooling for next-generation mold (potential 15% cycle time reduction)
- Evaluate MuCell microcellular foam injection to reduce sink marks and warpage
- Consider 8-cavity family mold for related parts to share tooling costs
Files & Resources
This showcase includes comprehensive mold design documentation:
- 📐 CAD Models: mold_assembly.step, cavity_core.sldprt (SolidWorks 2024)
- 📊 Moldflow Reports: fill_analysis.pdf, cooling_analysis.pdf, warpage_study.pdf
- ⚙️ Manufacturing Drawings: mold_drawings.pdf (ASME Y14.5 GD&T)
- 📸 Photo Gallery: 15 images of mold fabrication and first-article parts
- 📋 BOM: mold_components.xlsx (HASCO standard components)
- 📄 Process Parameters: injection_molding_parameters.pdf
- 🎥 Mold Trial Video: production_cycle.mp4 (showing complete 33s cycle)
This project showcases the complete injection mold design and manufacturing process. The methodology and best practices are applicable to a wide range of plastic parts in automotive, consumer electronics, and medical device industries.
