Injection Mold Assembly: Key Techniques, Procedures, and Quality Control

1. Identification and Preparation: Mold Structural Parts and Standard Components

1.1 Mold Bases and Standard Parts

• Mold Base: The framework that supports all mold parts. Check flatness and parallelism to ensure no warpage.

• Guide Pillars & Bushings: Ensure precise alignment between the moving and fixed molds. The fit clearance should be within 0.01–0.03 mm. Insert guide pillars first, then bushings, to guarantee smooth sliding without wobble.

• Ejector Pins & Springs: Core components of the ejection mechanism. Verify ejector pin length and spring stroke to avoid jamming or insufficient travel during ejection.

1.2 Core and Cavity Assemblies

• Inserts, Slides, and Lifters: Used for parts requiring side core-pulling. Before installation, confirm the angle of the angle pin and ensure the reset mechanism is free of jamming.

• Cooling Manifold: Ensure all corresponding cooling channels and quick connectors are intact and leak-free. Assemble first and conduct a pressure test.

2. Assembly Sequence and Techniques

2.1 Fixed Mold Plate First

• Place the fixed mold plate flat on the workbench and check its flatness.

• Install locating pins, bushings, and cooling plates. Perform a seal test using low-pressure air or hydraulic pressure initially.

2.2 Core Component Installation

• Insert the core assembly into the fixed mold plate. Adjust locating pins to ensure proper seating.

• Preinstall the ejection mechanism, check the ejector pin stroke, and apply a thin layer of grease to the ejector retainer for smooth sliding.

2.3 Moving Mold Plate Alignment

• Close the entire fixed mold plate with the movable plate, aligning via guide pillars on both sides.

• Gradually clamp the mold lightly. Use feeler gauges to check if the parting surface gap is uniform (recommended range: 5–10 μm) and ensure no deviation or unevenness after clamping.

2.4 Slide and Lifter Installation

• Install slide components on the moving mold side: first mount the guiding lifter mechanism, then tighten the lifter belt or connecting rod.

• After clamping the mold, manually push the lifter rods to confirm smooth sliding of the slides without collision or interference.

3. Alignment and Gap Adjustment

3.1 Parting Surface Gap Tuning

• After clamping, insert a 0.01 mm feeler gauge at the four corners and center of the parting surface to check gap consistency point by point.

• If deviations are found, fine-tune the parallelism of the parting surface by adjusting the length of locating pins or adding/removing shims.

3.2 Ejector Pin Stroke Setting

• The ejector pin stroke should be slightly longer than the product ejection stroke to avoid failure to eject (insufficient stroke) or ejector overshoot (excessive stroke).

• Use stroke limiters or measuring nuts to lock the maximum ejector stroke, and verify through multiple tests.

4. Auxiliary System Installation and Verification

4.1 Cooling System

• Connector Installation: Use quick connectors or compression fittings to connect water pipes. Conduct a leak test with low-pressure water first, then complete assembly after confirming no leakage.

• Flow Rate and Temperature Difference: Control the temperature difference between the inlet and outlet of the cooling circuit at 5–10 ℃. Verify uniform flow in each circuit using a flow meter.

4.2 Venting System

• Reserve 0.02–0.05 mm vent grooves at the end of the cavity and beside the slides. After assembly, perform an air injection test to ensure air escapes smoothly without melt leakage.

4.3 Heating and Temperature Control

• Heater Band Layout: Install heater bands and cover with high-temperature resistant silicone tubes in areas sensitive to temperature differences or prone to material sticking, avoiding excessive temperature gradients.

• Temperature Sensors: Embed thermocouples at key mold positions (gate, weld line, thin-walled areas). Conduct a simulated control test after assembly.

5. Mold Testing and Tuning

5.1 First Article Mold Test

• After assembly, conduct the first article mold test. Record molding parameters, ejection stroke, and product conditions in detail.

• Inspect for defects such as flash, weld lines, shrinkage, and warpage. Adjust the parting surface gap, cooling time, or vent position based on defect locations.

5.2 Fine-Tuning and Mass Production Debugging

• Injection Parameter Optimization: During mold testing, use Design of Experiments (DOE) to optimize injection speed, pressure, and holding pressure curves for stable molding.

• Automated Monitoring Integration: Connect mold assembly data with the injection molding machine’s monitoring system to achieve real-time mold temperature and pressure monitoring, improving subsequent switching efficiency.

5.3 Regular Maintenance

• After each production batch or every 5,000 cycles, perform mold calibration and inspect ejector pins/bushings. Replace worn parts promptly to maintain assembly precision and molding consistency.

6. Common Issues and Precautions

6.1 Assembly Environment

• Maintain a clean, dust-free assembly workshop. Control temperature at 20–25 ℃ and humidity at 40–60% to avoid part rust or dimensional drift.

6.2 Tightening Torque

• Follow mold specifications strictly for bolt tightening torque. Avoid over-tightening (causing deformation) or under-tightening (leading to loose fits).

6.3 Documentation and Traceability

• Record assembly steps, adjustment data, and mold test results in detail to facilitate subsequent fault tracing and process reproduction.

Conclusion