Injection Mold For Car Engine Hood

The injection mold for the car engine hood is a specialized precision mold used for mass production of the car engine outer cover / inner guard plate. The core of this mold is to form through high-pressure injection of thermoplastic materials (such as PA6+GF, PP-T20), meeting automotive-grade requirements such as dimensional accuracy of ±0.2mm, A-class surface, and high-temperature resistance of -40℃ to 140℃.

 

I. Overall Design of the Mold

1. Cavity Layout

Standard solution: One mold with one cavity (for large products with complex structures and multiple core-pulling requirements).

Small covers: One mold with two cavities (balanced layout).

 

2. Parting Surface Design

Principle: Select the largest contour of the product, taking into account demolding, venting, and processability.

Common for engine covers: Planar parting at the lowest point, combined with local piercing or abutment treatment for height differences.

 

3. Molding Parts (Core / Cavity)

Materials: Commonly used for cavities and cores are P20, 718H, and 2738 (pre-hardened HRC32~38); for sliders and inclined cores, SKD61 and H13 (quenched HRC50~54) are used.

Structure: Complex areas are modularized (for ease of processing, maintenance, and venting); ensure uniform wall thickness and balanced cooling.

 

 

II. Key System Design

1.Pouring system (mainly hot runner)

Type: Hot runner + cold runner multi-point gate injection (5 to 8 side gates / point gates).

Function: Balance filling for large flat surfaces, prevent short shots, reduce weld lines, and lower internal stress.

Design: Gate selection on non-visible surfaces and at wall thickness areas; equipped with cold slug wells; hot runner temperature control is precise (±1℃).

 

2. Lateral Core-pulling and Demolding

· Snap-fit / Interlocking: Oblique core pin (oblique ejector pin) (angle 3°~8°).

· Side hole / Side recess: Oblique guide pin slider / Bent pin slider (wear-resistant block, quenched guide surface).

· Ejection: Combination of ejector pin + ejector tube + ejector block; equipped with pre-reset and anti-white mark structure.

 

3. Temperature control (cooling) system

· Conformal cooling channels (8~12mm from cavity surface), diameter 8~12mm, temperature difference between inlet and outlet ≤2℃.

· Purpose: Uniform cooling, shorten cycle (45~60s), reduce warpage deformation.

 

4. Guidance and Exhaust

·Guiding: 4 sets of guide pins and bushings + conical surface positioning (mold closing accuracy ±0.02mm).

·Venting: Venting grooves on the parting surface (0.02~0.05mm deep) + venting through the gap between inserts and ejector pins; exhaust inserts are set in the trapped air area at the end.

 

 

III. Key Points of Design and Manufacturing

1. Moldflow Analysis: Validate filling, holding pressure, cooling, warpage, and optimize gate and process.

2. Processing: High-speed milling (HSK-E63), mirror EDM, deep hole drilling; surface polishing Ra ≤ 0.8 μm.

3. Mold Tryout: Focus on validating filling, warpage, core-pulling smoothness, and appearance defects.

4. Taizhou Huangyan Jiutai Mould Co., Ltd. specializes in automotive engine hood molds, adopting hot runner, strong cooling, and modular core-pulling, suitable for PP/PA+GF materials, meeting the requirements of a million mold cycles and lightweighting for new energy vehicles.

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