Carbon Fiber Engine Hood Mold

The carbon fiber hood mold is a specialized tooling used for forming the carbon fiber hood (CFRP Hood) of automobiles. The core requirements are high precision, high rigidity, and low thermal deformation to ensure the appearance surface, dimensional accuracy, and structural strength of the hood.

 

I. Selection of Mold Materials

·Aluminum alloy (such as 6061-T6): Lightweight, fast heat conductivity, good processing properties, suitable for small and medium batch production and rapid prototyping.

·Steel (such as P20, S50C): High strength, good wear resistance, suitable for mass production, but heavy in weight and high in cost.

·Carbon fiber composite material (CFRP): Low thermal expansion coefficient, good compatibility with products, lightweight, suitable for high-precision and complex curved surface molds, but high in cost.

 

 

II. Key Points of Mold Structure Design

1.Mold division design

• The structure adopts an inner and outer mold split design. The parting line is positioned on the non-appearance surface of the hood (such as the edge flange area), ensuring a complete appearance and smooth demolding.
• A designable flange edge module enables both integral molding and edge cutting.

 

2.Profile and Precision

• Based on the 3D scanning data of the entire vehicle, the modeling is carried out to ensure the accuracy of the fit with the vehicle body.
• The surface finish of the profile needs to reach grade A (Ra ≤ 0.8 μm), which directly determines the appearance of the product.
• The key dimensions are controlled within a tolerance of ±0.3 mm, and the installation holes are precisely positioned.

 

3.Strengthening and Support

• The back of the mold is equipped with grid-like reinforcing ribs (spacing 300–500 mm), which not only reduces weight but also enhances rigidity and prevents deformation under pressure.
• The support frame must be in close contact with the mold surface, evenly distributing the pressure and avoiding local stress concentration.

 

4.Ventilation and Vacuum System

• Ventilation grooves are set at the edges of the mold cavity (width 0.5–1.0 mm), preventing trapped air from causing surface blemishes or material shortages.
• It is necessary to be compatible with vacuum bags / hot press tanks processes. The mold must have good vacuum sealing performance (leakage rate ≤ 0.01 Pa・m³/s).

 

 

III. Adaptation of Mainstream Manufacturing Processes

RTM (Resin Transfer Molding)：The mold requires high rigidity and must have good sealing performance. It is suitable for medium-volume and high-quality products.

autoclave molding：The mold needs to be resistant to high temperatures (120–180℃) and high pressures (0.5–1.0 MPa), and has extremely high requirements for thermal stability.

Vacuum bag molding：The cost is relatively low, suitable for small batch production or trial runs, but it has high requirements for the surface of the mold and sealing performance.

Expansion core mold process：Using expandable core materials (such as Koridion), it can The complex structure of the body-formed duct with a ventilation channel,No secondary bonding is required, and the molding cycle is short (approximately 8–15 minutes).

 

 

IV. Key Precautions for Manufacturing and Usage

 

Round corners and transitions：Cavity corner, root of rib fillet R ≥ 3 mm,Thickness transition gradient (ratio ≤ 1:5), to avoid stress concentration and curing warping.

Heating / Cooling System：Built-in uniform heating pipeline ensures that the temperature difference during curing is ≤ ±5℃, preventing internal stress in the product.

Demolding and Maintenance：Use a special high-temperature-resistant release agent; after molding, slowly cool down and remove the mold evenly to avoid warping; regularly check the surface accuracy and sealing performance.

 

 

V. Typical Defects and Countermeasures

Surface bubbles / pinholes：Improve exhaust performance, enhance vacuum level, and optimize resin flow.

Product warping and deformation：Optimize the rigidity of the mold, control the cooling rate, and adjust the direction of the fiber layup.

Mold line misalignment：Enhance the mold positioning structure and improve the mold closing accuracy.

Layered structure：Ensure that the laminate is free of wrinkles, that the vacuum compaction is thorough, and that the curing parameters are appropriate.

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