Air Conditioning Shell Injection Mold

 

1.1 Wall thickness uniformity

• The air conditioning shell (such as the front panel, side panel) is usually a thin-walled structure (1.5-3mm). During design, it is necessary to ensure uniform wall thickness to avoid local thickening causing shrinkage marks or bubbles, or thinning causing insufficient filling.

• If there are wall thickness differences (such as reinforcement ribs, snap-fit areas), a gradual transition (slope ≤ 1:5) should be used to reduce stress concentration.

 

1.2 Draft angle

• To avoid scratches or deformation during product demolding, a reasonable draft angle should be set: the draft angle of the surface ≥ 1°, the non-surface ≥ 0.5°; the lower the surface roughness (such as high-gloss surface), the larger the draft angle (1.5°-2°).

• For surfaces with patterns or textures, the draft angle should be increased by 0.5°-1° to prevent the texture from being damaged.

 

1.3 Reinforcement ribs and anti-deformation design

• When the shell area is large, reinforcement ribs (height ≤ 3 times wall thickness, spacing ≥ 2 times wall thickness) should be designed to enhance rigidity and prevent deformation during transportation or assembly.

• The bottom of the rib strips should be rounded (R ≥ 0.5mm) to prevent stress cracking.

 

1.4 Snap-fit and assembly structure

• The air conditioning shell is often connected with other components through snap-fit; the design of the snap-fit needs to consider the feasibility of the mold:

• The angle of the snap-fit hook ≤ 45° to avoid complex mold core extraction;

• Sufficient space should be reserved for the mold ejection mechanism or inclined ejection design to prevent the snap-fit from being unable to demold after forming.

 

• The commonly used materials for air conditioning shells are ABS (low cost, easy to mold), HIPS (impact resistant), and PC/ABS alloy (high temperature resistance, high strength). The design needs to match the material characteristics:

 

• Flowability: ABS has medium flowability, the mold flow channel should be short and thick to avoid complex bends; PC has poor flowability, the injection size and injection pressure should be increased, and the flow channel should be more smooth.

• Shrinkage rate: Design the mold cavity size according to the material shrinkage rate (such as ABS shrinkage rate 0.5%-0.8%), reserve shrinkage allowance to ensure the product size accuracy.

• Thermal stability: PC and other materials are sensitive to temperature, the mold needs to optimize the cooling system to avoid local overheating causing material decomposition and color change.

1.1 Mold cavity quantity

• For small-sized shells (such as the indoor panel of the air conditioning), a multi-cavity mold (2-4 cavities) can be used to improve efficiency; for large-sized shells (such as the side panel of the cabinet air conditioner), due to injection volume and mold size limitations, it is usually a single cavity.

• Multi-cavity should ensure balanced flow channels to ensure uniform filling in each cavity.

 

1.2 Parting surface selection

• The parting surface should be selected as the edge or hidden part of the product's surface to avoid leaving parting lines that affect aesthetics;

• Ensure that the parting surface can smoothly exhaust and is convenient for mold processing (such as a flat parting surface is better than a curved surface).

 

 

1.1 Pouring type and position

• The surface should preferentially use point pouring (which can be removed later, with small traces) or hidden pouring (feeding from the non-surface);

• The pouring position should avoid the stressed parts (such as snap-fit, screw columns) and ensure that the plastic melt flow path is short and has low resistance to avoid trapped air.

 

2. Flow channel design

• The flow channel cross-section is preferably circular (smaller surface area, less heat loss), the diameter is designed according to the product size (usually 6-10mm);

• Multi-cavity molds should adopt balanced flow channels to ensure simultaneous filling of each cavity.

 

 

1. Cooling uniformity

• The cooling water channels should be close to the mold cavity surface (distance 15-25mm), and be evenly distributed around the product contour to avoid insufficient cooling in local areas, causing deformation or long molding cycle. 2. Waterway Layout

• Use series or parallel waterways to ensure stable water flow speed (1-2 m/s) and pressure;

• The temperature difference at the inlet and outlet of the waterway should be controlled within 5℃ to avoid excessive temperature difference in the mold.

 

In summary, the design of the plastic mold for the air conditioning shell needs to strike a balance among appearance quality, dimensional accuracy, molding stability and production efficiency, cost, as well as the material properties and the feasibility of mold manufacturing.

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