Summary of key design Points for Precision Injection Molded Parts

1. Mold Opening Direction and Parting Line

Plan the mold opening direction to align with ribs, buckles, and protrusions, reducing core-pulling mechanisms. Position the 

parting line to avoid visible marks on cosmetic surfaces, as seen in electronic device casings where strategic line placement 

enhances aesthetics.

2. Draft Angle

Smooth surfaces: ≥0.5°

Fine textures: ≥1°

Coarse textures: ≥1.5°

For deep cavities, use smaller external draft than internal to ensure uniform wall thickness and structural stability, critical for 

phone cases.

3. Wall Thickness

Maintain 0.5-4mm thickness; exceeding 4mm risks shrinkage. Ensure uniformity—abnormalities caused 15% porosity in appliance 

housings, reduced to <5% after optimization. Use gradual transitions for thickness changes.

4. Rib Design

Thickness: <1/3 of wall thickness to prevent sink marks

Draft: ≥1.5°

Automotive interiors use optimized ribs to boost rigidity without increasing weight or cost.

5. Fillets and Holes

Prefer circular shapes

Align axis with mold opening direction

Long-diameter ratio >2 requires draft

Blind holes: ratio ≤4

Edge distance > hole diameter (critical for electronic connectors)

6. Core-Pulling/Slider Avoidance

Minimize core-pulling to reduce mold costs and defects. Simplify structures by aligning holes/ribs with mold opening direction, as 

in toy components.

7. Precision and Deformation Control

Rigid structures (avoid flat panels)

Flanges, concave-convex features, and ribs

Tablet casings achieve minimal warpage through such designs.

8. Welding and Snap Fit

Multiple snaps extend service life

Control tolerances strictly

Reserve modification space

Common in electronics for easy assembly/disassembly.

In summary, precision injection part design demands holistic consideration of structure, materials, and manufacturing, with 

continuous optimization to meet market needs.