Shenzhen Alu Rapid Prototype Precision Co., Ltd.

In injection molding, the projected area (also called shadow area or silhouette area) refers to the total area of the molded part (or parts in a multi-cavity mold) as projected onto a plane perpendicular to the direction of mold opening and closing. This is a critical parameter because it directly influences the required clamping force to keep the mold closed during injection, preventing flash or parting line defects. The projected area helps determine machine tonnage needs and mold design feasibility.The calculation focuses on the "footprint" of the part in the plane normal to the ejection direction, ignoring thickness or features parallel to that plane. It's typically measured in square inches (in²) or square centimeters (cm²), depending on regional standards.

Step-by-Step Guide to Calculating Projected Area

Follow these steps to compute the projected area accurately, especially for complex geometries. For simple parts, it can be as straightforward as a single multiplication.

1.Identify the Part Geometry and Mold Direction:

Review the 3D model or blueprint of the part.

Determine the mold opening direction (usually the Z-axis or ejection direction). This is the reference plane—project all surfaces orthogonal (perpendicular) to this direction.

Note: Undercuts, side actions, or non-perpendicular features may require adjustments, but standard projected area assumes a straight-pull mold.

2.Break Down the Part into Simpler Shapes:

Decompose the part into basic 2D projections: rectangles, triangles, circles, or trapezoids.

Ignore features like ribs, bosses, or holes that are parallel to the projection plane (they don't contribute to the area).

For multi-cavity molds, calculate the projected area for one cavity and multiply by the number of cavities.

3.Calculate the Projected Area for Each Shape:

Rectangle: Length × Width.

Triangle: (Base × Height) / 2.

Circle: π × (Radius)².

Trapezoid: (Top Base + Bottom Base) × Height / 2.

Use CAD software (e.g., SolidWorks, AutoCAD) for automated projection if available—many tools have a "projected area" function.

4.Sum the Individual Areas:

Add up all the projected areas from Step 3 to get the total projected area (A_proj).

Formula: A_proj = Σ (Area_i), where Area_i is the projected area of each sub-shape.

5.Apply Mold Factor (If Needed for Mold Sizing):

For the overall mold projected area (including runners, gates, and sprues), multiply the part's A_proj by a factor of 1.5–3.0, depending on material flow and design complexity. This isn't always required for basic part calculations.