Shenzhen Alu Rapid Prototype Precision Co., Ltd.

In injection molding, the projected area (also called the shadow area or silhouette area) refers to the total surface area of the molded part (and any associated runners or gates) as projected orthogonally onto a plane parallel to the mold's parting line. This is essentially the "footprint" or shadow of the part if light were shone perpendicular to the parting line. It's a critical parameter because it directly influences the clamping force required to keep the mold closed during injection, preventing flash or mold opening.

Why Calculate Projected Area?

1.Clamping Force Estimation: The projected area is multiplied by a material-specific pressure factor to determine the minimum machine tonnage needed.

2.Mold Design and Machine Selection: Ensures the injection molding machine has sufficient clamping force (typically 2–8 tons per square inch, depending on material viscosity, temperature, and wall thickness).

3.Cost and Efficiency: Helps avoid over- or under-clamping, which can lead to defects like incomplete fills or excessive wear.

How to Calculate Projected Area: 

Calculating the projected area can be done manually for simple geometries or with CAD software for complex parts. The total projected area includes the part(s), runners, gates, and ejector pins if they contribute to the projection.

Steps for Manual Calculation (for Simple Parts):

1.Identify the Parting Line Direction: Determine the plane perpendicular to the mold opening direction (usually the direction of machine clamp force). This is the projection plane.

2.Project the Part's Outline: Visualize or sketch the part's silhouette when viewed straight-on from the parting line direction. Ignore depth—focus only on the 2D outline.

3.Measure Dimensions: For rectangular or prismatic parts, use length × width in the projection plane. For irregular shapes:Break it into basic geometries (e.g., rectangles, triangles, circles).

Calculate each sub-area and sum them.

Account for overlaps or voids by subtracting enclosed areas.

5.Add Runners and Gates: Include their projected areas (e.g., for a circular runner: π × (radius)²).

6.Scale for Multi-Cavity Molds: Multiply by the number of cavities if identical.

7.Convert Units: Use consistent units (e.g., in² for imperial or cm² for metric) based on your clamping force formula.