Shenzhen Alu Rapid Prototype Precision Co., Ltd.

In injection molding, the projected area is the 2D "silhouette" of your part as seen from the direction of the mold opening (the clamping direction). Calculating it correctly is critical because it determines the clamping force required to keep the mold halves together against the high pressure of the incoming plastic.

1. The Core Definition

The projected area is not the total surface area of the 3D part. It is the area of the part's shadow if you were to shine a light directly down the line of the mold's travel onto a flat surface.

2. How to Calculate the Area

The method depends on the complexity of your part:

A.For Simple Geometric ShapesIf your part is a basic shape, use standard geometry:Rectangular Part: 4$\text{Area} = \text{Length} \times \text{Width}$Circular Part: 5$\text{Area} = \pi \times r^2$ (or 6$0.785 \times \text{Diameter}^2$)7Irregular Shapes: Break the silhouette into simpler rectangles and triangles, calculate each, and sum them up.

B.For Complex Parts (The Industry Standard)

Modern engineers use CAD software (like SolidWorks or AutoCAD) to get an exact measurement:

Orient the 3D model so the parting line is parallel to your screen.

Use the "Project Curve" or "Silhouette" tool to create a 2D outline.

Use the "Measure" or "Area" tool on that 2D outline.

Don't Forget the Runner System

If you are using a cold runner system, the plastic in the runners also exerts pressure.You must add the projected area of the runners and gates to the projected area of the cavities.

Total Projected Area = (Area of One Cavity x Number of Cavities)+Area of Runners

3. Using Projected Area to Find Clamping Force

Once you have the total area ($A$), you use it to calculate the machine tonnage ($F$) using the formula:

    F = P x A 

Where:

. F= Clamping Force(usually in Tons). 

. P= Cavity Pressure (or a"Clamp Factor" provided by material suppliers). 

. A = Total Projected Area. 

Common Pitfalls

1.Ignoring Holes: If your part has a large hole in the middle (like a donut), subtract that hole from the total area; there is no plastic there to push the mold apart.

2.Draft Angles: For very deep parts with significant draft, ensure you use the dimensions at the parting line (usually the widest point) for the most accurate projection.

3.Safety Factor: Always add a 10% to 20% safety margin to your final tonnage calculation to account for viscosity changes or machine wear.