1. What is an Injection Molding Tonnage Calculator?

Definition: This calculator estimates the required clamping force (in tons) for an injection molding machine based on the projected area of the part, injection pressure, and safety factor.

Purpose: It helps manufacturers select the appropriate injection molding machine size and ensures proper mold filling without flash.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( T \) — Clamping force (tons)
• \( A \) — Projected area (square inches)
• \( P \) — Injection pressure (psi)
• \( SF \) — Safety factor (typically 1.5-2)

Explanation: The projected area multiplied by injection pressure gives the total force in pounds, which is converted to tons (divided by 2000) and adjusted by a safety factor.

3. Importance of Clamping Force Calculation

Details: Proper clamping force prevents mold separation during injection, ensures part quality, and avoids machine damage from excessive tonnage.

4. Using the Calculator

Tips: Enter the projected area (including runner system), typical injection pressure (default 5000 psi), and safety factor (default 1.5). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is projected area?
A: The total area of the part (and runners) as seen along the axis of mold opening, including all cavities in multi-cavity molds.

Q2: What's a typical injection pressure?
A: Most materials use 3000-8000 psi, with 5000 psi being a common average for general purpose calculations.

Q3: When would I increase the safety factor?
A: Use higher factors (1.8-2) for thin-walled parts, high-viscosity materials, or critical applications.

Q4: How do I find the projected area?
A: Use CAD software to measure the area or calculate manually for simple geometries (length × width for rectangular parts).

Q5: What if my calculated tonnage is between machine sizes?
A: Always round up to the next available machine size to ensure sufficient clamping force.