1. What is Clamp Force in Injection Molding?

Clamp force (tonnage) is the force required to keep the mold closed during the injection process. It prevents the mold from opening due to the high pressure of the injected plastic material.

2. How Does the Calculator Work?

The calculator uses the clamp force formula:

Where:

• Projected Area — Total surface area of the part including runners (cm²)
• Injection Pressure — Pressure applied to the plastic during injection (bar)
• 1000 — Conversion factor from kg to tons (1 ton = 1000 kg)

Explanation: The formula calculates the minimum clamp force needed to counteract the injection pressure over the projected area of the mold.

3. Importance of Tonnage Calculation

Details: Proper tonnage calculation ensures the injection molding machine can keep the mold closed during injection, preventing flash (excess plastic escaping the mold cavity) and ensuring part quality.

4. Using the Calculator

Tips: Enter the projected area in cm² and injection pressure in bar. Typical injection pressures range from 300-1500 bar depending on material and part geometry.

5. Frequently Asked Questions (FAQ)

Q1: What is projected area?
A: The total surface area of the part (including runners) as seen from the direction of mold opening, measured in the parting plane.

Q2: How do I determine injection pressure?
A: Injection pressure depends on material viscosity and part geometry. Material suppliers typically provide recommended pressure ranges.

Q3: What happens if clamp force is too low?
A: Insufficient clamp force can cause mold flashing, short shots, or dimensional inaccuracies in the final part.

Q4: Should I add a safety factor?
A: Yes, it's common to add 10-20% safety factor to the calculated tonnage to account for variations in material and process conditions.

Q5: Can I use this for multi-cavity molds?
A: Yes, calculate projected area for all cavities plus runners, then use the total area in the calculation.