1. What is Shot Size in Injection Molding?

Shot size refers to the volume of material required to fill the mold cavity, accounting for material shrinkage during cooling. It's a critical parameter in injection molding process setup.

2. How Does the Calculator Work?

The calculator uses the shot size formula:

Where:

• Part Volume — Volume of the final part (cm³)
• Shrinkage — Material shrinkage factor (decimal)

Explanation: The formula accounts for the additional material needed to compensate for shrinkage as the plastic cools and solidifies in the mold.

3. Importance of Shot Size Calculation

Details: Accurate shot size calculation ensures proper mold filling, prevents short shots, and helps optimize material usage and cycle times.

4. Using the Calculator

Tips: Enter part volume in cm³ and shrinkage as a decimal (e.g., 0.02 for 2% shrinkage). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How do I determine part volume?
A: Part volume can be calculated from CAD models or by measuring part dimensions and using geometric formulas.

Q2: Where do I find shrinkage values?
A: Material suppliers provide shrinkage data sheets for their specific resins under standard processing conditions.

Q3: Should I include runner volume in shot size?
A: Yes, total shot size should include both cavity volume and runner system volume, both adjusted for shrinkage.

Q4: How does gate size affect shot size?
A: While gate size affects fill pattern and pressure, it doesn't significantly change the total shot size calculation.

Q5: What's a typical shrinkage range for plastics?
A: Most thermoplastics shrink 0.2-3%, with semi-crystalline materials generally shrinking more than amorphous ones.