Enter the dimension of the mold cavity before molding and the final dimension of the molded part into the calculator to determine the mold shrinkage percentage; this calculator can also evaluate any of the variables given the others are known.

## Mold Shrinkage Formula

The following formula is used to calculate the mold shrinkage percentage:

MS = (D - F) / D * 100

Variables:

- MS is the mold shrinkage percentage
- D is the dimension of the mold cavity before molding
- F is the final dimension of the molded part

To calculate the mold shrinkage percentage, subtract the final dimension of the molded part from the dimension of the mold cavity before molding. Divide the result by the dimension of the mold cavity before molding. Multiply the quotient by 100 to get the percentage.

## What is a Mold Shrinkage?

Mold shrinkage refers to the phenomenon that occurs in the plastic injection molding process where the molded part shrinks and contracts as it cools down and solidifies in the mold. This shrinkage is caused by the thermal contraction of the plastic as it cools from the processing temperature to room temperature. The degree of shrinkage is influenced by several factors including the type of plastic material used, the design of the part, the molding process parameters, and the design of the mold itself. It is a critical factor to consider in the design and manufacturing process as it can affect the accuracy and precision of the final product. If not properly accounted for, mold shrinkage can lead to parts that do not fit together properly or function as intended.

## How to Calculate Mold Shrinkage?

The following steps outline how to calculate the Mold Shrinkage:

- First, determine the original dimensions of the mold.
- Next, determine the dimensions of the molded part.
- Next, subtract the dimensions of the molded part from the original dimensions of the mold.
- Finally, divide the difference in dimensions by the original dimensions of the mold and multiply by 100 to get the Mold Shrinkage percentage.
- After calculating the Mold Shrinkage percentage, check your answer with the given specifications.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

Original dimensions of the mold: 10 cm x 10 cm x 5 cm

Dimensions of the molded part: 9 cm x 9 cm x 4.5 cm