Cavity Dimension Calculator
Determine the injection mold cavity dimension accounting for processing shrinkage. The calculator computes the dimensional compensation required to obtain a part with the specified nominal dimensions after material shrinkage.
Input Parameters
Results
Fill in the data and click Calculate
ARGUS automatically recalculates cavity dimensions when the material changes
A material change means a shrinkage change — ARGUS automatically updates all cavity dimensions, eliminating the risk of errors from manual recalculation.
How do we calculate mold cavity dimension?
The injection mold cavity dimension must be larger than the nominal part dimension in order to compensate for processing shrinkage. Shrinkage is the dimensional change of the part that occurs during cooling from processing temperature to ambient temperature. Every polymer has a characteristic shrinkage range that depends on molecular structure, processing conditions, and part geometry.
The calculator applies the shrinkage compensation formula — the fundamental relationship between part dimension, material shrinkage, and the required mold cavity dimension.
Dcavity — cavity dimension [mm]
Dpart — nominal part dimension [mm]
S — processing shrinkage [%]
Processing shrinkage depends on many factors: polymer type, cooling conditions, packing pressure, wall thickness, and flow direction. Amorphous materials (ABS, PC, PS) have low shrinkage of 0.3–0.8%, while semi-crystalline materials (PP, PA, POM) shrink considerably more — 1.0–3.0%. Shrinkage values in material datasheets are ranges; actual shrinkage depends on processing conditions.
Processing shrinkage of common polymers
The following values are typical ranges for standard processing conditions. Actual shrinkage depends on wall thickness, packing pressure, and mold temperature.
PC — 0.5–0.7%
PP — 1.0–2.5%
PA6 — 0.8–1.5% (dry), 1.5–2.5% (conditioned)
POM — 1.8–3.0%
HDPE — 2.0–3.5%
PS — 0.3–0.6%
For parts with tight dimensional tolerances (IT13 class and above) it is necessary to account for shrinkage anisotropy — shrinkage in the flow direction is typically 10–30% higher than in the perpendicular direction. In such cases use the Shrinkage Compensation calculator, which accounts for directional factors.
When to use this calculator
This calculator is ideal for quickly estimating the cavity dimension for a single nominal dimension. For a full 3D analysis accounting for shrinkage anisotropy, tolerances, and flow direction, use the Shrinkage Compensation calculator. In the ARGUS system, cavity dimensions are automatically recalculated with every material change.
ARGUS automatically recalculates cavity dimensions with every material or process parameter change
See it for yourself — book a presentation and discover how ARGUS connects dimensional calculations with the full project context.