Meaning
Dimensional adjustment made to a tool design to account for the predictable shrinkage or expansion of plastic during the cooling phase. Engineering teams use mold steel compensation to ensure the final part matches the nominal CAD dimensions exactly. This calculation starts with the material data sheet provided by the resin supplier.
Shrinkage Rate
Plastic parts contract as they move from a molten state to a solid state inside the cavity. Calculating the mold steel compensation involves multiplying the part dimension by the expected shrinkage factor. Semi-crystalline materials require larger adjustments than amorphous ones.
Precision Tooling
Machining the cavity slightly larger than the target part prevents out-of-tolerance rejects. A mold steel compensation error discovered during the first article inspection usually requires expensive tool rework. Production yield falls when the adjustment does not account for the specific gate location.
Thermal Control
Cooling channel placement influences how the material behaves as it sets. Applying mold steel compensation across complex geometries requires non-uniform scaling to handle different wall thicknesses. A demonstrated rate of quality parts depends on the thermal stability of the tool.
Calling the design finished before simulating the flow of the resin increases the risk of part failure.
