Meaning
Injection moulding tool designs must account for the mechanical extraction of finished parts from the steel core. A deep draft cavity represents a hollow mould feature where the vertical walls are designed with a minimal taper over a significant height, presenting challenges for both material flow and part release. These geometries are found in housings and containers where straight walls are functionally required but difficult to eject.
Tooling Geometry
Mold designs with vertical walls of height exceeding fifty millimetres require careful angle calculation to prevent part deformation. In a deep draft cavity, the taper is restricted to less than one degree per side to maintain the straight outer profile of the product. This restriction demands precise machining and alignment of the core and cavity inserts.
Ejection Force
Demoulding parts with high aspect ratios creates strong vacuum and frictional forces against the tool steel. When using a deep draft cavity, the solidified polymer shrinks onto the core, requiring substantial mechanical force to push the part free. Without adequate ejection systems, the stress can crack the plastic or leave visible pin marks.
Surface Finish
Mold surface textures can either assist or hinder the release of moulded parts from deep recesses. For a deep draft cavity, a highly polished draw line finish prevents the polymer from mechanical interlocking with the steel. Applying textured finishes in these zones is avoided to prevent scuffing.
