Core print clearance

Based on operational experience, the following factors are to be taken into account when defining the core print clearance for pattern equipment.

  • Mold material, mold process
  • Position of the cores within the mold
  • Number, size and shape of the cores
  • Core processing and core assembly
  • Face coating of the cores

Typically, the core print in the pattern is slightly larger than the core print of the core box which corresponds to the nominal dimension in the drawing; this relationship is illustrated in Fig. 1.The dimensional core print difference ΔM can be derived from Fig. 1 and eq. 1 as follows:

Eq. 1:

The core print clearance sF per unit area is as follows according to eq. 2:

Eq. 2:

Checking the core print clearanceWith complex pattern equipment, in addition to carrying out dimensional checks on the core prints of the pattern and core box, model molds and model cores (control molds and control cores) are prepared for verification.

When inserting the model core, the model mold can be used to reliably verify the core print clearance, wall thicknesses and core setting sequence.

In contrast to the core print clearance, the core location clearance (core clearance, core gap) is defined as the dimensional difference between the core location dimension of the mold and the core location dimension of the core.

  • Fig. 1: Core print clearanceN = nominal dimension in the drawingMK = Core print dimension in core boxMM = Core print dimension in patternsF = Core print clearance/surface area