The mould main body should be cast from INAFOND C5 (Cu>%4, Si <%0,3) material with mechanical properties of: Rm 355 N/mm2; Rp (0.2) 255 N/mm2, A %5, HB 80-110 The seller should prompt the composition analysis and the heat treatment of cast material.
If it's decided to have a welded structure from Al platens because of better cooling the Avional and/or Anticorodal material can be used.
The surface should be machined by NC / CNC for dimensional accuracy.
The cast Al should not contain any porosity and/or pinholes on the surface. The mould surface should be first machined with N7 quality, then polished with using sand paper to have perfect surface everywhere without any visible junction marks. No mirror surface is required.
The thickness of the cast Al should be 20-30 mm.
After casting the inner surface should be cleaned by sandblasting.
If there is any need to use Al sheet(s) especially in place positive or negative shapes not higher than 50-60 mm in height, anticorodal or avional Al should be used.