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EXTERNAL CORE ARMATURES
An alternative and very effective method of core support is to construct a steel framework around the outside of a cored wax pattern. This technique works especially well with HYBRID INVESTMENTS (plaster and grog/ceramic shell systems combined). Plaster and grog core is poured into the wax pattern’s cavity whilst still supported by the rubber mould and plaster case, but no armature is set in at this stage. The wax pattern is then stripped from the mould and retouched (see below).
Once the wax has been prepared for investment, the founder then constructs an outer steel framework close to the wax’s surface. From this framework, steel pegs can be driven deep into the core and fixed to the frame by careful welding. The framework and pegs not only function as a core armature, but also double up as core pins and a support structure for the outer investment mould (see also image on SAND VENTING page).
MOULD STRIPPING > |
