INVESTMENT CASTING CERAMIC CORE PREPRESS

Investment Casting Ceramic Core Tooling & Shell Prepress Guide

Precision investment casting (lost-wax process) of aerospace single-crystal superalloy turbine blades and hollow medical implants relies upon sacrificial ceramic cores and multi-coat refractory ceramic shells. Accurate CAD core geometry and shell dewax parameters prevent wall distortion and shell blowout.

1. Ceramic Core Stability & Dewax Stress Mechanics

Fused silica and alumina ceramic cores provide internal serpentine cooling passages. During fast-cycle steam autoclave dewaxing, pressurized steam rapidly melts pattern wax before volumetric thermal expansion exceeds shell modulus of rupture. Core support pins (chaplets) maintain exact airfoil wall thickness.

2. Engineering Specifications & Tolerances

3. Ceramic Core Die Tooling DXF Prepress Rules

• Dual Shrinkage Allowance: Ceramic core tooling DXF geometry must compound both wax injection shrinkage (0.8–1.4%) and alloy solidification shrinkage (1.8–2.6%).
• Tie-Bar Pinning Concentricity: Core support pin holes must maintain $\pm 0.025\text{mm}$ true position to prevent internal airfoil wall thinning.
• Leaching Channel Escape Ports: DXF core print tabs must extend a minimum of $8.0\text{mm}$ beyond casting envelopes to allow boiling KOH/NaOH chemical core dissolution.