Investment Casting

Investment casting (lost wax) produces near-net-shape metal parts from ceramic-shell molds, delivering high detail, good surface finish, and complex geometry capability.

Overview

Investment casting (lost wax casting) builds a ceramic shell around a wax pattern, melts out the wax, then pours molten metal to create near-net-shape parts. It handles complex geometry, thin walls, fine features, and undercuts that are difficult in conventional molds, with better surface finish than most sand-based processes.

Choose it for low-to-medium volumes where machining would waste material or require many setups, and where consistent as-cast dimensions matter. Typical tradeoffs: higher tooling/pattern cost and longer lead time than sand casting, size limits driven by shell handling and pour mass, and process sensitivity to section thickness and hot spots. Expect some secondary machining for critical datums, holes, and sealing surfaces, plus gating/runner removal and possible heat treat depending on alloy.

Common Materials

  • 17-4 PH stainless steel
  • 316L stainless steel
  • Inconel 718
  • A356 aluminum
  • Cobalt-chrome

Tolerances

±0.005 in

Applications

  • Turbine blades and vanes
  • Pump impellers
  • Valve bodies and trim
  • Firearm receivers and components
  • Orthopedic implant components
  • Gear housings with integrated features

When to Choose Investment Casting

Investment casting fits complex metal parts that benefit from near-net shape: thin walls, smooth surfaces, and integrated features that reduce machining and assembly. It’s a strong choice for prototypes through medium production when you can amortize pattern/tooling cost and need repeatable cast geometry. Plan on light finish machining where tight GD&T, threads, and sealing faces are required.

vs Sand Casting

Choose investment casting when you need finer detail, thinner walls, and better surface finish with less machining stock. It also improves repeatability for small-to-mid-sized parts where sand casting variability would drive extra machining and inspection.

vs Die Casting

Choose investment casting when you need alloys beyond typical die-cast grades (especially steels, stainless, and high-temp alloys) or when geometry requires thicker sections and less risk of porosity from high-pressure fill. It’s also better for lower volumes where die tooling cost and iteration speed are problems.

vs Permanent Mold Casting

Choose investment casting when the part needs more geometric complexity, sharper feature definition, or thinner walls than permanent mold can reliably fill. It’s also preferable when you want near-net shape in materials or designs that would require extensive cores and machining in a permanent mold.

vs Centrifugal Casting

Choose investment casting for non-axisymmetric shapes, discrete features, and complex external geometry that centrifugal casting can’t form efficiently. It’s a better fit when the part isn’t a tube/ring-type geometry and you need controlled detail across multiple faces.

vs Shell Mold Casting

Choose investment casting when you need finer feature resolution and smoother as-cast finish than shell mold typically delivers, especially on small intricate parts. It also helps when you want to minimize draft and parting-line constraints that drive rework and machining.

Design Considerations

  • Hold uniform wall thickness where possible; transition with generous fillets to avoid hot spots and shrink porosity
  • Define machining datums and leave intentional machining stock on critical faces, bores, and sealing surfaces
  • Avoid long thin unsupported sections; add ribs or local thickening to improve shell strength and filling
  • Specify realistic minimum radii and edge breaks; sharp corners increase cracking risk in the ceramic shell
  • Call out any critical internal features early (cores, passages, undercuts) so the foundry can design gating and cores upfront
  • Provide expected annual volume and revision stability; pattern/tooling approach and cost depend heavily on iteration risk