Casting

Casting forms parts by filling a mold with liquid metal or resin, enabling complex shapes, internal cavities, and cost-effective production at scale.

Overview

Casting creates parts by pouring molten metal or liquid resin into a mold, then allowing it to solidify into near-net shape. It excels at complex geometries, internal passages, and thick-to-thin sections that are costly or impossible to machine from solid. Metal casting covers a wide range of alloys and part sizes, while polyurethane/urethane casting uses RTV molds for shorter runs, elastomeric parts, and quick-turn functional prototypes.

Use casting when you need complex shapes, moderate to high volumes, or when material and tooling choices make other processes expensive. Expect good but not machining-level tolerances, and plan on adding critical features with secondary machining. Metal casting offers higher temperature performance and structural strength for production parts. Polyurethane casting is well-suited for bridge production, overmolds, gaskets, housings, and low-volume end-use parts where you want molded quality without full production tooling cost.

Common Materials

  • Aluminum 356
  • Aluminum 6061
  • Gray iron
  • Ductile iron
  • Stainless steel 316
  • Polyurethane resin

Tolerances

±0.010" to ±0.030"

Applications

  • Engine blocks and housings
  • Pump and valve bodies
  • Impellers and turbine housings
  • Industrial brackets and mounting lugs
  • Consumer product enclosures
  • Seals, gaskets, and soft overmold parts

When to Choose Casting

Choose casting when your part has complex geometry, filleted internal cavities, or varying wall thicknesses and you need repeatable parts beyond prototype quantities. It suits medium to high volumes for metal parts and low to medium volumes for polyurethane parts, especially when tooling cost can be amortized over a production run. It works best when you can tolerate moderate dimensional variation and plan machining only for critical features.

vs CNC machining

Pick casting when material removal from solid stock would be inefficient due to large volumes of waste, organic shapes, or extensive internal cavities. Use casting to lower per-part cost at volume, then machine only critical interfaces, rather than machining the entire geometry.

vs 3D printing

Choose casting when you need production-grade metals or urethanes with stable mechanical properties and better per-part cost at scale. Use 3D printing for very low quantities or complex internal details, then transition to casting when you need higher throughput and more consistent surface finish.

vs Injection molding

Use casting when your volumes do not justify hard steel injection molds or when you need metal parts instead of thermoplastics. Urethane casting is effective for low-volume molded-like parts, bridge production, and design validation before investing in injection mold tooling.

vs Sheet metal fabrication

Choose casting when the part requires 3D contours, thick sections, integrated bosses, or fluid passages that cannot be formed from flat stock. Casting consolidates assemblies of bent and welded sheet metal into a single, stiffer, leak-tight component.

vs Forging

Select casting when you prioritize complex geometry, near-net shape, and lower tooling cost over the extreme strength and directional properties of forgings. Casting is better for intricate housings and detailed features that are difficult or uneconomical to forge.

Design Considerations

  • Maintain uniform wall thickness where possible and use smooth transitions to reduce porosity, shrinkage, and warpage
  • Add generous fillets and radii at all internal and external corners to improve mold filling and reduce stress concentrations
  • Include proper draft (typically 1–3 degrees) on all vertical faces to aid pattern removal and urethane demolding
  • Define critical dimensions and machined surfaces clearly on the drawing and allow looser tolerances on as-cast features
  • Design accessible, flat pads and bosses for secondary machining of holes, threads, and tight-tolerance interfaces
  • Avoid unnecessary fine features and ultra-thin walls; they increase scrap rate, tooling complexity, and cost without adding much functional value