Surface Treatments in Investment Castings

2025-12-12

Investment casting can achieve precise and repeatable dimensional accuracy. Typical as-cast tolerances fall within ±0.003–0.004 inch per inch, although actual performance depends heavily on part design and geometry.

Factors Affecting Tolerance Capability

Part Configuration
Uniform and symmetrical parts shrink more consistently, resulting in tighter tolerances.
Shrinkage Prediction
Variations in shrinkage account for around one-fifth of the total tolerance range.
Tooling Accuracy
Tooling contributes a smaller portion of dimensional variation but still affects overall results.
Process Variation
Wax pattern formation, shell-building, and casting steps contribute most to variation.

Improving Tolerances

Premium tolerances can be achieved through:

Optimizing part design with ribs or reinforcing features
Fine-tuning wax injection tooling after initial trials
Straightening or coining critical areas
Enhanced inspection and gauging
Secondary machining for tight-fit features

With proper optimization, certain features can reach ±0.002 inch, though ±0.004 inch per inch remains a realistic high-precision standard.

Category	Description
Typical As-Cast Tolerance	±0.003–0.004 in per inch
Main Influencing Factors	Part geometry、shrinkage behavior、tooling accuracy、process variation
Sources of Variation	Shrinkage prediction、tooling tolerance、wax–shell–casting process steps
Ways to Improve Accuracy	Design optimization、tooling tuning、straightening/coining、extra inspection、partial machining
Premium Capability	Certain features achievable to ±0.002 in

Feel free to contact us for a quote~