ProductionTOLERANCES
Investment Casting Tolerances and Dimensional Accuracy
Investment casting is an important manufacturing method that enables metal components with complex geometries to be produced with high dimensional accuracy. However, since the geometry, size, alloy, mold structure, and production conditions of each investment cast component differ, the applicable dimensional tolerances may also vary depending on the project.
At KHD Investment Casting, when component design and production planning are carried out, the technical drawing, critical dimensions, intended application, and requiredinvestment casting tolerances are evaluated to determine the appropriate manufacturing method.
Dimensional Tolerances in Investment Casting
During the production of cast components, dimensional changes may occur due to the solidification and cooling of the metal. Therefore, when designing the mold, the characteristics of the metal alloy, component geometry, and variables associated with the casting process are taken into consideration.
With proper mold design and a controlled production process,investment casting dimensional tolerances can be maintained within narrower ranges compared to many conventional casting methods.
Thanks to this feature, investment casting is a suitable manufacturing method for:
Components with complex geometries
Thin sections
Detailed surfaces
Small and medium-sized metal components
Repeatable mass production
The Effect of Component Geometry on Tolerances
One of the most important factors affecting the dimensional accuracy of investment cast components is their geometry.
The overall length of the component, section thicknesses, variations in wall thickness, holes, channels, angles, and complex geometric details can affect the achievable tolerance values.
Therefore, duringinvestment cast component design, not only nominal dimensions but also manufacturability and dimensional changes that may occur after casting should be evaluated.
The Effect of the Alloy Used on Tolerances
Different metal and steel alloys have different solidification and cooling behaviors. This can result in variations in the dimensional changes that may occur after investment casting.
KHD can manufacture components using carbon steels, alloy steels, carburizing steels, tool steels, 300 and 400 series stainless steels, heat-resistant stainless steels, copper alloys, and various specialized alloys.
Therefore, the material to be used for each project should be evaluated and theinvestment casting tolerance should be determined before production.
Surface Quality in Investment Casting
One of the important advantages of the investment casting method is not only dimensional accuracy but also its ability to provide high-quality surface finishes.
Thanks to the ceramic mold process, complex details and surface geometries of cast components can be reproduced with high accuracy. This can help reduce the need for extensive machining in many applications.
However, the final surface requirements vary depending on the intended application of the component. Additional operations such as grinding, polishing, or machining can be applied to areas requiring more precise surfaces or dimensions.
Machining Allowances in Investment Casting
The same tolerance may not be required on all surfaces of a component. Machining may be required after casting for mounting surfaces, bearing seats, connection areas, or specific dimensions requiring high precision.
In such cases, the requiredmachining allowances are determined in advance during the design of the investment cast component.
Providing the correct machining allowance helps with:
Reducing unnecessary material usage
Reducing machining time
Optimizing production costs
Achieving final dimensions more accurately and consistently
Geometric Tolerances
In investment cast components, not only linear dimensions but also geometric characteristics such as flatness, parallelism, perpendicularity, and circularity are important.
Especially for components requiring assembly, the geometric tolerances specified in the technical drawing should be evaluated before production.
For surfaces requiring very high geometric accuracy, final dimensions can be achieved through post-casting machining or grinding.
Dimensional Inspection in Investment Casting
After production is completed, the dimensional inspection of cast components is performed according to the technical drawing and project requirements.
With the profile projection and various measurement equipment available in KHD's production infrastructure, critical dimensions of components can be inspected.
In addition, quality control methods such as chemical analysis, hardness testing, and microstructure examination are also used to verify material quality.
How Is the Correct Investment Casting Tolerance Determined?
It is not appropriate to specify a single standard tolerance value for every investment cast component. Applicable tolerances should be evaluated according to:
Therefore, when preparing a newinvestment casting project, it is important to clearly indicate critical dimensions on the technical drawing.
KHD Investment Casting can review technical drawings, samples, or project information provided by customers and evaluate manufacturability, tolerances, and the appropriate production method.
High Dimensional Accuracy with Investment Casting
When proper mold design, controlled wax pattern production, ceramic shell preparation, metal analysis, and appropriate casting parameters are considered together, the investment casting method can provide high dimensional accuracy and repeatability.
Thanks to these characteristics,investment casting tolerances provide important advantages in numerous industrial applications, from the automotive and machinery industries to medical applications and the valve and pump sectors.
KHD Investment Casting provides solutions for the production of dimensionally controlled, high-quality investment cast components suitable for mass production by evaluating project-specific tolerance requirements.