Investment Casting Design Considerations and Tips

October 7, 2018

Today, investment casting is becoming a very popular manufacturing processes due to the many advantages that it offers. One of the key benefits is the ability to produce near net parts from strong and wear resistant materials allowing the elimination expensive and time-consuming post processes. Properly designing a part for the process is a critical first step, and several considerations must be made. This post discusses the various design considerations and tips shared by American Casting Company.

Design Considerations for Investment Casting

The following are key considerations to be made while designing the casting:

  • Wall Thickness: Uniform or slightly tapered wall thickness is an important factor. In a mold, the molten material solidifies from thick to thin. If a wall changes thickness or pinches off, the solidification will be negatively affected and can create unwanted porosity. The minimum wall thickness of a casting part will depend on the type of material, as well as the distance traveled by the molten metal.
  • Linear Tolerances: These are differentiated into the below-given three categories:
    • General Linear Tolerances: These values are suited for most features, which demand standard dimensional precision.
    • Premium Linear Tolerances: These values are suited for selected dimensions that are critical, and may require secondary operations. The premium linear tolerances achieved depends on the part geometry and the type of alloy used in some cases.
  • Radii: Corner radii and large fillets are two factors that improve the castability of the part. Also, these factors help reduce stress on the part, as well as improve the part’s final appearance. Experts at American Casting Company recommended the minimum radii of 0.030″ – 0.060ʺ for inside and outside corners.
  • Surface Texture: Standard surface roughness is 125 RMS and premium finish is 90 RMS.

Tips for Investment Casting Design

The following are a few important tips, which will help create a perfect casting.

  1. Part Size and Weight: Part size and weight contribute to the cost of the part due to how many parts can be cast on the same mold. This is because the capacity of the mold entirely depends on the part size and weight. At American Casting Company, the maximum part size achieved is 16″ Cube, whereas the maximum part weight is 25-30 LBS.
  2. Number of Gates: The gates serve as the feature where metal flows into he mold and feeds the casting during solidification. The gate is where the part attaches to the mold and is where the part is cut later in the process. It is highly recommended to design the parts with a single gate or as few of gates as possible. This leads to a lower cost part and better quality in some cases.
  3. Component Castability: This is one of the most important investment casting factors. An investment casting should be designed with a gate location available on the thickest section of the part and should get thinner as the part goes away from the gate. This allows for feeding from thick to thin.

Unlike other manufacturing techniques, the above-mentioned factors can be utilized for creating a better quality investment casting with the potential for less defects at a lower cost.