Investment Casting Design Guide
Signicast’s goal is to work in partnership with our customers to produce superior, high-quality investment cast components for enhanced performance and durability in partnership with customers. This requires sound mechanical design of the investment casting, reliable process controls, consideration of marketplace economic requirements, and clear communication among all parties.
In any manufacturing process, the price of a product will increase as the dimensional tolerance and inspection criteria become more stringent. Early involvement and input by Signicast’s technical staff allow customers to overcome traditional casting tolerance issues. This is accomplished by innovation and technology to provide 100% conformance to specifications as-cast, delivered on time, at the lowest total cost. The most important guideline to remember is to get Signicast involved early in the design stage.
Investment Casting Design Considerations
Size and Weight
Part size and weight are the most critical factors in determining part cost because mold capacity is limited by both size and weight. The more pieces that can run on a mold, the lower the part cost. Our design team will work with you to remove any unnecessary mass in an effort to reduce part weight.
Number of Gates
When possible, a part should be designed so that a single gate can feed the part. This will generally yield more pieces per mold and help to reduce the pour weight per mold. Single gate feeding also enhances the dimensional stability of a given part by providing a directional solidification pattern.
Castability
If a design contains features that will raise scrap or rework rates (and piece price), the Signicast Estimating Engineer will recommend design modifications to keep the piece price down.
Investment Cast Tooling
Signicast utilizes a system of tooling standards to ensure uniform high-quality design and fabrication of the wax injection die which is generally guaranteed for the life of the part. We offer several different types of tooling: manual, semi-automatic and fully automatic.
In addition, configurations that do not allow metal cores in tooling to be drawn due to undercuts or complicated internal shapes must be treated with one of our collapsible, soluble, or ceramic core inserts.
Wall Thickness for Investment Castings
Minimum wall thickness and corner radii depend upon part configuration and size. Small investment castings may have walls cast to .030” thickness. Medium to large castings require .060”-.100” walls depending on the part geometry.
Tolerances for Investment Casting
The investment casting process is capable of excellent repeatability. As-cast process capability of +/- three standard deviations when a single point location is repeatedly measured, is typically +/- .003 to +/- .004 per inch. However, tolerance capability is largely influenced by part configuration. Symmetrical shapes with uniform wall sections will solidify with much less variation and distortion than non-symmetrical, non-uniform shapes.
Symmetrical shapes with uniform wall sections will solidify with much less variation and distortion than non-symmetrical, non-uniform shapes.
As-Cast Design Features
Did you know that Signicast is capable of casting other design features into components with little to no secondary operations? Our capabilities include:
Splines, Gears & Threads
Gear and thread profiles can be produced with accuracies of +/- .004” per .5” of pitch. Longer lengths or larger diameters can be held to normal or premium linear tolerances as necessary.
Numbers/Logos
Normally, raised letters or numbers in protective depressed pads are easiest to manufacture. A .020” high character on a depressed pad yields sharp, castable features. Logos can be investment cast to almost any design.
Gaging
Signicast performs a 100% visual inspection of all parts. If dimensional verification is required, a sampling plan and process control is less expensive than 100% gaging of each part. It is important to remember that whenever custom gages are used, there should be identical gages at Signicast and at the customer’s facility. Fixed gages such as go-no-go are less expensive to use than gages with dial indicators.
Investment Casting Company
With world-leading engineering experts, rapid prototyping and delivery, and the most advanced investment casting facilities in the world, Signicast is redefining how today’s manufacturers create, refine, and deliver products. If you need high performance, design freedom, and flexibility, we should talk.
