We are excited to provide die casting services to our clients! When we receive a new die casting project request, one of the first steps our engineers take is to assess the design for manufacturability. If a design is not suitable for the intended manufacturing process, it can lead to delays and higher costs. To help ensure your design is both feasible and cost-efficient, we’ve put together a collection of expert tips to guide you in creating die casting part designs that streamline production and maximize the success of your project from the outset.
The Primary Principles That Make for Successful Die Casting:
- The molten metal can easily flow through the mold, filling it to produce a solid part.
- The metal solidifies evenly and quickly.
The part ejects without damaging itself or the tooling. - The part design minimizes the complexity of the tooling required.
- The part function is prioritized over its shape.
- Tolerances should be kept as open as possible without affecting the fit, form, or function.
By following these principles and considering the tips outlined below, you’ll be on the right track to creating a design that is both reliable and cost-effective to manufacture. If you have a die casting project in the works, don’t hesitate to request a quote from us today! Our team of experts is ready to assist you throughout the process and address any questions you might have.
Fillets and Radii
Incorporating both fillets and radii into your design offers several advantages. For one, they facilitate the even flow of molten metal throughout the part and help prevent localized heat buildup around corners and transitions. These features are also critical in avoiding cold shuts, which occur when the metal begins to solidify before fully filling the mold cavity. Even cooling of components reduces stress on the tooling, enhancing its durability and lowering maintenance needs. Additionally, fillets can help mitigate stress concentrations, particularly in areas where intersecting features would otherwise create sharp edges. Below are some additional guidelines for adding fillets and radii to your design:
- Add fillets or radii to sharp edges and corners to improve the design.
- The deeper the corner or pocket, the larger the fillet should be.
- Fillets help create smooth transitions between features, which support better metal flow and enhance the part’s structural strength. Generous radii are recommended where features intersect.
- Constant-radius fillets ensure consistent edges and smoothness throughout the part.
- When the fillet is perpendicular to the parting line, draft angles are necessary. The degree of draft needed will depend on the draft of the intersecting surface.
Wall Thicknesses
When it comes to wall thickness, the most important factor is consistency. Maintaining uniform wall thickness throughout the part ensures smooth metal flow and even cooling. Variations in wall thickness can lead to differing shrinkage rates, resulting in defects like sink marks or cracks. Below are additional factors to consider when designing wall thicknesses:
- Thicker walls allow molten metal to flow more easily.
- Alloys like zinc are capable of producing parts with thinner walls.
- It’s important to avoid large protruding features that can drastically increase wall thickness, as this can lead to uneven cooling and slower solidification rates.
Ribs and Coring
Ribs are design elements that offer several advantages in die cast parts. Their main function is to enhance rigidity and strength, particularly in areas with thin walls. Ribs also improve the flow of molten metal, enabling it to reach and fill connected sections more efficiently.
Introducing coring, such as the spaces between ribs or walls, helps reduce material usage, acting as a metal-saver and improving the overall quality of the cast parts. Coring displaces the casting alloy, reducing material consumption and making the part lighter. By effectively utilizing ribs and coring, you can prevent heat buildup in areas with excessive material, thus reducing part weight while maintaining strength. When integrating ribs and coring into your design, it’s important to consider the following factors:
- Designers should incorporate ribs into thin-walled sections for added strength.
- Opt for an odd number of ribs to better distribute internal stresses and prevent thick intersections from forming.
- Include fillets on ribs and metal saver edges to smooth out sharp corners and improve metal flow.
- Avoid placing ribs too closely together, as this can reduce the efficiency of the metal savers.
- Ensure generous draft angles on the sides of metal saver pockets to facilitate easier mold release and reduce tool wear.
Holes and Windows
Holes and window features require special attention, as they introduce unique challenges in the die casting process. During cooling, the inside surfaces of holes and windows can bond to the steel die, potentially affecting the ejection process and making it more difficult to release the part. This can lead to increased tool wear and part defects.
Furthermore, holes and windows can disrupt the flow of metal throughout the mold. For larger windows, techniques such as bridge features or runners may be employed to facilitate proper metal flow, but this can result in additional steps and higher costs for trimming these features post-casting. If your design includes holes or windows, the following design guidelines will help ensure your part remains manufacturable:
- Holes and windows need the most draft angle compared to other features.
- The edges of holes and windows should be radiused.
- In certain situations, it may be more efficient to machine holes after casting, although this will increase production time.
Post-Machined Features
Post-machining is frequently used for many die-cast components. Since die-cast parts generally have tight tolerances and intricate shapes, most post-machined features are relatively small. While machining adds cost per part, it helps reduce tooling complexity and ensures precise tolerances or surface features when needed. When planning for post-machined features, consider the following points:
- Post-machined features follow the same design considerations of CNC machining services.
- The more machining operations, the higher the cost per part.
- Call out machining features wherever tolerances are beyond die casting conditions. For example, a bearing fit.
- Provide two designs and technical drawings: the first being the as-cast part and the second for the final finished workpiece.
Parting Lines
Parting lines are the areas where the two halves of the die meet and interact. When designing your parts, determining the locations of the parting lines should be one of the first considerations. Parting lines can be either straight or segmented, depending on the part geometry and the die components required. Here are the main points to keep in mind when considering parting line locations:
- Parts with straight parting lines are typically less costly than those requiring broken parting lines, as they need less intricate tooling.
- Controlling quality along parting lines can be challenging, so it’s best to avoid placing parting lines across critical features or areas with tight tolerances.
- Parting lines often result in flash, which is a thin strip or fin of excess material caused by the clearances needed for die operation. Flash is removed during the trimming process, and it should be located in an area that is easy to access.
Die Casting Surface Finish Classses
It’s important to specify the desired as-cast external surface finish in your design. The finish grade you select can have a significant impact on the final cost, as higher-quality finishes require additional processing and more advanced die designs. Therefore, it’s advisable to choose the lowest finish classification that still meets your application requirements to help reduce costs.
The North American Die Casting Association (NADCA) provides guidelines to assist in classifying your surface finishing needs in a general manner. Please refer to the chart below for these classification standards. Keep in mind that this serves as a general reference, and the final finish quality is typically determined through agreement between the customer and the manufacturer.
Die Casting Surface Finish Classses
| Class | As-Cast Finish | Final Finish or End Use |
| Class 1 – Utility Grade | No cosmetic requirements. Surface imperfections (cold shut, rubs, surface porosity, lubricant build-up, etc.) are acceptable | Used as-cast or with protective coatings; anodize (non-decorative), chromate |
| Class 2 – Functional Grade | Surface imperfections (cold shut, rubs, surface porosity, etc.), that can be removed by spot polishing or can be covered by heavy paint, are acceptable. | Decorative coatings: lacquers, enamels, plating (Al), chemical finish, polished finish |
| Class 3 – Commercial Grade | Slight surface imperfections that can be removed by agreed upon means are acceptable | Structural parts (high-stress areas), plating (Zn), electrostatic painting, transparent paints |
| Class 4 – Consumer Grade | No objectionable surface imperfections. Where surface waviness (flatness), noted by light reflection, is a reason for rejection special agreement should be reached with the die caster. | Special decorative parts |
| Class 5 – Superior Grade | Surface finish, applicable to limited areas of the casting and dependent on alloy selected, to have an average value in micro inches as specified on print. | O-ring seats or gasket areas |
