Tooling may refer to the die, tool, or mold through machining. The mold can then be used to cast other metals/alloys of relatively lower temperature than the mold material. And designing this equipment has great significance in product quality, performance, and cost. They require special considerations for an optimized design. The blog features a simple yet insightful aluminum die-casting tooling design guide to create workable, efficient, and supportive molds.
Aluminum Die Casting Tooling Materials
Steel is the primary die casting mold material. Though few high-strength aluminum alloys also have applications as the mold material. Either one has respective benefits and limitations based on mechanical properties.
Steel
H13 and P20 are two of the most common tool steel used in aluminum die casting production. They exhibit excellent hardness, stability, and polish with corrosion, rust, and wear resistance. They can support enormous production rates based on specifications. PAS940, Maraging 300, and Berlin Copper are some expensive alternatives.
Aluminum
Aluminum molds are suitable for low-volume production activities. It provides good heat transfer, heat treatment, production cycle, and cost efficiency. Aluminum 7000 series alloys (7075) and 6061-T651 alloys are suitable materials for mold-making. Though they have limited application in die casting and are usually used for blow molds, injection molds & structural foam molds.
DFM for Die Casting Tooling
DFM, or Design for Manufacturability, is a core aluminum die casting tooling design guide strategy. It is synonymous with production/manufacturing optimization. This focuses on ensuring the performance of aluminum die casting molds to their specifications.
These avoidable operations can cover as much as 80% of the cost. DFM provides an effective approach to minimizing the cost without inefficiencies before production. Some important parameters for DFM of die casting tooling are outlined below –
- Weight –More materials will take an extra filling and solidification time, increasing the tooling cost. The inclusion of hollow and pocket sections can reduce the weight.
- Wall Thickness –Uniform thickness facilitates integrity, flow, and solidification for improved quality. Provide a gradual transition in case there is a change in wall thickness.
- Draft Angles –It is the tapering of the casting surfaces perpendicular to the parting line. Insufficient draft angle makes the ejection of Aluminum die casts difficult and vulnerable.
- Parting Lines –The meeting point of a moving half and a fixed half introduces a parting line. A designer must know the line’s position and avoid placing metals to reduce the tooling cost.
- Surface Finish –Smooth exterior texture is always desirable for aluminum die casting. Specifying the roughness or finishing grade can help obtain a shiny, polished, bright finish.
- Ejector Pins –These pins are crucial in solidification, shrinkage, and removing parts from the die. Place an ejector pin on sturdy features like ribs and bosses for easy and even removal.
- Ribs & Corners –They add stiffness to increase strength, designed with hollow sectional savers. Using ribs instead of thickness is preferable. But overusing the ribs must be avoided.
- Fillets & Radii –Rounded outer edges are called radii, while rounded inside corners are called fillets. They can facilitate smooth flow and less disturbance, encouraging superior integrity.
- Undercuts –Avoiding these costly additions is the best option. But keeping the number outside also helps unavoidable situations. Also, placing them under bosses can cause issues.
- Material Flow –Simulation through software can identify issues regarding the metal flow. Modern casting design is highly dependent on these simulation programs for perfection.
- Bosses –They are the stand-offs and mounting points in tooling. Right entails large fillets to enable smooth flow and sufficient drafts. A uniform wall thickness is also necessary.
- Shrinkage –Metal shrinkage or contraction is unavoidable. Thin sections with metal-saving cores can reduce shrinkage. Additional local squeeze pins also minimize contraction.
- Holes/Windows –Multiple holes and windows for electronic parts may make the ejection difficult. Small yet workable openings eliminate the eventual clamping down of molten metals.
For more information on these parameters and detailed specifications, you can refer to Sunrise Metal’s Aluminum Die Casting Design Guide.
Die Casting Tooling Design Considerations for Gating and Runner Systems
A gating and runner system features all the entering passages for molten metal into the mold. This includes –
· Pouring Basin
· Gates
· Runner
· Risers
· Sprue
It should incorporate no impact/splash/impurity/slag/gas/wastage. Easy dispatch of the mold from the solid high-pressure die-casting aluminum is also desirable.
Improper gating system design can lead to severe defects like oxidation, shrinkage, porosity, and erosion. The following considerations are crucial to ensure a workable design –
Freezing Time
Good control over metal flows can fill the cavities quickly, keeping the density. Liquid metal in the riser should freeze at slower rates than casting. Therefore, the freezing time is more in the riser for solidification.
Feed Volume
The risers must possess sufficient capacity to fill the cavity for proper solidification. The metals need to remain liquid in risers for freezing the cast. Electric arcs and exothermic compounds can maintain this situation. Freezing time and freezing demand usually decide the required feed volume capacity.
Feeding Range
Large castings of complicated shapes will require multiple risers. Diving the castings into different zones will let separate risers feed the mold. These risers should have a constant temperature gradient attached to the heavy solidifying section.
Importance of Simulation For Die Casting Tooling
A simulation program delivers a virtual presentation of the entire casting process. As making physical prototypes of a product is quite costly in die-casting, software-based simulations provide a fast and economic solution.
Advanced simulation software can analyze a casting model to evaluate its different variables related to the product quality, including –
- Pouring rates to control evaporation and gas porosity
- Turbulence to avoid erosion, inclusions, and entrapment
- Hot points to eliminate additional molten inclusions
- Thermal gradient to consider shrinkage, cracks, splits
A perfect depiction of the mentioned variables can terminate die casting aluminum mold design errors. Adjusting the variables to change the outcome becomes effective, simple, and immediate.
Sunrise Metal is an expert die casting tooling manufacturer with advanced CNC machining and rapid tooling capabilities. Contact us for any queries on the latest tooling practices and cost-reduction tips for your die casting project.