The photos shown below are parts/products we manufactured for our customers over the years.
The Importance of Mold Design
Mold design is one of the most important steps in the process because the shape and attributes of the mold directly affect the final product. The die casting procedure forces molten metal into molds using high pressure, requiring a mold with exact specifications to achieve the task.
Mold design affects the shape, configuration, quality, and uniformity of a product created through the die casting procedure. Improper specifications can result in tool or material corrosion, as well as inferior product quality, while an effective design can improve efficiency and production time.
Factors Contributing to Quality Mold Design
There are a number of mold design factors to consider when deciding on the appropriate specifications for a project, some of which include:
Draft
Draft is the degree to which a mold core can be tapered. A precise draft is necessary to smoothly eject the casting from the die. However, draft is not constant and varies according to factors such as the angle of the wall, the type of molten alloy used, the shape of the wall, and the depth of the mold. Mold geometry can also influence draft. In general, untapped holes require tapering due to the risk of shrinkage. Likewise, inner walls can also shrink and therefore require more drafting than outer walls.
Fillets
A fillet is a concave junction used to smooth an angled surface. Sharp corners can hinder the casting process, so many molds have fillets to create rounded edges and reduce the risk of production errors. With the exception of the parting line, fillets can be added to almost any location on a mold.
Parting Line
The parting line, or parting surface, connects different sections of the mold together. If the parting line is imprecisely positioned or becomes deformed from work strain, material may seep through the gap between the mold pieces, resulting in non-uniform molding and excessive seaming.
Bosses
Bosses are die-cast knobs that serve as mounting points or stand-offs in mold design. Manufacturers often add a hole to the interior structure of the boss to ensure uniform wall thickness in a molded product. Metal tends to have difficulty filling deep bosses, so filleting and ribbing may be necessary to alleviate this issue.
Ribs
Die-cast ribs can be used to enhance material strength in products that lack the required wall thickness for certain applications. Selective rib placement can reduce the likelihood of stress cracking and ensure uniform thickness. Additionally, it is beneficial for reducing product weight and improving fill capabilities.
Holes and Windows
Including holes or windows in a die-cast mold directly affects the ease of ejecting a completed molding and enables the creation of substantial drafts. Additional features, such as overflows, flashovers, and cross feeders, may be necessary to prevent unwanted casting within the holes or poor material flow around them.
Symbols
Manufacturers often include brand names or product logos in the mold design of die-cast products. While symbols typically do not complicate the die casting process, their use can affect production costs. In particular, a raised logo or symbol requires additional molten metal volume for each manufactured part. Conversely, a recessed symbol requires less raw material and can reduce expenses.
Die and component material and hardness for various cast metals
The most important material properties for dies are thermal shock resistance and softening at elevated temperatures. Other important properties include hardenability, machinability, heat checking resistance, weldability, availability (especially for larger dies), and cost. The longevity of a die is directly dependent on the temperature of the molten metal and the cycle time. Dies used in die casting are usually made of hardened tool steels because cast iron cannot withstand the high pressures involved. Therefore, dies are very expensive, resulting in high start-up costs. Metals cast at higher temperatures require dies made from higher alloy steels.
