Casting molds
A casting mold is a tool with a cavity in the shape of the future casting, which is filled with liquid metal. Once the metal solidifies, an expendable mold is broken up, while a permanent mold is opened and reused. The type of mold determines the accuracy and surface quality of the casting, the tooling cost and the economical batch size.
Types of Casting Molds
| Mold | Material | Durability | Application |
|---|---|---|---|
| sand casting | molding sand: silica sand with binder | expendable | prototypes, small and medium runs, larger castings |
| shell mold | resin-coated sand, thin hardened shell | expendable | more accurate series castings |
| ceramic (lost wax) | ceramic slurry applied to a wax pattern | expendable | small precision castings |
| permanent mold | cast iron or steel | many thousands of pours | medium and large series, gravity die casting |
| die (high-pressure die casting) | tool steel, cooled by channels | very high number of cycles | large series, high-pressure die casting |
Expendable molds require a pattern that reproduces the shape of the casting in the molding sand. Permanent molds – cast iron or steel permanent molds and die casting dies – cost more to make, but in larger series the mold cost is spread over many castings.
What a foundry mold consists of
- Mold cavity – reproduces the shape of the casting, enlarged to allow for metal shrinkage and machining allowances.
- Parting plane – the point where the mold opens; its position affects the removal of the pattern or casting and the marks left on the casting.
- Cores – form the holes and internal cavities of the casting; in the mold they are located in core prints.
- Gating system – the channels through which metal flows into the cavity: pouring basin, sprue, runner and ingates.
- Risers and vents – risers feed metal that shrinks during solidification, while vents carry off air and gases.
- Draft angles – slight taper on the walls that lets the pattern or casting release easily from the mold.
- Coatings – protective coatings on the mold and core surfaces that improve the surface quality of the casting and protect the mold.
How a sand mold is made, and how a permanent mold is made
- Sand mold – the molding sand is dosed into flasks and compacted around the pattern. After the pattern is removed, cores made in core boxes are placed in the mold and the mold is assembled. At our foundry the sand is mixed, dosed and compacted automatically, and for some molds we use self-hardening and heat-hardening sands.
- Permanent mold – it is designed in CAD, machined on CNC machines, and before casting it is coated with a protective layer and heated to operating temperature. Holes and undercuts in the casting are formed by metal or sand cores.
In short: foundry molds fall into expendable (sand, shell, ceramic) and permanent (cast iron or steel permanent molds, die casting dies). Every mold has a cavity, a parting plane, a gating system and usually cores. An expendable mold pays off for small series, a permanent one for larger series.
Molds for aluminum castings at our foundry
We make patterns, core boxes and permanent molds in our own pattern shop (for some projects, with trusted partners), and sand molds in our own molding shop. Foundry pattern making has been our family tradition since 1950. For large series we make steel patterns; for short runs and prototypes, wooden or resin ones. We work with CAD/CAM systems, CNC machines and 3D printing; tooling usually takes from a few days to a few weeks. We machine die casting dies on our own CNC machines.
More: casting patterns and molds, casting technologies, permanent mold casting, sand casting i high-pressure die casting.
Need a mold and aluminum castings? Send a drawing or 3D model to odlewnia@adjatech.pl or call: +48 61 662 43 37 (Mon–Fri 8:30 a.m.–4:30 p.m.).
Scope of services: foundry production capabilities.