Molding and 3D printing casting processes

One of the oldest and most widespread methods of casting is sand casting. In this process, liquid metal is poured into a sand mold. To create the molds, you will require a model. Usually made of wood or similar, the model is molded in quartz sand to which various binders are added. Cavities can be represented by sand cores that are inserted into the 3D print casting mold. After casting, the mold, including its cores, is destroyed. This principle is called “lost mold”. Due to its high dimensional accuracy and surface quality, sand casting is particularly suitable for core-intensive, multi-part molds and complex cast components and, in addition to prototype construction, is also used for small and medium series batch sizes. Sand casting can also be used to process virtually all castable alloys.

Another of the casting technologies, investment casting can be used to produce high-precision and filigree castings. Among the various types of 3D casting processes, investment casting stands out as complex and cost intensive. Instead of molding a negative from a solid model, the desired component is modeled from wax or plastic as a positive. The model is then coated with several layers of ceramic in the foundry to produce a mold. When the ceramic is fired, the model melts and a hollow ceramic mold remains. The molten metal is then poured into this. Depending on the component, the multiple encapsulation process can take several days to a number of weeks. After the melt has solidified, the mold is destroyed, and the cast component is reworked or refined for final use.

Lost wax casting, one of the world’s oldest manufacturing methods, has stood the test of time as a method renowned for its ability to create intricate and high-precision castings. In the course of the process, a manually created wax pattern is covered with ceramic material. Afterward, the pattern is melted out of the ceramic shell before molten metal is poured into the resulting cavity. When the metal has solidified, the mold is destroyed, and the cast component is post-processed for final use. This principle is called “lost wax”.  Despite continuous advancements in the industry, lost wax casting remains mainly manual, with only a limited number of steps being automated and streamlined.

Similar to sand casting, gravity casting is used in permanent mold casting. However, instead of a sand mold, permanent molds or metal molds are used to cast 3D prints. Metal is more thermally conductive than sand. As a result, the heat of the melt is dissipated more quickly, and the melt solidifies faster and with a denser structure. This leads to higher strengths in the cast component. Due to the repeatability of the process steps and the reusability of the 3D print casting mold, permanent mold castings can also be (partially) automated for higher volumes. In permanent mold casting too, mainly alloys with low melting points such as aluminum and magnesium are used.

Die casting is a casting process used primarily for mass and serial production. Alloys with a lower melting point, such as aluminum or magnesium, are mainly cast. In the die casting process, the molten metal is pressed under high pressure into a usually metallic permanent mold. Cooling channels embedded in the mold ensure rapid solidification of the melt, and the components are released from the mold with a pusher. As a mass-production casting manufacturing process, very large quantities can be produced in a very short time and at a low cost per piece. One disadvantage, however, is that the possible complexity of the components is limited.