Casting has been known since the Copper Stone Age – over the millennia it has developed into an industrial standard and it is impossible to imagine a wide variety of industries without it as a shaping process. Today, there are a wide variety of methods for the production of castings. Below we offer an overview of various casting processes.

What are the molding and casting processes?

Sand casting

One of the oldest and a widespread method of casting is the so-called sand casting. In this process, liquid metal is poured into a sand mold. To create the molds, you usually need a model. Usually made of wood or similar, this is molded in quartz sand to which various binders are added. Cavities can be represented by sand cores that are inserted into the mold. After casting, the mold including 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 molded and complex cast components and, in addition to prototype construction, is also used for small and medium series batch sizes. Sand casting can be used to process virtually all castable alloys.

Investment casting

Investment casting can be used to produce high-precision and filigree castings. Among the various 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 weeks. After the melt has solidified, the mold is destroyed and the cast component is reworked or refined for final use. Virtually all castable alloys can be used for the investment casting process.

Die casting

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 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. This casting manufacturing process allows very large quantities to be produced in a very short time and at a low cost per piece, but limits the possible complexity of the components. The cast components are characterized by very good surface properties, tight tolerances and high accuracy.

Gravity die casting

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 in this casting process. 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 mold, permanent mold casting 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.

What innovative techniques does voxeljet offer for casting processes?

With our binder jetting technology, we offer innovative solutions for both sand casting and investment casting that streamline time-consuming and cost-intensive value-added processes while ensuring high-quality (casting) results. Using modern 3D printing technology, we produce molds and models on our industrial 3D printers without tools and with the highest precision. We use standard foundry materials such as quartz sands and typical binder systems such as furan and phenolic resins as well as inorganic binders.

Binder jetting for sand casting

For sand casting, classic quartz sands are suitable for mold making. For core printing, we rely on various special sands such as cerabeads or chromite. 3D printing produces the molds in a fully automated layer building process. In this process, an ultra-thin layer of sand is applied to a build platform and then selectively bonded by a print head. A new layer of sand is then applied and bonded again. These process steps are repeated until the mold is completely printed. Digital CAD data is used as the construction plan. After 3D printing, the molds are manually lifted out of the sand bed and freed from excess, unbonded sand. After unpacking and finishing, the molds are ready for immediate use and casting.

Binder jetting for investment casting

For investment casting, we use a fine acrylic powder (PMMA / polymethyl methacrylate), from which we 3D print models in a layered construction process, just like sand printing. Again, a fine layer of powder is applied to a build platform and selectively bonded by a print head. The printed models are then dipped in a wax bath to seal the surface and ensure a precise casting result. The printed PMMA models can be handled just like conventional wax patterns and can be seamlessly integrated into existing investment casting processes. The negative coefficient of expansion of the polymer powder ensures residue-free burnout of the model during firing of the ceramic mold.

How are castings produced with the new casting processes?

For casting, it makes virtually no difference whether the mold or model was 3D printed or conventionally manufactured. Thanks to the use of tried-and-tested materials that are commonly used in foundries, additively manufactured components can be easily integrated into existing production processes. A hybrid application is also possible: less complex molded parts can be manufactured conventionally and only complex or filigree core structures can be 3D printed. The casting process as such remains the same, which has been practiced for thousands of years.

How does the foundry industry benefit from voxeljet's new casting processes?

Binder jetting technology from voxeljet offers the foundry industry many advantages: Time-intensive manufacturing processes for tools are eliminated, undercuts no longer play a role due to the geometric freedom of 3D printing, and product development cycles can be shortened many times over.

  • Optimize costs
  • Produce at any scale
  • Accelerate time to market
  • Make the impossible possible
  • Seamless integration
  • Freedom in product design

What other industries can use voxeljet's molding and casting processes?

Within a vertical value chain, the foundry industry is one of the most important pillars for a wide range of industries. The automotive and marine industries, the energy sector, aerospace, or the pump and heavy industry, among others, benefit from 3D printing in industry. They can all realize significant and sustainable gains from advanced binder jetting technology and 3D printing of molds and patterns for the casting process – especially as products become more complex under the umbrella of lightweighting optimization. Away from metal casting, 3D-printed components are also being used in architecture, the film and entertainment industry, and the sports and leisure sector, among others.

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