Hybrid production of castings by 3D printing

3D printing of metal parts is still a hot topic and metal 3D printers are often the focus of companies. Metal 3D printers have been on the market for some time, but they are not the only additive technology that can produce parts from metal. Voxeljet technology combined with standard foundry processes offers an interesting alternative to produce metal parts using 3D printing.

Each technology has its own ideal type of application where it is technologically and economically most advantageous.

The production of parts using Voxeljet technology is primarily concerned with very complex medium-sized parts (approximately the size of a shoebox), which are more in the nature of shells or thin-walled parts. These types of parts are generally unsuitable for CNC machining, and for metal 3D printing using SLM/DMLS/EBM powder technologies where they are often too costly.

What does the manufacturing process look like?

The Voxeljet printer itself prints parts using Binder Jetting powder technology. The printing material is PMMA powder, which is bonded together using Binder (binder). The printed part is waxed by dipping it in a wax bath after it is removed from the printer and cleaned of the surrounding powder. A quick hand-finish is then usually carried out and the part is ready to be sent to the foundry.

The foundry can now work with the print as a conventional wax model for the lost mould casting method (lost wax method). The PMMA material is very flammable and behaves like wax for these purposes.

The waxed PMMA print is wrapped in ceramic breccia, allowed to dry and then fired. During the firing process, the wax model (made by a 3D printer) is molded out of the mold and a cavity (cavity) is left that follows the exact shape of the wax model. Metal is then poured into the resulting cavity.

The whole process from 3D printing the wax mould to the casting itself can be seen in the video:

Before the actual wrapping of the wax model with the ceramic slurry, the sprue systems, which are also made of wax, are placed on the model. These ensure that the metal is evenly distributed during the casting process. After the casting has cooled, the ceramic shell is shattered and the part is finished, usually by water blasting or sandblasting. The final step is to cut off the sprue system and clean up these contact points.

When is hybrid casting production suitable?

The use of 3D printing of the mould for subsequent casting is a very interesting alternative. It offers the advantage of 3D printing (complex shapes, speed of production and more) while ensuring standard mechanical properties of the final castings thanks to proven casting procedures.

3Dees currently has a Voxeljet VX500 printer. The size of the print chamber is 500 x 400 x 300 mm. In cooperation with our partner foundry, we are able to supply metal castings directly, primarily in aluminium and magnesium.

If you are interested in more information, you can contact an application engineer at adam.rehak@3dees.cz.