Mar.25, 2014

In the automotive industry or machine building, the production of complex parts such as FEAD brackets, gearboxes and other powertrain components for development or small series production often needs to be quick and efficient. But conventional investment casting has several disadvantages in this respect.

Thomas Peipp, Investment Casting Manager at Ennepetal, Germany based Schmolz+Bickenbach Guss GmbH said: "The problem is the immediate production of the required wax patterns often result in expensive injection moulding tools and wax presses. These tooling cost can become prohibitively expensive and time consuming when the tooling are used for development or small series production, as they result in very high unit prices."

Schmolz+Bickenbach turned to 3D printing to produce these complex parts. The modern 3D printers of the Augsburg-based provider voxeljet helps the company to produce investable patterns quickly, precisely and also cost-effectively.

Create lost models in record time

The printers can produce a plastic model for a Francis wheel with a diameter of 500 mm in less than 24 hours. The material used in this process is PMMA, which softens at 73° C and burns out without residue at temperatures over 700° C. It means that the parts are ideally suited for use as lost models for investment casting purposes.

"In the past, we had the models printed at the voxeljet service center. The advantages of the 3D printing technology, along with rising order volumes, prompted us to invest in our own voxeljet printer in 2013." says Peipp. "With the VX1000 printer, our investment casting plant can print parts up to a size of 1060 x 600 x 500 mm and a maximum unit weight of 70 kg. Now we can offer our customers even more rapid and efficient support."

The VX1000 features a high-performance print head that reaches a resolution of up to 600 dpi at a high build speed. The models are built using the layer building method: As part of this process, each layer is created by spreading a thin layer of powder over the surface of a powder bed. Solvent is then selectively printed onto the polymer particles. The solvent ensures that the particles are glued together. The desired object is printed layer by layer. The unbound powder supports temporarily unconnected portions of the component as the structure is built but is removed after completion of printing, so that even complicated free form surfaces with undercuts can be created. After the printing process, the residual particle material is removed from the finished model, which is then infiltrated with wax. This provides the plastic models with a closed and clean surface, which has a positive effect on the quality of the investment cast parts.

Plastic models are replacing wax models

The subsequent handling process is the same regardless of whether the model has been conventionally produced with wax or printed on a 3D printer. First ceramic coatings are applied then the models are put into the kiln. Once the temperature reaches to 700°C and more, the mold will burn out completely without any residue. The one-time use of the model explains why these models are called "lost models".

Installation of the gating system

Casting of the impeller

Cooling process

Removal of the ceramic shell

The casting dies must be blown out before the hot steel or aluminum alloys are poured into the dies. After cooling down, the casting dies must be removed along with the casting and feeding systems. Then engineers need to deburr sharp corners and remove surface defects before conducting non-destructive inspections and dimension controls.

Post processing

"Whether prototype, individual part or small series–3D printing technology makes it possible to produce highly complex design and investment casting models quickly, easily and cost-effectively. It is an enormous advantage for our customers," concludes Thomas Peipp.

Posted in 3D Printing Applications

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Angel Capodiferro , Lead Designer wrote at 7/18/2015 5:52:44 PM:

I need to know about if you have different size machine and at what cost point ? Also Max Part Size for each machine ? Any Post processors that take into consideration material shrinkage, draft angles, for different materials . I will be using Cast Iron, Steel, and Aluminum

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