| 11:23 AM EST
Accelerate - June 2013
Development Aid Made
3D printing companies pride themselves on creating one-off objects or working parts when wider-scale production is too expensive or time consuming. But the stakes usually aren’t as high as, say, in Ethiopia, where a small hospital was without electricity thanks to a defective turbine wheel.
The clinic, in Walga, Ethiopia, did not have the funds to replace the commonly used, yet very intricate Francis wheel. The clinic worked with German 3D printing firm voxeljet technology GmbH (voxeljet.de), which created a mold for a replacement wheel via its 3D printing technology.
voxeljet produced a 250-mm mold for the wheel in about five hours. voxeljet says accuracy reached 0.2mm on the X- and Y-axes. That’s one of the smaller molds for voxeljet, whose large-format printers have churned out objects sized 4 x 2 x 1 meters.
The molds were forged based on CAD designs and created in layers made of 300-mm thick quartz sand that were glued together with a binder via the system’s print head. Once the printing was done, and the mold cleaned of excess sand, it was ready for casting.
“In this case, we decided on a combination of a 3D-printed sand core for the complicated turbine geometry and a conventionally produced exterior mold,” said voxeljet CEO Ingo Ederer. “This means that we use the advantage of 3D printing where it pays off the most—for the production of the complicated interior. Instead of many individual core segments which are strung together, the mono sand core impresses with higher component accuracy, smaller tolerances and fewer cleaning requirements, and does away with the need for many core separation devices.” Also contributing to the project was German steel foundry Wolfensberger AG, which cast the wheel; and solar and heat technology firm H. Lenz AG from Switzerland.