Highly complex, from a standing start

Pump specialist GVT takes care of the maintenance of the power plant’s cooling water pumps. To ensure the long-term operation of older pumps, at least one of the rarely required spare parts is always kept in stock. When the last original spare part for the guide vane housing was used, a new one was needed for the shelf. GVT turned to the CASTFAST team to recast the component as a one-off casting using 3D sand printing technology. The patternless process is often the only economical method for complex one-off parts, but is also worthwhile for simpler cast parts in small series due to its speed and precision.

Old component, modern casting process

Marcel Tschillaev from CASTFAST, explains:

“The pump weighs over 10 tons and measures six meters in length. The guide vane housing is the largest cast part and has a rather complicated inner workings. Fifty years ago, highly complex sand molds with elaborate cores were used to manufacture the original part. Repeating this process today would not be economical for a single spare part. The complexity would be expensive for the customer and would mean a months-long model construction phase. With 3D sand printing, we can print the mold directly without adding complexity.

” The sheer size of the guide vane housing nevertheless presented the team with challenges. There were two problems to overcome: Firstly, although the 3D sand printer doesn’t need a wooden model to create the casting mold, it can’t do without everything. The print file needs 3D data for the component. However, there were not even any drawings available. Denis Germann from GVT explains: “To reconstruct drawings of the spare part, we work together with the measurement specialists from Sigma 3D. They also measure very large parts on site, using mobile 3D scanners and sophisticated software. This enabled us to send the 3D data directly to the CASTFAST team.”

A core with an increased level of difficulty

The second problem was the size of the core required to reproduce the internal geometry of the guide vane housing. Cores are normally simply printed in the 3D sand printer. However, this core, with a diameter of over one meter, exceeded the installation space of the sand printers at CASTFAST. It had to be printed externally in an even larger printer, securely packed in sand, shipped and carefully unpacked at the last minute in the foundry and installed in the mold. The casting took place in Mainz in December 2023. The next step was post-processing and coating to make the guide vane housing resistant to salt water. Finally, there was a trip to Bremen, to the special test bench for extra-large pumps. The new pump part is now ready for use and can step in at any time if the last original component currently installed can no longer do the job. Denis Germann concludes:

“Having to manufacture very old pump parts from scratch using reverse engineering – that doesn’t happen very often. We can usually still obtain them from the original manufacturer. If that’s not possible, the CASTFAST team’s 3D sand printing now provides us with a method that makes the process a lot easier for us. And the next time we need that specific spare part, we can order it at the touch of a button.”

Profile

Component size (raw casting): 1400x1400x1050 mm Component weight: 2500 kg Material: EN-GJL-250 Process: 3D sand printing: Shape: Quartz sand with furan resin binder Core: extra fine quartz sand with furan resin binder

Partners involved

• GVT (pump specialist)
• Sigma 3D (surveying, reverse engineering)
• CASTFAST(3D sand printing)
• Römheld & Moelle (cast)