Most people who work with machining software often think in terms of wing spars, aerospace blisks, and auto subassemblies.
Once in a while, though, there's the unique request--say, programming to make a replica of the head of the Roman Emperor Constantine, considered the ancient empire's first Christian ruler.
In one of its largest and most unusual projects to date, Germany's Delcam GmbH developed programs to machine the giant replica. The 2 1/2m head was needed for an exhibition in Trier, Germany, after it was determined that the original pieces were too heavy and too delicate to be shipped from Rome.
Delcam engineers started the project with a STL file created by ArcTron 3D, using a combination of laser scanning and structured light scanning. The size and complexity of the file had already defeated several other CAD/CAM companies, but it could be processed using PowerMILL, one of very few CAM systems developed from day one to be able to machine STL files.
The next problem was the material to be used--a 25-ton block of marble.
"Marble was completely new territory for us," admits Delcam's sales manager Ferdi Hoischen. "We had absolutely no data on milling tools, cutting values, or suitable processing strategies for this material. Following intensive research on the tools and after comprehensive tests of various machining strategies in cooperation with EEW Maschinenbau GmbH in Kiel, we were finally able to start the programming of the Emperor's bust."
A further challenge came because CAM specialist Ingo Busse could not be present at EEW for all the time needed for the NC programming.
"I had to undertake much of the programming using geometry based on the residual material model in PowerMILL," says Busse. "I had to be able to rely completely on the accuracy of the roughing programs created by PowerMILL when programming the finishing tool paths."
The task was made even more difficult by the fact that five-axis machining had to be used for parts of the bust.
Overall, a total of 230 NC programs were produced in this way. When they were run by EEW, PowerMILL fully justified the confidence placed in the software's ability to calculate the residual material model and to undertake collision checking of the milling machine.
The close cooperation between Delcam and EEW was largely responsible for the successful completion of the project.
"Only with an expert team of top-quality software and the...