December 2023 | In keeping with the pre-Christmas season, OPEN MIND shows how an exact image of the world-famous nutcracker from the Ore Mountains is milled from aluminum. The example demonstrates a consistent digital process chain and efficient 5-axis machining with hyperMILL.
Together with EMUGE-FRANKEN, the CAD/CAM manufacturer OPEN MIND set itself a task: a 40 centimeter tall nutcracker should be digitally recreated as accurately as possible and milled from aluminum as efficiently as possible. The traditional Seiffener Volkskunst eG provided the wooden figure, which was handcrafted in around 150 steps and consisted of around thirty individual parts.
From scan to surface model
OPEN MIND turned to WESTCAM for the 3D scan of the Nutcracker. The Austrian partner is not only characterized by its hyperMILL expertise, but also has broad know-how in 3D measurement technology. The result of the scan was a high-resolution network model consisting of 1.2 million triangles. At OPEN MIND, a surface-based 3D model was created using the CAD/CAM solution hyperMILL and constructed completely parametrically. The latter has the advantage that subsequent production-related changes to the model can be made very easily. For production, the nutcracker model was divided into a top part, legs, arms and levers, which were pinned and glued together after completion.
Roughing and residual material processing
The production took place in FRANKEN’s Rückersdorf application center on a Hermle C32 in one clamping in a 5-axis and 5-axis simultaneous process. This meant that the surfaces could be processed consistently without segmentation. The opening cut for the large middle pocket of the upper body was achieved efficiently using 5-axis helical drilling, which not only enables particularly high material removal, but is also more gentle on tools than a helical plunging movement. Strategies from the high-performance hyperMILL MAXX Machining package were used for further roughing. The 5-axis residual material processing function then ensured that the roughing work was completed safely and efficiently. It makes programming easier by automatically finding a job. The new centric clamp EvoGrip from EMUGE was used for workpiece clamping. With its modular and slim system structure, secure clamping was guaranteed.
Finishing with circular segment milling cutter
During finishing, the “high-precision surface” mode was used, in which hyperMILL generates tool paths on the real CAD surfaces and not on a calculation model. For the large surfaces of the nutcracker, which are curved in two directions, it was possible to use the circular segment cutters from FRANKEN in various shapes: cone and teardrop shapes with cutting radii of 200 mm to 1,000 mm. The tools, also known as barrel cutters, allow particularly efficient production of high-quality surfaces despite large infeed or large line jumps. hyperMILL offers optimal control of the cutting area of circular segment milling cutters.
“With the nutcracker machining example, we had the problem that the component dimensions were actually too large for the machining space of the machine – a challenge that many manufacturers have already faced,” explains Michael Förster, Senior Product Marketing Manager at OPEN MIND Technologies AG. “What would normally require a lot of manual adjustments and individual simulations in order to avoid exceeding limit switches and find safe positions can be implemented quickly and reliably thanks to the virtual machine and NC code-based simulation.”
