Challenge: Vibration and its consequences – slower production, poor surface finish and short tool life – often limit the performance of long milling tools. Solution: Additive manufacturing offers a new way to reduce the weight of a milling cutter by 80 percent for significantly better performance and up to 200 percent increased productivity, in combination with the Silent Tools™ damping technology.
The combination of complex component features with deep cavities in demanding materials is a typical milling challenge in aerospace and oil and gas applications. The long overhangs that these applications require often cause a bottleneck due to vibration problems and related performance issues.
Sandvik Additive Manufacturing, a new division established within the Sandvik Machining Solutions business area in 2017, has looked into new ways to tackle this challenge. The result, offered by Sandvik Coromant, is the new, lightweight CoroMill® 390 milling cutter combined with dampened Silent Tools™ holders.
The main goal was to decrease the weight of the cutter to improve the performance at long overhangs. Several alternatives were available, such as using a lighter material or machining holes in the tool body, but additive manufacturing turned out to offer the optimal solution in this case.
To maximize the damping effect in the adapter and reduce the vibrations as much as possible, the main consideration is to minimize the mass between the damping mechanism and the cutting edge, and to have the cutting edge as close to the damper as possible.
With the aid of additive manufacturing and the use of titanium, the new solution minimizes both the mass and the distance, thereby considerably increasing metal removal rates. The mill was topologically optimized, removing as much material as possible, and the material was also changed from tool steel into titanium, which has the advantage of combining low weight with strength.
The design principle for the cutter body was straightforward: the loads caused by the cutting action were analyzed and the cutter design was simply optimized for the highest possible strength.
A conventional CoroMill® 390 shoulder milling cutter in 50 mm diameter and with three size 11 inserts served as a starting point. Additive manufacturing reduced the weight by 80 percent. The metal removal capacity increased by up to 200 percent in face milling at large radial cutter engagements. The test material was SS 2541-03 medium-carbon low-alloy steel with a hardness of 290HB (EN 34CrNiMo6 / AISI 4340; MC code P2.5.Z.HT). Also, the length of the cutter body was reduced to decrease the distance between the vibration damper mechanism and the cutting edges.
The best performance and smoothest cutting action is achieved by combining the new cutter with Silent Tools™ damping technology. This internal damping system, consisting of a heavy mass supported by rubber spring elements, creates a counter-action to induced vibrations and dramatically reduces them.
Sandvik Coromant is constantly looking for the best available technology to optimize the performance for metal cutting applications. Additive manufacturing offers completely new and exciting opportunities to improve tool design and performance in specific conditions and applications.