5-Axis Machining: A Way of Life
Eifel has built an arsenal of top-of-the-line 5-axis CNC machining centers that include a Hermle C40U, a Hermle C30U, and a DMG Mori DMU100P.
Successful zero stock machining relies on a strategic synergy arising from a coordinated implementation of advances in four broad areas of manufacturing technology:
- Super-rigid, super-accurate machine tools for high-speed machining
- Workpiece fixturing that is flexible and highly repeatable
- Rigid holders for cutting tools with exceptionally accurate radius at the tip
- CAM software capable of producing tool paths for high-accuracy machining in the lights-out mode
At Eifel, zero stock machining became “a way of life” around 2005. A pair of Hermle 5-Axis VMCs represents Eifel’s main resources for zero stock machining. A Hermle model C40 was installed in 2008, and a slightly smaller model C30 was installed in 2011. The new machine has high-pressure through-the-spindle coolant delivery, a feature that has proven valuable for milling and drilling the latest generation of coated carbide cutters with coolant holes.
Otherwise, the machines are similar. Both feature a rotary table in a trunnion supported at both ends for the fourth and fifth axes.
The trunnion-style configuration is especially important at Eifel because 3+2 machining is the shop’s preferred mode. In this mode, the rotary axes are used to orient the workpiece so that cutting can be performed in three axes (X, Y, and Z).
The 3+2 machining is ideal for molds with small, deep pockets and numerous undercuts. One of the main benefits is being able to reach workpiece features with a shorter, more rigid cutting tool assembly. A shorter, stiffer tool enhances high-speed machining (HSM) techniques that are at the heart of the zero-stock machining concept. HSM involves taking light cuts at high feed rates with closely spaced stepovers.
A stiff, short tool will withstand higher feed rates without deflection, allowing us to achieve the optimum chip load at the optimum depth of cut, even for cutters under 1mm in diameter. This also helps the shop get the full productivity from the 18,000 RPM spindles on these machines.
CAM Programming Software: PowerMill from Autodesk
Eifel’s reliance on 3+2 machining has implications for CAM programming as well. For all zero-stock machining, the shop uses PowerMill from Autodesk. This software offers a variety of options for approaching the workpiece surface with the cutting tool, which is especially helpful when reaching into tight spaces at the bottom of a deep pocket.
The software also enables the visualization of the stock model. PowerMill displays material left behind by the operations performed with the previous cutter. This allows the programmer to choose “rest machining” options for the next smaller cutter to ensure that the cutter will not encounter unexpected material.
Finally, advanced collision detection provides another layer of protection in the 3+2 operations. Collision detection catches the oversights that might otherwise lead to broken tools or spindle nose crashes.
To say that zero-stock machining is a “lifestyle” for a mold shop is no exaggeration. Behind this lifestyle is a set of “philosophical principles” that Eifel believes are essential, and these principles fall into three categories that we identify as our triangle of service: People, Process and Technology.
Most importantly, this approach creates a shop environment in which a capable workforce can sense its empowerment and vitality. As a result, it’s the type of shop lifestyle that attracts a new generation of young talent to mold manufacturers. Ultimately, that is the renewal on which every future depends.
5-Axis Machining Advantages
- Virtually perfect mold surfaces bypass several steps that add to mold production lead times.
- Roughing, semi-finishing, and finishing operations can be performed on the mold in the hardened state.
- Time on the spotting press to verify core/cavity alignment is reduced to hours instead of days.
- Molds produced with zero-stock machining run longer and more efficiently.