CERATIZIT's OptiLine 5-, 6- and 7-flute end mills provide variable helix and/or pitch geometries and are made with premium substrate, all of which suppress harmonics and reduce vibration.
Ceratizit's Dragonskin coating enables its tools to withstand the rigors of complex toolpaths in difficult workpiece materials.
Since its early adoption by aerospace companies in the 1980s, high-efficiency machining (HEM) and its subset strategies of helical interpolation and trochoidal milling continue to grow in acceptance and are now commonly used throughout manufacturing to improve efficiency, tool life, and machine performance. However, to adequately capitalize on the benefits of HEM, shops must pair the practice with advanced computer-aided manufacturing (CAM) software and cutting tools optimized for the application.
Defining HEM
HEM increases the axial depth of cut (ADOC) to nearly a tool's length and decreases the radial depth of cut (RDOC). Although more radial passes are required, those passes can be made at higher speeds and feeds over traditional milling. And where traditional milling uses only a small portion of the tool to do the cutting, HEM uses a tool's entire cutting edge on the radial pass, eliminating the concentration of stress and heat at the tool tip. Instead, both are spread across the cutting edge.
HEM's light radial engagement, combined with deep axial cuts at high feedrates, make the process suited for a variety of materials, particularly high-strength, low-machinability materials such as Inconel, titanium, and hardened steels.
Advantages of HEM include:
- Reduced heat generation: HEM minimizes thermal distortion, which is crucial when working with materials prone to work hardening.
- Consistent chip load: CAM systems optimize toolpaths to maintain even loading on each flute, reducing the risk of premature tool wear or breakage.
- Higher material removal rates: Because the process is less abusive on the tool, machines can run faster without sacrificing tool life or accuracy. Material removal rates are up to 100% greater than traditional machining, according to Ceratizit.
- Decreased tool deflection: By reducing the RDOC, stress on the tool is reduced, resulting in a more stable cutting process for better precision and surface finishes.
Taking a Different Path
Helical interpolation and trochoidal milling are essentially HEM processes that take different toolpaths. Where HEM is most commonly associated with linear toolpaths in a single plane, helical interpolation and trochoidal milling operate in the X, Y, and Z axes while moving in a circular or curved motion.
In traditional machining, creating holes larger than the tool diameter often requires specialized drills or boring tools. Helical (or circular) interpolation changed that by allowing the end mill to follow a circular path while ramping down in the Z-axis. This technique not only eliminates the need for dedicated drills, but also reduces lateral cutting forces, enabling high-precision holes in even the hardest materials. Where high production is not a concern, this cutting method is an excellent strategy for entering difficult to machine materials or irregularly shaped parts as an alternative to drilling. Using helical interpolation reduces the number of tools needed to perform an operation and eliminates instability caused by wandering drills during the pre-drill process on irregular parts.
Advantages of helical interpolation:
- Versatility: One tool can introduce a range of hole sizes, reducing the number of tools needed and lowering changeover times.
- Surface finish and roundness: When executed correctly, helical interpolation produces enhanced hole quality and tight roundness tolerances, making it suited for parts like bushings, fastener holes, or press fits.
- Tool pressure management: Because the cutting is gradual and distributed, the technique reduces tool pressure-a major advantage when machining thin-walled or high-stress parts.
Trochoidal Milling
Similar to helical interpolation, trochoidal milling-sometimes described as dynamic milling-is a strategy built around constant tool engagement. It involves moving the tool in a looping, trochoidal path, minimizing radial contact while maximizing axial depth. It is suited for deep slotting, pocketing, and side milling. This technique excels when machining hard, wear-resistant materials and is particularly relevant in applications where components must meet extreme durability requirements.
Advantages of trochoidal milling:
- Lower cutting forces: With reduced and consistent radial engagement, the cutting forces are more manageable, even in hardened materials.
- Improved chip evacuation: The cyclical toolpath allows chips to evacuate more easily, reducing the risk of recutting and heat buildup.
- Extended tool life: Consistent loading across all flutes reduces wear concentration on any single edge.
HEM Optimization with CAM Software
For maximum benefit, HEM requires robust CAM software to drive the complex toolpaths involved in trochoidal and helical interpolation. In many cases, legacy machine tools are not equipped with sufficiently dynamic software packages to take full advantage of the HEM's benefits, and manually coding for HEM is too difficult to be practical. This is especially true in applications where multiple aspects of HEM are needed to process a part. For example, it would be excessively time consuming to manually program a toolpath that required helical interpolation on entry, transitioning to a trochoidal pocket maneuver then milling around the circumference of a part. With the proper CAM software, however, the application could be programmed easily by an operator with little to no coding experience.
The benefits of CAM are only fully realized, however, when the cutting tool can withstand the increased demands being placed on it. In fact, the capabilities of current CAM software often drive new tool designs. Manufacturers are increasingly turning to toolmakers like CERATIZIT, for example, whose designs are aligned with software-driven strategies.
CERATIZIT designs its tools to meet the requirements of current CAM software. A strong, solid substrate combined with the proper geometry and micro geometry on the cutting edge and the company's Dragonskin coating help ensure its tools can withstand the rigors of complex toolpaths in difficult materials. Additionally, CERATIZIT tool engineers incorporate chip splitter designs into their tools to counter HEM's tendency to create bird nests of long, stringy chips. If the machine is not consistently stopped for cleaning, the chips create havoc in the machining process, including spindle damage, inefficient machining and inferior surface finishes.
Ultimately, poor chip evacuation, excessive wear, or unstable geometry negate any gains programmed into the HEM toolpath.
Choose the Right Tool
Given the large chip loads HEM generates, manufacturers and toolmakers are increasingly moving to tools with heavier core diameters and more cutting teeth and flutes. Shops can consider a wide flute range for better chip evacuation and improved surface finishes under the light, high-speed passes of HEM.
To suppress harmonics and reduce vibration when applying a HEM strategy, CERATIZIT's OptiLine 5-, 6- and 7-flute end mills provide variable helix and/or pitch geometries and are made with premium substrate. OptiLine end mills are protected by multiple nanometer-scale layers of Dragonskin coating to provide thermal and shock resistant capabilities required to counter fluctuating cutting and cooling intervals.
For helical interpolation, the OptiLine five-flute's constant helix and variable pitch make it suited for helical interpolation. Further, to avoid costly rework, the tool's coating lowers friction and improves heat resistance, allowing repeatability.
Finally, tools used for trochoidal milling must be rigid and capable of smooth chip evacuation. In addition, since it is a milling technique favored for hard-to-machine materials, OptiLine 4- and 6-flute end mills provide geometries that support consistent radial engagement while minimizing tool deflection, which is a must for achieving precision durability and tolerances required of critical components.
More manufacturers are implementing HEM for its versatility and efficiency. Its popularity is projected to expand as CAM software and machine tool capabilities advance and improve. To maximize the benefits of HEM, helical interpolation, and trochoidal milling, manufacturers must ensure their machining centers are integrated with advanced CAM software as well as equipped with tools specifically engineered to meet the demands of the advanced strategies.
Authored by Scott Walrath, Business Development Manager Solid Round Tools, CERATIZIT USA
For more information contact:
CERATIZIT USA, LLC
2050 Mitchell Blvd.
Schaumburg, IL 60193
800-783-2280
www.cuttingtools.ceratizit.com