Cutting Tools

More Aggressive, More Efficient

Not so long ago the speed and rigidity of the fourth and fifth axes in five-axis machines were significant limiting factors in how aggressively you could do full 5-axis machining. With today’s technology, however, much higher speeds and feeds can be accomplished and cutting tools should meet that challenge.

Being able to accurately feed and articulate the tool to workpiece so quickly enables much more efficient use of cutting tools. With simultaneous five-axis machining, you can maintain a constant tool vector to a 3D workpiece surface, which with a ball nose end mill should not be a vertical orientation. When feeding a ball mill vertical to a workpiece surface, you are essentially dragging the tip of the tool across that surface at zero rpm, which is hardly an efficient cutting process. By tilting the tool relative to the surface you utilize the effective flute length of the tool efficiently. This effectively increases the surface footage of the tool and can boost metal removal rates by as much as 40-50%, yet still generate better surface finishes and blends.

Cutting with the side of the tool

Likewise regular end mills can be used much more effectively by doing more cutting with the side of the tool, utilizing much of the flute length and not just cutting with the end of the tool. By applying cutting strategies such as high efficiency milling with larger depths of cut but smaller stepovers, roughing cycle times can be dramatically reduced over conventional machining.

Still another advantage of 5-axis machining is that you can use shorter cutting tools which reduces vibration enabling faster machining which generating better surface finishes. This ability is very useful in pocketing applications, such as milling honeycomb materials, and machining deep cavities in dies and molds.

Higher Feedrate

Tipping a ballnose endmill relative to the workpiece surface utilizes the effective flute length of the tool more efficiently.

Shorter Cutting Tools

Five-axis machining makes it possible to tip away from workpiece obstructions, thus enabling the use of shorter tools (and thereby decreasing load on the tool for longer tool life and reduced breakage).

NEW OPTIONS IN CUTTING TOOL PROFILES

Reducing Finishing Cycle Times

Five-axis machining has new cutting tool options that can also reduce finishing cycle times. When finish machining with ballnose endmills the main tradeoff has always been surface finish vs. cycle time. The need for smooth surface finish on many features often requires small diameter tools with tiny stepovers and traditionally consumes the majority of machining time. Larger diameter tools speed the process by naturally leaving wider and shallower surfaces between cusps. But the size of that cutting diameter is restricted by the nature of a cylindrical ballnose endmill, so extremely large cutting diameter tools are impractical or impossible. But thanks to the development of finishing tools that are shaped to present large profiled cutting areas with the side of the tool, rather than cutting from only with the tip, finishing cycle times can be substantially reduced while still generating better surface finishes and blends.

Circle Segment finishing tools, and similar tools such as barrel cutters, mitigate the limitations of ball mills in many applications. For example, this oval form cutter shown in the animation below has a large radius contour on the side of the tool that better fits a sloping workpiece surface, yet also has a small radius form at the point which can reach fine features such as the bottom edges of a pocket. This tool essentially combines an otherwise impossibly large diameter ball mill and small radius cutter in a single tool. It allows the slope to be cut with much larger stepdowns, yet still reduce cusp height for a better finish.

Thanks to the development of finishing tools that are shaped to present large profiled cutting areas with the side of the tool, finishing cycle times can be substantially reduced while still generating better surface finishes and blends.

The True Potential of Five-Axis Machining

The ability to generate cuts like this unlocks the true potential of a five-axis machining center to more efficiently generate smooth surface finishes on contoured forms. And these tools can also be used on 3-axis machines to more efficiently cut some sloped features such as the draft angle on a mold cavity.

Note that to use these tools your CAM system will need to support profile shaped cutters in order to create efficient toolpaths for five-axis machining. More CAM vendors now have features specifically designed for these tools including Mastercam, Open Mind Technologies and Siemens NX.

Circle Segment Cutting Tools

Circle Segment finishing tools, and similar tools such as barrel cutters, mitigate the limitations of ball mills in many applications.

Oval Shaped Cutter

In this animation the lines represent what the stepdown might be with a very large ballnose endmill. With the oval shaped cutter the surface can be machined with far fewer passes without increasing cusp height.

FIVE-AXIS MACHINING