Iscar Barrel cutter shapes a new milling trend

Editor: Steffen Donath

Advances in 5-axis machining and in CAM systems have significantly expanded the boundaries of barrel endmill applications.

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Iscar offers oval- and lens- shape endmills in diameter ranges of 8 - 16 mm and .312" - .500"
Iscar offers oval- and lens- shape endmills in diameter ranges of 8 - 16 mm and .312" - .500"
(Source: Iscar)

The design principle of a cutting edge as the segment of a large-diameter arc has been realized successfully in other types of milling cutter — the tools for high feed milling (HFM), also referred to as ‘fast feed’ (FF) milling. The concept provides a toroidal cutting geometry that ensures productive rough machining at extremely high feed rates due to a chip thinning effect. Unlike high feed milling tools, barrel endmills are intended not for roughing but for finish and semi-finish machining of 3D surfaces with low stock removal

Traditionally, ball-nose and toroidal cutters perform these machining operations. However, the large-diameter arc of the endmill cutting edge results in a substantial reduction of the cusp height generated between passes machined by a ball-nose or toroidal cutter. Another advantage of this type of cutting edge versus ball-nose and toroidal cutters is a significant increase in the distance between passes (a stepover or a stepdown, depending on the direction of a cutter displacement after every pass) - at least five times more without degradation of the surface finish parameters. This means that the number of passes and, subsequently, machining time can be noticeably reduced. Increasing the distance between passes also improves tool life and, therefore, diminishes tool cost per part.

The classical barrel shape in endmills has undergone some changes: Combining a ball-nose tip with peripheral large-arc cutting edges creates a multi-purpose ‘cutting oval’, which facilitates the use of a barrel endmill as a ball-nose milling tool.

In taper endmills, transforming the profile of a major cutting edge into a large-arc segment generates another cutting oval — a taper barrel. When compared with a common taper endmill, the taper barrel provides theoretically pinpoint contact between the major cutting edge and a machined surface that decreases accuracy errors and prevents recutting of a produced shape. The taper shape also contributes to reducing tool overhang.

The barrel endmills provide efficient tools for machining 3D surfaces. Nevertheless, for a long time the complexity of CNC programming for applying barrel endmills was a constraining factor in actively integrating these promising tools into the appropriate branches of the metalworking industry. The growing use of 5-axis machine tools and the latest progress in CAM software has changed the situation dramatically, however.

The future of barrel milling cutters

Barrel milling cutters are not in incredibly high demand by the metalworking industry; they are intended for very specific parts and effective application of such cutters requires highly engineered multi-axis machines and, especially important, leading-edge CAM systems. However, advanced workpiece manufacturing technologies, innovative machine tools, and a quantum leap in digitising of manufacturing will increase the needs for finishing complex surfaces with minimum machining stock. In this light, Iscar’s specialists estimate that barrel endmill consumption in the metalworking industry will increase exponentially, and cutting tool manufacturers should be shaping up to what may be a promising new industrial trend.