"Manufacturing companies that produce parts geared toward the energy sector present those of us in the cutting tool industry with some of the most challenging materials to machine," said an Iscar spokesperson. These challenging materials are met with a variety of tools designed for various part features to be machined (facing, shouldering, pocketing, etc.) and with a common goal of producing parts as productively as possible. When it comes to milling applications, there can be numerous ways to approach the production of a workpiece and the popularity of using speed (whether in terms of high speed or high feed) as an ally in productivity has become mainstream, especially in difficult to machine materials.
"During the past 15 years, fast feed milling has become one of the most popular roughing strategies used for milling applications," said a company spokesperson. Although the milling principles used to operate at faster feedrates remain the same (i.e., mathematical computations to increase feedrates when using shallow depths of cut), one of the biggest changes during this time has been the development of cutting tools designed specifically for fast feed milling.
To have a better understanding of the design enhancements, one needs to look no further than a copy mill (or button cutter), which can work well as a fast feed cutter so long as it does not encounter areas, such as a vertical wall, that change the angle of engagement on the insert from a very small value, for example, 10 to 20°, to 90° (or full engagement). With that said, the insert/cutter design of an effective fast feed cutter provides the following attributes: lead angle; back taper; reduced stress/force on screw; ramping capability.
Lead Angle and Back Taper
Having a shallow entry angle, along with back taper, is a key feature for a cutter designed specifically for fast feed milling. Most fast feed cutters will have somewhere between 9° and 15° lead/entry angle. This shallow entry angle will drastically reduce the thickness of the chip and, therefore, cutting recommendations will be much higher in terms of feed per tooth and overall inches per minute feedrates. As for back taper, this design characteristic helps to avoid the previously described scenario of engagement changing drastically when vertical and intersecting planes are encountered.
Force Reduction on Insert Screw
Another key design attribute of modern fast feed cutters (and probably most important) is the design of the insert and the pocket in the cutter body. One of the biggest weaknesses of an indexable milling cutter is the screw that is used to secure the insert into the pocket of the cutter body. Today's fast feed cutters incorporate designs, such as dovetail and tangential designs, that drastically reduce the stress/force on the screw. This leads to cutter bodies that last longer and which are capable of operating at drastically increased cutting parameters.
Ramping Capability
"The ability to ramp into material effectively is something that can be taken for granted," said the spokesperson. "Indeed, many indexable milling cutters do not perform typical ramping operations (i.e., linear ramping, helical interpolation) very well (some not at all) and this can be noticed in chipping and/or fracturing on the cutting edge of the inserts, as well as chip formations that have extremely jagged (or torn) edges. This can also be said for some indexable fast feed cutters, especially those designs that use square (ISO type) inserts. In order to ramp more effectively, the insert must be purpose built to handle the task. This is the case for modern fast feed tools."
For more information contact:
ISCAR Metals, Inc.
300 Westway Place
Arlington, TX 76018
817-258-3200
info@iscarmetals.com
www.iscarmetals.com