Modern Machine Shop

JAN 2018

Modern Machine Shop is focused on all aspects of metalworking technology - Providing the new product technologies; process solutions; supplier listings; business management; networking; and event information that companies need to be competitive.

Issue link:

Contents of this Issue


Page 62 of 163

End Mill Design Modern Machine Shop 61 indicated by the callout. The other ref lections alongside it are, respectively, the land and the cutting edge of the f lute normally found on a spiraled end mill. Mr. MacArthur says this added edge is just enough to keep the flute in contact with the workpiece until the next flute is engaged (the end mill has three tightly spiraled flutes for this reason). This highly polished edge minimizes frictional rubbing, so it creates virtually no heat and does not alter the workpiece surface. The constant contact prevents both the tool and the workpiece from "going their separate ways" in response to various forces inducing vibration. Thus, the tool and workpiece keep moving in unison to maintain synchronization regardless of the frequency of the vibration. Neither the tool nor the workpiece can "bounce away" from the other and fall into a different rate (frequency) of vibration, Mr. MacArthur says. This out-of-sync condition can occur instantly, and once it starts, the tool and workpiece begin bouncing off one another more forcefully with each passing of the f lutes across the workpiece. This worsening condition is detectable as chatter. "A machinist can hear the rise and fall in the sound of this chatter as the frequencies go in and out of phase," he says. Keeping vibration in sync to avoid negative The tool and workpiece keep moving in unison to maintain synchronization regardless of the frequency of the vibration. consequences does impose certain requirements on the machining process. According to Mr. MacArthur, the tool must be used with f lood or through-tool coolant to keep chips from interfering with the action of the Mirror Edge. The tool works best in aluminum, because the high spindle speeds used for cutting this material tend to create higher cutting frequencies than those encountered at lower spindle speeds when machining harder materials such as steel or tita- nium. (However, Mr. MacArthur notes that the Mirror Edge can be added to end mills customized The ability to cut thin walls that are straight, smooth and accurate is one of the benefits of using an end mill that damps vibration effectively. Got a basic question about chatter? Get answers here: BAD VIBES

Articles in this issue

Links on this page

Archives of this issue

view archives of Modern Machine Shop - JAN 2018