“Modeling Static and Dynamic of Milling Machine End Mill and Tool Holder”
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Date
2010-03
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Addis Ababa University
Abstract
An end mill is a tool used on a milling machine. A milling machine is a machine found in
a metal working shop that is used to remove material from a metal block to make it into a
finished part. And it is one of the tools used on the milling machine to make a particular
type of cut. Productivity and surface quality in milling processes have direct effects on
cost, production lead time and quality of machined parts.
Chatter vibrations in milling, which develop due to dynamic interactions between the
cutting tool and the workpiece, result in reduced productivity and part quality. Machine
tool chatter causes machining instability, surface roughness, and tool wear in metal
cutting processes. The excessive vibrations of the cutter and workpiece result in poor
surface finish, dimensional accuracy and may damage the workpiece and machine tool. In
addition to this cutting force produce deformations of the tool and this cause dimensional
and form errors on the workpiece.
In this research, generalized equations are presented which can be used for predicting
static and dynamic properties of the cutting tool. Milling forces are modeled for given
cutter geometry, cutting conditions and work material. The static and dynamic
characteristics of tool and tool holder can be obtained by using finite element analysis
(FEA); simplified equations are created to predict deflections of tools for given geometric
parameters and material properties and also for natural frequencies and mode shapes of
cutter dynamics. Finite Element Analysis (FEA) results are compared with the results
obtained from analytic equations, Comparison of natural frequencies between carbide and
HSS end mills. And a simple method to analytically calculate the approximate optimum
depths of cut and determine the corresponding spindle speeds by creating the stability
lobe diagram. Chatter vibration free spindle speeds and axial depth of cuts can be
selected from stability chats. The characteristics and limitations of the stability lobe
diagram are discussed. Case studies are also provided to illustrate the method and verify
the results.
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Mechanical Design Engineering