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Abstract High speed machining is a cost effective method of machining hardened steels for injection moulds. Recent works of the hardened steel
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machining industry suggests that substantial gains in productivity can be realised by better part programming and by better utilisation of
machine tools machining parameters. Dimensional precision and surface quality are the two key factors, which determine the quality of
manufactured parts. Machining parameters such us spindle speed, feed per tooth (mm/z), axial depth of cut and radial depth of cut deeply
affect both dimensional precision and surface quality. Therefore, an optimal selection of these manufacturing parameters is very important
in order to obtain high precision parts and to reduce the manual fit operations and the cost. This paper presents a mathematical modelling
of the surface roughness in high speed milling of hardened steels for injection moulds using design of experiments. These models will
allow us to determine in advance the surface quality of manufactured parts, obtained by high speed milling processes using the technique
of design of experiments (DOE) which allows us, by only performing a small number of experiments, to select the optimal machining
conditions so that meet manufacturing specifications.9347
© 2004 Elsevier B.V. All rights reserved.
Keywords: High speed machining; Mould and die manufacturing; Roughness; Precision
1. Introduction
Nowadays, the manufacturing of moulds and dies is more
and more exigent and competitive, presenting greater re-
quirements of dimensional precision and surface roughness
as well as a decrease in costs and manufacturing times [1].
With the introduction of new technologies such as high speed
machining, it is possible to achieve these requirements in an
efficient way. However, the complexity of a precise control
of such technologies, along with their continuous evolution,
make it difficult for the final user and the manufacturer of
moulds and dies to select the optimum operation conditions
in an repetitive and reliable way.
On the other hand, the great number of factors of influ-
ence, which is precise to take into account, makes it really
difficult to select the operation conditions properly. Among
these factors, one could mention: geometric specifications
for the parts, the geometry of the part before being ma-
chined, the material of the part, the machine-tool in work
conditions, the position of the part in the machine-tool, the
fixture system of the part, the method of machining, the
tool-holder and the fixture of the tool, the cutting tool, the
∗ Corresponding author.
E-mail address: cluis.perez@unavarra.es (C.J. Luis).
cutting conditions, the cutting fluid and the location of the
tool–part interaction.
With respect to the theoretical models to predict the sur-
face roughness in the high speed machining, these are really
limited, being empirical the majority of them and based in
experiments in laboratory conditions. In the present, there
are only a few mathematical relations between surface pa-
rameters and cutting conditions allowing us to predict sur-
face roughness in a correct and general form [2].
A basic model is that which provides the roughness by
means of the profile of the tool and the form of the move-
ments of the latter with respect to the part. Nevertheless,
the real values of the roughness present great differences
in relation to the theoretical ones as a consequence of the
movement errors, edge building-ups and changes in the tool
profile due to wear. In the same way, there are also some
other influential factors such as: chattering, deflections in
the tool, machining strategies, CNC parameters, the CAM
system used, etc. being difficult to model all these effects.