Investigation of cutting edge movement in finish milling with indexable end-mills

Abstract: This master thesis has been performed on and written at Sandvik Coromant in
Sandviken which is a division of Sandvik AB. Sandvik AB is an engineering
industry with focus on high technology and the companies turn over for 2004
were 7 billion USD. The business is located in 130 different countries and
has an estimated number of 38 000 employees all over the world.

This master thesis is a continuance of a previously conducted thesis made by
Petter Stenmark. The purpose of the this project were to investigate the
factors that affect the form error in finishing milling with insert mills
and present effective ways of decreasing these errors.

Seven different variables has been investigated in this thesis and these
are:
• Axial rake angle
• Feed per tooth
• Radius of cutting edge
• Young’s modulus
• Mass distribution
• Workpiece material
• Milling machines

A increase in axial rake angle has, through simulations, calculations and
experiments with solid mills, been verified to decrees the form error which
was one of the conclusion Stenmark had made. No conclusions could, however,
be made regarding the percentile reduction of the form error the axial rake
angle had.

The influence of the feed and the radius of the cutting edge showed to be
somewhat linked to each other. An increase of cutting feed did not
necessarily increase the normal force Fy that controls the magnitude of the
deflection to the presumed levels. This had a lot to do with the relation
between the edge radius and the chip thickness. If the edge radius were very
large would the divergens between a feed 0.1 and 0.3 mm not effect the form
error very much.

The next two variables, which are Young’s modulus and mass distribution, are
also linked to each other. Many prototype cutters in different material were
produced and experimented with so that different material related
calculations could be verified. The result form these experiments and
calculations were that the cutter shaft stiffens was secondary while the
mass location had larger importance on the form error.

Different materials have different machine ability. For tougher materials
larger cutting forces are required to cut a chip. The workpiece material
will because of this influence the form error.

The selection of milling machine is one of the most influential parameter
that governs the form error. Different machines have different dynamic
characteristics because of variation in bearing diameter and positions, mass
distribution in the spindle and so on and the variations in form error as a
result of these characteristics showed to be large.