Page 40 - machining_titanium_05_2019

MILLING TITANIUM Fast Feed Milling Titanium

Fast feed milling (FF), also referred to as high feed milling (HFM), is usually associated
with productive rough machining steel and cast iron. However, this effective method of
rough milling may be successfully applied to manufacturing titanium components.

Rather than using a traditional high metal removal technique – milling with considerable depths
and widths of cut – FF proposes machining with similar widths of cut but with a much smaller
depth of cut. FF cutters feature small cutting edge angles that allow significant increasing in
feed per tooth fz and therefore feed speed Vf due to the effect of chip thinning (Fig. 19).

90˚
apmax
χ 1 χ 1
fz apmax fz1>>fz apmax
hmax=fz h1<<hmax h2=hmax

Fig. 19 Geometrical relations between feed per tooth, cutting edge angle and chip thickness

Another distinctive feature of fast feed milling is reducing the bending moment, which
an FF tool takes. The small cutting angle leads to minimizing the radial effect of the
cutting force and maximizing its axial influence. The bending moment depends on the
force acting on the tool perpendicular to its axis. This bending force is the resultant of
the radial and the tangential components of the cutting force, substantially decreasing
the bending moment. The axial force acts towards the spindle axis, i.e. the direction of
maximum machine tool rigidity. The result – improved milling stability, reduced vibration
and increased productivity. Decreasing the bending force is especially important in
machining titanium, due to the already mentioned “springiness” of the material.
The classical cutting edge of the FF tool is an arc or large diameter. Today, this
geometry mainly features solid carbide endmills and replaceable heads. The
cutting edge of the indexable tools is usually one or two chords of the arc.

ISCAR has a rich variety of FF tool families: indexable mills, SCEM and MULTI-MASTER cutters.
Indexable tools carry inserts that differ in type (one- and double sided), shape (trigon, quadrihedral,
hexagonal etc.) and size.
Table 24 provides general guidelines for choosing the most suitable indexable
family for fast feed milling titanium, from ISCAR’s standard product line.

A new birth of FF tools
Originally, FF tools were indexable cutters of relatively large nominal diameters. Advances in
multi-axis grinding machines enabled development of FF geometry in tools of solid design:
SCEM and replaceable heads of considerably less diameters. Further attempts to find a cost-
saving alternative to more accurate solid tools resulted in a small-size indexable solution.
For high feed milling titanium, ISCAR proposes the recently-introduced MICRO3FEED
– a family of multi-flute indexable FF cutters with a 10 mm minimum diameter.

38 ISCAR