Page 28 - machining_titanium_05_2019

MILLING TITANIUM Example

Find the feed for the example, which was discussed previously, if the range of usable feeds is
specified by Fig. 14 where fzmin=0.15 mm/tooth (.006 ipt) and fzmax=0.3 mm/tooth (.012 ipt).
apmax=4.6 mm (0.18 in) – the catalog data, ap/apmax=3.5/4.6=0.76.
According to Fig. 14, arithmetic average feed fzav may be considered
as the limiting value that corresponds to the above ratio.
Hence, following our rule of thumb, the starting feed, which was chosen
as the arithmetic average, will be 0.225 mm/tooth (.009 ipt).
In the shown example, applying the rule of thumb method gave a result that can be
accepted with some reserve. The received value is about 10% more than the starting
feed, which was found with the use of chip thickness calculations previously.

In finding starting feeds, empirical rules led to acceptable results in relatively
limited cases. However, calculating the feeds using required chip thickness is more
accurate and therefore preferable, particularly as this calculation is simple.

Starting feed fz can be determined by several ways. For rough estimates, setting fz as the
average value in the feed range from a catalog (a technical brochure), using rules of thumb such
as in the outlined above example or own experience may be quite enough. A more accurate
and less complicated method requires taking into consideration the chip thickness factor.

 In any case, maximum chip thickness hmax should not exceed maximum feed fzmax
specified for the considered inserts, solid carbide endmills or MULTI-MASTER heads

26 ISCAR