Page 27 - machining_titanium_05_2019

Example

A planner of the process department that works under improving technology,
examines applying face mill IQ845 FSY D125-09-40-R07 carrying inserts
IQ845 SYHU 0704ADN-MM 808 to machining the top surface of a titanium component.
The catalog specifies the insert feed range as 0.15-0.3 mm/tooth (.006-.012 ipt) and the cutting MILLING TITANIUM
tool angle of the mill as 50°. The mill diameter is 125 mm (4.92 in).
At which feed should the mill be operated to ensure average chip thickness 0.12-0.15 mm
(.005-.006 ipt), if the depth of cut and the width of cut are 3.5 and 100 mm correspondingly?

With a use of equation (4a) the feed per tooth for ae=100 mm (4 in) will be
0.12×√125/100×1/sin 50° =0.18 (mm/tooth) (.007 ipt) and 0.15×√125/100×1/sin 50°=0.22
(mm/tooth) (.0087 ipt) for average chip thickness 0.12 and 0.15 mm correspondingly.

Hence, the programmed feed can be recommended of 0.2 mm/tooth (.008 ipt) with
a possible increase of up to 0.22 mm/tooth (.0087 ipt) for maximal productivity.

Note. In brief calculations that are made without taking chip thickness as an important factor
in setting correct cutting data, the feed per tooth is found in the following manner:
the required hm is (0.12+0.15)/2=0.135 (mm) (.0053 in) in average,
if consider the found value as hmax,
fz=hmax/sin 50°=0.135/ sin 50°=0.176≈0.18 (mm/tooth) (.007 ipt).
Alternatively, fz can be calculated, if 0.15 mm will be referred as hmax:
fz=0.15/sin 50°=0.195≈0.2 (mm/tooth) (.008 ipt).
Comparing these results with the values found previously shows that considering chip thickness
as a function of ae gives more precise data and ensures better productivity.
Another simplified way for setting the feed is simply to take the average value from a declared feed range as the
programmed data. In our example it will be
(0.15+0.3)/2=0.22 (mm/tooth) (.0087 ipt). In our case it is equal to fz, which was found for hm=0.15 mm (.006 in), if
ae=100 mm. However, if ae=80 mm (3.15 in),
for 0.15 mm (.006 in) chip thickness the feed should be already 0.24 mm/tooth
(.0094 ipt) that is approximately 10% more than the average value from the feed range.

Alternatively, instead of the feed values as a function of chip thickness, cutting tool producers
often provide the data about the recommended feeds organized as a chart, which specifies a
bounded area of application graphically (Fig. 14). The chart shows a range of possible feed from
minimum (fzmin) to a limiting value depending on a cutting data parameter (usually depth of width
of cut). If, as in Fig. 14, the parameter is the ratio of working depth of cut ap to maximum depth
of cut apmax, the starting feed in feed milling with ae=(0.6…0.8)×d may be simply found with the
use of a thumb rule: the feed is the maximum feed that corresponds to the ratio in the chart.

ap
apmax
1

3
4
1
2

1
4

fz
fzmin fzav fzmax
fzmin + fzmax
fzav =
2
Fig. 14 A typical field of feeds in face milling for ae=(0.6…0.8)×d

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