Page 32 - machining_titanium_05_2019

MILLING TITANIUM Example

A producer of jet engines plans to apply ISCAR’s 12 mm dia. 7 flute solid carbide endmills for
machining slots in titanium integrally bladed rotors (blisks) by trochoidal milling technique. The
titanium grade is Ti-6Al-4V, HRC 33-35. In milling slots, the width of cut is 1-1.2 mm, and the
depth of cut is variable. The selected endmills are made from cemented carbide IC902. The
machine tools intended for this operation are in good condition and clamping rotor rigidity is high.
Estimate cutting data for calculating cycle time.
According to equation (1) cutting speed Vc=Vo×Km×Ke×Ks.
Vo=75 m/min (246 sfm) from Table 8,
Km=1 (Table 9),
Ke=1.5 (Table 10),
Ks=1 (operational stability is sufficient),
Vc=75 ×1×1.5×1=112 (m/min) (370 sfm),
n=2971 rpm.
fz=fzo×Ks×Kf (equation (6)),
fzo=0.115 mm/tooth (0.0045 ipt) from
Table 16,
Kf=0.78 (Table 17),
fz=0.115×1×0.78=0.09 (mm/tooth) (.0035 ipt).

Feed speed Vf=0.015×7×2971=312 (mm/min) (12.3 ipm).

Example

Find cutting data for edging operation to be performed by a 63 mm (2.5 in) dia. extended flute
endmills with DIN69871 tapered shanks carrying T490 LNMT/LNHT 13... tangentially clamped
inserts. The endmill has 4 flutes (effective teeth). The workpiece material is titanium alloy “triple
5” VST 5553 (Ti-5Al-5Mo-5V-3Cr). The width of cut varies from 6 to 8 mm (0.236…0.315
in), the depth of cut is around 50 mm (2 in). The inserts are made from carbide grade IC882.
Cutting conditions are estimated as stable. Ratio ae/d is accepted as 0.12 in average.
Usually, edging relates to removing a skinned material. As a rule, the extended
flute tools with integral shank feature high overhang. Based on these
conditions, the type of machining is assumed as hard (Table 6).
Vo=38 m/min (125 sfm) (Table 7), Km=0.51 (Table 9), Ke=1.3 (Table 10), Ks=1.
Vc=38 ×0.51×1.3×1=25 (m/min) (83 sfm) (equation (1)),
N=126 rpm.
fzo≈0.2 mm/tooth (.0079 ipt) (Table 15, a value that lays between
data corresponding to ae/d=0.15 and ae/d=0.1).
fz=0.2×1=0.2 mm/tooth (.0079 ipt).
Vf=0.2×4×126=100.8 (mm/min) (3.97 ipm).
The average chip thickness and the maximum chip thickness are
0.07 mm and 0.13 mm correspondingly (Table 15).

30 ISCAR