Sandvik Coromant Heat resistant super alloys - Manual (Page 12)

10
ISM – Intermediate stage machining – 0.5 to 5 mm depth of cut
At this stage the material is mainly in the
final hard/aged condition, (the hardness is
typically 36 to 46 HRC) having undergone
some form of heat treatment after FSM.
The ISM process involves profiling of the
component with varying depths of cut at
moderate tolerances, where productivity is
important but insert security is equally vital.
In this area, ceramics offer the best produc-
tivity where stability allows. Due to the com-
plex shape of the components, ISM may
involve a high degree of grooving/ recess-
ing and profiling, which can require a large
amount of special tool holders.
Material to be
removed
LSM – Last stage machining – 0.2 to 1 mm depth of cut
LSM represents the least amount of mate-
rial removal, but imposes the highest
demands on surface quality. For this critical
stage of production, the tools, tool paths
and cutting data are sometimes certified by
end producers of the aerospace engine.
These parts should be machined with
cemented carbide grades, to ensure a mini-
mal deformation zone and correct residual
stresses in the finished component sur-
face.
Material to be
removed
Factors which affect the residual stresses
most are:
Speed – not above 60 m/min for critical
parts.
Tool wear – maximum 0.2 mm. Use S05F
for best tool life.
Chip thickness (feed/radius combination)
– too low chip thickness (below 0.1 mm)
generates more heat and work-harden the
surface. For round inserts and large radius
increase the feed. (see page 19).