FIELD OF THE INVENTION
The present invention relates to a universal adjustable device
for root and shroud milling of steam turbine blades on CNC
horizontal machining center.
BACKGROUND OF THE INVENTION:
Steam turbine blades for turbines of various ratings vary in
physical aspects such as shape, sizes etc. depending upon the
application (HP/IP/LP). Steam turbine blade is a very precise
and critical component of Steam turbine system. Each stage
of steam turbine blades which are fitted into the turbine
rotor has to be very precise dimension wise.
Root and shroud milling of steam turbine blades is carried
out by using two adjacent planes in the blade root and
shroud as well as the root slot to completely define the
position of the blade in the fixture on a horizontal milling
machine.
At present root and shroud milling is carried out by using
fixed pads at root and shroud to clamp the blade horizontally
in such a way that blade central axis remains parallel to the

machine fixture. In this system, different fixed pads are
required for each type of blade. Each fixed pad is of a
standard height and angle which has to be changed for
different blades and this leads to a large inventory, longer
cycle time for procuring/manufacturing of these pads and
increased setting time, which in turn results in decrease in
productivity. In addition, maintaining and repairing of such a
large number of pads is difficult.
Where there is a requirement to manufacture wide range of
blades the frequent changing of pads becomes cumbersome,
time consuming and increases the possibility of error during
setting.
OBJECT OF THE INVENTION
It is therefore an object of the present invention to propose
a universal adjustable device for Root and shroud milling of
Steam turbine blades on CNC horizontal machining center
which eliminates the disadvantages of the previous existing
fixed pad system.
Another object of this invention is to reduce the inventory of
pads required for RS milling of steam turbine blades.
A still another object of this invention is to reduce the setting
time for RS milling of steam turbine blades.

Yet another objective of this invention is to improve the
productivity of RS milling of steam turbine blades.
A further object of this invention is to improve the quality of
steam turbine blades by eliminating rework & rejection.
SUMMARY OF THE INVENTION:
Accordingly, there is provided an adaptable adjustable
device for Root and shroud milling of Steam turbine blades
on CNC horizontal machining center, comprising :
(a) Base blocks (2 Nos.) (1)
(b) Resting Pads (2 Nos.) (2)
(c) Resting pad coupling bolts (4 Nos.) (3)
(d) Wedges (2 Nos.) (4)
(e) Height adjusting Bolts in base blocks (2 Nos.) (5)
(f) Height adjusting Bolt Housing (2 Nos.) (6)
(g) Shroud locator block (7)
(h) Shroud locator pad (8)
(i) Height adjusting bolt in shroud locator (1 No.) (9)

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: shows a 3D model of the device in the machine
explaining the entire Root and shroud milling setup.
Figure 2: explains the principle of operation of root and
shroud milling.
Figure 3: shows an assembly of base blocks to be used at
root and shroud of the blade.
Figure 4: shows the side view of the base block assembly of
figure 3.
Figure 5: shows the internal view of base block assembly
explaining the mechanism of its operation.
Figure 6 : a single base block of base block assembly of figure 3
Figure 7a shows the inner view of a blade resting pad of the
base block assembly of figure 3.
Figure 7b shows the outer view of blade resting pad of figure 3.

Figure 8 : shows a wedge (4) to be used inside the base block
assembly for facilitating movement of blade resting pads.
Figure 9 : shows an Height adjusting bolt housing .
Figure 10 : shows an assembly of height adjustable shroud
locator.
Figure 11: shows a shroud locator block .
Figure 12 : shows the assembly of shroud locator pad and
locking bolt.
Figure 13 : shows the mechanism of all three assemblies in
operation
Figure 14 shows the prior art device with fixed pads.
DETAILED DESCRIPTION OF THE INVENTION
The device used for root and shroud milling works on the
principle that the blade axis and the device axis must remain
aligned parallel to each other for carrying out the root and
shroud milling (as explained in figure 2).

To achieve this, present system uses pads of various heights
and shapes in accordance with shape and size of the blade
to be machined.
However, according to the invention, same pad
arrangement can be used with blades of all designs and
sizes. The blade rests on the resting pads (2) on root and
shroud. These resting pads (2) are housed in respective base
blocks (1) coupled with wedges (4) through coupling bolts
(3). The position of wedge (4) can be changed by height
adjusting bolt (5) thereby changing the height of blade
resting pads (2) at both root and shroud to accommodate
different size of blade at root and shroud. Now, in addition
to the above, an adjustable locator is also required at shroud
of the blade. This locator also comprises of a shroud locator
block (7) which houses a shroud locator pad (8) which can
again be adjusted through a height adjusting bolt (9). Now,
to lock the position of blade in longitudinal direction, a
standard root locator is used at the root slot which
completely defines the position of the blade with respect of
the machine.

Thus, by providing adjustable resting pads at base and
shroud locator position, this arrangement can be used to
machine blades of any design and size.
In the invented system, different rhomboid angles can also
be accommodated by using a set of Blade Resting pads (2),
one for each angle, which usually six in numbers.

WE CLAIM:
1. An universal device to standardize root and shroud milling
operation of steam turbine blade comprising :
at least two base blocks (1);
at least two resting Pads (2);
a plurality of resting pad coupling bolts (3);
at least two wedges (4);
a plurality of height adjusting Bolts (5) in the base
blocks;
a height adjusting Bolt Housing (6);
a shroud locator block (7);
a plurality of shroud locator pad (8); and
a height adjusting bolt (9) in the shroud locator;
wherein the resting pads housed in the base blocks are
coupled with wedges through the coupling bolts the position
of the wedges being changed by the height adjusting bolt to

allow corresponding change in the height of the resting pads
at both root and shroud, which makes it possible to
accommodate different size of blades.