FIELD OF INVENTION :
The present invention relates to a common locating pad for root and
shroud milling for right and left hand turbine blades on HMC machines. More
particularly the invention relates to common pad for root and shroud milling of
steam turbine blades application for both left and right hand blades of any tang
height greater than 9 mm.
BACKGROUND OF THE INVENTION :
BHEL have 6 nos. HMC machines for machining of steam turbine blades
for root & shroud milling operation for maintaining blade tang height for fixing
blades in rotor/casing and total blade height for completing the row in the form
of donut in rotor/casing for steam flow. So, this operation is very important for
turbine assembly fitting,
There are 2 main operations:-
1) Root milling: for maintaining tang height for fixing in rotor/casing.
2) Shroud milling: for maintaining blade total height for completing the row
in the form of donut in rotor/casing for steam flow.
In HMC machines, the fixture is designed in such way the one can make
blades of both hands by changing pads which are separate for left and right
hand blades. The changing of pads at the time of setting of new stage consumes
precious machine hours and is an obstacle in improving productivity in the area.

OBJECTS OF THE INVENTION :
Therefore, it is an object of the invention to propose a common locating
pad for root and shroud milling for right and left hand turbine blades on HMC
machines which is capable of root and shroud milling of right and left hand
turbine blades in the same setting.
Another object of the invention is to propose a common locating pad for
root and shroud milling for right and left hand turbine blades on HMC machines
which is capable of saving precious machine hours and thus improving
productivity.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS:
Fig. 1 : Shows locating pads for right hand blade as well as for left hand blades
separately used before improvement.
Fig.2 : Shows a different views of the same locating pad for right hand blades
and for left hand blades separately used before improvement.
Fig.3 : Shows a common locating pad for right and left hand blades with key step
for each of right and left hand blade machining according to the invention.
Fig. 4 : Shows Front and Top view of common locating pad with key and bolts
according to the invention.
Fig. 5 and 6 : Shows the tang height, root end surface, slot surface, suction
side and pressure side of the blades.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:
Before the invention, the system of machining right hand and left hand
geometry of blade needed the use of separate locating pads. The main reason

was that there was only one locating key mounted on the pad that could be used
only for one hand. The location of the key was fixed on the pad which limited its
use for a particular geometry of blade.
Now with the new invented common locating pad provision is made for
relocating the key at two positions depending upon left hand / right hand
geometry of the blade.
The common locating pad is to be used for both left and right hand blades
with two positions for the locating pin or key (B). The key (B) is for taking
reference for both left hand blades and right hand blades for setting them for
machining. The key (B) has threaded holes (D) for clamping with pad by bolts
(C). Two bolts (C) clamps the key (B) with Pad (A). In the key (B), there is a ball
(F) for blade reference. The key (B) is fixed to the key step (4) for right hand
blades machining and is fixed to the key step (H) for left hand blades machining
after 180 degree rotation of pad (A) on fixture. The fixture (not shown) is
disposed for holding the blades. The pad (A) is clamped to the fixture through
four holes (E). The common locating pad is used in root and shroud milling of
steam turbine blades of both left and right hand geometry and with any tang
height (T) greater than 9 mm. The common locating pad (A) is of L-shaped and
hardened and ground. As shown in Fig. 5 and Fig. 6 the tang height (T) is the
distance between the slot surface and root end surface and this tang height is to
be greater than 9mm to avoid any cut in fixture by a cutter.
The invention reduces the operator's manual labor during setting of new
stages for root and shroud milling operation. The invention increases productivity
of root and shroud milling operation by reducing the setting time.

WE CLAIM
1. A common locating pad for root and shroud milling for right and left hand
turbine blades on HMC machines comprising;
a L-shaped mild steel block having a ball stopper (F) for blade for guiding
and reference of the said blade;
a common key (B) for reference of both Left hand and Right hand blade
for setting the said blades for machining;
a plurality of threaded holes (D) on the key with two of said holes (Dl) for
right hand blade and two of said holes (D2) for left hand machining;
a plurality of bolts (C) for clamping the key (B) with the pad (A);
a plurality of holes (E) for clamping the pad (A) with fixture;
characterized in that,
a key step (G) on pad (A) is set for right hand blades machining wherein
another key step (H) is set on same pad (A) for left hand blades machining after
180 degree rotation of common Pad (A) on fixture.
2. A common locating pad as claimed in claim 1 is made of mild steel,
hardened and ground.

ABSTRACT

A L-shaped common locating pad (A) having a ball stopper (F) for blade
for guiding and reference of the said blade is disposed in the system for
machining both left hand and right hand blades without changing the locating
pad (A). The said pad (A) has a common key (B) for reference of both left hand
and right hand blades for setting them for machining. There are four threaded
holes (D) on the key (B), two (D1) of these holes (D) are for right hand and two
(D2) of these holes (D) are for left hand blade machining. The key (B) is
clamped to the pad (A) while the pad (A) is clamped to the fixture with bolts. A
key step (G) is set for right hand blades machining when another key step (H) is
set for left hand blades machining after 180 degree of common Pad (A) on
fixture.