FIELD OF INVENTION
The present invention relates to an improved process for internal shroud fillet
milling of bar type steam turbine blades of rhomboid shape with a new clamping
method.
BACKGROUND OF INVENTION
Before this invention there were issues related to repeatability of desired quality
in the process of internal shroud fillet milling of bar type blades. It was necessary
to develop a new process to eliminate the non conformance in internal shroud
fillet milling operation. Accuracy, quality S' and 'D' dimensions matching of fillet
was another criteria behind this invention. After this invention all issues related
to product quality have been addressed. Due to inherent problem (i.e. improper
location and reference of blade) in earlier process of fillet milling process it was
necessary to invent a new process of internal shroud milling. The process was
invented and in this process blades is properly located, properly referenced from
root in the fixture.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved process for
internal shroud fillet milling of bar type steam turbine blades of rhomboid shape

with a new clamping method which is capable of maintaining the accuracy of
important dimension of internal shroud fillet milling repetitively.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig.1 - Shows detailed description of improved process of internal shroud
fillet milling.
Fig.2 - Shows Drawing of Root end locating Plate.
Fig.3 - Shows Drawing of Cylinder mounting plate.
Fig.4 - Shows views of new developed hydraulic clamping assly.
Fig.5 - Shows fixture with new hydraulic clamping unit.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
This arrangement was having its inherent problems of improper location and
reference of blade. All sizes in blade drawing are given from root of blade. As
blade height (H) after perpendicular milling can be in +/-0.2mm so different in
any two blades can be of 0.04mm. As machining was carried out with reference
to shroud end of blade, variation in fillet sizes were observed. As reference was
shroud end of blade, blade height variation was resulting variation in fillet milling
size, hence nonconformance in operation. S and D dimensions of blades were
also having mismatch from blade to blade.

The disadvantages set forth above are eliminated by the present invention which
is new process of Internal Shroud Fillet Milling with new developed clamping
process. A new process to improve the quality of Internal Shroud Fillet milling so
that nonconformance should get reduced to zero. Similarly to improve the
Quality of fillet during Polishing operation with the developed new clamping
process. With the development of new clamping method Blades are properly held
and located with reference from root, during Internal Shroud Fillet Milling
operation.
Sketches are shown. In fig. (1) which is invented process for internal shroud fillet
milling of Bar type blade. In which newly developed clamping is also shown. A
support plate (2) for location at root is provided which resulted consistency of
dimensions in all blades.
In the invented process we use new arrangement of clamping system to press
clamp from shroud side. Due to this difference, the blade height from blade to
blade does not effect on fillet milling process. For the new clamping system (1),
another Hydraulic cylinder (8) is fitted to operate the clamp at the shroud end
(3). The old cylinder head (5) at the root end is removed. Two pads (6) are fixed
to accommodate the clamping bolts (7). A mounting plate (4) is fixed to the
cylinder head (8) for fixing it on the fixture (F).

WE CLAIM
1. An improved process for internal shroud fillet milling of bar type steam
turbine blades of rhomboid size with a new clamping method comprising:
removing old hydraulic cylinder (5) of prior art from the root end (9);
fixing a new hydraulic cylinder (8) at the shroud end (3);
fixing a mounting plate (4) with hydraulic cylinder (8);
fixing locating plate (2) for support at root end (9) for achieving
consistency of dimension in all brades; wherein
a clamping system (1) is disposed in the fixture (F) to clamp the hypoidal
shaped bar type steam turbine blades (10) with the aid of said hydraulic
cylinder (8) at the shroud end (3) by pressing the clamp on the said bar (10)
when root end (9) is made as reference to carryout the internal fillet milling
of bar type blades.
2. The improved process as claimed in claim 1, wherein the mounting plate (4)
is fixed to the hydraulic cylinder (8) for fixing it on the fixture.