FIELD OF INVENTION
The present invention relates to the development of a new fixture and tooling for fast
machining of baffle rings of 600/660 MW steam turbine run generator rotor. More
particularly the invention relates to the development of fixture for fast and accurate
machining of baffle rings
BACKGROUND OF THE INVENTION
As BHEL has started manufacturing; of 600 MW generator for the first time in India, the
technology for the tooling setup is in the evolution stage.
Therefore to meet the increased production rate, the prime objective is to reduce the
cycle time of manufacturing.
To increase the production, it is essential to control and reduce the machining time of
baffle ring which is on critical path.
On analyzing the total time, considerable time was consumed during the manufacturing
of baffle rings thus having direct bearing on total production time. Average
manufacturing time cycle of baffle ring before invention was 26 days.
Crux of the problem is that in case of both 600 & 660 MW rating rotors, the machining
of baffle ring takes large time. Also as it is a new design, vertically and horizontally
machining and bore turning is difficult, which was a challenge. Also this will release
horizontal and vertical boring machine for other jobs for longer periods.
Turbo generator converts mechanical energy into electrical energy and has two main
parts:
1. TG Stator
2. TG Rotor

In between the air gap of stator and rotor, Baffle ring assembled to monitor the flow of
the cooling gas hydrogen /air. The baffle ring are assembled on the insert cover near
rotor blades.
Baffle ring is a special metal forging. Forging is the operation by which a job (segment)
is made followed by different machining operations at various angles and faces and
then such six similar jobs (segment) are joined together end to end (Fig. 2) to form a
complete baffle ring.
Thus, after the receipt of forging, following operations are carried out on the forged
parts to convert it into a finished job (segment):
- Marking of forging taking rough references
- Milling of the face of the forging by keeping it horizontal by matching the rough
surface on machine bed.
- Vertical milling at 60 degree angle by placing it on rotary table of horizontal boring
machine.
- Checking of dimensions by assembling all six segments and checking of ID. Re-milling
with revised markings
- Marking for drilling of holes on one side
- Drilling on the horizontal boring machine. On all segments on one side.
- Marking of holes on other side by matching with other segment holes.
- Rough turning of ID after joining of all six segments.
- Spot facing and pinning holes. Rejoining after de-burring
- Final diameter making on vertical boring machine.

- Groove cutting for blade fitting in three rows.
Earlier the received forging was directly milled horizontally without any fixture and then
the segments were to be joined assuming horizontal milling as the base. Thus much of
the time was consumed in matching the six segments as at least 3 times rework was
required because of hit and trial method used earlier.
Problems in prior art:
- Improper marking of forgings because the edges of the forging were taken as the
base for marking.
- Improper joining of segments due to lack to perpendicularity after vertical milling.

1. Carrying art detailed analysis as per root cause analysis.
2. Designing and developing a customized special fixture suitable for horizontal and
vertical milling segments.
3. Developing accordingly a drawing for the fixture for machining of baffle ring
segments.
OBJECTS OF THE INVENTION
1. The object of the present invention is to design & develop a fixture for machining
of 600/660 MW generator baffle rings.
2. Another object of the invention is to design & develop a fixture for machining of
600/660 MW generator baffle rings so as to establish a technology which can
reduce the repetitive work in manufacturing the baffle ring.
3. A still another object of the invention is to design & develop a fixture for
machining of 600/660 MW generator baffle rings which reduces the total
manufacturing time.

4. A further object of the invention is to design & develop a fixture for machining of
600/660 MW generator baffle rings which is versatile and can be used in both
kinds of machines i.e. conventional as well as CNC machines.
To overcome the problem, the following methodology was envisaged.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 Process chart for manufacturing a baffle ring as per the prior art
Fig 2 Six segments joined end to end to form a baffle ring
Fig 2A Individual segment
Fig 3 Complete fixture in actual as per photographic views
Fig 4 Complete fixture with all constituent items 1 to 5
Fig 5 Item 1 (Rectangular base plate)
Fig 6A Item 2 (Rectangular Pad):
Fig 6B Three Rectangular Pads aligned at 60° (between the extreme pads) to
support a segment for performing vertical milling operation.
SUMMARY OF THE INVENTION
The present invention, i.e., fixture for machining of 600/660 MW generator baffle
rings comprises the following items:
- Item 1: Rectangular Metallic plate as base of the fixture
- Item 2: Rectangular Pads (3 nos.) welded on the base of fixture

- Item 3: Dummy segment (2 nos.) welded on the base of fixture
- Item 4: Locking and axle pins (3 nos.)
- Item 5: Threaded hole (3 nos.)
Accordingly, the job is accurately machined by the use of above mentioned fixture
as per following steps (fig. 1)
DETAILED DESCRIPTION OF THE INVENTION
Step 1) Item 1 is a rectangular metallic plate which is kept on the machine bed. It
serves as the base of the fixture as items 2 and 3 are welded on this plate helping in
machining of the job while guiding/ locking/ handing arrangements are provided
through items 4 and 5 during manufacturing.
Step 2) Forging job (segment) is put over item 3 for Horizontal milling on surface 'B'
fig 2A such that outer diameter of the item 3 and inner diameter of the job matches
with each other. Item 3 and forging are then clamping by U shaped clamps and both
side threaded studs. Three studs are inserted in T-slot provided in machine bed for
proper clamping of the job. Thus item 3 and clamping arrangements serves for
facing and plane machining of the job such that its inner surface lying over item 3 is
perpendicular to all the adjacent faces.
Step 3) Since the outer diameter, inner diameter and angle of item 2 is in line with
the job requirements, thus, the horizontally milled job (segment) after step 2 is put
on item 2 for vertical milling on face A (fig 2A) at 60 degree angle after having
proper clamping arrangements; with help of item 5. This solves the problem of
mismatching of segments when joined end to end as in fig. 2 due to improper
milling while maintaining angle of 60 degree without fixture. The fixture developed

is such that it rotates so as to facilitate machining at required different angles and
thereby saving time in manual reorientation of the job.
Step 4) Item 4 are three holes for locking the fixture while performing horizontal
milling on face B (fig 2A) as in step 2 and rotating as well as locking for performing
step 3.
Step 5) Item 5 are three threaded hole for clamping of job during vertical milling as
in step 3.

WE CLAIM
1. A fixture for machining baffle rings of 600/660MW turbo generator rotor comprising:
a rectangular metallic plate (1) forming a base of the fixture;
a plurality of dummy segments (3) welded on the base (1) for resting of baffle ring
segments (8) on the curved surface during horizontal milling;
a plurality of rectangular pads (2) welded on the base plate (1) used for holding the job
(8) during vertical milling;
a plurality of locking and axle pins (4) used for locating and locking the job as welfas
rotating while performing vertical milling;
a plurality of threaded hole (5) on the base plate (1) for clamping the job in fixture
during vertical milling of job.
2. The fixture as claimed in claim 1 is made of Mild steel plate.
3. The fixture as claimed in claim 1 wherein the item (3) are having curved surface in
upward direction which matches the curvature of baffle ring segment.
4. The fixture as claimed in claim 3 wherein the outer diameter of item (3) is same as
inner diameter of baffle ring segment (7).
5. The fixture as claimed in claim 4 wherein the rectangular pad (2) are having curved
slots which matches the curvature of baffle ring segment for proper gripping.
6. The fixture as claimed in claim 1, wherein the included angle between the two outer
rectangular pads (2) is 60°.
7. The fixture as claimed in claim 5 wherein the central rectangular pad (2) is used for
resting of job.

8. A method of performing horizontal and vertical milling of baffle ring (8) in the fixture
as claimed in claim 1 comprising:
holding the baffle ring segment individually on the surface of dummy segment (item 3)
such that the inner curved surface of the forged baffle ring (8) rests on the item (3)
and clamping the job with the base plate (1) on the machine table with the help of u-
shape clamp and both side threaded studs by inserting in the T-slot provided in the
machine rotary table;
performing facing and plane machining of the job for horizontal milling such that the
inner surface lying over item (3) is perpendicular to all the adjacent faces;
releasing the job by unclamping the U- clamp and mounting the baffle ring segment on
rectangular pads (item no. 2) such that the job fits into curved slot of pad (3) in upright
position wherein locking and axle pins (item 4) are used for rotating as well as locking
and threaded holes (item 5) are used for clamping the job during vertical milling.

ABSTRACT

A fixture for machining baffle rings of 600/660MW turbo generator rotor comprising a
rectangular metallic plate (1) forming a base of the fixture; a plurality of dummy
segments (3) welded on the base (1) for resting of baffle ring segments (8) on the
curved surface during horizontal milling; a plurality of rectangular pads (2) welded on
the base plate (1) used for holding the job (8) during vertical milling; a plurality of
locking and axle pins (4) used for locating and locking the job as well as rotating while
performing vertical milling; a plurality of threaded hole (5) on the base plate (1) for
clamping the job in fixture during vertical milling of job.