FIELD OF INVENTION
The present invention relates to a fixture for making small fillers
adapted in the manufacturing of Rotor Coils of 600 MW turbo generator sets and
the method of making the same on a milling machine.
BACKGROUND OF THE INVENTION
With increase in power demand in the nation and competition from
foreign counterparts, the need for more efficient and higher rating Power
equipment was felt. This led to development of 600MW sets by BHEL to meet
this requirement.
The 600MW sets manufactured by BHEL uses supercritical
technology which is highly fuel efficient and clean on the environment.
Turbo generator rotor is an important part of the TG-ST set where
• the field for electricity generation is produced. It consists of an arrangement of
copper conductors formed into 7 sets of coils (A,B,C, to G). There are 2 poles in
rotor, 7 coils in each pole (coil no. A, B, C, D, E, F & G). One coil is made of 2
half coils. There are 28 conductors in each coil for A coil to G coil. Thus a total
196 nos. conductors is used.
In the turbo generator set large currents flow through the rotor in
the range of 4000 Amps. The heat generated is cooled by Axial cooling of the
rotor by allowing hydrogen to pass through axial slots cut in the rotor.
To maintain the flow all over the rotor, slots are to be cocked at
certain places for uniformity and meeting design requirement. Fillers of three
different sizes are used for this purpose which is to be manufactured through
milling of one piece at a time. Almost 2066 nos. fillers are used in each set which
required a lot of time for milling one by one. Fillers are made from copper rods.
Hence there exists a need to develop a fixture that can reduce time
for milling.
The primary object of the invention was to reduce the cycle time
required for milling of Small Fillers used in the Cocking of the Gas slots and radial
cooling slots in 600 MW set turbo generator.
Secondly, no proper process for milling of small fillers of definite
sizes was there which called for standardization of the process by making a
fixture.
Thirdly, quality of the fillers manufactured was not so good and
were frequently rejected.
The process for making fillers of required profile was complicated
which required highly skilled manpower for manufacturing.
Lastly, fillers of different sizes are required to be manufactured
separately. The fixture will help in multiple jobs processing in a single operation.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a fixture for
making small fillers adapted in the manufacturing of Rotor Coils of 600 MW turbo
generator sets and the method of making the same which is capable of making
4/5 fillers at a time.
Another object of the invention is to propose a fixture for making
small fillers adapted in the manufacturing of Rotor Coils of 600 MW turbo
generator sets and the method of making the same which is capable of
producing fillers of correct size avoiding rejection.
A still another object of the invention is to propose a fixture for
making small fillers adapted in the manufacturing of Rotor Coils of 600 MW turbo
generator sets and the method of making the same which is able of produce
multiple size of fillers in a single operation thus saving time and manpower.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig. 1A and 1B - Shows the fixture according to the invention.
Fig.2 - Shows a spacer sleeve of 11 mm to be used in the arbor of the
milling machine according to invention.
Fig.3 - Shows a spacer sleeve of 24 mm to be used in the arbor of the
milling machine according to invention
Fig.4 - Shows the parallel plate used in the fixture
Fig.5 - Shows the locking plate used in the fixture
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The fixture according to the invention for cutting of fillers on a
milling machine consists of three assemblies as shown in fig. 1 which are (I)
main fixture with plurality of slots (1), (II) two plates (2) fixed to the fixture (III)
the locking plate (3). Both parts 1 and 2 are mounted on the machine vice. The
jaws of the machine vice are first dismantled and replaced with new invented
fixture. The fixture is clamped to the sides through screws of dia. 10 mm (9).
The raw material, called filler rod (10) is mounted in the groove of the fixture.
The fixture (1) guides the raw material in place and guides the slitting saw cutter
for cutting 5 Nos. of fillers of three different lengths (11, 24 and 74 mm) at a
time. The fixture block has 6 slots (8). The centre distance of first two slots, 2nd
and 3rd slots and 3rd and 4th slots are 11 mm plus half of the width of the cutter
say y, while centre distance of 4th and 5th slot is 24 mm and that of between 5th
and 6th slot is 74 mm plus half of the width of the cutter say y. It means the
slitting saw cutter will produce 4 nos 11 mm / 2 no. of 24 mm and 1 no. of 74
mm filler at a time in a single operation. For this, spacer sleeves (4 and 5 of fig.
2 and fig. 3) of 3 Nos. of 11mm, 2 no. of 24 mm are mounted in the arbor
between the cutters. There will be 6 nos. slitting cutters to produce 5 Nos. of
filler. X1, X2, X3, X4 , X5, X6 are the centre lines of the cutters. The sleeves also
ensure that the cutters do not move axially from their position so that correct
size of filler of 11 mm, 24 mm and 74 mm length are produced.
Fig. 1 shows the diagrammatic representation of part 1,2 and 3.
Part 1 and 2 are both mounted on the machine vice. The jaws of the machine
-vice are first dismantled and replaced with New Invented fixture in both the
sides. These are clamped to the sides through screws of dia. 10mm (9). The
Fixture helps in properly keeping the Raw material in place and guides the
slitting saw for cutting 6 nos. fillers at a time.
Mounting of fixture
First the machine vice with fixture is adjusted on the horizontal
milling machine platform. The slitting screw is mounted on the plane arbor as per
required filler dimensions and separated with plane bush -3 nos. There are two
options for mounting.
Option 1: Setting cutter for 11 mm filler -4 Nos.
3 slitting saw cutter and 3 spacer sleeve 11 mm (4) mounted on plain Arbor
Option 2 : Setting cutter for 24 mm fillers- 2 nos. and 74 mm 1 no.
2 slitting saw cutter and two spacer sleeves of 24 mm (5) and one 74 mm
mounted on plane arbor.
Setting of Raw Material
' Filler Rod of square 10mm x 10mm x 1000mm is mounted in between the vice
with fixture and elevation given through parallel piece (6). The plate (6) is placed
beneath the copper filler rod for resting.
Cutting Operation
Slitting saw is adjusted for centering with fixture slots (8) and cutting done at
appropriate feed.
Earlier, only one filler was cut at a time using the same machine and time. With
the development of this new fixture multi job processing is done at a time using
the same machine and man hours. Also due to standardization of the process of
cutting of fillers the accuracy of cutting of copper rod has increased and wastage
of raw materials is also reduced.
Fig:-1A and 1B shows the fixture block which is made of mild steel.
It shows the fixture block (1), which has 4 slots (8) for 11mm or 2
slot for 24 mm and 1 slot for 74 mm. By provision of these slots it is easy to cut
the fillers of length 11 mm, 24 mm, and 74 mm. this fixture is attached to bench
vice in place of jaws. In this fixture filler rod is clamped, which after cutting
operation by multiple cutters produce desired lengths of fillers i.e. 11mm, 24mm,
74mm. First of 11 mm length square rod is cut in the first slop when distance
from the face of the locking plate (3) to the cutter is 11 mm.
Fig:-2 shows the spacer sleeve of 11 mm (4). This sleeve (4) is used to attach
on plain arbor for maintaining 11 mm distance between cutters, so that cutters
don't move from their positions during cutting operation and hence give good
finishing. These sleeves are made of mild steel, hardened and ground.
Fig:-3 shows the spacer sleeve of 24 mm. This sleeve 5 is used to attach on
plain arbor for maintaining 24 mm distance between cutters so that cutters don't
move from their positions during cutting operation and hence give good
finishing. This sleeve is made of mild steel, hardened and ground.
Fig:-4 shows the parallel plate (6) which is used to support the filler rod during
cutting operation. It is placed beneath the filler rod during clamping of filler rod
in vice. Due to this filler rod remain in correct position during cutting operation.
This plate is made of mild steel, hardened and ground.
Fig:-5 shows the locking plate (3) which is used as a barrier for filler rod. It
maintains length of filler rod to be cut in the vice. It is a stopper plate placed on
one side of fixture block so that required length of filler rod can be maintained in
vice. This plate is also made of mild steel, hardened and ground.
Due to this fixture various arrangements for filler cutting can be obtained. In one
cutting operation we can cut 4nos of 11 mm / 2 no. of 24 mm filler and 1 no. of
74mm fillers.
WE CLAIM
1. A fixture for making small fillers adapted in the manufacturing of Rotor
Coils of 600 MW turbo generator sets comprising;
a block (1) having a plurality of slots (8) for accommodating the slitting
cutters mounted on the machine for cutting the filler rods (10);
Characterised in that,
a locking plate (3) fixed on one side of the block (1) and disposed as a
stopper plate for maintaining the required length of the filler rod wherein
a parallel plate (6) is disposed beneath the filler rod during clamping of
filler rod in vice.
2. The fixture block (1) as claimed in claim 1, wherein the block (1) is made
of mild steel.
3. The fixture (1) as claimed in claim 1, wherein the locking/stopper plate (3)
is made of mild steel, hardened and ground.
4. The fixture (1) as claimed in claim 1, wherein the parallel plate (6) is
made of mild steel, hardened and ground.
5. A method of making small fillers on a fixture claimed in claim 1
comprising;
dismantling the jaws of a machine vice to accommodate the fixture block
(1);
Putting the fixture (1) in the vice and clamping the fixture inside the vice
with screws;
disposing the parallel plate in the fixture to allow the filler rod to seat on it
properly during clamping and to remain in correct position during cutting;
arranging the fixture on the platform of the milling machine to
accommodate the cutters disposed on the arbor of the machine, wherein
the spacer sleeves (4,5) are disposed on the arbor maintaining a fixed
distance between the cutters to cut the required length of filler rods.

ABSTRACT

A fixture for making small fillers adapted in the manufacturing of Rotor Coils of
600 MW turbo generator sets consists of a block having a plurality of slots for
accommodating the slitting cutters mounted on the machine for cutting the filler
rods on one side of the block, a locking plate is fixed to act as a stopper plate for
maintaining the required length of the filler rod. A parallel plate is disposed
beneath the filler rod during clamping of the filler rod in a vice.