FIELD OF INVENTION
The present invention relates to an improved process for milling of small
fillers for 600 MW turbo-generator Rotor Coils and the improved fixture for the same.
More particularly, the invention relates to a reduction of man power requirement, cycle
time and number of operation in the process and the increase in productivity.
BACKGROUND OF THE INVENTION
A:- 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.
600 MW rotor has two poles denoted by POLE 1 and POLE 2 respectively.
Each pole have 7 coils denoted by A, B, C, D, E, F and G respectively. Each coil is made
of two halves. For example A coil of first pole is made of AIR and AIL halves also called
left and right half. Similarly a coil of second pole is made of A2R and A2L coil halves.
Thus a rotor of 600 mw has 28 no. of rotor coil halves.
Also, a rotor coil half of 600MW is made of 7 conductor groups. Overhang
conductors are brazed on left rotor coil halves only while right coil halves no overhang
brazed according to drawing.

B:- USE OF SMALL FILLERS IN 600 MW TG.
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
(11MM, 24MM and 74MM) of 10.4 mm diameter are used for this purpose.
C:-NO. OF FILLER REQUIRED IN 600MW TG
According to drg. we found that cond. No 1 to 6 have 6 no. of fillers (3
filler front side and 3 filler back side) and cond. No.7 has only 2 fillers on both side.
(I) AMOUNT OF 11 MM FILLERS:-
a:- On straight conductor =[{3 filler X 6cond.)+l filler (on 7 no cond.)} X 2(both side)]
X 28 halves = 1064 NO.
b:- On over hang of left halves:- (2 filler X 7 cond.) X 14 half =196 NO
(II)- Amount of 74 mm and 24 mm fillers:- 28X28=784NO (note:-each half
contains 14 no. 24 mm filler and 14 no. 74 mm fillers)
TOTAL NO OF FILLERS REQUIRED IN ONE ROTOR OF 600 MW=2044NO

DISADVANTAGES OF THE OLD PROCESS
In old process following working steps are required for completing a filler for
use:-
• Cutting of filler from filler bar
• Deburring of cutting edge of filler
• Slotting of filler
4 types of fixture are used. They are,
> Fixture for cutting 11mm, 24mm and 74mm fillers
> Fixture for slotting 11mm fillers (11X11.4X10.4) mm
> Fixture for slotting 24mm fillers (24X11.4X10.4) mm
> Fixture for slotting 74mm fillers (74X11.4X10.4) mm
Cutter setting is changed 3 times for filler cutting:-
♦ For 11mm filler
♦ For 24mm filler
♦ For 74 mm filler
In this process only 2 filler can be slotted at a time and two man power is
involved, one for running the machine and the other for deburring of filler.
Due to many no of operation and limit of no of fillers slotted at a time this
process consumes high manpower and large cycle time. Also this process was not able
to provide the requirement of fillers timely which created hold up of manufacturing of
rotor coils.
Hence, there existed a need to develop a new process with improved
fixtures to make it more economical by reducing man power and cycle time.

OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved process
for milling of small fillers for 600MW turbo-generator Rotor Coils and the improved
fixture for the same which is capable of reducing the man power.
Another object of the invention is to propose an improved process for
milling of small fillers for 600MW turbo-generator Rotor Coils and the improved fixture
for the same which is able to reduce the cycle time of the process and hence the
productivity.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - Shows the required fillers of 11mm, 24mm and 74mm diameter.
Fig. 2 - Shows the location of fillers in places A, B and C used to cock the slots.
Fig. 3 - Shows the cutter setting with 8 Nos. of cutters for 11 mm filler.
Fig. 4 - Shows the cutter setting with 6 Nos. of cutters for 74 mm and 24 mm fillers.
Fig. 5 - Shows the new fixture with support, stopper and locking sleeves.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
In the new process, cutting of the fillers as per the required sizes (11mm,
24mm and 74 mm) and the slotting operation on each filler are combined in one
operation. This is shown in Fig. 3 and Fig. 4.-Also in the new process, deburring work is

not required and hence excluded from the process. In this process, final ready filler is
made at a time in a single operation thus saving manpower and cycle time.
The new process involves the following;
I) a new fixture to suit the requirement of cutting and slotting in one
operation;
II) selection of cutters.
In this process two cutters of different diameters are selected. According to
the requirement of fillers the difference of radius of these two cutters is to be minimum
7.4 mm. Hence, 100 mm (C1) and 125 mm dia (C2) cutters are used for the purpose.
The small dia cutter is used for slotting and big. dia cutter is used for parting the fillers.
In the new process, in a single operation, one 74 mm and two 24 mm
fillers are produced while four number of 11 mm filler are produced in a different set
up. These are shown in fig. 4 and fig.3 respectively.
Locking sleeves (bushings) of 4mm, 10mm and 11mm thickness are used
on the milling machine arbor for separating the cutters during setting of the cutters on
the machine. 4mm thickness bushing (A) for 11mm fillers whereas 10mm (B) and
11mm (D) thickness bushings are used for 74mm and 24mm fillers.
The process requires a special fixture. The fixture (F) as shown in fig. 5 is
for cutting and slotting of fillers in a single set up and machining. The fixture (1)
consists of three assemblies as mentioned below.
i) slotted jaw (left and right part) (1)
ii) support plate (2)
iii) stopper (3)

The locking sleeve (bush) is used on the arbor of the milling machine for
setting the cutters as per requirement of machining the fillers.
Slotted left and right jaws of invented fixture 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 alien screws of dia.
10mm.
The Fixture helps in properly keeping the Raw material in place and
guides the slit in saw for cutting and slotting 4 nos. 11mm fillers and 3 nos. of 74mm
and 24mm at a time.
Mounting of fixture:-
First the machine vice with fixture is adjusted on the horizontal milling
machine platform. The slit in screw is mounted on the plane arbor as per required filler
dimensions and separated with plane bush.
Option 1: Setting cutter for 11 mm filler - 4 nos.
4 slitting saw cutter 100mm dia., 4 slitting cutter 125mm dia. And 7
spacer sleeve 4mm thickness mounted on plain Arbor according to cutter setting
diagram.
Option 2: Setting cutter for 24mm fillers - 2 nos. and 74mm 1 no.
3 slitting saw cutter 125 mm dia, 3 slitting saw cutter 100 mm dia., 3
spacer sleeve of 10mm thickness, 2 spacer sleeve of 11mm thickness mounted on plane
arbor according to cutter setting diagram.

Setting of Raw Material
Filler Rod of cross section 10.4mm x 11.4mm x I where I is 11mm or 24mm
or 74mm is mounted in between the vice with fixture and elevation given through
parallel support piece.
Cutting Operation:-
Slit in saw is adjusted for centering with fixture slots and cutting done at
appropriate feed.
Earlier, the two operation (i) cutting, (ii) slotting could not be completed
at a time. With the development of this new fixture both operation done at a time using
the same machine with reduced manpower and cycle time. Also due to standardization
of the process of cutting and slotting of fillers the accuracy of cutting and slotting of
copper rod has increased and wastage of raw materials is also reduced.

WE CLAIM
1. An improved process for milling of small fillers for 600 MW turbo-generator
Rotor Coils comprising;
dismantling the jaws of the machine vice;
mounting a fixture (F) on the machine vice in both sides;
clamping the fixture (F) to the sides
holding the raw material in the fixture (F);
setting the slitting saw cutters (1) to machine the slot and slitting cutters (2)
to part the pieces along with the bushes on the arbor of the machine;
adjusting the stopper on the fixture to guid the length of piece to be cut
wherein the fixture on the machine vice is adjusted as per the cutter setting
in the arbor to machine the slot and cutting off the pieces in a single
operation.
2. The process as claimed in claim 1, wherein bush of 4mm for 11mm filler and
bushes of 10mm and 11mm for 74 mm and 24mm fillers are disposed in the
arbor in two different settings of the cutters.
3. A process as claimed in claim 1 and 2, wherein 100mm diameter cutter is set
in the machine arbor for slotting and 125mm diameter cutter is set in the
machine arbor' for parting of fillers.
4. A process as claimed in claim 1 to 3, wherein 4 slitting saw cutter of 100 mm
diameter and 4 slitting cutter of 125mm. diameter and 7 numbers of
sleeves/bushes (A) of 4mm. thickness are set in the machine arbor to
produce 4 numbers of 11mm. filler in one time machining.

5. A process as claimed in claim 1 to 4, wherein 3 slitting saw cutter of 100 mm.
diameter and 3 slitting cutter of 125 mm. diameter and 3 sleeves/bushes B of
10 mm thickness, 2 sleeves/bushes D of 11 mm. thickness are mounted in
the arbor of the machine to produce 1 number of 74mm and 2 numbers of
24mm. fillers.
6. A fixture for the process claimed in claim 1 comprising;
slotted jaw (1) having left and right part;
at least one support (2) for supporting the slotted jaw (1); wherein
a stopper (3) is provided for guiding the cutting of the required length by the
cutter when the fixture is clamped in the machine vice and adjusted with the
cutters set in the machine arbor.

ABSTRACT

The invention relates to an improved process for milling of small fillers for
600 MW turbo-generator Rotor Coils and the improved fixtures for the same. The
process comprising dismantling the jaws of the machine vice to mount a fixture (F) on
the machine vice in both sides. The fixture (F) is clamped to the sides and holds the
raw material. Slitting saw cutters to machine the slot and slitting cutters to part the
pieces are set in the machine arbor along with the sleeves and the stopper is fixed on
the fixture to adjust the length of the piece to be cut wherein the fixture on the
machine vice is adjusted as per the cutter setting in the arbor to machine the slot and
cutting off the pieces in a single operation.