FIELD OF INVENTION
The present invention relates to a new boring bar with supporting flange
and collars for back boring operation on Horizontal Boring machine in Rotors &
Casing of H.P, LP, L.P Steam turbine (Ratings - 200/250/500/600 MW). More
particularly, the invention relates to a new boring bar with clamping support
flange such that the said flange partially takes the load from the hydraulic
clamping of the cutting machine during back boring so that the cycle time can be
reduced, quality of the back boring can be improved with minimal rework in
cutting tool and machine.
BACKGROUND OF THE OPERATION
Rotor manufacturing undergoes various operations on the Production line
and one of the major activities during rotor manufacturing is carrying out
coupling holes machining on rotor.
One of the operations during the coupling holes machining process is back
boring on the turbine side and generator side of the rotor. Back boring is
required for machining the seats for clamping bolts/Nuts head.
These operations are being done on a horizontal boring machine (refer
Fig.l). Usually normal milling is carried out on such machines which result in
axial cutting force acting towards machine. Therefore such operations do not
affect the clamping arrangement of the machine as very less force is experienced
by the machine.
In back boring operation the process is to enlarge an existing drilled hole
by means of a boring tool (refer Fig. 7) and then boring on the "back" side of the
work piece (relative to the machine headstock) and it is done when we insert the
mandrel in the spindle of the machine and mandrel is clamped by the hydraulic
mechanism of the machine.

After clamping of Mandrel hydraulically, we insert the mandrel into already
drilled holes of the job. Then we mount the cutter on to the mandrel and we
start the boring by pulling the cutter toward machine. This pulling force is
generated by the hydraulic ram of the boring machine. These results in strong
opposing axial force directed away from the machine, thereby imparting heavy
cutting pressure over the hydraulic clamping arrangement for the mandrel
resulting in machine breakdown and hence, lower productivity.
Just to get an idea about the cutting forces during back boring operation,
the cutting forces acting on cutting tool (refer Fig. 7) are:
1. Axial Pull (Ft) : Acting away from the machine spindle
2. Feed force (Ff): Acting towards machine spindle
3. Radial force (Fr) : in vertical plane perpendicular to the feed direction
Now the Feed force which acts away from the machine spindle is to be
avoided because it will reduce the effect of hydraulic clamping of the machine. In
order to avoid this force to reach to the hydraulic clamping by which the mandrel
is clamped, a support flange (refer Fig.2) is developed and introduced before the
collar of the mandrel .Now the pressure/forces which were coming to the
clamping through mandrel are taken up by this support flange.
PROBLEM EXPERIENCED IN PRIOR ART
1) High Cycle time: Since large axial force was experienced by the
machine hydraulic clamping mechanism and this can results in possible damage
of hydraulic pipes, we had to restrict the cutting speed and feed to very low
value. This results in long cycle time and hence productivity decreases. Earlier,
average time taken by machine for Back boring operation per rotor came around
63.33 Hours.

2) Poor Quality: Since we did back boring operation on low rpm, it resulted in
poor surface finish and irregularities like scratch mark on the bored surface.
3) Frequent Machine Breakdown: As large axial forces were directly going
on to the hydraulic mechanism. So, if we run the machine on slightly high rpm,
clamping alarm will ring and it will shut down the machine resulting machine
breakdown.
4) High Operators fatigue: As cycle time for each rotor was very high due
to machine breakdown, the operator had to offset the machine breakdowns and
hence these factors results in high Operators fatigue.
5) Delayed Delivery to the Internal Customer: Due to high cycle time as
discussed above we were not able to meet delivery schedule and delivery to
internal customers used to get delayed.
Therefore, there was a need to develop a clamping arrangement which
take on to the heavy axial cutting force during back-boring process and imparts
very less cutting force on the existing hydraulic clamping arrangement of the
mandrel and thus overcoming the said problems in the existed machining
methodology.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved boring
arrangement with a boring bar having a supporting flange and collars for reverse
boring operation in Rotors and Casing of steam turbine which is capable of
reducing the machining time of back boring operation per rotor by 30 to 35%.

Another object of the invention is to propose an improved boring
arrangement with a boring bar having a supporting flange and collars for reverse
boring operation in Rotors and Casing of steam turbine which imparts very less
cutting pressure on the existing hydraulic clamping arrangement of the boring
bar/mandrel and thus prevents frequent machine breakdown.
A further object of the invention is to propose an improved boring
arrangement with a boring bar having a supporting flange and collars for reverse
boring operation in Rotors and Casing of steam turbine which is able to produce
high quality surface finish without any scratch on the bored surface.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 : Shows the boring machine where the boring bar/mandrel according
to the invention is used.
Fig. 2 : Shows the supporting clamping Flange used with the boring
mandrel in accordance with the invention.
Fig. 3 : Shows the orthographic view of boring arrangement with boring
bar (1) with supporting flange (4) and adapter/collar(6) as per the
invention.
Fig. 4 : Shows an isometric view of boring arrangement with boring
bar/mandrel (1), boring tool (2), supporting flange (4) and
adapter(6) as per the invention.
Fig. 5 : Shows a graph showing reduction in Average cycle time for back
boring operation.
Fig. 6 : Shows the cutting tool and the mandrel.
Fig. 7 : Shows the different forces acting on the job during machining
operation .
Fig. 8 : Photographic view of developed attachment.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The present invention relates to an improved boring arrangement. The
boring arrangement includes a boring bar/mandrel (1) having a new supporting
flange (4) with adapter/ collar(6) with boring tool suitable for reverse (back)
operation for manufacturing of Rotors and casing of H.P, LP, L.P Steam turbine
for 200/250/500/600 MW ratings on a horizontal boring machine. The
arrangement comprising following items:
i) Mandrel (1)
ii) New supporting flange (4)
iii) Plurality of collars provided on mandrel (6)
iv) Single point cutting tool (2)
v) Plurality of M 20 threaded hole
The inner diameter of the supporting flange matches the outer diameter
of the boring bar/mandrel. The supporting flange is introduced in the system for
supporting the boring bar as well as guiding it to reduce the axial force on to the
hydraulic clamping arrangement of the machine. Also it acts as bush bearing of a
cantilever boring bar and reduces its length of cantilever and the vibration of the
bar to almost zero.
As shown in fig.3 & 4, front end of the mandrel is inserted into the job (3)
without cutter then we assemble the required bore diameter cutting tool (2) over
the mandrel (1) and start the reverse boring operation. Back end of Mandrel is
inserted into this supporting flange (4) and then it goes into the spindle of the
machine to the machine head (8) where it is clamped hydraulically. The flanges
and spindle (7,1) are coupled together and are bolted (5) in the annular space

between them. Two collars (6) are provided on the mandrel out of which one
acts as the mechanical stop for the developed flange (4) and other as the
mechanical stop for the mandrel (1) for going further in the spindle.
During reverse/back boring, the spindle can move back and forward for
giving the feed motion to the cutter so as to perform the cutting operation like
back boring.
So, this supporting flange provides additional clamping and restricts the
axial force to reach the spindle and hydraulic clamping. This makes hydraulic
clamping of machine safe and secure from the axial forces as all the force are
taken by newly designed supporting flange. Therefore, the back/reverse boring
operation can be carried out with high R.P.M. and high feed which increases the
Productivity, save the time and improves the quality.
Hence, the developed Supporting Flange for back boring bar with adaptor
for back boring tool, eliminates the disadvantages of prior art.
Benefit Incurred:
Productivity: Cycle time has been reduced (refer Fig. 10) as with the
developed flange arrangement, machine can be operated at high R.P.M. and high
feed.
Average Time per Rotor without using Supporting Flange = 63.33Hours
Average Time per Rotor Using Supporting Flange = 42Hours
1. Quality : By carrying out the back boring operation on high R.P.M. and high
feed. Quality of the job has increased and problems like scratch on the job have
got totally eliminated.

2. Utility of the design: Since we are having 9 SKODA Boring machine in our
shop. This Supporting clamping flange can be used over all these machines.
Hence, advantages of this supporting flange will get manifold when it will be
used over other machines. This can be used plant wide.
3. Power Saving: With this design we can save 1066 Units of power per rotor.
Annual saving on Power consumption has been calculated around 1066 X 48 i.e.
51168 Units.

4. Safety: With the introduction of this supporting flange arrangement,
hydraulic mechanism experiences no axial forces. Therefore, problems like
Hydraulic clamping failure are not at all there. This makes machine safe to
operate. In addition to it, earlier due to clamping failure there was sudden
stoppage of machine and as a result cutter used to get damaged. Now it has
been eliminated.
5. Environment Aspects: The intensity of cutter sound is tremendously
reduced due to developed tool holder.
6. Health & Working Condition: Elimination of handling & reworking of
components has increased in safe working condition for men, machine &
material. High fatigue of the operator due to bed postures has been eliminated.
Handling and working of finished Rotor to other machine is eliminated.
This has reduced engagement of heavy crane, handling staff & also reduced
fatigue to the operator. Hence improved health & working condition.

GAINS:
1. Cycle time Reduction.
2. Improvement in quality.
3. Breakdown eliminated.
4. Power saving.
5. Strengthening of work center.
FINANCIAL SAVINGS:
Projected savings for a period of 12 months is 18.53 lacs of recurring
nature.

We Claim:
1. An improved boring arrangement with a boring bar having a supporting
flange and collars for reverse boring operation in Rotors and Casing of steam
turbine, the said arrangement is comprising of;
a boring bar (1);
a cutting tool (2) fixed on the boring bar (1) for performing reverse boring
operation;
a supporting flange (4);
two collars (6) provided on the boring bar/mandrel (1);
Characterized in that,
the supporting flange (4) being coupled to the spindle with bolts (5) is
provided for supporting and guiding the boring bar wherein the collars (6) are
disposed in the boring bar, one for acting as the mechanical stop for the flange
(4) and the other for acting as mechanical stop for that mandrel for going further
in the spindle wherein the reverse boring operation is carried out with high rpm
and high feed.
2. An arrangement as claimed in claim 1, wherein the outer dia of boring bar
matches with inner diameter of the flange.
3. An arrangement as claimed in claim 1, wherein the supporting flange is
made of alloy steel.
4. A method for reverse boring rotors and casing of steam turbine by the
arrangement claimed in claim 1, comprising;
inserting the back end of a boring bar (1) into a supporting flange (4) and
then into the spindle of the machine;
clamping the spindle in the machine head hydraulically;

fixing a supporting flange (4) with the spindle of the machine by bolts (5)
to guide and support the boring bar (1);
providing two collars (6) on the boring bar (1), one to act as a mechanical
stop for the flange (4) and the other to act as a mechanical stop for the boring
bar for going further in the spindle wherein a cutting tool (2) is disposed in the
front end of the boring bar to perform the reverse boring operation with high
rpm and high feed.

ABSTRACT

The present invention relates to an improved boring arrangement with a
boring bar (1) having a supporting flange (4) and collars (6). The boring bar is
inserted into the supporting flange and to the spindle of the machine. The
spindle is clamped to the machine head of the machine hydraulically. The
supporting flange is fixed to the spindle by bolts (5) and is disposed for
supporting and guiding the boring bar. The boring bar (1) is provided with two
collars (6), one for acting as a mechanical stop for the flange and the other as a
mechanical stop for the boring bar for going further in the spindle. A cutting tool
is disposed on the boring bar for machining reverse boring operation.