FIELD OF INVENTION
The present invention relates to a tip checking device for fir tree blades of
steam turbine on vertical machining center (VMC) machine and method of checking. More
particularly the invention relates to a blade tip checking device which checks the blade on
the same machine.
BACKGROUND OF THE INVENTION
After Tip copying operation of the fir-tree blades which are machined on the
VMC machine have to be checked on the vertical stand for dimension checking. If any
deviation in dimension of the blade height then again blade has to tip copying and send
back to check the dimension. After machining of two to three blades, the exact dimensions
are achieved.
Steam turbine blade is a very precise and critical component. At present, the
blades have to be checked at different points after various operations. First, checking of
blade center, after fir tree root machining on HMC machine. Second, profile and blade
height checking, after tip copying of blades, to maintain the final size of the blades.
During the tip checking of the blades, two to three blades have to be
machined in upper tolerance and then final size is maintained. During this operation, blade
setting time is increased. Again these blades have to be checked after twenty blades to
maintain the repeatability of machining.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a tip checking device for
fir tree blades of steam turbine on vertical machining center (VMC) machine which is

capable of providing blade checking facility on the same machine on which the blade is
machined eliminating the dependency on the vertical stand checking device.
Another object of the invention is to propose a tip checking device for fir tree
blades of steam turbine on vertical machining center (VMC) machine which is able to
provide accuracy and repeatability of the method of checking.
A further objective of the invention is to propose a tip checking device for fir
tree blades of steam turbine on vertical machining center (VMC) machine which is capable
of tip checking for all types of fir tree blades.
A still further objective of the invention is to propose a tip checking device for
fir tree blades of steam turbine on vertical machining center (VMC) machine which is able
to shorten the setting time on the VMC machine for tip copy operation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - Shows the base plate of tip checking device of steam turbine blades.
Fig. 2 - Shows the rectangle block for holding the hydraulic pump.
Fig. 3 - Shows the control segment.
Fig. 3.1 - Shows the pressure pin of control segment.
Fig. 4 - Shows the fir tree blade.
Fig. 5 - Shows the master former.
Fig. 6 - Shows the rectangle block for adaptor attachment.
Fig. 7 - Shows the key for base plate.
Fig. 8 - Shows the detailed assembly of blades checking device.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Fig 8 shows the detailed assembly of fir tree blades checking device (6). This
blade checking device (6) comprises of base plate (1), square block (2), control segment
(3), fir tree blade (4), master former (5) and key (6). In this system, the program on the
VMC is made according to the blade drawing and then master blade is checked to correct
the errors in the program. This program (data) is saved on the VMC m/c. To check the
other blade, master former, dial gauge, hydraulic pump, control segment and base plate
are used. The machined blade is checked on the VMC machine as it is checked on the
vertical stand where the master former moves on the blade tip as per the saved program
and the deflection on the dial gauge will show the exact dimension. For checking the
blades, it is placed on the vertical stand and hydraulic pump is used to lift the blade. Then
as per saved program, the master former moves on the blade tip which is attached with
the machine spindle head. The deviation in any dimension will be compensated in the next
blade. As shown in fig. 8, the control segment (3) rests on the base plate (1) guided by the
key (6) and tightened by the nut and bolt (8). The fir tree blade (4) rests on the control
segment. A hydraulic pump (10) at the bottom center of base plate (1) clamped with the
help of square block (2) which gives the pressure through pin (7) to the blade (4) to lift as
the same condition in the rotor of steam turbine. The master former (5) attached with
spring loaded dial gauge (9) and spindle of the machine, moves on the blade tip as the
program starts. After the complete assembly of blade, the master former (5) moves on the
blade tip as per the program i.e. spindle moves on the tip and any deflection in the dial
gauge indicator will show the correct blade height and radius of the blade.
The fir tree blade (4), base plate (1) and control segment (3) are on the
same vertical axis where as the master former (5) attached with spindle adapter (11) can
move freely on the blade tip. As shown in fig. 3 different control system is used each for
Left hand blade and Right hand blade.
The advantage of the present invented checking device is that it can be used
for blade tip checking on the same machine where blade is machined.

WE CLAIM
1. A tip checking device (C) of fir tree blades of steam turbine on VMC machine
comprising;
a base plate (1);
a support block (2) for clamping a hydraulic pump with the base plate (1);
a control segment (3) resting on the base plate (1) being guided by the key (6)
and tightened by the nut and bolt (8) for allowing the fir tree blade (4) resting
on it;
a hydraulic pump (10) clamped at the bottom center of base plate (1) with the
support of square block (2) for providing pressure through pin (7) to the blade
(4) to lift;
characterized in that,
the master former (5) is attached with spring loaded dial gauge (9) and with
spindle adapter (11) for free movement on the blade tip as per the program for
producing deflection in the dial gauge indicator for showing the correct blade
height and radius of the blade.
2. A method of blade tip checking of fir tree blades by a tip checking device
claimed in claim 1, comprising;
making a program on the VMC machine in accordance with the blade drawing;
checking a master blade to correct the errors in the program;
saving the program on the VMC machine;
resting the fir tree blade (4) on the control segment (3);
applying pressure to the blade (4) to lift through pin (7) by providing hydraulic
pump (10) at the bottom center of base plate (1) and clamped with square
block (2);
wherein the master former (5) attached with spring loaded dial gauge (9) and
with spindle adapter (11) moves freely on the tip of the blade (4) as per
program and produces deflection in the dial gauge indicator to show the correct
blade height and radius of the blade.