FIELD OF THE INVENTION
The present invention relates to a referencing device for Root and Shroud milling
operation on HMC machines to accommodate all sizes steam turbine lock blades.
BACKGROUND OF THE INVENTION
Horizontal Machining Center (HMC) is known for machining technological
allowances provided at both root and shroud end of steam turbine blades. The
technological allowances (extra material) are normally provided at both ends of
steam turbine blades for clamping of these blades on 5-axis machines while
machining. After machining of these blades on 5-axis machines, the technological
allowances (extra material) are to be milled off on HMC machines to maintain the
drawing dimensions of blades at both root & shroud end.
The prior art referencing devices used on HMC machines, are capable of
machining technological allowances only for normal blades having slots at root. A
Locating pad in the device takes reference from the slot at root of the blade and
on the basis of this reference only, the process of milling the technological
allowance is carried out on the normal steam turbine blades. But the Lock type
blades used in turbines are not having slots at root. Hence, technological
allowance milling of lock blades is not possible with the prior art devices.
The disadvantage with the known referencing devices used in HMC is that the
lock type blades cannot be appropriately located in the device upon clamping the
blade on the device. The inventors noted that inappropriate location of the lock
type blade on the device of HMC, is that the locating pad of the device acts as an
obstacle in proper placing of the lock blades only due to nonexistence of slots at

root of the blade. And due to nonexistence of slot at root of the lock blades, the
reference can not be taken because known locating pad takes references from
the slot only.
A new locating fixture and referencing fixture is required on HMC machines so
that the locating fixture can support the blade from the side and referencing
fixture can provide reference to the lock blades to maintain the entire dimension
in technological allowance milling operation.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a referencing device for HMC
to mill off technological materials from lock type-turbine blades.
Another object of the invention is to propose a referencing device for HMC to mill
off technological materials from lock type-turbine blades, which is enabled to
take reference at root end near fillet area of the lock type blade.
A further object of the invention is to propose a referencing device for HMC to
mill off technological materials from lock type-turbine blades, which allows
milling of technological allowances of all sizes lock type turbine blades in HMC
machines.
SUMMARY OF THE INVENTION
Accordingly, there is provided a referencing device for HMC to mill off
technological materials from lock type-turbine blades, comprising : - a locating
member having a vertically placed base plate provided with hexagonal threaded

holes for inserting of one each fixing bolt and referencing bolt, a vertical column
absent-of a projected portion fixed to the base plate at a horizontal plane; and -
referencing member having a holding plate vertically located, a referencing bolt
movably placed at upper end of the holding plate, and a fixing bolt fixed at lower
end of the holding plate, wherein the locating member locates the referencing
member at the opposite side of the lock type turbine blade when placed on a
horizontal machining center (HMC), and wherein the referencing member takes
reference at root end near fillet area so that the technological allowances can be
milled off by the HMC.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS/PHOTOGRAPHS
Figure 1 Schematic drawing of new Referencing device.
Figure 2 (a) Schematic drawing of prior art and inventive device.
Figure 2 (b) Schematic drawing of inventive locating device.
Figure 3 Photographs explaining technological allowances of normal and lock
blades.
Figure 4 Photographs showing detail problem & solution for technological
allowance milling of Lock blade.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
To cut technological allowances (extra material) of normal blade at both root and
shroud end, the blade is placed on the device by taking reference at the root slot
of the blade with the help of a locating pad (3 of figure 2) provided in the device.
The locating device is designed in such a way that it takes reference at slot of
normal blades and the technological allowances of the blade at both root and
shroud end remain overhung outside the device so that these technological

allowances can be milled off with the milling cutter of the HMC without damaging
the device. The tang height at root end and blade length can be maintained as
per drawing requirement.
To maintain the dimensions of a lock blade during milling off technological
allowance, it is necessary to place the lock blade in the device in such a way to
maintain axis of lock blade parallel to the axis of the device. But due to
nonexistence of slot in the lock blades, the lock blade can not be placed properly
in the device to maintain parallelism of lock blade axis with the device axis as the
locating pad acts as an obstacle to keep the lock blade straight. The prior art
locating device is designed in such a way that only accommodates normal blades
in this device.
To accommodate the lock blades in the prior art device, an improved locating
device and new referencing device is proposed so that the dimension during
technological allowances milling can be maintained on the basis of new
referencing device only.
Due to nonexistence of slot in the lock blades, it is necessary to take reference
from the other part of lock blade. Only the solution left was to take reference
from platform of the lock blade at root end near fillet area and to modify the
existing device as per lock blades. Accordingly, the portion of the locating pad
which goes inside the slot of normal blades for referencing is eliminated for lock
blades. The referencing device is now placed at the opposite end of the lock pad
when clamped on the HMC, and the device takes reference from platform at root
end near fillet area of the blade.

Accordingly, a new Referencing number (figure 1) and a locating number was
manufactured (figure 2) and fitted in the device. Now all the lock blades of any
size can be milled off in the present device.

WE CLAIM :
1. A referencing device for HMC to mill off technological materials from lock
type-turbine blades, comprising :
- a locating member having a vertically placed base plate provided with
hexagonal threaded holes for inserting of one each fixing bolt and
referencing bolt, a vertical column absent-of a projected portion fixed to
the base plate at a horizontal plane; and
- referencing member having a holding plate vertically located, a
referencing bolt movably placed at upper end of the holding plate, and
a fixing bolt fixed at lower end of the holding plate,
- wherein the locating member locates the referencing member at the
opposite side of the lock type turbine blade when placed on a
horizontal machining center (HMC), and wherein the referencing
member takes reference at root end near fillet area so that the
technological allowances can be milled off by the HMC.
2. A referencing device for HMC to mill off technological materials from lock
type-turbine blades as substantially described and illustrated herein with
reference to the accompanying drawings.

ABSTRACT

The invention relates to a referencing device for HMC to mill off technological materials from lock type-turbine blades, comprising : a locating member having a vertically placed base plate provided with hexagonal threaded holes for inserting of one each fixing bolt and referencing bolt, a vertical column absent of a projected portion fixed to the base plate at a horizontal plane; and referencing member having a
holding plate vertically located, a referencing bolt movably placed at upper end of the holding plate, and a fixing bolt fixed at lower end of the holding plate, wherein the locating member locates the referencing member at the opposite side of the lock type turbine blade when placed
on a horizontal machining center (HMC), and wherein the referencing member takes reference at root end near fillet area so that the
technological allowances can be milled off by the HMC.