FIELD OF INVENTION
The present invention relates to an improved clamping system in workpiece
holding adapter of a double spindle 5 axis machines for reducing the clamping allowance of
blanks of turbine blades. More particularly, the invention relates to a more rigid clamping
that results to a highly economical blank production used for machining of turbine blades.
BACKGROUND OF THE INVENTION
Presently the blanks are clamped for machining of turbine blades in workpiece
holding adapters of double spindle 5 Axis machines by a system built in the machine by the
machine supplier. The job is held on the adapter where the clamping is done holding the job
diagonally. This necessiates a clamping allowance of 25 mm on the blanks machined for
making turbine blades. This is a huge loss as regard to the Cost of manufacturing of the
blanks.
Hence, there was a need to reduce the clamping allowance on the blank to
make the manufacturing of the blank more economical and at the same time to make the
clamping more rigid.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved clamping
system in workpiece holding adapter of a double spindle 5 axis machines for reducing the
clamping allowance of blanks of turbine blades which is capable of making the clamping
system more rigid.

Another object of the invention is to propose an improved clamping system in
workpiece holding adapter of a double spindle 5 axis machines for reducing the clamping
allowance of blanks of turbine blades which results for a highly economical production of
blanks for turbine blades.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - Shows the existing adapter for holding the rectangular blank diagonally.
Fig. la - Shows the existing clamping system holding the job diagonally with 25
mm holding allowance.
Fig. lb - Shows the thickness of adapter
Fig. 2 - Shows the existing clamping system and Fig. 2a
Fig. 3 - Shows the improved clamping system and new assembled adapter with
new manufacturing pad.
Fig. 4 - Shows the job clamped in new adaptor according to the invention.
Fig. 5 - Shows the new clamping pad according to the invention.
Fig. 6 and Fig. 6a - Shows the locating centre pad and locating centre pin
according to the invention
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
As shown in Fig. 1 and la, 2 and 2a in the existing practice the blank is held by
the existing clamp diagonally with 25 mm holding allowance, in the workpiece adapter of
double spindle 5 axis machines.
As shown in Fig. lb, part 2 has a thickness of 25 mm and hence the holding
allowance is also kept 25 mm.

As shown in Fig. 3, an improved clamping system (c) is adapted in the machine
where a centre pad (4) is bolted on the workpiece adapter (6) of the machine. The centre
pad (4) has a tapered hole at the middle to accommodate a locating pin (5). The locating pin
is made of carbide. The locating centre pad (4) and locating centre pin are shown in Fig. 6
and Fig. 6a.
Fig. 4 shows the job clamped in new adaptor (6) where the job is held along
the width with 10 mm holding allowance. Holding the job widthwise instead of diagonal
holding has made the clamping (c) more rigid.
As shown in Fig. 3, the improved clamping system is comprised of a workpiece
adapter (6) on which a locating centre pad (4) having at its middle a locating centre pin (5)
is mounted. A pair of new manufactured clamping pads (3) of 10 mm height for holding the
blank are disposed on the left and right side of the adapter assembly (6). These pads (3)
hold the width of the job to make the clamping more rigid. The pads (3) have Knurling (7)
throughout the width of the part for an improved gripping of the job. The clamping pads (3)
are made of EN-24 carburised, hardened and ground and maintaining a hardness of Rockwell
50-55. The clamping pads (3) (Left hand and right hand) each having dimension 90 x 48 x
10mm having two counter bores for M8 alien bolt. The clamping pad (3) is fixed on the
adapter base (6) by two M8 alien bolts. Before clamping, the blank is located and held on
the base of the workpiece adapter by the locating pin (5). The function of the locating centre
pad (4) along with the locating pin (5) is to restrict the movement of the blank along
clamping pads (3). The clamping pad (3) has a 10mm projected portion and 16 mm slotted
window which gets fixed in 10 mm slot and 16 mm projected portion of the part (1) of the
adaptor. The existing clamping pad has a thickness of 25 mm which means with the
improved clamping system where the new clamping pad is of 10 mm thickness, the extra
material allowance of 15mm is saved.

ECONOMICAL IMPLICATION
Due to the reduction in extra allowance of 15 mm kept for clamping purpose,
there will be savings in material cost for that 15mm.
In the 'blade shop' we have (9) double spindle machines
Total blade to be manufactured/year in (9) double spindle m/c - 38000 approx.
Total length saved - 38000 x 15/1000=570 meter
Average cross section of the blank is 72/1000 x 38/1000 m2
density of material = 7800 kg/meter3
Average rate = 200 Rs/kg.
Material saved in kg/year = volume x density
= 570 X (72/1000) x (38/1000) x 7800
= 12164 Kg.
Total saving in material = weight x Rate
= 12164 x 200
= 24.32 lacs

WE CLAIM
1. An improved clamping system in workpiece holding adapter of a double spindle 5
axis machine for reducing the clamping allowance of blanks of turbine blades,
comprising;
providing a workpiece adapter (6);
disposing a locating centre pad (4), bolted on the adapter (6);
assembling a tapered locating centre pin (5) in a tapered hole of the pad (4) to
locate the blank to restrict the movement;
wherein clamping pads (3) having 10mm projected portion are fixed on the
adapter (6) and disposed on left and right hand side of the said adapter to hold
the blank along its width rigidly.
2. An improved clamping system as claimed in claim 1, wherein the clamping pads
(3) being made of En 24 material, carburised and hardened, are fixed on the
adapter (6) by M8 alien bolt.
3. An improved clamping system as claimed in claim 1 and 2, wherein clamping pads
(3) hold the blank for 10 mm clamping allowance.
4. An improved clamping system as claimed in claim 1 to 3, wherein the clamping
pads (3) are Knurled to provide a better gripping and rigid clamping of the blank.

ABSTRACT

A workpiece adapter (6) is provided on a double spindle 5 axis machine to reduce the
clamping allowance of blanks of turbine blades when a locating centre pad (4) is bolted on
the adapter (6). A tapered locating pin (5) is disposed in the tapered hole of the locating pad
(4) to locate the blank and to restrict the movement of the blank along clamping pads (3).
The clamping pads have 10 mm projected portion and are fixed on the adapter (6) and hold
the blank width wise to provide rigidity of the clamping. The pads (3) are knurled for better
gripping.