FIELD OF THE INVENTION
The present invention relates to a set up of fixture for manufacturing varied length of wedges used in rotor shaft with field lead of 250/600/800 MW Turbo-Generator with less effort, safely and at improved quality.
BACKGROUND OF THE INVENTION
A field connection device which provides an electrical connection between the rotor winding and the exciter consists of:
• Field current lead at end winding.
• Radial bolts.
• Field current lead in shaft bore.
The field current lead at the end winding comprises hollow rectangular conductors. The hollow conductors are inserted into the shaft slots and insulated and these secured by steel wedges to prevent the effects of centrifugal force. One end of each field current lead is brazed to the rotor winding and the other end is screwed to at least one radial bolt. Cooling hydrogen is admitted into the hollow conductors via radial bolts. The hot gas is discharged into the air gap together with the gas used to cool the end winding.
The field current leads located in the shaft bore are connected to the conductors inserted in the shaft slots through radial bolts which are secured in position with slot wedges.

Contact pressure is maintained with a tension bolt and an expanding cone formed in each radial bolt. Contact pressures increase due centrifugal force during operation. All contact surfaces are silver-plated to attain a low contact resistance. The radial bolt is made from forged electrolytic copper.
The leads are run in the axial direction from the radial bolt to the exciter coupling and consist of two semi-circular conductors insulated from each other and from the shaft by a tube. The field current leads are connected to the exciter leads at the coupling with a multi contact plug-in contact which allow for unobstructed thermal expansion of the field current leads.
In the existing practice there was no arrangement to hold wedge on bed of milling machine. Therefore manufacturing of the job was done by taking tolerance in thickness and width of wedge which could be maintained during grinding. But during the process, enormous problems were faced like additional man-power was required to maintain dimensions of wedge. Quality of finished product was affected because in absence of no proper arrangement to machining of wedge which ultimately causing less productivity because of increase of cycle time of manufacture and in case of failure during quality control check further increasing cycle time, as well as increased material wastage because of high rejection rate.

OBJECT OF THE INVENTION
An object of the invention is to develop a fixture which facilitates manufacture of varied length of wedges used in rotor shaft with field lead of 250/600/800 MW Turbo-Generator by providing a simpler manufacturing process for different types of wedges.
Yet another object of the invention is to develop a fixture which facilitates manufacture of varied length of wedges used in rotor shaft with field lead of 250/600/800 MW Turbo-Generator by reducing the man-power requirement.
A further object of the invention is to develop a fixture facilitating to manufacture varied length of wedges used in rotor shaft with field lead of 250/600/800 MW Turbo-Generator by reducing the cycle time of job.
A still further object of the invention is to develop a fixture facilitating to manufacture varied length of wedges with less variation from standard dimensions.
Yet another object of the invention is to develop a fixture facilitating the manufacture of varied length of wedges which reduces the cost of production by reducing the waste in rework.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig. 1 Block (1) having 90° step to hold bottom part of blank wedge.
Fig. 2 Block (2) having 90° step over full length to hold bottom part of blank wedge.
Fig. 3 Block (3) for clamping block (2).
Fig. 4 Locking bolt (4) for holding the job by providing end support.
Fig. 5 Base plate (5) which act as a holder for locking bolt (4) for maintaining wedge axis in longitudinal direction.
Fig. 6 Locking bolt and nut (6).
Fig. 7 Clamp (7) for rigidly holding wedge blank during machining.
Fig. 8 Tightening bolt (8).
Fig. 9 Complete assembly during machining.
Fig. 10 Line diagram of complete assembly.
Fig. 11 Fixture for making wedge.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION:
Figure 1 represents block (1) having 90° step at top to hold bottom part of blank wedge, and a key at bottom to fix in the slot of milling machine bed. A further arrangement is made by providing a base plate (5) with a locking bolt (4) at the extreme end of block (1).

Figure 2 represents a block (2), having 90° step through full length at top for holding bottom part of blank wedge and provide with a key at bottom for fixing in the slot of milling machine’s bed. Position of this block is in the middle. There is a provision provided in front of block (2) to match with block (1). Both the block (1) and block (2) are assembled by nut, and bolt arrangement and a space is provided in block (2) for accommodating head of bolt. Putting variable length of block (2) as per need for different rating of Turbo-Generator.

Figure 3 represents a part of fixture block (3) for clamping block (2). A step is provided to tight the fixture with milling machine’s bed by nut and bolt arrangement.
Figure 4 represents a locking bolt (4) which is used to hold the job by providing end support. As the front area of wedge is less and machining is done across length and cutter is moving at top of wedge. Then we select position of holder at front of block (1) and area of holder is less than front area of wedge. By doing this arrangement, axis of wedge and holder is in same line and fixing of wedge is done in proper manner.
Figure 5 is a base plate (5) acts as a holder. A hole is made in base plate and position of the hole is in same axis with wedge in longitudinal direction. Shape and size of the base plate is in such a way that the holder can move axially with wedge.

Figure 6 represent a bolt so as to avoid derailing of fixture due to machining forces during the machining of wedge.
Figure 7 represents a clamp used for fixing the wedge (job) when machining is done across length and cutter is moving at the top of wedge, the wedge gets lifted at some point that causes dimensional variation. A clamp is designed and made of specific shape and size and placed at proper location to avoid lifting of wedge.
Figure 8 represents a tightening bolt of specific shape and size for holding the wedge vertically.
Figure 9,10,11 represent a photographic view of wedge (job) held in the developed fixture on a horizontal milling machine.
- two blocks (block 1 & block 2) having V shape at the top to put blank wedge. V shape is made at the same position for both the blocks so that wedge can be put properly after assembly of two blocks. If there is a variation in position of V shape then it results alignment problem that affects product quality;
- provided a 4 mm square cut at the center of V shape across the length in two blocks (block 1 & block 2). Blank size of wedge is 21x21XL(variable). Problems were faced during fixing of wedge at fixture due to pressure of sharp edge. 4mm square cut provide space for proper fixing of wedge blank;

- provided with a locking bolt of specific shape and size. As the front area of wedge is less and machining is done across the length and as the cutter moving at top of wedge and up to the end. A mechanism has been provided in front of block 1 for locking the wedge blank from the front face;
- provided a third block (3) for preventing movement of block (2);
- designed and made a key of size width (14 mm) and depth (10 mm) at bottom in two blocks (block 1 & block 2) to fix in the slot of milling machine’s bed;
- main parts of fixture (block 1, 2, 3) are made of glass textolite material. This material is made by layers of glass fibre and resin compound. Then during manufacturing of wedge, if extra jerk is applied along the thickness, there is chance of delayering. A hole is made perpendicular to glass fibre and tightened with nut bolt arrangement;
- block 1 and block 2 are assembled by nut and bolt arrangement;
- care is taken while machining is done across length. A plurality of claims (7) has been provided to avoid lifting of wedge;
- an arrangement is made (slot) in block 2 and clamp for sliding the clamp as per position of cutter based on the essential length of wedge for clamping purpose. 4 mm square cut is made in clamp also to provide space for proper clamping of wedge blank. A hole is made in the clamp to tight wedge vertically.

We claim
1. A fixture for holding the wedges of varied length used in rotor shaft of turbo-
generator during machining operation comprises:
a first block (1) having a V-groove at the top surface for holding the blank wedge and a key at the bottom for fixing in the slot of machine bed;
a second block (2) having a similar V-groove at the top and a key at the top for fixing in the machine bed slot placed alongside the block (1) to accommodate the varied length of blank wedge;
a third block (3) is provided at the distal end of the second block (2) for preventing any movement of the blocks (1,2) in longitudinal direction, the fixture being provided with an arrangement at the proximal end comprising a base plate (5), a bolt (6) and a locking bolt (4) for tightly holding the blank wedge from the proximal end side wherein a pair of clamps (7) can slide along the V-groove of blocks (1,2) left and right for clamping the wedge blank (7) by tightening bolts (8) at desired location for preventing any deflection of the job during machining operation.

2. The fixture as claimed in claim 1 wherein the blocks (1,2) are provided with a square
cut/slot at the centre of V-groove in the axial direction for accommodating the tip of
wedge blank.