FIELD OF INVENTION
The invention relates to development of a fixture for friction stir welding of USC (Ultra
Super Critical) palm to blanking plate component and a method of friction stir welding
thereof.
BACKGROUND OF INVENTION
Friction Stir Welding (FSW) is a solid state welding process, which involves heat
generation through friction created by a rotating tool which is plunged inside the
material being welded. As the tool traverses perpendicular to its axis of rotation, it
plasticizes the material. The plasticized material flows along the threaded portion of the
tool to its rear side, gets forged due the pressure of continuous material flow and hence
forms the weld.
The FSW process is utilized for the fabrication of palm to blanking plate assembly which
forms a major sub assembly of the bus duct which is used for transmission of power at
power plants. This component (palm to blanking plate) has a cylindrical head (blanking
plate) with palms attached to it in certain specified shape (rectangular, hexagonal,
octagonal, etc.). The component is fabricated by performing FSW of a T-joint formed
between the two parts (i.e. blanking plate and palms). In order to achieve perfect
defect free weld it is mandate to provide back up support against the working tool, a
support that can hold the palms and the blanking plate in accurate position. Thus a
fixture was designed, modeled and developed, which will guide and support the job
while it is being welded using FSW process.
On searching of patent application on similar subject, as on date no such fixture has
been found to be prepared which will assist in fabrication of palm-blanking plate
component using friction stir welding process.

SUMMARY OF THE INVENTION
The invention is about equipment deployed for the welding of USC palm to blanking
plate assembly by friction stir welding process. The parts of the component viz.
blanking plate and palms are positioned and held together with the help of clamping
forces and constraints are applied in a manner such that the required joint configuration
is achieved. The development was felt necessary in order to avoid any disorientation,
misalignment, deformation of the component (made of aluminium) which sustains
tremendous forces by the means of FSW tool during welding operation. To prevent any
downward slippage/ movement of the palms during welding, a removable support block
is provided in the fixture as shown in figure 1.
OBJECTS OF THE INVENTION
- An object of the present invention is to develop fixture for friction stir welding of USC
palm to blanking plate component that assists in fabrication during friction stir welding
of palm to blanking plate assembly.
- Another object of the invention is to provide a method that ensures simplified
arrangement for clamping, holding and releasing of the component by providing sliding
type fixturing and fasteners
- Another object of this invention is to perform T-joint welds in octagonal form with
sheer precision, considerably low manufacturing cost and time duration
- Another object of this invention is to fabricate USC palm-blanking plate component
without affecting/altering the design or structural aspects of the component
- Another object of this invention is to provide a feasible design solution in the form of
a removable backing plate that will prevent unwanted material flow, sticking/joining of
the component to the parts of the fixture

- Another object of this invention is to create equipment that will assist in fabricating
components of different engineering designs by utilizing product specific external and
internal casings without changing the basic configuration
- Another object of this invention is to achieve defect free component meeting
stringent quality requirements of the customer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1- 3D model of the fixture developed for friction stir welding FSW of palm-blanking
plate assembly
Fig 2- Blanking plate
Fig 3- Palms arranged in octagonal form
Fig 4- Palms placed in the fixture
Fig 5- Blanking plate fixed on the surface of the assembly
Fig 6- Fabricated component
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
1. Base structure (1), which supports the external andintemal casing, transfersthe
dynamic forces sustained by the equipments during the welding operation towards the
bed of FSW machine.

2. External casing (2), helps in clamping the component from outside. It has rails which
provide cross movement along the base structure, for easy assembly/dislodging of the
fixture and component. It also has slots for fasteningpalms of the component in
octagonal shape.
3. Internal casing (3), provides resisting support to the palmsfrom inside during
welding. It has slots that help in holding palms with the external casing using fasteners.
It also holds the backing plate on its upper face.
4. Backing plate (4), provides back up support to the blanking plate to prevent any
material flow or deformation of the component during welding operation by FSW tool.
5. Support block (5), provides back support to palms during welding operation.
6. Locking Slots (6), for locking and holding the external casing at specified location
with the help of fasteners.
7. Fasteners (7), for holding and locking of the complete assembly.
8. Palms (8), a sub component of the equipment to be manufactured. Palms positioned
in octagonal shape with the help of internal and external casings and fasteners.

DETAILED DESCRIPTION OF THE INVENTION
The base structure (1)as shown in figure lis fixed using fasteners to the bed of FSW
machine. Then the external casing (2) is slid into the base structure usingthe guide rails
provided on it. Beneath the external casing, a support block (5) is placed to provide
back support to palms (8). Further, independent and similar shaped palms are placed
along the internal periphery of the external casing forming an octagon. Then, the
internal casing (3) is placed in position and the complete assembly is fastened
altogether using fasteners (bolts and nuts). Backing plate (4) is rested freely onto the
upper surface of the internal casing, encompassing the palms in octagon shape in
between the external casing and the edges of the backing plate (4). On the assembled
set up, the blanking plate (9) is clamped and welding operation is performed using FSW
machine. The external and internal casing, along with the support block ensures that
the palms remain in position during welding operation. Backing plate (4) will prevent
any material flow towards the bottom side when the FSW tool is operating.
Once completed, the fasteners and support block is removed, internal casing and
backing plate falls down under their own weight. The external casing is expanded and
the welded component is removed.

WE CLAIM:
1. A fixture for friction stir welding of USC palm to blanking plate component
comprising: a base structure (1) erected on the bed of Friction Stir Welding machine
(FSW) having a base at the bottom and guide rails at the sides;
- an external casing (2) a replica of the octagonal shaped job having oversize dimension
for sliding into the base structure (1) using the side guide rails;
- a support block (5) placed on the bed for supporting palms (8);
- the job is then placed sideways one after another each abutting the inner surface of
the external casing;
- an internal casing (3) placed on the inside of the sub assembly such that internal
surface of the job abut the external surfaces of the internal casing (3).
- a backing plate (4) disposed over the top surface of internal casing (3) for proper
positioning of the job enclosed between the inner surface of external casing (2) and
outer surface of internal casing (3);
- the blanking plate (9) then kept over the assembly and clamped for performing the
friction stir welding operation.
2. A method for performing friction stir welding of palms to blanking plate by a fixture
as claimed in claim 1 comprising:
- sliding an external casing (2) through the guide rails provided in the base structure
(1);
- placing a support block (5) over the machine bed to provide back support to the
palms (8);

- placing the independent and similar shaped palms (8) along the internal periphery of
the external casing (2) forming a shape like an octagon;
- placing the internal casing (3) in position;
- fastening the complete assembly together with the help of nuts and bolts;

- placing the backing plate (4) freely on the upper surface of internal casing (3)
encompassing the palms (8) in octagonal shape in between the external casing (2) and
the edges of the backing plate (4) while the internal casing keep the palms (8) in
position;
- placing the blanking plate (9) over the assembly;
- clamping the blanking plate (9) with the sub-assembly;
- performing the welding operation in FSW machine;
removing the fasteners and support block after the completion of welding operation the
backing plate (4) and internal casing falls down because of self weight;
removing the job by expanding the external casing.

ABSTRACT

A welding process namely as friction stir welding can be applied for the fabrication of
bus duct component with the help of a tooling fixture. The development of this fixture
is for the welding of USC palm to blanking plate component.
The fixture helps in the fabrication of USC palm-blanking plate component by holding
the subassemblies of the component (viz. palms and blanking plate) and providing
adequate support to withstand the dynamic forces of FSW machine during welding
operation. 8 palms are positioned in octagonal form and welded to blanking plate with
the help of friction stir welding process.