FIELD OF THE INVENTION
The invention relates to a device to implement an improved friction stir welding
process for joining cylindrically-shaped objects.
BACKGROUND OF THE INVENTION
Friction Stir Welding (FSW) is a solid state welding process in which plasticized
material is processed to form a weld. Friction Stir Welding involves heat
generation through friction created by a rotating tool which is plunged inside the
materials being welded. As the tool transverses perpendicular to its axis of
rotation, it plasticizes the material. The profile of the tool forces the plasticized
material to flow towards its trailing edge and forge the material to form a
consolidated weld.
The process is utilized amongst others, for fabrication of bus duct, a product
used for transmission purpose at power plants. This bus duct is cylindrical in
shape, usually very lengthy in size with a diameter varying from hundreds to
thousands of millimeters. The component is presently fabricated by employing
the longitudinal seam welding along its length using FSW. In order to achieve a
defect free weld, it is mandatory to provide a flaw-less support against the
working tool.

US 7, 815,094 B2 teaches a method of manufacturing cylindrical body,
comprising the Steps of forming cylindrical body by bending a plate like work
having projected fingers at four corned parts, allowing the end faces to abut
each other. It is then held by a friction stir welding device, the tool is buried from
the either end of the abut formed and advanced towards the other end. An
apparatus consisting of plungers applying heavy hydraulic force Ts used to hold
the sheet at joint and perform welding.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a universal device to guide
and support a cylindrical work piece during friction stir welding process, which
eliminates the disadvantages of prior art.
Another object of this invention is to propose a universal device to guide and
support a cylindrical work piece during friction stir welding process which allows
to perform longitudinal seam joint incurring low cost.
Another object df this invention is to propose a universal device to guide and
support a cylindrical work piece during friction stir welding process which enables
welding of semi-circular dissimilar materials by performing two longitudinal
joints.

SUMMARY OF THE INVENTION
Accordingly, there is provided a universal device to guide and support a
cylindrical work piece during friction stir welding process. According to the
invention a plate is rolled into a cylindrical shape and held to abut the tool using
a hydraulically operated device. The device can be used for fabrication of hollow
cylindrical body with excellent quality and appearance. The cylindrical body is
provided with a hydraulic support from the bottom to prevent any distortion,
bending or slip during welding.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a programmable Friction Stir Welding machine accommodated
with the device of the invention.
Figure 2 - shows the device of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
As shown in figure 2, the device consists of the following items:
1. Base plate (1) with equi spaced slots for fastening the device to a friction
stir welding machine on adjustable basis. The base plate (1) can
accommodate a clamping assembly at different locations for meeting the
desired need of different lengths of cylindrical body.

2. Bottom clamp assembly (2) for providing support to the cylindrical body
during welding. This clamp assembly (2) is made up of a base clamp (4)
and a swing clamp (5) with hinged joint in between the two clamps (4, 5)
for easy positioning and removing of the cylindrical component being
welded.
3. Top clamp (3) for holding a seam joint in line to perform a longitudinal
seam welding and accommodate any variation in diameter of the
cylindrical component being welded.
Initially, a sheet of desired length is rolled into cylindrical shape. Then, the base
plate (1) of the device is fastened to the FSW machine maintaining the desired
tool travel length. Depending upon the length of the cylindrical body, the bottom
clamp assemblies (2) are fastened to the base plate (1). Thereafter, the swing
clamp (5) is opened wide and the cylindrical body is placed in the device resting
freely on the base clamp (4). The swing clamp (5) is closed and the top clamp
(3) is positioned over the seam joint. Nut-bolts with springing arrangement are
used to fasten the top clamp (3) with the bottom clamp assembly (2). As the
bolts are fastened turn by turn, the arced cylindrical body contracts until the
edges meet to form an enclosure. Screw jacks are placed inside the device with a
double L-channel to provide resisting force against the tool. The friction stir
welding is performed as per need in a programmable/pendant controlled FSW
machine.

ADVANTAGES OF THE INVENTION
The proposed device is of simplified design and allows performing longitudinal
seam welding on a cylindrical body.
The development of the device eliminates any need of a skilled worker without
any compromise in the weld quality. The device can be used to form cylindrical
body of dissimilar metals for thermocouple applications. Further the device
reduces fit up time and cost incurred towards tooling without any compromise in
weld quality. Additionally, the device allows welding on components for a wide
range of thickness of different materials. Finally, the device can be used for
robotic/fully automated or semi-automated FSW process.

WE CLAIM:
1. A universal device to guide and support a cylindrical work piece during
friction stir-welding process comprising :-
- a base plate (1) having a plurality of slots configured at equi-spaced
locations to mount the plate (1) on a programmable friction stir welding
machine;
- a clamping assembly (2) accommodable on the base plate (1) at multiple
locations depending on the length of the cylindrical body, the clamping
assembly (2) providing an error-free support to the cylindrical body during
the welding; and
- a top clamp (3) holding a seam joint in line with a longitudinal seam
welding through adjustment in variation in the diameter of the cylindrical
objects being jointed.

2. The device as claimed in claim 1, wherein a base clamp (4) and a swing
claim (5) With a hinge means provided between the clamps (4, 5) to allow
easy positioning of the cylindrical body and removal of the cylindrical
components after completion of FSW-welding.

ABSTRACT

The invention relates to a universal device to guide and support a cylindrical
work piece during friction stir welding process comprising a base plate (1) having
a plurality of slots configured at equi-spaced locations to mount the plate (1) on
a programmable friction stir welding machine; a clamping assembly (2)
accommodable on the base plate (1) at multiple locations depending on the
length of the cylindrical body, the clamping assembly (2) providing an error-free
support to the cylindrical body during the welding; and a top clamp (3) holding
a seam joint in line with a longitudinal seam welding through adjustment in
variation in the diameter of the cylindrical objects being jointed.