FIELD OF THE INVENTION
The present invention generally relates to a Friction Stir Welding (FSW)
procedure. More particularly the invention relates to an automated method of
welding short circuit rings of large electric machines.
BACKGROUND OF THE INVENTION
Friction stir welding (FSW) is a well established welding process. According to
another process, short circuit ring for electric machines is carried out by welding
of copper sheets by using MIG ( Metal Inert Gas) process. However, a
requirement of preheating of the copper material prior to MIG welding exists.
Further, fumes generated during welding and by the consumable such as argon
and filler wire, are injurious to health of the operator and vitiates the
environment. Therefore, a need was felt to develop an alternate technology
using FSW for welding of copper short circuit rings.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an automated method of
welding of non-ferrous short circuit rings for electrical machines.

Another object of the invention is to propose an automated method of welding
non-ferrous short circuit rings for electrical machines which reduces the defect
rate and improve the efficiency of the weldment
A still another object of this invention is to propose an automated method of
welding non-ferrous short circuit rings for electrical machines which reduces the
cycle time of production as well as the number of manufacturing steps.
A further object of this invention is to propose an automated method of welding
non-ferrous short circuit rings for electrical machines which eliminate the use of
consumables for example electrode and gases.
A still further object of this invention is to propose an automated method of
welding non-ferrous short circuit rings for electrical machines which constitutes a
non-fusion welding process for the non-ferrous circuit rings which being very
sensitive have a tendency to get oxidized during the MIG welding process.
SUMMARY OF THE INVENTION
Accordingly, there is provided an automated method for welding of short circuit
rings for electrical machines by Friction stir welding process.

In the proposed method, a friction tool made of harder metal than that of the
base material is used during the FSW, and the tool is plunged at high rotational
speed into the rings. After full penetration, a transverse motion is given either to
the tool or to job so that both ends of the rings get welded.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a Friction Stir Welding process of non-ferrous rings according
to the invention when thickness of the rings is more than the width.
Figure 2 - shows a friction stir welding process of non-ferrous rings according to
an alternative embodiment of the invention when thickness of the
rings is less than the width.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The welding method of short circuit ring by Friction Stir Welding (FSW) according
to the invention is illustrated in figures 1 and 2. Each figure describes a different
method of holding the job in the fixture. Figure 1 explains the holding position of
the job during welding, when the thickness of the ring is more compared to the
width. The holding position of the job during welding, when thickness of the ring
is less than the width is shown in figure 2. After the rings to be welded are fixed
in position, the FSW tool is inserted on the tool-holder of the FSW machine, and

rotatably moved in transverse direction into the job by applying pressure on the
top surface. Simultaneously, the job starts the transverse movement along the
welding direction of the job. Thus, the friction stir welding of the short circuit
rings takes place.
According to figure 1, two numbers of rings (3) are held in horizontal position as
shown in Top. Front and isometric views. Both the rings (3) are held firmly to
ensure that the position of the job remains fixed during welding. A Rotating Tool
(4) is then plunged into a start block (5) at corresponding RPM and plunge rate.
After the complete penetration takes place, a transverse motion of the job is
started along the weld line of the rings (3) or the tool (4) movement. It moves
until it reaches into an end block (6). Thus, both the rings (3) get welded. After
welding, both the rings (3) can be extracted out by a cutting operation. As well
as the start block (5) and the end block (6) can be removed.
According to figure 2, three or more numbers of rings (7) are held vertically as
shown in Top, Front and isometric view. Firstly, all the rings (7) are clamped so
that the rings (7) maintain their position during welding. Rotating Tool (10) is
plunged at a corresponding RPM and plunge rate into a start block (8) and after
full penetration, a transverse motion is started along the weld line of the rings
(7) or the Tool (10) which can be moved. It moves until it reaches an end block
(9). Thus all the three rings (7) get welded. After welding the rings (7) can be
removed off by a cutting operation.

WE CLAIM:
1. An automated method of welding of non-ferrous short circuit rings for
electrical machines comprising the steps of:
- providing a Friction Stir Welding machine having a rotating tool, a
machine base to hold a plurality of job by clamping through a start block
and end block;
- providing a plurality of non-ferrous short circuit rings either disposed
horizontally or vertically on the machine base;
- fixing the rings firmly with the support of a start block;
- activating the machine tool and allow gradual increase of rotational
including transverse motion till complete penetration of the tool on the
start block;
- imparting a transverse movement of the rotating tool along weld line of
the rings or the tool causing the rings to move at an end block such that
the plurality of rings get welded at one pass;
- separating the rings from each other by a known cutting operation; and
- removing the start and end blocks to their respective positions.

2. The method as claimed in claim 1, wherein the tool is made of material
harder than that of the rings.
3. The method as claimed in claim 1, wherein the non-ferrous rings are one
of Copper ring, Aluminum ring, stainless steel and Brass.
4. The method as claimed in claim 1, wherein a required force is applied
during the welding so that the rotating tool is plunged into the metal and
start welding at plastic temperature.
5. The method as claimed in claim 1, wherein an orbital motion of the
rotating tool is provided for penetration of the tool into the job.
6. The method as claimed in claim 2, wherein different types of contours ,
material size, job material, and material thickness can be configured.