FIELD OF THE INVENTION
The present invention relates to an apparatus and method for automatic spot
welding of ventilation spacers on punoling lamination sheets of various ratings of
turbo generators.
BACKGROUND OF THE INVENTION
Stringent project completion targets, competition in global market and reduced
man power have highlighted the need for automation in all major work areas of
any organization, leading to higher productivity. A manufacturing company has
to put up sufficient efforts for automating core technology areas. Spot welding of
ventilation spacers is one such area, which can benefit heavily from automation,
focusing on automatic robotic welding process. Ventilation spacers are required
on laminations for cooling the stator core of the steam turbine generator. The
ventilation spacers are welded to a lamination sheet using resistance welding
(spot welding) process. The lamination sheet is made up of Silicon steel, having
thickness of 0.65mm. The ventilation spacers are made up of Mild steel. At
present three types of spacers are being used depending on the generator
rating. These spacers are being welded to the lamination sheet manually using a
template.
With the known manual process, a huge time is required for welding a complete
lamination which can be reduced by using a robotic automation process with less
human effort.

In the known manual method of spot welding of ventilation spacers on punoling
lamination sheets, the welding is done by a spot welding machine electrodes by
activating them with a foot switch. This manual method is not very accurate and
cumbersome leading to large cycle time of the component.
Some apparatus and methods have been previously employed in the art for spot
welding of ventilation spacers on punoling lamination sheets but not of the
apparatus or methods have used the fixed spotwelding machine connected to
robot.
In one method, (Refer Patent No.20140001165), a spot welding system has been
proposed using a 6 axis robot fitted with spot welding gun.
In another method (Refer Patent No. US 20090001056), a positioning method of
spot welding robot having a moving welding gun has been disclosed.
In yet another method (Refer Patent No. US 4842451), a spot welding robot
system which comprises a spot welding gun unit fixed to an articulated general-
purpose robot or the like, and having a servo motor as the open/close drive
source of spot welding chips, a robot controller, a welding current control section
and a main controller has been proposed.
US Patent No. 20050263496, provides a system comprising a spot welding
system including first and second spot welding robots, and a communication line
connection the first and second spot welding robots with each other so as to
permit communication there between.

The present invention relates to an automated apparatus and a method for spot
welding of ventilation spacers on punoling lamination sheets using robotic
automation with fixed spot welding machine and robot handling the work piece
for various ratings of turbo generators.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an apparatus for
automatic spot welding of ventilation spacers on punoling lamination sheets on
turbo generators.
Another object of the invention is to propose an apparatus for automatic spot
welding of ventilation spacers on punoling lamination sheets on turbo
generators in which a fixed spot welding machine with robotic automation
process is used.
A further object of the invention is to propose an apparatus for automatic spot
welding of ventilation spacers on punoling lamination sheets on turbo
generators which improves the accuracy, decreases cycle time of welding
process and reduces human efforts.
A still further object of the invention is to propose an automated method for spot
welding of ventilation spacers on punoling lamination sheets on turbo
generators.

SUMMARY OF THE INVENTION
Accordingly, there is provided an apparatus for automatic spot welding of
ventilation spacers on punoling lamination sheets of a turbo generator
comprising a robot mounted on a horizontal plate, a fixed spot welding machine,
a robot controller, a gripper mounted at the end of robot wrist, two pneumatic
sliding tables and a control system for sequential control of equipment, wherein
the robot controller is enabled to initiate a communication through Ethernet IP
or other communication protocols to a PLC, wherein the lamination sheets are
manually loaded on the sliding tables with top loading of a template, wherein a
plurality of spacer bars are manually placed at different locations within
correspondingly configured slots and wherein an automatic spot welding is
implemented by the welding machine according to the programmed sequence.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a layout of the automated apparatus showing a 6 axis robot with an
end of an arm tool to grip the stamping, two sliding tables for loading and
unloading of stampings and a spot welding machine for welding the bars to the
lamination sheet.
Figure 2 is a drawing of ventilation sheet.
Figure 3 : Drawing of Ventilation Lamination Spacer bars.

Figure 4 : Drawing of Template
Figure 5: Drawing of bottom supporting structure with holding cups.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an automated apparatus and a programmable
method for automatic spot welding of ventilation spacers (11) (Figure 3), on
different variants of punoling lamination sheets (10) (Figure2 ), of a turbo
generator.
The robot (1) (Figure 1), through a robot Controller (6) (Figure 1),
communicates with a PLC 8 (Figure 1) through Ethernet IP or other
communication protocols.
Operator manually loads the lamination sheet (10) (Figure 2), on a 'Sliding
Table V (3) (Figure 1). After successfully placing of the lamination sheet, the
operator then keeps a template (12) (Figure 4), along with the holding cups and
a bottom supporting structure (13) (Figure 5). With reference to that placed
template (12) (Figure 4), the operator keeps the spacer bars (11) (Figure 3) of
suitable length in the slots.
For spacer bars (11) (Figure 3), of length more than 500 mm require 4 spot weld
points and that of less than 500 mm require 3 spot weld points are required.

Operator presses the 'Ready' button on operator pendant (7) (Figure 1). The
lamination sheets along with template and spacers move inside the robotic work
cell (5) (Figure 1).
After receiving the signal from PLC (8) (Figure 1), Robot (1) (Figure 1) moves
from its home position towards 'Sliding Table 1' (3) and picks the whole
assembly with the holding cups using 3 jaw grippers (9) (Figure 1). Robot then
moves to the spot welding machine (2) (Figure 1).
Robot is programmed in such a way so that it will move the whole assembly to
different locations as per the location of weld points and the spot welding
machine performs the welding. In the meantime operator will place spacers (11)
(Figure 3), with the help of template (12) (Figure 4), on the lamination sheets
(10) (Figure 2), on 'Sliding Table 2" (4) (Figure 1). When done operator will hit
the 'Ready' button on operator pendant (7) (Figure 1).
After welding is finished the robot moves towards 'Sliding Table 1' to place the
welded sheet.
Then robot then goes to 'Sliding Table 2' and picks the second lamination sheet
along with templates and spacer bars. Operator unloads the finished component
and loads a new one on the 'Sliding Table 1'.

WE CLAIM:
An apparatus for automatic spot welding of ventilation spacers on punoling
lamination sheets of a turbo generator comprising a robot mounted on a
horizontal plate, a fixed spot welding machine, a robot controller, a gripper
mounted at the end of robot wrist, two pneumatic sliding tables and a control
system for sequential control of equipment, wherein the robot controller is
enabled to initiate a communication through Ethernet IP or other
communication protocols to a PLC, wherein the lamination sheets are manually
loaded on the sliding tables with top loading of a template, wherein a plurality of
spacer bars are manually placed at different locations within correspondingly
configured slots and wherein an automatic spot welding is implemented by the
welding machine according to the programmed sequence.

ABSTRACT

The invention relates to an apparatus for automatic spot welding of ventilation
spacers on punoling lamination sheets of a turbo generator comprising a robot
mounted on a horizontal plate, a fixed spot welding machine, a robot controller,
a gripper mounted at the end of robot wrist, two pneumatic sliding tables and a
control system for sequential control of equipment, wherein the robot controller
is enabled to initiate a communication through Ethernet IP or other
communication protocols to a PLC, wherein the lamination sheets are manually
loaded on the sliding tables with top loading of a template, wherein a plurality of
spacer bars are manually placed at different locations within correspondingly
configured slots and wherein an automatic spot welding is implemented by the
welding machine according to the programmed sequence.