Page 35 - Welding Robots Technology, System Issues, and Applications

Introduction and Overview
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1. Two industrial robots ABB IRB6400 equipped with the S4C+ controllers.
2. Especially designed electric-pneumatic grippers to hold firmly the glasses.
3. Two automatic deburring belts controlled by the robot controller IO
system.
4. One industrial PLC (Siemens S7-300) that manages the cell logic and the
interface to the adjacent industrial systems, providing to the robot
controllers the necessary state information and the interface to the factory
facilities.
5. One personal computer to command, control and monitor the cell
operation.

Briefly the system works as follows: the first robot verifies if conveyor 1 (Figure
1.8) is empty and loads it with a glass picked from the pallet in use. The system
uses a rotating circular platform to hold three pallets of glasses, enabling operators
to remove empty pallets and feed new ones without stopping production. After
releasing the glass, the robot pre-positions to pick another glass which it does when
the conveyor is again empty. If the working glass model requires deburring, then
the centering device existing in the conveyor is commanded to center the glass so
that the second robot could pick the glasses in the same position. With the glass
firmly grasped, the deburring robot takes it to the deburring belts and extracts the
excess of PVC by passing all the glass borders on the surface of the deburring belt.
When the task is finished the robot delivers the glass on conveyor 2, and proceeds
to pick another glass. The deburring velocity, pressure, trajectory, etc., is stored in
the robot system on a database sorted by the glass model, which makes it easy to
handle several models. Programming a new model into the system is also very
simple and executed by an authorized operator. There is a collection of routines
that take the robot to pre-defined positions, adjusted by the given dimensions of the
glass, allowing the operator to adjust and tune positions and trajectories. He can
then “play” the complete definition and repeat the teaching procedure until the
desired behavior is obtained. This means being able to control the robot operation
with the controller in automatic mode, which is obtained by including some teach-
pendant features in the process for operator interface.

Another important feature included in this robotic system is the possibility to adjust
production on-line, adapting to production variations. This objective is obtained by
using a client-server architecture, which uses the cell computer (client) to
parameterize the software running on the robot controller (server). That can be
achieved offering the following services from the robot server to the clients:

1. All planned system functionalities by means of general routines, callable from
the remote client using variables that can be accessed remotely.
2. Variable access services that can be used remotely to adjust and parameterize
the operation of the robotic system.

With this features implemented and with a carefully designed operator interface
(Figure 1.9 and Figure 1.10) and robot server software, it’s possible to achieve a
system that requires limited human intervention related with adjustment tasks to