LIBRARY ı6ıul 0) - Cranfield University

Step 21
Step 22
If the wire feed speed, WFS , is smaller than its maximum allowable value,
then increment its value by a fixed amount (e. g. 0. S m/min) and return to
Step 5. Otherwise proceed to Step 22.
Output the list of predicted sets of welding parameters in a growing order of
possibility of defects being present, using as a sorting factor either Pr(arc), if
GAP > 0, or Pr(und) otherwise.
This algorithm was used to generate welding parameters for the welding trials.
3.3.2.2 Robot programming
In the robot programming branch (dashed line in Figure 3.2), the weld joint
positions are defined and the program extracts geometrical information about the
joints. Two outputs can be obtained: a) the robot program (ASCII file), ready to be
compiled, and b) a co-ordinates file, which can be used in an off-line programming
software, such as Workspace to generate the robot program and to simulate it. The
robot program is then translated to the specific binary code and downloaded to the
robot controller for execution. The current implementation generates robot programs
in ARLA (ABB Robot Language) and includes Workspace commands for simulation
purposes and also commands for communicating with the control system.
The off-line programming module assumes that the plane formed by the X and
Y axes of the CAD world co-ordinates frame (WCF) is parallel to the robot
installation floor and that the Z-axis points to the space above the floor in. a direction
opposite to the gravitational force vector. The welded component should be designed
in its final welded form as a continuous solid, using the solid modelling tools provided
by AME (AutoCAD Modelling Extension), such that its orientation relative to the X-
Y plane of the CAD WCF is as close as possible to its real orientation relative to the
X-Y plane of the robot WCF (i. e. relative to the welding cell floor), since such
orientation is used to extract information about the welding position and will affect
the welding parameter generation. The origin of the CAD world co-ordinates frame is
considered to be the origin of the workpiece co-ordinates frame in the real cell. The
origin of the robot's world co-ordinates frame is assumed to coincide with the origin
of the co-ordinates frame fixed at the robot basis. These considerations are easier to
visualise by using graphical simulation of the robot workcell (see Figure 3.5).
The weld joint is defined by the user by either selecting the corresponding
edge in the solid model or by selecting the edge adjacent surfaces (see Figure 3.6),
whose intersection forms the edge that corresponds to the weld joint. By using built-
in AME AutoLISP® functions' different types of intersection curves and related
information can be obtained, depending on the types of surfaces that form the
intersection. In the current implementation, only linear intersection curves were
1A description of the AME AutoLISP functions and their sintax can be found in the AutoCAD
Release 12 - AME 2.1 AutoLISP and API Manual.
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