T-FLEX Parametric CAD. Fundamentals. 2D Design

Fundamentals. Two-Dimensional Design
490
Note that modifications in variables and expressions driving the construction lines, also affect the
dimension display and dimension values.
The dimensions themselves can be also used for modifying position of the construction lines, with
which these dimensions are connected, and as a consequence, values of the variables determining
parameters of these lines. To do that, it is necessary to point the cursor at the dimension value and hit
. Chosen dimension value is selected for editing. Upon modifying the dimension value, the system
automatically changes position and parameters of construction lines, on which the given dimension is
based. If position of the given line was determined by a variable, the value of this variable will be
also changed.
When using variables as construction line parameters, try not to use complicated expressions. The
recommended approach is defining construction line parameters via a standalone variable or a simple
expression. All complicated mathematical relations can then be defined within the variable editor. This helps
keeping definitions in one place, without need of visiting all possible commands and searching through all
elements for handling.
Variables and Visibility Levels
It is often convenient to define visibility level values by
variables. This helps covering a wider variety of configurations
by a single parametric model. Consider, for example, the
parametric drawing on the diagram.
The two views are interdependent. The slanted line was
constructed as passing through a node, at a specified angle to the
horizontal. A variable AL is introduced as the parameter of the
line. The configuration on the diagram corresponds to the value
of AL = 130. Let’s modify the variable value to AL = 60.
The upper dashed graphic line on the side view stays after
modifications, which is wrong. This graphic line was originally
created on top of a construction line parallel to the horizontal line
and tangent to the circle. This flaw can be fixed by using the
variable LEVEL as the value of the visibility level of the dashed
graphic line.
The value of this variable can be defined by the following
expression:
LEVEL = AL > 90 ? 0 : -1
The visibility interval for graphic lines is set from 0 to 127 (inclusive). In our case, if the variable AL is
greater than 90, then LEVEL equals 0, which is within the visibility interval. Therefore, the graphic line will
be drawn. If AL is less than 90, then LEVEL = -1, which is outside the visibility interval, and the graphic
line will not be drawn. This drawing sample can be found in the directory “Documentation
samples/2D Design\Variables\Drawing 1.GRB”.
This approach allows creation of models representing a family of product modifications. An example could
be a drawing of a bolt with various head styles.