T-FLEX Parametric CAD. Fundamentals. 2D Design

«BOTTOM-UP» DESIGN
«Bottom-Up» Design
When using the “Bottom-up” approach, the assembly model design starts from creation of separate assembly
elements – fragments. A fragment drawing is originally created as a standalone T-FLEX CAD document. In
the process of creation, it is necessary to follow the certain rules that will allow in future to “snap” the
fragment to the elements of the assembly drawing.
A special mechanism is provided in T-FLEX CAD for correct positioning of the fragment drawings in the
assembly − Fixing points or vectors. Such elements should be created in a fragment drawing in advance,
before inserting it into an assembly drawing.
When inserting a fragment, you need to specify the position of the reference elements in the assembly
drawing, which will define the fragment position, orientation and size. The fragment image will be built
according to the specified fixing points or vectors. If no attachment elements are created in the fragment
drawing, such fragment will be attached to the coordinate system of the assembly drawing page according to
its initial coordinates in this page. The position of such fragment can be modified only by editing. To get
associated relations between the fragments and the assembly drawing, attached fragments to the nodes of the
assembly drawing (including the nodes of other fragments).
Ways of Attaching Fragments
When designing assemblies by «Top-down» approach, two ways of positioning the fragment on the drawing
are primarily used in the T-FLEX CAD system:
• Defining fixing vector. In this way, first create the drawing, and then define the necessary number of
fixing vectors. Each fixing vector defines the origin and the positive direction of the X-axis of one
local coordinate system in the drawing. An arbitrary number of fixing vectors can be defined within a
fragment drawing. The fixing vector defines the fragment position and orientation one the assembly
drawing and controls elements visibility.
• Defining fixing points using variables. In this way, the drawing is created first, following certain
rules. The base vertical and horizontal lines are assigned the parameters with the reserved variable
names. Upon assembling, the system will identify the intersection point of such lines as a fragment
fixing point. Multiple fixing points are allowed. All the rest of fragment constructions are done with
respect to the base lines defining the fixing points. The fixing points can define the position,
orientation and size of the fragment within the assembly drawing.
The main difference between the fixing vector and fixing point approaches is in the sequence of creation
steps of the fragment drawing. When using fixing vectors, you need to create the drawing first, and then
specify the fixing vectors. When using the fixing points, one has to create fixing points first, and then build
the drawing of the part based on the fixing points.
There are also differences in the uses of fixing vectors and points. Fragments with fixing vectors are created
as follows: first, the image of the fragment is formed, taking into account the visibility layers. Next, the
complete image is moved to the specified point and rotated by the specified angle without distortions.
Fragments with fixing points are created differently: upon specifying the fixing points, all construction
elements dependent on those points are rebuilt first, and then the image of the fragment is obtained.
575