KOMPAS-3D v24

A number of constraints can be defined without express input of numeric values (for example, perpendicularity, fixing, condition for tangency of two curves). To the contrary, such constraints as dimension values must be expressed exactly by numeric values. Some constraints may be defined as expressions (for example, as a function specifying a dependency of the object’s parameter on other objects' parameters).

Some constraints (points coincidence, parallelism, etc.) can be automatically generated during object construction. parametric mode, if the user has enabled this option. For example, points coincidence and position of point on the curve are parameterized via the snap (global or local), and the conditions of parallelism, perpendicularity, and tangency — in the corresponding object input processes. Automatic generation of constraints and relations can be disabled at any time.

Additional constraints can be assigned to graphic document or sketch objects at any time while working with the them.

Associativity of objects (dimensions, hatches, etc.) only occurs during their input due to direct or indirect specification of base graphic objects. There are no separate commands for setting associativity.

Constraints are applied by the following methods:

•By executing the corresponding command and specifying the parametrized object (for example, you run the Alignment command and specify segments which should be horizontal).

•By executing the relevant command and specifying a couple of interrelated objects (for example, you invoked the Parallel command and specified couples of segments which should be parallel).
In this case, only constraints applied expressly (either by referring to the appropriate parametrization command, or by drawing in parametric mode) are saved. Note that new constraints resulting from several previously applied constraints do not emerge automatically, even if they seem completely evident.
For example, you drew three segments and set parallelism of the first segment to the second and of the second to the third. In this case, the constraint between the first and third segments is indirect, as it is created via the second segment. Immediately after deleting the second segment, the first and third ones will be parallel, however they will be edited independently as there is no direct link between them.

•One more way of applying constraints is fixing an associative dimension. If a dimension is associative, it can be fixed with an appropriate command. When a dimension is fixed, its value remains constant after any rebuilding of objects which constitute the image. The dimension value always characterizes a geometrical parameter. For example, the value of an associative linear dimension corresponds to a distance between characteristic points of objects (or of one object) and the value of an associative radial dimension corresponds to a radius of a base circle or arc. Therefore, by fixing the dimension you can establish equality of an object parameter to a constant. The value of each particular fixed dimension can be changed with a special command but cannot be changed by editing objects themselves.
If dependence between parameters of objects should be set in analytical form, then you should first create variables corresponding to the dependent parameters. Then you can enter expressions with the created variables. For example, you can add fixed dimension for a segment length (this will be the linear dimension between the segment ends) and assign the variable name to this dimension. The dimension value may be used in expressions (which are entered on the Variables toolbar).

See Also

Working with constraints in the graphic area

Viewing and deleting constraints using commands