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Methods of parametrizing sketches |
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Full parametrization of geometry is recommended for creation of sketches (the basic principles of parametrization are given in section). What is a parametric image). Applying parametric constraints ensures predictable behavior of the sketch geometry during the process of working with the model. If full parametrization of a sketch is required, it is necessary not only to create all the required constraints but also to affix dimensions governing the geometry.
In the scope of parametric mode in the sketch, a system of constraints is created. Constraints can be applied to objects manually or automatically.
Sketch objects are parametrized automatically if in the document the parametric mode is enabled (this mode setup is described in section Parametrization). In this case, the following actions are performed in the building process.
•Constraints are applied to the created objects according to the features of their position. For example, the constraint Horizontality is applied to the horizontal segment.
•Constraints are created that connect different objects if during the construction of these objects a snap was triggered. For example, on segments whose extreme points coincide, a constraint Coincidence of points is imposed.
•Projection links of sketch objects with model objects are formed if used in the construction. Snap to model objects.
•Center marks and centerlines created by the command Auto Centerline, are associatively linked to the objects to which they are affixed.
•Dimensions are created as associative ones — managing or informational. In the future, by changing the values of control dimensions, you can modify the geometry of sketches and the objects constructed based on them in the model. Changing the dimension value is possible:
•in a sketch,
•during execution of the operation, whose source object is a sketch, and in the dimensions displaying mode of the element constructed based on the sketch (see sections Dimensions of sketches and operations: Overview and Changing the operation dimension value,
•using the corresponding variable.
Automatically created constraints can be deleted, replaced with constraints of other types, and missing constraints can be added (viewing and deleting constraints are described in the sections). Working with constraints in the graphic area and Preview and Remove Constraints using commands, creation of constraints manually — in the section Adding constraints manually).
When the parametric mode is disabled, constraints and projection links are not created automatically during the sketching process but can be manually applied to objects. If you have chosen this method of work, it is recommended to add the necessary constraints during the construction of the image, rather than after the entire sketch geometry has been created. This will avoid geometry distortions during the parameterization process.
Sketch objects can be obtained by projecting model objects into a sketch and intersection of model objects with the sketch plane. Such objects are parameterized automatically regardless of whether parametric mode is enabled or not.
The created constraints and dimensions are deleted from the sketch objects Degrees of freedom, which ensures preservation of the specified position and dimensions of objects. The presence of degrees of freedom in the sketch indicates its status. If there are degrees of freedom, then the sketch is not completely defined. It means that the possibility of unforeseen changes to its geometry remains. When all degrees of freedom of objects are removed, the sketch becomes defined. When editing the model, such a sketch will change correctly without distortions (for example, when editing the model object that the sketch object is linked to, or when changing the value of the sketch's controlling dimension through a variable). We recommend that all sketches in the model have the status defined. Detailed information on the statuses of the sketch and indication of its objects depending on the presence of degrees of freedom is provided in the section. Diagnostics of a parametrized sketch.
See Also
Using model objects when building a sketch
Notes on using certain types of objects in sketches
