In FreeCAD, as many other CAD systems, we use Sketches to draw out features of a 3D shape. When the feature is defined we use a 3d tool like Pad or Pocket to turn that 2D profile into a 3D feature.
There a few basic concepts that will be useful in beginning to understand how Sketches work in FreeCAD. Of course always keep in mind that FreeCAD is an Open Source piece of software and is constantly evolving and improving. Advice and instruction can become out-dated quickly.
If you would like to learn just by doing just jump down to the Step-By-Step portion.
First, we need to understand that the Sketch in Part Design need to function as a subpart of the a Body in order to be useful. When you create a sketch it will be added to the Active Body
The Active Body , is simply the object you are currently working with, changes are applied to this Body. It is Highlighted in Blue.
IMPORTANT: Many stumble of the Active Body. To make the body active you simply Double Click.
Second, you can not modify a Sketch unless you are editing the sketch. The toolbar will be grayed out and can not be selected.
The sketch by default shows WITH white lines when it is NOT being edited, AND NOT selected.
The sketch, by default, shows with light green lines when selected.
When you open the Sketcher workbench the Toolbar will be shown as available.
When editing the sketch you will be shown the Sketcher Grid and the sketchlines. The Sketch will be rotated so you are presented the XY plane as viewed from the top.
There are two main toolbars you will spen most of your time with in Sketcher. These are the Geometries and the Constraints
The geometries toolbar contains all the shapes that we will use to construct or 2D profile.
Constraints describe the properties, or behavior of the geometries. For example we can Constrain a line to a given length.
Degrees of Freedom
Degrees of freedom is used to indicate, in which ways, the sketch is unconstrained. It is normal practice to “Fully Constrain” you sketch. This is done by givining it dimensions and anchoring. In a simple example a square may have length and width and have a “Coincident” constraint with the origin. This makes the square fixed in space and in size and would become fully constrained.
The Tasks Tab Dialog
All of the activities that take place in Sketcher are reflected in the Tasks Tab and the multiple dialogs shown there. There are five dialogs.
- Solver messages Dialog – The solver messag displays remaining degrees of freedom and errors encountered by the solver. This dialog will see a lot of use.
- Edit Controls – Edit controls allow you to change the ways to interact with the sketch while editing.
- Constraints Dialog – Presents the list of Constraints in the Sketch for editing.constraints
- Elements – Presents the list of elements in the Sketch for editing.
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