In sketch based modelling, sketches are attached, or placed on the face to which they will ad or subtract the feature the sketch is modeling.
Mapping a sketch to a face gives us the ability to give an “un-attached” sketch a mapping to orient the Sketch, or to Re-Map a sketch that is connected to the wrong Face.
One of the more common uses of re-mapping a sketch is when a sketch loses it’s underlying element. This happens when design history is changed. The internal named of FreeCAD loses track of the name assigned to the sketch.
To Map a Sketch to a Face begin by selecting the Face. The sketch I will be using is currently “Mapped” to the XY_Plane. So the Sketch Origin is at the Body XY_Origin.
Sketch Origin and Circle Center
Sketch in Relation to Cube
Sketch Origin and Body Origin Overlapping
Select the Top Face of the Cube.
Click the Map Sketch to Face Icon
Select the sketch you wish to map from the list and Click OK.
You will be presented with the various attachment methods. The dialog will list all available attachment methods for your selection. If the only options is Don’t Attach, it means your selection is invalid.
For our exaample, use the pre-selected, “FlatFace” and Click OK.
The Sketch will be re-position so that the Origin of the Sketch is on the lowest numbered Vertex of the Plane. Notice when we show the Circle it is not the circle origin that is placed it is the Sketch origin.
This portion is overly technical, you may want to wait to complete this portion of the exercise until you understand Attachments and Placements more.
Now let’s move the Box and see the sketch move with it. We will need to Attach the BOx first so that it can have its own position inside the body.
Select the Box, and click the Ellipsis
In the Attachment mode select XY on plane, and in the Attachment select XY_Plane ( you will have to have the Body XY Plane Showing, and select it from the view). and Click OK.
Next add support, Click the ellipsis in the Support entry, Click on XY_Plane
Now your Box has it’s own placement and can be re-positioned within the Body. ( Normally this is not the recommended approach. ) Although, the transform tool is not available you will need to use the properties.
Change the X and Y Position in the attachment and you can see that the sketch moves with the Box, while the Body Origin remains the same.