Extrude and Cut
Use Extrude to give the closed areas of a sketch a third dimension. Select one or more regions, type a distance, and choose what the result does to the bodies already there. The same tool with Combine set to Subtract is how you take material away again.
What it consumes: regions, not lines
An extrude consumes regions: the closed areas a sketch splits itself into. Regions and Profiles covers how a sketch becomes them. Pick one, pick several, or turn on All regions and let the sketch decide.
The switch matters more than it looks. Pick regions by hand and the feature holds on to those specific areas, so a circle you draw somewhere else in the sketch later is ignored. A circle you draw inside a picked region is not: any region you did not pick that sits inside one you did is cut out on every rebuild, so it arrives as a hole. Turn All regions on and the feature re-reads the sketch every time it rebuilds, so anything you draw later is swept in automatically.
A region you select is always filled. Holes come from the regions you leave out.
Which way, and how far
| Setting | What you get |
|---|---|
| One direction | One prism, growing from the sketch plane |
| Symmetric | The distance split evenly about the plane, half each side, as one solid rather than two glued together |
| Two directions | A distance forward and a different one back, each its own field |
Distance takes anything a dimension takes: a number, a parameter, an expression. Keep it up to 500 mm, and note that it cannot be zero.
One rule decides which way is forward. A sketch on a world plane always grows along its normal. A sketch on anything else, meaning a face of the model or a reference plane, grows along the normal when you are adding or making a new body, and into the material when you are subtracting. A cut sketched on a face therefore does the obvious thing without you flipping anything.
New body, add, or subtract
| Mode | What happens |
|---|---|
| New body | The prism becomes a body of its own, touching nothing |
| Add | It joins whatever it touches. Nothing to touch? You get a new body |
| Subtract | It is removed from one body you name |
The two are not symmetric. Add has no target: it tests every body, fuses into the ones it overlaps and merges them into a single survivor. Subtract asks you to name the body to cut, so pick it before you confirm.
Where it goes in the timeline
Creating an extrude hides the sketch it consumed. The sketch is not gone. It is a step in the timeline like any other, so re-open the sketch to change the shape, and open the extrude to change the numbers: distance, direction, and what it combines with.
See also
- Where an Extrude Stops: where the prism stops and where it starts
- Regions and Profiles: what it consumes
- Union and Intersect: joining bodies that already exist
- Cut and Push Face: removing material without a sketch