Last modified on 27 April 2014, at 11:15

OpenSCAD User Manual/STL Export

STL ExportEdit

To export your design, select "Export as STL..." from the "File --> Export" menu, then enter a filename in the ensuing dialog box. Don't forget to add the ".stl" extension.

Trouble shooting:

After compile and render GCAL (F6), you may see that your design is simple: no. That's bad news.

See line 8 in the following output from OpenSCAD 2010.02:

Parsing design (AST generation)...
Compiling design (CSG Tree generation)...
Compilation finished.
Rendering Polygon Mesh using CGAL...
Number of vertices currently in CGAL cache: 732
Number of objects currently in CGAL cache: 12
   Top level object is a 3D object:
   Simple:         no                <*****************
   Valid:         yes
   Vertices:       22
   Halfedges:      70
   Edges:          35
   Halffacets:     32
   Facets:         16
   Volumes:         2
Total rendering time: 0 hours, 0 minutes, 0 seconds
Rendering finished.

When you try to export this to .STL you will get a message like:

Object isn't a valid 2-manifold! Modify your design..

"Manifold" means that it is "water tight" and that there are no holes in the geometry. In a valid 2-manifold each edge must connect exactly two facets. That means that the program must be able to connect a face with an object. E.g. if you use a cube of height 10 to carve out something from a wider cube of height 10, it is not clear to which cube the top or the bottom belongs. So make the small extracting cube a bit "longer" (or "shorter"):

difference() {
	// original
	cube (size = [2,2,2]);
	// object that carves out
	# translate ([0.5,0.5,-0.5]) {
	    cube (size = [1,1,3]);	
Correct use of difference

Here is a more tricky little example taken from the OpenSCAD Forum (retrieved 15:13, 22 March 2010 (UTC)):

module example1() {
		cube([20, 20, 20]);
		translate([-20, -20, 0]) cube([20, 20, 20]);
		cube([50, 50, 5], center = true);
module example2() {
		cube([20.1, 20.1, 20]);
		translate([-20, -20, 0]) cube([20.1, 20.1, 20]);
		cube([50, 50, 5], center = true);

Example1 would render like this:

A not valid 2-manifold cube (simple = no)

The example1 module is not a valid 2-manifold because both cubes are sharing one edge. They touch each other but do not intersect.

Example2 is a valid 2-manifold because there is an intersection. Now the construct meets the 2-manifold constraint stipulating that each edge must connect exactly two facets.

Pieces you are subtracting must extend past the original part. (OpenSCAD Tip: Manifold Space and Time, retrieved 18:40, 22 March 2010 (UTC)).

For reference, another situation that causes the design to be non-exportable is when two faces that are each the result of a subtraction touch. Then the error message comes up.

difference () {
   cube ([20,10,10]);
   translate ([10,0,0]) cube (10);
difference () {
   cube ([20,10,10]);
   cube (10);

simply touching surfaces is correctly handled.

translate ([10,0,0]) cube (10);
cube (10);