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Exporting to STL

STL, which stands for Standard Triangulation Language or Standard Tesselation Language is a file format used by stereolithography software. STL-Files describe the surface of 3-dimensional objects. BURRTOOLS can export single shapes into STL files so that 3D printers can quickly fabricate prototypes of them.

Introduction to 3-D printing

There are two popular forms of 3-D printing: SLS and FDM.

The SLS (ShapeWays and TNO) laser sinters nylon. ShapeWays currently charges by the volume of sintered nylon. SLS pieces are always white.

FDM (Stratasys) charges by the time it takes to make the piece. It has two modes: solid and sparse. Sparse mode is quicker and uses less material. In sparse mode the interior of the pieces are honeycombed.

Having a hollowed piece will be cheaper and quicker for SLS — it will be the same cost and speed for FDM because a hollow piece will still have a support structure inside the hollow, but it will be of a different material. The thing to realize is that with SLS, if there are no holes to the hollow part of the piece, the nylon "sand" will be captured. This should not be a problem except for the weight of the piece. But keep in mind that some printing services will charge you for the surrounded volume as well as the for the actually printed volume.


The main menu entry Export - STL opens the window seen in Figure StlExportWindow. The window has a shape selector, a 3-D view of the selected shape and some parameters that control the shapes created. The exact parameters depend on the grid of the current puzzle. The 3-D view displays the shape the same way as it will be exported into the STL file, so you can see what the shape will look like.

On the bottom in the status line you can see what volume the current shape with the current settings has.

In the status line are also two buttons to choose how the shape is displayed. Either normally from the outside. The 2nd view will show you the inside of the shape. This is useful if you print hollow shapes and need to see what the internal void looks like.

Figure: The STL-Export window

Hollow Shapes

There are mainly 2 different exporters. One for the sphere puzzles and one for all other polygon based puzzles.

When creating spheres you can simply create hollow shapes by giving the inner radius a value that is different from zero. The resulting shapes will automatically have a lot of holes that connect the inside and the outside. Those holes will be symmetrically placed and they are in places on the sphere where they normally don't interfere with solving.

For polygon based puzzles things are not that simple. Here a hole at the wrong place could make pieces stop from sliding or get stuck into one another. That is why you can specify where exactly you want the holes. Initially there are no holes at all. By shift-clicking onto faces of voxels you can "drill" a hole through this face. The hole will always be in the centre of the face. Ctrl-clicking on the face will remove the hole again.

Don't forget to first set a proper wall thickness and tube size to actually see the holes.


The following parameters control the generated shape and file.

Filename and Path control the name and path of the generated file. Those are common parameters for all grids.

Binary STL: controls whether a binary or a text STL file is created. Normally binary files are the right choice because they are much more compact. But sometimes it might be useful to use the text form. For example when you want to see what is going on in the inside of an STL file, or when your printing service has problems with the binary file.

For polyhedron based grids there are the following parameters that control the shape of the generated pieces

For spheres the parameters are as follows:

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