Getting Started with Puzzle Printing

Printing Your First Puzzle

For a first puzzle print, I suggest Half-Hour by Stewart Coffin. In addition to being a fine puzzle, it's very easy to print, with simple pieces that can tolerate printer imperfections.

To print it, first go to the Thingiverse page for Half-Hour, here: https://www.thingiverse.com/thing:3355035/

Download the STL file coffin.half-hour.pieces-smaller.stl, load it into your slicer, and render ("slice") it for printing. The default settings in your slicer should work fine: Half-Hour is easy to print and should tolerate most settings. If you'd prefer to print the pieces one (or a few) at a time, your slicer software should provide options to split apart models and rearrange the components.

Then, just follow your 3D printer's instructions to print the rendered model. After some time (around 7 hours on my printer), you'll have a functional copy of Half-Hour. Enjoy!

This is a good time to mention an important principle. All puzzles on the Printable Puzzle Project are freely available and open source: anyone may download and print them for personal use. However, the puzzle designs and models are copyrighted. They're posted with the generous permission of their designers, and the designers retain all rights as copyright holders. Our non-commercial license allows for unlimited personal use, but strictly prohibits selling or otherwise monetizing any of the models or other work posted here.

Snap Joints

Half Hour is a particularly simple model; each of its pieces can be printed directly as a single component. Many interlocking puzzles, however, have pieces that are more complex. For example, in the figures above, you can see one of the pieces from another Stewart Coffin design, Coffin's Quartet. No matter how this piece is rotated, some part of it will always extend over empty space - an overhang.

As discussed above, FDM printers operate by building objects in layers on a print bed, so overhangs create a challenge. One solution is to print using supports - temporary structures that provide a base of support for the overhanging components, which can be removed once the print is complete. Unfortunately, supports are not ideal for puzzle printing. They tend to leave visible scars on the surface of the object, which at best disturb the puzzle's appearance, and at worst interfere with the fit and render it inoperable.

This challenge is neatly addressed using "snap joints". Pieces with overhangs can be printed in multiple components, with connectors that snap together once the print is complete. This allows a very wide range of piece shapes to be printed, while ensuring that the pieces have a consistent, smooth finish. The pictures above illustrate how this works for Coffin's Quartet.

If you look closely, you can see a letter "B" stamped on the surface of the joint. There is a corresponding letter "B" stamped on the inside surface of the female joint, which is a bit harder to see in the photo. This makes it easy to determine which joints go together when printing a collection of pieces with many snap joints. In addition, the joints are tapered on one end, ensuring that they fit together in one orientation only, in order to make assembly of the puzzle as "foolproof" as feasible.

The snap joints in our puzzles are designed to be tight and to form a strong, permanent connection. Because the dimensional accuracy of printers varies (more on this below), you might find that some joints come out a bit too loose or too tight. Joints that are too tight can almost always be hammered or clamped into place, and joints that are too loose can be reinforced with a few drops of ordinary superglue. It's a good idea to keep a hammer and some glue on hand; the extra effort will be worth it!

Resizing Puzzles

You may occasionally wish to print a puzzle in a smaller or larger size than the one provided, and you might be tempted to use your slicer software's "resize" feature to do this. Don't do it! Resizing the puzzle in your slicer will, as a side effect, also resize the tolerances, making the puzzle fit tighter (if the size is reduced) or looser (if it's enlarged).

The recommended way to resize a puzzle is to re-render it at the desired size using OpenSCAD. This will alter the size of the puzzle while preserving the intended tolerances. For details on how to do this, refer to the Puzzle Modeling tutorial.

Which brings us to:

A Word on Tolerances

If puzzle pieces were printed with mathematically perfect dimensions, they wouldn't fit together at all, because the surface of a piece isn't perfectly smooth. In order to account for this, all of the puzzle piece surfaces are inset by a small amount, ensuring that there is some empty space between them so that they can slide smoothly together. This allowance is the tolerance of the puzzle pieces.

Tolerances are a tricky business: If they're too small, then the puzzle will be uncomfortably tight and difficult to operate. If they're too large, then the puzzle will be loose-fitting and won't hold its shape well. This is a particular challenge with 3D printing, because not all printers yield the same dimensional accuracy or smoothness of output. Even the brand of filament can make a noticeable difference in the fit of the puzzle.

We've taken pains to find tolerances that provide a good balance on most printers. For interlocking puzzles, our tolerances are generally calibrated to be slightly too tight. This is because 3D printed puzzles tend to loosen over time: with a little use, some of the roughness of the surface grinds away due to the natural motion of the pieces sliding together. Keep this in mind if your prints come out slightly too tight; try playing with them a bit, and they should loosen. (If they're so tight that the puzzle is difficult to operate, that's another story; the fit is probably not quite right for your printer. We love feedback, so if this happens, please report it to the PPP team.)

All of our models are generated from source code using OpenSCAD, with adjustable tolerances, so if you want to play around with different settings, you can generate new STL files from the OpenSCAD source. This requires a little more effort, though - see the Puzzle Modeling tutorial for details.

That's all! Head over to our Puzzle Index for some other great designs to print, or check out our other tutorials.