My wife hated the builder supplied garage window inserts in our house (depicting a sunrise), and wanted instead the Stockton style (grid) inserts. I looked around, nothing in Canada, pretty expensive to order from USA ($305 CAD with shipping and taxes, for a set of 8), so I designed and printed them myself. As each one is much larger than the size of my printer's bed (220x220 mm), I had to come up with a way to stitch four parts together for each window. My first design was relying on epoxy glue, and I made one such insert - it seems to hold, but it was rather messy, it doesn't look very pretty (glue shows), and who knows how the PLA + epoxy combination will withstand the elements.

So I designed a new (glueless) version, which completely relies on friction to hold the parts together. I already printed 5 complete window inserts this way, it seems to work very well, it looks better than the glued version, and is plenty strong for the task. To connect the parts, I use a plain medium-size hammer. I start first by connecting the two left side parts, then two right side parts. Just place the parts on the solid flat surface, match the protruding elements with the corresponding gaps, and gradually drive the former into the latter with the hammer (don't drive one connection all the way, as the plastic will crack; instead drive all of them partially, then even deeper, then drive all of them to the limit).

As the second step, connect the assembled left side with the assembled right side, using the "inserts" (dowels). You will need to print 10 dowels for each window. Here you don't need to be as careful, and can drive each dowel individually all the way.

Window insert dimensions (when assembled):

• Full width: 436.8 mm (17.2 inch) - this is a bit less than the original insert width (440 mm, or 17.3 inch), but this is the maximum my printer would accept, and it still works perfectly fine.
• Full height: 280 mm (11.0 inch)
• The protruding elements width (the part which should fit into your window opening): 412 mm (16.2 inch)
• The protruding elements height: 248 mm (9.8 inch)

I am also providing the original (Autodesk Fusion 360) design. You can use it to fine tune your print. For example, if you go to Modify > Change parameters menu option, you can adjust the following parameters if needed:

• hgap (=0.2 mm): horizontal gap between the interlocking elements. If you cannot drive the interlocking elements into the corresponding gaps at all, try to increase this parameter a bit. If on the other hand you can drive it, but the resulting connection is loose, try to decrease the parameter (but it cannot be 0 or negative).

• zgap (=0.4mm): vertical (z) gap between the interlocking parts. Increase it if you cannot drive the protruding parts into the gaps all the way. Decrease it if the part goes inside too far (it sinks). It cannot be zero or negative.

• slant (=0.001 dgr): by default this angle is essentially zero (it cannot be exactly zero, or negative). If the fully assembled insert is slightly convex (when looking at the window from outside), you can try to increase it (something like 0.4-0.8 dgr), until the part becomes flat or slightly concave (which is acceptable as the window glass will be pushing it from behind making it flat).

Finally, if your printer's bed is larger than mine and can accommodate the full required width of the inserts, you can merge the included additional bodies Body30, Body67, Body68, and Body69 with the corresponding model parts.

The weight of each assembled part is ~240g, so one can print 4 inserts from 1 kg filament spool. So it comes to ~$7.50 CAD per window (tax included), or $60 CAD for 8 windows - much cheaper than buying the original parts ($305 CAD). With my printing settings, it takes around 6 hours per part (24 hours per window) of printing time.

I used PLA, as ABS would be warping too much. Also, it's much easier to print bridges with PLA. We will paint the inserts, so hopefully it will last.