When I bought my 3d printer in 2024, a Prusa Mini+, one of the first insights was that my prototype parts were too big, with long waiting times between printed iterations, plus wasted filament. So I opted for M3 screws and learned that nut reachability required a lot of room that could have been used for other construction purposes. So my third attempt was binders aka fasteners (Verbinder) inspired from joinery in wood working: Dovetails, ribbed plugs and sawtooth holders, all designed in FreeCAD.
The given dimensions of 6x(2x3)x4 mm are only half the truth: I use those lengths on the receptacle (receiving end), and reduce the binder size by 50µm or so. The exact value depends on environmental conditions (no kidding); I found that the colder my place, the larger I had to print the binders. A friend also reported that this is material-dependent, e.g. the effect is larger for PLA than for PETG. For reference, my prints here use natural PLA filament.
My prints often have base plates that everything else is mounted upon. With dovetail binders, instead of having one big base plate, I can print multiple pieces and adjust the final plate size later on with intermediate plates. For example, a corner plate looks like this, with horizontal and vertical receptacles for dovetail joints.
Lowest plate thickness is 1.5mm, which is the thinnest to be somewhat stable; below that, breaking and strong bending is probable. With these 1.5mm, the horizontal binder receptables have a total height of 1.5+2.5=4mm, and the vertical binders 1.5+3=4.5mm. I used this particular corner plate (60x60mm) for a second iteration of my ergonomic hand-wired keyboard with originally 120mm length, later upgraded to 140mm with the help of a 20mm "mid plate".
Soon I discovered that for vertical binders, the receptable (red below) had a hard-to-print overhang; a gable roof (Satteldach) was the solution. Printing with support structures, or relying on short bridges coming out ok, would have been possible options too. I prefer the roofed dovetail though.
On my printer, 60° between vertical line and roof line is a realistic scenario; 65° is pressing my luck and 70° not feasible anymore. Note that the "top nut" slot (blue) uses the same roof principle. Corresponding to the receptacle, the 1-roof dovetail binder uses the same 60°.
And shortly afterwards I had a scenario where both bound parts were printed vertically, but in opposite directions, necessitating double roofs.
The 2-roof binder completes the classic horizontal and vertical scenarios.
You might have wondered about the blue "plug" in the multi-receptacle part three images prior. The plug exists for receptacles that have to be printed sideways; this happened e.g. on my keyboard "per-finger strips", which absolutely have to be printed sideways.
The "ascent" (green) portion of the receptacle cannot be dovetail-formed because the outer edge would have to be printed into thin air. The "reverse dovetail" forms a half-roof again, but this has no holding power whatsoever, so vertical "ribs" (red) of 0.3mm depth and 1.2mm between ribs do the holding. And yes, this is at the limit of what the printer can do, and it took me a lot of tries to find a combination that holds well, and also can be plugged and unplugged in a reasonably comfortable manner.
The corresponding plug has the same ribs, this time with 0.2mm depth (instead of 0.3mm). The thickness of 8mm outer and 4mm inner (violet) can be well printed. I did a thinner one with just 2mm inner and 4mm outer, which is pretty much at the limit: The thin plug can only be printed as single piece on the plate, otherwise filament remains at the extruder are already enough to knock it off the plate.
As an alternative that adheres better to the hotbed plate, I designed an 8-array with additional ground as "knock protection", which can be broken off later. Everything is optimized to reduce pauses where the printer is moving without extruding, e.g. the beveled dovetail top.
Sometimes it is not easy to say at which height a rod or other structure should be mounted. For this I designed a sawtooth holder, used e.g. in my rollermouse to hold the rolling cylinder.
Since the holder needs to grip tighter than the (more easily removable) plug, the holder teeth are 1.5mm apart (instead of 1.2mm) and have 0.7mm depth (instead of 0.2mm). Again after much experimentation, I found that ladder steps below 1.5mm were really not that feasible. The receptacle has a lot more teeth so that vertical adjustment has a lot of options.
A slight flatting of 0.2mm at the sawtooth ends is a trade-off between easy slide in and remaining grip. Like all other receptacles, I embed the sawtooth receptacle directly in the target part, e.g. into the palm rest for my keyboard/rollermouse combination.
After reading everything above, you might want to try it -- so here is the binder FreeCAD file (2025-03) with the exact dimensions. Often I used angles to determine distances, instead of using the distances directly, so some sizes given above are not exact; this will become clearer by looking at the sketches. Almost all binders have "array" counterparts so you can print 8 pieces at once.
The etched triangles in some parts are for print orientation in the slicer, because my FreeCAD bodies are generally in target orientation, not 3d print orientation. Receptacles are test parts only; for your target part, copy the pertinent sketch to your body and make your own pocket. And with that, I hope you learned a bit here today, and have fun printing and binding!
EOF (Apr:2025)