Update, the first: I just had a belt snaplock break today, so decided to ad an adjuster loop so that I can unpick and resew the outer buckle end and have an adjustable sliding inner at the the other end, reusing the existing belt's webbing strap. Reduce, reuse, recycle. New SCAD and STL uploaded, pics in the morning. Late night playing with thing designs here, so it's bedtime and a bit beyond as I write this.
I watched the Makers Muse video on designing snaplocks recently and decided to have a crack myself. It's been on my to-do list for a while, so a big-up and thanks to Angus for getting me off my a*** and finally having a crack, and for all the skills he shares. What I know about the actual art of 3D printing is down to Angus! Subscribe to the channel here [https://www.youtube.com/channel/UCxQbYGpbdrh-b2ND-AfIybg], if you're not already.
Anyway, the trick to designing one of these, as Angus points out, is clearances. The better your printer, the tighter (and tinier) your buckle can be. I work with a cheap Tronxy P802E, so I designed mine (scad file included in things) with 0.5mm of space around all mating faces and the resultant buckles in PLA are free moving and positive latching in PLA. The design evolved, from some not quite well enough spaced bits (wouldn't snap together without filing) to the now relatively refined design (evoIII) I've uploaded here.
You engineers out there (I'm an audio electronics tech, not a mechanical engineer) may find it over designed, but it's not injection moulded ABS, and these are eventually intended for real world application, both in future sewing projects and in my magnum opus, 3D printed hardshell panniers for my touring bicycle, to replace my 25yo Torpeako "karimor pattern" cloth panniers. (Will also include a "rackless" mounting system I am already trialling in a "hobo hack" tool bottle on my bike. I will be opening the source to all of these under a CC4.0 A-NC-SA licence, as per my Dryline project.)
I was planning to do my final prototype in PETG, but my printer is still not quite playing nicely and I kept getting thermal runaway errors. Probably need to tweak my Cura profile for the brand of PETG I use. PLA will do for the projects I have in mind.
Tronxy P802E (Prusa i3 clone)
0.2mm with 0.2mm starting layer
3D Fillies PLA+
60% cubic (Cura infill option)
Red (blue for some prototypes)
Ultimaker Cura slicer settings
On top of layers and infill, support was turned on but only where the overhang was directly above the buildplate, not above other layers. I used a skirt as my "adhesion layer", just to purge the nozzle and get printing started properly. There are no supports used inside the snaplock, as cleaning them out is likely to create obstructions. the bridging is short enough that no drooping occurs to cause obstruction, even at an overall buckle width of 30mm.
Wall thicknesses are 1.2mm, hence the springy parts, like the clip prongs are solid, but the voxels are aligned. This makes for a solid, but elastic prong.
Part cooling is minimal. 50% is as high as I would bother with on PLA with a heated bed. On an unheated bed, I wouldn't run a fan at all, especially on a cold day in the workshop!