My first set of sketches for the SLC (Spring Loaded Clasp) fastener. The goal was to create a 3D-printable fastener for a backpack that was durable, inexpensive, and utilized a minimal number of plastic parts in addition to off-the-shelf components.
The SLC design was originally modeled in Solidworks. Pictured here is the fourth major revision.
I went through a heap of physical prototypes. What you’re seeing here is a very small fraction of those. Early versions were printed on an FDM 3D printer using PLA, a great material for fit testing, but not very durable.
The progression of prototypes (moving from right to left), which shows that early designs proved too flimsy and difficult to open.
When I arrived at a design I was fairly happy with, I took the prototyping process a bit further by sanding and painting each part before final assembly. These additional steps made it clear I needed a material that was more durable and required less post-processing.
In an effort to learn another CAD program, I remodeled the SLC-MK4 in Fusion 360. While remodeling, I saw a number of improvements that could be made, including strengthening some thinner sections of the body, increasing the slider rigidity, and reducing the part count.
Like the PLA prototype, the new version of the buckle was printed on an FDM printer, but this time using a much more durable nylon-carbon fiber composite material. The result is an assembly with higher strength, higher abrasion resistance, and a more desirable matte black finish, which eliminates the need for sanding and painting.
An assembled SLC-MK4 prototype. Like the other projects, there are still a number of improvements that can be made including hiding the latch rod ends, eliminating the need for screws and captive nuts in the assembly, and redesigning the latch so it is less prone to debris-jamming.
Lifting the thumb latch separates the two halves of the buckle.