Many sleeping bags have the option to zip together, which is really great to cuddle and steal warmth from a significant other. In order to zip together, two mummy bags must each be one right-zip and one left-zip and the zippers need to be of the same manufacturer. My SO's and my sleeping bags (REI mummy bags) fit this criteria; however, we discovered two reasons as to why our sleeping bags could not connect:
1. Firstly, both of the zipper fasteners were on their respective bag’s top zipper. One would have to be on the bottom and one would have to be on the top in order to zip properly. You could potentially flip one of the bags over, but then the head part of the mummy bag would cover your face- not ideal:
2. Secondly, even if the zipper fasteners were on their correct side, you couldn’t attach the fastener to the zipper due to a blocker on the head (item circled):
I really wanted to be able to create one giant sleeping bag to cuddle with my SO while camping, so I turned to 3D printing to find a solution. The zippers on each of the bags were of the same manufacturer, so I knew if I printed an additional fastener with a larger height than the blocker, I could fit it on and zip the two together. I took the measurements of the fastener using a caliper and snapped a couple photos from plan and elevation views. I then brought the images and measurements into Rhino and modeled the zipper fastener, adding one millimeter of height in order for the blocker piece to fit through it.
Some initial 3D models (meshes and STLs):
The final STL:
Once modeled and exported as an STL, I printed two of the zipper fastener models on the Mojo 3D printer at Techshop (this was before I had my very own Prusa :P ):
Once it was printed, I went ahead and tested one of the prints with positive results. The 1mm of height gave the zipper fastener just enough clearance to fit over the blocker while still being close enough to connect the zippers:
I printed two fasteners so that you can zip and unzip all at once (like a typical sleeping bag):
It works! Overall, I was pleased with how this project turned out. 3D printing is a great way to solve real world problems!
When we took the bags out in the wild and tested the prints, we did run into one issue. My SO's bag is a little bit taller than mine, so when we zip the two together, there is a bit of a gap at the bottom (his poor toes were chilly...):
I'm still trying to figure out a way to resolve this issue... but that's for another day. Hope you enjoyed this project- I attached my STL for anyone who needs to zip together an REI Flash and REI Helio bag!
You can find a more detailed blog post here, which includes a GIF of me zipping the bag up :)