Concept is to use magnets to provide the closure force for a bag clip. Original concept also included a magnetically preloaded kinematic hinge concept, but it had a higher parts count and was a little bit of a PIA to assemble, so I switched over to this flexure hinge which I think/hope will be all around easier!…here’s hopin
Here is the hammock sketch…I mean, “concept sketch” :)
The idea being that the magnets at the front are attracting and those in the squeezey side are repelling. This config should help linearize the force of the magnets (kinda :) ). In the center is a notch flexure that will act as the hinge. I was aiming for a simple constant cross-section to make for a quick, easy test print.
And here is the first rev in Fusion. As you can see I basically just copied the sketch. I designed around these 30x10x3 bar magnets. They are almost certainly going to be a little overkill, but I wanted to make sure to have sufficient field to overcome the gaps and hold the bag securely….we shall see (first test print running as I type :) )
I was a little disappointed in the strength of the magnets, and I definitely made the clamp longer than it needed to be (…length? I guess I don’t have a naming convention… Length == distance from one pinchy end to the other pinchy end….#engineered). But even with that, it works otay! And to be fair to the magnets, I think it’s probably a little unfair to expect them to permeate multiple layers of plastic AND whatever bag they’re on, so I should cut em some slack :)
But I did do a number of small tweaks, playing with magnet configs and dimensions. Here is the most recent version, and the one I’m currently using, but I’m sure another revision will come along once I get frustrated with this one for whatever reason. The most significant difference was the change in magnets. To make the print faster while I iterate, I decided to go with these shorter magnets…but lots more of em :) They are 12x6x3mm bar magnets in the same push/pull config as before. Although I made it ‘thinner’ to speed the prints, I kind of like the form factor on these. If you end up making some, I’d love to hear suggestions!
That’s all on this one for now!