This is a two-piece clip to seal bags hermetically (under ideal circumstances). It can be used to seal bags of food and can even turn disposable filament packaging into resealable airtight bags. The latter is especially interesting if your filament came in mylar bags, because those are much better at keeping out moisture than plain plastic bags and it is a pity to simply throw them away. Although some manufacturers offer zip-lock plastic bags with their filament, non-metallic plastic bags will slowly but certainly transfer moisture to the inside and you need to refresh desiccant more often.
The clip has two gaps, one narrow gap with a little zig-zag in which the bag should be inserted, and one wider gap for an insert (the clip has an extra ridge at this side). By pushing the insert into the clip, it clamps the bag shut. See the video for an example. You can use this on a cleanly cut bag without needing to fold it, but easiest is to fold the bag and slide the clip over the fold.
To open the clip, slide out the insert. Usually you should be able to pull the closed clip off the bag with a bit of effort, if not then you will have to open it first.
There are two ways to make a custom clip that fits your bag:
- The recommended way is to use Customizer to create a new model from scratch. This offers some advantages: you can configure the model to have extra nubs that make it easier to open, and it will also have chamfered corners at one side that make it easier to insert a bag. If Customizer is broken on the Thingiverse website, here are instructions to run it on your own computer.
- Take one of the provided 10 mm STL models and scale it in the X direction to the desired length, using your slicer program or a 3D editor. (Eg. for a 6cm clip, scale X to 600%.) This method is quick and easy but you won't have the advantages of the models that can be made in Customizer.
To determine what gap width works best for a particular bag, you can print and test a few small test clips, and then make a larger clip for the one that clamps the bag well without being difficult to remove. If you have accurate calipers or a micrometer, you can make a good guess at the optimal gap width by adding 0.5 mm to the thickness of the bag (folded or not, depending on how you want to seal it). You probably shouldn't go below a 0.8 mm gap though.
Print with at least 2 perimeters and a good number of top and bottom layers.
If your printer is not large enough to print a single clip for a large bag, just print two and mount them side-by-side (see photos of filament bags).
These work in any material although PETG is the filament of choice due to its flexibility and durability. PLA will provide a stiff clip, but it does tend to bend over time and lose some of its springiness (especially in warmer environments). It also has a higher risk of breaking especially after it has absorbed some moisture. ABS is somewhere in between PETG and PLA when it comes to stiffness and durability.
Be sure to cut any stringing that may be present in the gaps, so they are not obstructed. You may want to apply a little sanding to the nubs to make them more comfortable to use.
Before using the clip, push in the insert and slide it out a few times to make it work smoother. If you want to make it even easier to open the clip, apply a very small amount of silicone oil to the insert.
Added the option to include ‘nubs’ in the model that make it easier to push open the clip. Also added a chamfer to the corners to make it much easier to insert the bag into the clip.
Reduced material usage for the insert. The old beefier model can still be obtained by enabling the ‘Heavy duty’ option. Also minor tweaks to the profile shapes.