Hi, I made a silicone mold for the Eureka Mignon bellows, which float around on Thingiverse and Printables since years. The original file, for which this mold uses a modified version of for the “insert” of the mold, likely came from user “rmanalan” on https://www.thingiverse.com/thing:4703218. 
 

I created this mold as an experiment, as I had some silicone mold mix lying around and always wondered if I could recreate the silicone bellow that people sell on Etsy for the Eureka Mignon. Turns out I can, I think... 

Instructions Printing: 

• First print “bellows_base” (Photo 2) as this will be the base for all other prints to slot into
• Then print 2x “bellows_wall” and slot 1 wall into the base (Photo 3)
• Print “bellows_inside_with_hole” and slot it into the center of the base as well (Photo 4)
• Now slot in the 2nd wall 
• Lastly, print “bellows_hole” and slot it into the hole on top of the center piece in order to create an air hole in the mold later (imo. important as for the bellows to suck less grinded coffee back up the grinder later). 
• Alternatively just print as step 3 the “bellows_inside_no_hole” and skip step 5 

Instructions Silicone: 

• In order to create a gap as tight as possible on the 2 walls before pouring silicone, you should put some tape on the outside (Photo 5). Additionally you could put some rubber band around the mold to hold it even tigther. 
• Now pour your silicone mix into the mold (Photo 6). I mixed my neutral looking silicone mix with black acrylic paint to create a darker color. 
• Make sure to shake and move the mold a bit around during & after pouring to get rid of as many air bubbles as possible. (Make sure that the mold does not slot out of the base if you move it around, otherwise it will be a mess!) 
• Let it set a bit and pour again a little bit more after a few minutes to fill the mold as high as possible until the top (Photo 7). This should create a perfectly flat top. 
• After the silicone cured (I waited 18hrs or so), open the mold by removing the base first and then the 2 walls. I did this by slotting a knife into the slits where the walls meet and pry it open (make sure to do it slow and steady in order to not break the mold if you want to reuse it another time). Dont forget to remove the base first. 
• Then you can remove the inside by just “degloving” it. 
• This should now result in a finished silicone bellows (Photos 8 & 9) that should fit the existing single dose hopper from user “rmanalan”! (Photo 1)
• The final thickness of the bellows is around 3 mm and the mold should use around 50ml of silicone. Maybe mix a little bit more just to be safe. 
   

Disclaimer:

The silicone I used is relatively soft as it is meant for mold making. If you would buy silicone just for this project, you should buy silicone that is relatively more rigid after curing. 

For me this resulted in a bellows that does work well, but that is deforming relatively easy at the base which makes it a bit annoying to put in and take out of the hopper.

I mitigated this problem by cutting of my old bellows just above the first fold (printed in TPU) and putting it like a glove around the first fold of the silicone bellows (Photos 10 & 11). 
This rigidness at the base makes it perfect now to easily slide in and out of the hopper and hold its form when pressing onto it. (Photo 12)

If you would happen to run into the same problem because you might also use mold making silicone, but dont have an hold hopper to cut up, I included a file called “bellows_stabilizer” that you could print in TPU (But I think PLA should also work… Let me know if you try that out) and put like a glove around the base & first fold of the silicone bellows. 

Happy grinding!