Rancilio Rocky Doserless Bellows

I introduce a bellows system for the Rancilio Rocky Doserless grinder. 

I've been drinking a lot of filter coffee recently. Instead of adjusting my other grinder between espresso and filter settings, I pulled the Rocky Doserless out of the corner it occupied in my pantry instead. As any Rocky owner knows it has problems with the retention of grinds.

So I set out to design a bellows like you might find on other grinders to alleviate this problem. A single push should get 90-95% of the remaining grinds out.

After a few iterations and much reprinting, I present my design for your use! It includes a plate designed to be inserted in the top part while printing to increase the rigidity of the part you actually push on without using a larger amount of TPU.

I printed this in black Novamaker TPU95A with 0.25 mm layers on a 0.4 mm nozzle. Printed at 225 C on the hotend and 55 C for the bed. I would recommend a release agent for the bed as one of my successful prints was ruined when it required the might of a god to pull it free from the build plate. I would recommend a quality TPU for printing this - the Novamaker TPU95A I had was horribly wound on the spool and it required some tension on the filament to despool it. This combined with more than 1 or 2 retractions would cause it to jam in the feeder gears. Follow the manufacturer recommended speed settings. Use 100% infill for this, and the 5 top/5 bottom layers @ 0.25 mm. Go slow for the last ~10 mm or so, you need the TPU to bond well here.

Print the plate in your favorite material, PLA, PETG, etc. This plate is designed to fit tightly into the other print, so your printer needs to be accurate for this to fit correctly. I would recommend increasing the perimeters to at least 6 and removing the top and bottom solid layers. For infill, increase the extrusion width by 50% and use a density around ~40%. I did this and printed it with the honeycomb infill pattern and it worked beautifully. The plate was flexible and strong.  I would not recommend 100% infill as those were prone to warping once set in the top, with would often cause the print of the bellows to fail.