I was looking for a better solution for removing the coffee grounds from the portafilter of my DeLonghi EC 680. Up until now I used a spoon or knocked the grounds on a kitchen towel. Both made a big mess. With my interlocking/screw on knockbox it is just two to three raps and the grounds drop as a puck in the box and can be put into the bin or the compost. The knockbox has enough room for two pucks but i usually empty it after every load. It might fit other portafilters from different brands but I have not tested this. This fits the 52mm inner diameter and three tabs of the portafilter of a Delonghi EC 680 perfectly.

Model: This is a remix of a interlocking funnel. Thanks to the original designer for figuring out the correct dimensions for the interlocking mechanism. The model already has supports for the interlocking tabs, which can be removed easily. I printed mine in TPU with a high infill, so I can rap away on my kitchen counter without worries. The prototype was PLA and it worked great as well but might break earlier.

UPDATE 13.10.2020: V2 replaces original file, fixing some minor non-manifold errors.

UPDATE 01.11.2024: Added a version without build in supports. HUGE thanks to user https://www.thingiverse.com/AndrasKovach for changing the model in Fusion and sending it to me!