Good morning Barista,

I got my Niche Zero on Saturday and after pulling 25ish shots to setup the grinder and the new machine (BDB) I instantly felt the need for a knocker. So i used the time on Sunday to draw and print a few iterations and here's what I came up with:



I saw the old thread here in the forums and also some variations on Thingiverse but I wanted to go a different route. I tried to use as little as possible additional hardware and so all it really needs is a setscrew and a thread insert to lock it in place. It needs some fine tuning but works great already. I printed it in PETG which should work quite well in terms of resistance and longevity of the plastics. Especially the latter is still to be determined of course.

If anyone of you is interested in printing it yourself and trying it out please let me know and I can share the STL privately. As soon as it's tested a bit more I might also publish it somewhere.

Also please share your thoughts.

Helmi,
That is Very Nice! It looks good too.
Are you pleased with how it is working?

I don't have anything to compare to but it works fine I think. It's more effective than snapping my finger against the chute and hurting my nail

So you're using the tension/elasticity of the plastic itself to generate force? The iterations I've seen have used a metal spring, nice that this is self-contained and doesn't require additional parts beyond the set-screw.

yes, indeed, it's only using the spring force of the plastic. Not sure how long it lasts but as tension and movement are quite small I assume it should hold up a while. May try some different materials on the long run.

It could even be made more accessible by using a standard screw and nut to tighten the ring around the chute but personally i like the thread inserts a bit more and I had them lying around.

I'm curious what threaded insert and set screw you're using. I've done this with some thicker parts, but never with anything this thin.

I'm curious if you've tried a "puffer" and, if so, how much it pushes through after using the knocker.

crwper wrote:I'm curious what threaded insert and set screw you're using. I've done this with some thicker parts, but never with anything this thin.

I tricked a bit there. I wanted it to look thin on the front so I created it with varying thickness. Also I added an additional "hump" for the threaded insert as it really needs some material to be held. Here's a render shot of the part.

Jeff wrote:I'm curious if you've tried a "puffer" and, if so, how much it pushes through after using the knocker.

Unfortunately I don't have one. Need to see if I can get one. But i did try to use other methods to get coffee out after knocking and all I got was very little - maybe about a tenth or less of what I could knock out before by snapping 2-3 times.

The one I have been using is the Fanwer for around US$10 https://www.amazon.com/dp/B07HNLNLZP/

With lighter roasts and around 30-50% RH I get about 0.1-0.3 g with a couple puffs. If I could get equivalently close to "zero exchange" with the thwacker and ones less loose part, that would be great!