Parametric TPU bellow for single dose grinder mods
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jt123
- Posts: 4
- Joined: 3 years ago
After playing around with 3D printers for a few years, I finally got around to trying out TPU. After trying an existing model from thingiverse that was a bit off in terms of dimensions for my Mazzer Mini, I decided to model my own: https://www.thingiverse.com/thing:4851382. It's fully parametric and one can customize it online using the thingiverse app, but you could also just download the .scad file and compile it yourself in OpenSCAD. In particular the option to leave to top "open" doesn't seem to work in the online version.
I haven't measured the actual retention, but compared to brushing the grind exit using a paintbrush its a lot easier!
One thing I noticed is that on mine a 2 shell perimeter seems to be difficult to print with good aesthetic results (its still airtight, just not so pretty to look at), and 3 perimeters seem to work better. However, the tradeoff with more shells is that it doesn't collapse as neatly around the folds, and I think the zigzag shape needs to be wider to compensate. This is one of the reasons having a configurable wall thickness might become handy... Nevertheless, the version in the above image seem to work pretty well!
I'm actually a bit surprised at how well my stock Ender 3 printed TPU. Other than some dragging/oozing of the filament when it travels, the result was quite clean overall. The material I used was 91A Shore hardness TPU, from filaments.ca
Hope someone else may find this useful!
I haven't measured the actual retention, but compared to brushing the grind exit using a paintbrush its a lot easier!
One thing I noticed is that on mine a 2 shell perimeter seems to be difficult to print with good aesthetic results (its still airtight, just not so pretty to look at), and 3 perimeters seem to work better. However, the tradeoff with more shells is that it doesn't collapse as neatly around the folds, and I think the zigzag shape needs to be wider to compensate. This is one of the reasons having a configurable wall thickness might become handy... Nevertheless, the version in the above image seem to work pretty well!
I'm actually a bit surprised at how well my stock Ender 3 printed TPU. Other than some dragging/oozing of the filament when it travels, the result was quite clean overall. The material I used was 91A Shore hardness TPU, from filaments.ca
Hope someone else may find this useful!
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jrham12
- Posts: 272
- Joined: 5 years ago
JT,
Looks great! I did something similar to model and print a bellows for my Lagom P64 and then also used the same base design to make a "bellows lid" for an old Rocky that I was using for brew grinding.
I used some 85A TPU from Amazon (https://www.amazon.com/gp/product/B01M9 ... UTF8&psc=1) to give it a bit more flexibility than the typical 95A stuff but not as expensive as NinjaFlex. I also found that a single wall (vase mode) was too flimsy and 3 walls was a bit too stiff. I finally got it dialed in to where the "Z" geometry worked very well with 2 walls. Unfortunately after a couple months of use, one layer right at the minimum diameter of the "Z" started to come apart on one side. In the end, I think 2 walls is just right for the right amount of flex vs. rigidity (so the "Z" retains it's shape when compressed), but it's just not durable enough. At least with the filament I used.
Eventually I want to order some real ninjaflex and give it another go to see if it holds up better than the cheap stuff I bought. I printed it on a Mingda D2 which is direct drive, but the extruder and hot end both leave a bit to be desired!
Josh
Looks great! I did something similar to model and print a bellows for my Lagom P64 and then also used the same base design to make a "bellows lid" for an old Rocky that I was using for brew grinding.
I used some 85A TPU from Amazon (https://www.amazon.com/gp/product/B01M9 ... UTF8&psc=1) to give it a bit more flexibility than the typical 95A stuff but not as expensive as NinjaFlex. I also found that a single wall (vase mode) was too flimsy and 3 walls was a bit too stiff. I finally got it dialed in to where the "Z" geometry worked very well with 2 walls. Unfortunately after a couple months of use, one layer right at the minimum diameter of the "Z" started to come apart on one side. In the end, I think 2 walls is just right for the right amount of flex vs. rigidity (so the "Z" retains it's shape when compressed), but it's just not durable enough. At least with the filament I used.
Eventually I want to order some real ninjaflex and give it another go to see if it holds up better than the cheap stuff I bought. I printed it on a Mingda D2 which is direct drive, but the extruder and hot end both leave a bit to be desired!
Josh
