suction balcony door knob

Onshape Project URL: https://cad.onshape.com/documents/a72caaa9468cfb1c1f8fcdd4/w/e099a04e25b7ec96936a03ef/e/cb81bed87c14383b0c171f0d?renderMode=0&uiState=675c6def03e03152a01c9942

how to print

• YOU NEED TO PRINT THIS ON A SMOOTH PRINT SURFACE
• I chose to overextrude a lot to ensure smooth bottom surface with no holes.
• I used 5 perimeters for strength and that may have been too much because it's quite hard to squeeze (might be good? I'm not a suction cup scientist).
• I used 90A filament but I assume that all flexibles up to 95A should work
• no supports
• should print quite easily if your printer is tuned for tpu

how to use

• squish the knob before attaching to a smooth surface
• push the flat side against a smooth surface
• let go of the knob
• the knob should magically stick itself to the surface using the power of physics!
• to unstick the knob just squish it again and it should let go without a fight
  • it might become harder to squish with lower outside temps

story

I wanted to be able to close balcony door when I'm going out for several reasons, mainly to stop my cats escaping and dying (it's 12th floor) or to stop cold or cigarette smoke from going inside.

I found Suction Cup 2.0 model and while it worked great for a while, it quickly lost it's suction power from when it was first printed and needed to be constantly reset. My girlfriend also broke one because ‘she didn’t see it' through a see-through door. Since I have a few brain cells left I thought how could I create more vaccuum for better suction to a smooth surface.

Then it occured to me that if I squish a TPU knob it will suck air in while unsquishing, so I opened Onshape to quickly draft that idea. I'm happy to say that the knobs are still strongly hanging on my balcony door, although they do get harder to squish with lower temps.

Design by japonicki on MakerWorld (license: CC0).