Isopropanol Dispenser 🚰

This dispenser is watertight. However, it's not that easy to get it watertight. Apart from proper print settings some parts have to be sealed with silicone.

The design evolves around the physics effect of keeping water inside an upside down bottle because of atmospheric pressure. A 3D printed spring pushes a piston into a closed-position. When the push buttons are pressed, the piston moves upwards against the spring, letting air in and liquid out. 

The model is not perfect, but it works. For me it worked well enough so that I can use it as an isopropanol dispenser. 

The thread for the bottle is a PCO1881 and works for most soft drink bottles and similar. The other threads are M40x3 adjusted for 3D printing.

❗  Be careful and mount it in a safe place. Although it might be convenient to have it near the printer, it contains a highly flammable liquid. 

Print Info (Prusa Slicer v2.5):

I used the following settings for all parts to improve watertightness:

• 0.6mm nozzle (allows for bigger extrusion width and less chance of gaps)
• random seams (reduce chance of overlapping seams to cause leaking)
• 3 perimeters (instead of 2, less chance of gaps)
• 0.3mm layer height (less layers = less seams = less prone to leaks)

Other:

• PETG (especially for the spring)
• infill 15%

Slicing Tips

Lid
Print with supports like shown on the pictures. I used Snug style supports.

Piston
Same as for the Lid, print with supports.

Adapter
Print it with small diameter side on the print bed. Use supports. Pay attention to not let it create supports inside the thread, otherwise it's hard to remove afterwards.
 

Spring
The spring has many overhangs and will probably not be the nicest looking print. But this is not really important. To make it work only few supports are necessary
 

Others
The remaining parts are straight forward to slice and don't require supports.

Post processing steps

Put silicone in the cutout areas marked below. The parts which are important for sealing are the adapter and the piston.

Assembly

See GIF below. Use a M3 screw and a hex nut to connect the piston to the push buttons. Close the screw mounting holes with the round covers (not visible on gif)