Bar Soap Dispenser

Materials needed

1. 2x Compression springs  --> 10 mm diameter / 50 mm length
   
    
2. 4x Tension springs --> 4 mm diameter / 30 mm length
   
    
3. Double sided adhesive tape
   
    
4. 3D printed parts
   

How to Print

1. All parts are oriented in the right direction
2. All 6 parts are printed only once
3. Support material should only be needed here:

2x under the left and right spring hooks and across the whole bottom.

1. Support on “Grate with Funnel” can be eliminated by having good bridging settings
2. Printing in PETG preferred due to wet bathroom environment

Assembly

1. Remove support material
    
2. Insert Part “Side Press” from above and then through the designated 4 holes.
   Screw Part “Side Nut” onto part “Side Screw” and then screw in the hole part through the back of “Main Body” until snapped in place and connected to “Side Press”
   
    
3. Put in one compression spring into each hole in the front of “Main Body”. Push in “Grate with Funnel”. Attention❗ The end-stop on the “Grate with Funnel” needs to be pushed down gently 2 times until its locked in it's final position.
   
    
4. Attach the tension springs to the “Top Press”. 2 on each side should be enough. Slide them all in from the top into “Main Body” and attach them to the bottom hooks.
   
    
5. Attach the finished assembly to the wall using double sided tape.
   
    
6. Turn “Big Screw" as far out as it is possible. Pull “Top Press” up using 3 fingers. Press with your palm against “Main Body” to not tear the whole apparatus from the wall. Insert bar soap with your other hand from the back. Release “Top Press”. Turn “Big Screw” until soap is held secure in the front. Make sure not to over tighten the screw so the soap doesn't get stuck. Once correctly adjusted secure the position tightly with the “Side nut”
   

How I designed this

I have been using liquid soap for about my whole life. I switched to an electric liquid soap dispenser about 3 years ago, but I am not very satisfied with it. The lack of adjustment in the dispensed volume and the high prices for the branded refills has bothers me to the point that I was looking for an alternative. Recently I tested some foam dispensers, but they aren't better either.

After comparing liquid soap, foam soap and bar soap I found out that bar soap boast the most advantages over the other two contesters. Bar soap lasts longer, can be transported easier and more environmentally friendly and it can also be used for other purposes like in a washing machine. The only disadvantages are the complicated soap application compared to liquid soap and hygiene concern if used in public spaces. Two fix both of these issues a soap grater would be the ideal solution. An additional benefit of bar soap is, that it is also more suitable for use in caravans and on ships due to no spillage. And another benefit I found out after finishing this project was that the bar soap can sometimes also double as an aroma diffuser.

This has obviously been done before as seen here Zero Waste Soap Bar Dispenser: Eco-Friendly Hand Washing! or here Soapflaker Soap Dispenser for Solid Hand Soap or here Dispenser Shaves Soap-Bars Into Fluffy Flakes | WIRED. All of these solutions either use their own custom bars of soap which locks the user into their ecosystem, or they aren't that well received because they do not seem to work that well.

There is also this design patented model which looks to work really well Hand Washing, Super Saver Soap Shaver Home. Unfortunately, they do not seem to sell them anymore, but their work was a good inspiration for me.

Thingiverse User gilhilel has also made a nice design as seen here soap greater by gilhilel. I do however dislike the fact that is only usable with two hands instead of one like the other models.

Armed with knowledge and ideas I started testing different 3D printed grate patterns. Using a preexisting metal grate was an option for me but was not necessary for my first design. PETG spikes turned out shockingly effective against most soap. 

I also tested 3D printed springs Spring Material Test, but using them would have made the design significantly larger because of their week pulling force.

Comparing different soap sizes was also done at this stage to ensure the design would fit most soap bar sizes. Most extra-large sizes should be at least be able to be used if cut in half.

After much trial and error, the final version 1 features:

1. Low material cost
   Around 4€ material cost + 1€ for the springs
2. One handed use
   If one hand is really dirty or occupied
3. Adapts to different soap bar sizes 
   up to around 100 mm x 40 mm x 60 mm
4. If soap bar is brittle, it produces enough flakes on one push for hand washing
   Less stiff more elastic bar soap needs 2-3 presses.
5. Low maintenance
   1 bar of soap lasts me for around 10 months
6. All other benefits which come with open-source 3D printing 😊
   Like easily replaceable parts, custom design possibilities, etc.

Further improvements and known bugs

This is still version 1 of my idea, and yes there are many ways to improve the design. Some changes I have been thinking about include:

1. Make the funnel part of the crate better fit to multiple sizes of hands
2. Make the changing of soap easier to use
3. Make the soap compartment fit even larger bars of soap
4. Make a cover for the springs or other modifications to make it look less technical
5. Use a metal grate instead of plastic, which should last longer and create more flakes even on softer soap bars.
6. Reduce the amount of flakes which don't land in the palm of the hand

Thank you for trying me design and feel free to remix as you please 👍