Also check my newer ukulele model - Hex ukulele

I've decided to design 3d printed ukulele. This one is different from other designs. I've reached all my design goals which are:

• Can be 3d printed on almost every printer on the market (fits 210x210 bed)
• No additional parts (Nothin except string is required (no tuning pegs, bridges, bolts, nuts etc), everything is 3d printed (you can add carbon fiber strips but it is optional)
• No glue - all parts can be assembled and disassembled with 3d printed bolts and joints. You can always use some glue for rigidity, but this is optional. (the idea that tuning pegs can be printed came from noamtsvi and his guitar tuners project)
• No supports needed (just print parts, assemble put the strings on, tune it and play).
• Nice shape - the goal is to make as many hearts as possible - this is special design for Valentine's day competition on Printables :)
• Full feature 4-string ukulele - scale length is 350mm

Does it work? Just watch (Mahalo smile for compare):

This is the ukulele after updates from 14.02.2023. 

BOM:

• about 500g of PLA
• about 50 of PETG (can also be PLA)
• one pack of soprano ukulele strings
• (optionally) 2 pieces of carbon fiber strips 2x8mm (about 35 cm length each)

General

All parts can be printed without support. All parts can be printed with 0.6 nozzle. All parts can be printed on 210x210 printer. I have printed mine with PLA (except dots and nuts). PETG can be to soft for neck and body, but you can give it a try. For pegs and dots (small screw) You can add brim to ensure it stays on the bed.

Orientation

Orient all the parts with largest flat side on the bed (all files should be already oriented for printing).

Printing instruction:

Print all the parts:

• Dots:
  • dot6_x1.stl - 1piece
  • dot8_x5.stl - 5 pieces
  • bridge_nut_x5.stl - 3 or 5 pieces

(print more dots than needed - they are easy to break) I've printed mine in PLA but maybe PETG would be better for layer adhesion

• Pegs and gears:
  • peg5_x1.stl - 1 piece (shortest for E string)
  • peg10_x2.stl - 2 pieces (G and A string)
  • peg15_x1.stl - 1 piece (longest for C string)
  • gear_x4.stl - 4 pieces (all gears are equal)
• Fretboard:
  • fretboard.stl - 1 piece (add color change at 3.5mm for different color of frets)
• Neck:
  • neck-head.stl - 1 piece
  • neck.stl - 1 piece
  • joint.stl - 1 piece
• Body:
  • body.stl - 1 piece
  • bridge.stl - 1 piece
  • bridge-inset.stl - 1 piece
• Reinforcement:
  • strips.stl - print it if You don't have real carbon fiber strip

Assembly steps:

Here is assembly video. Text description below the video

1. Take neck-head. Insert two strips (printed or carbon fiber)
2. Add neck part and put joint inside (holes in joint should be closer to body (do not rotate joint yet)
3. add body - and close everything together.
4. Using small allen key start turning joint through the hole in neck part
5. When connection is tight add fretboard and screw it with dots (use small flat screwdriver - do not overtight). Use shorter dot (dot6_x1) on tenth fret!!!
6. Use bridge-nuts to connect bridge to body.
7. Insert bridge-inset to the bridge (should fit tight
8. time to add strings - make knot on one end of the string (I use Figure 8. knot)
9. Put this end in proper gap on the string
10. lead string through the hole in head and then through the gear (thinner end first)
11. place gear in proper hole in the head
12. secure gear with peg and start turning peg (keep string tensioned from behind
13. after couple of gear turns string should be tensioned
14. Repeat steps for three other strings
15. That's all - You have 3D printed heart shaped ukulele

Keep in mind that the strings will get out of tune quickly at the beginning. Be patient and tune your ukulele many times and eventually it will stay in tune for longer.

Final thoughts

I think the the project is a success. You get fully printable soprano ukulele. You can modify any part, disassemble and assemble it. There is a lot to improve. “dots” are very fragile and break easy (i cannot make them larger because they have to fit between 11th and 12th frets. The neck bends a bit - so maybe it is good idea to implement some bend outwards - so after putting the strings on everything goes straight (I'm still waiting for carbon strips delivery to check how much this helps). Other thing that might help is lowering the bridge.

I invite You to the adventure of improving this design - print your own and maybe we can make it even better together :)

Upgrades 

08.03.2023 (gears with string names, secured with conical screw):

There was a small problem - when the string end was pushed into the gear part sometimes string was loosing tension - This was rare case, but i designed newer version, where end of the string was secured to the gear part with small conical threaded screw - and now the problem's gone. Print it with filament change for string names in different color.

Assembly tips:

• put string in the groove made in thread of gear part.
• Align the string so it is secured by thread bot not sticking out from the gear
• Use flat screwdriver to secure string in gear and to fast wind the string - then put the tuning peg.

14.02.2023 (no more bended neck):

I was not completely happy because of bended neck and high action. So while waiting for my package with carbon fiber strips I've made three small upgrades to my ukulele.

Upgrade 1.

I have retightened internal rod - i appears that there was ¼ of rotation still possible. Then I bended the neck backwards and pushed tiny 0.4mm spacer between neck and neck-head parts.

Upgrade 2.

I designed shorter bridge and shorter bridge-inset. this helps keeping action low.

All stl's are in Upgrades folder. Now my neck is flat and my action is perfect. And ukulele stays in tune up to the last tiny fret :)