Banjo Ukulele (Banjolele)

by AndreasBastian, published

Banjo Ukulele (Banjolele) by AndreasBastian Jul 14, 2013

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This banjo-ukulele is the result of a several weeks of iterative design and collaboration with Geoff Wiley of the wonderful Jalopy Theater in Brooklyn, NY. The project began in May of 2013 when I decided to learn more about music by printing out a a Makerlele and learning to play it. After showing the printed instrument to Geoff, we had a great discussion about musical instrument design and concluded that perhaps a banjo-ukulele would be well suited for adaptation to 3D-printing. Geoff lent me an old banjo-uke frame from which I took the basic measurements that informed my design. After several weeks of revising and testing and regular design discussions with Geoff, I arrived at a design that holds pitch and has a nice, full tone. It still needs some work, but it is at a point that I'm happy to share it and I'm beginning to actually learn chords on it. Please derive and post you design feedback. Musical instrument design with a technology as powerful and versatile as this is an exciting challenge.

I've included old versions of the body for anybody who is curious. They have different bridge support structures (rev1), webbing designs (rev2 & rev3), and membrane thicknesses (rev4) that all impact the tone significantly. I designed the instrument to allow the head portion to be swappable to allow for easy exploration of head design.

Finally, be sure to check out the spectrograms comparing open string plucks of the printed instrument and of a classic ukulele. More on that here.

See the video on Vimeo! [And on Youtube!]( http://youtu.be/hS0AWEd63kU)


  1. You will need a set of soprano ukulele strings, six M4 nuts, four (you can get away with two) M4x50 socket head screws, and two M4x14 socket head screws. I bought the first couple sets of ukulele strings at Jalopy and subsequent sets from Amazon. The metric hardware can be purchased from BoltDepot: M4 hex nuts, M4x14 socket head cap screws, and M4x50 socket head cap screws.

  2. Slice the files. I used MakerWare 2.2 with at a layer height of 0.2, hexagonal infill at 30%, and 4 shells (all for additional strength). I recommend printing "PLATE 1.stl" without a raft and printing "PLATE 2.stl" with both rafts and supports.

  3. Prepare your build surface. I recommend using blue painter's tape for printing the first plate as it provides just the right level of adhesion to the thin membrane that composes the first two layers of the banjo "head" that it isn't damaged during removal from the build plate. If you don't have blue tape, wash the frosted size of the acrylic plate with soap and water (to normalize adhesion) and then vigorously rub your fingers over the middle of the build plate to deposit skin oils. This will reduce adhesion under the delicate middle of the head membrane and will maintain adhesion around the perimeter.

  4. Level your bed. The large, thin membrane of the head is only half a millimeter thick and is very sensitive to variations in build platform height. I recommend "hot leveling" the bed by starting the "PLATE 1" print and watching the perimeters of the first layer as the extruder lays them down to ensure that they both stick to the platform and are of a consistent width. After one or two rounds of hot leveling, the bed should be level enough to start the real print. Be sure to watch the first layer of the membrane as is goes down just to be safe.

  5. Print "PLATE 2" (with both raft and supports!). The solid raft gives both sides of the neck and head a similar surface finish, which is nice, and eliminates curling on the neck. After printing, remove support material from the neck and headstock. Pay special attention to the conical holes in the headstock-- an even surface is important when tuning.

  6. Drop the captive nuts into the neck and secure the headstock. Be careful not to over-tighten the bolts as they can cause the neck to crack.

  7. The neck can be secured to the head using the two M4x50mm bolts nearest to the back edge of the head frame. Technically, you can skip the two closest to the membrane and use epoxy on that portion of the joint as it will be in compression (and the bolted joint is in tension). Alternately, you can secure the neck with all four bolts, though the two nearest the membrane require a lot of patience.

  8. String the thing! Insert the nut into the matching gap between the neck and the headstock and tie your first string (use these knots) to hold it in place, then add the other three strings, following this diagram. Insert the bridge at the base of the neck, flip it to its target orientation, and then carefully slide it onto the membrane, while pulling back on the stings (too keep pressure off the edge of the membrane). The ideal location is about a third of the diameter of the body away from the edge, but try several different locations to get a feel for the different tones and volumes possible.

  9. To tune, get each string close, back out the peg, and then twist it into the headstock with pressure to lock it in. Adjust the nut depth either by carving the notches or by scaling in Z in MakerWare. Add notches to the bridge after marking where the strings lie.

  10. Iterate! This design is still active and has a long way to go. The next step is to eliminate the fasteners in favor of dovetail joinery. Fasteners really raise the barrier to manufacture one of these things, as they do many other projects. Additionally, the nut height, bridge geometry, webbing design, and fret and string spacing all could use optimization. I would love to see this instrument land in the hands of somebody with greater musical knowledge who can take the design the final distance.

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I went ahead and customized 3d printed bolts to save the 11 bucks on the cost of the bolts and nuts. These won't be nearly as good as metal ones, but should work fairly well.
M4x50- https://www.thingiverse.com/thing:2630762/#files
M4 hex nut- https://www.thingiverse.com/thing:2630759/#files
M4x14- https://www.thingiverse.com/thing:2630749/#files

M4x50 socket head cap screw
M4 hex nut
M4x14 socket head cap screws

Im printing it right now. This isn't a project that I'm heavily invested in so I think Im going to cad some pegs to fit the the boltholes and superglue it together.

Please, how long may it take to print it?

Will the minimum amount of support material work inside the body?

How much plastic does this take at 30% fill? Or how many grams does it weigh?

I thing a read somewhere it should be about 500 grams

Your "following this diagram" link is no longer active.
Can you add the image to your Thing?

Comments deleted.

I see that you have multiple bodies. Which works best or are they all the same?

should this be printed with 100% infill?

100% infill is not necessary-- I used 30% for all the parts. You may find some differences in acoustics with different infill densities.

has anyone tried adding standard metal machine heads to this design? I have not printed it yet, but looking at the head stock holes, it seems like you could add metal threaded machine heads to improve tuning (albeit not being "pure" 3d printed any more :)

Hi eveybody! Has anyone printed this in a RepRap prusa i3? I am trying to do it but I'm afraid PLATE2 doesn't fit.

Hey Andreas,
Do you think that with a large build platform that could fit the neck and body, I could possibly make this a neck-through bajolele?

Just found out my school has a free to use 3D printer, and would love to try this! I'm an avid guitar and ukulele player. I've also read about minor adjustments of fine details like the bridge placement. As I understand, the 12th fret needs to be exactly half-way between either ends of the string (from the nut to the bridge, then give yourself a little wiggle room to finely adjust the intonation). Just measuring it on the main image, it looks like you've got about 288 pixels from the nut to the 12th fret, then 223 pixels from the 12th fret to the bridge. That's about 77% as far as it needs to be. For ideal tuning, it would need to be almost where the honeycomb pattern stops, but that probably wouldn't resonate well. I would love to try either adding more frets (which would move the 12th fret closer to the nut, which would let us keep the bridge in the middle part of the membrane), or creating a slightly larger body. I was going to suggest a longer ukulele shape, but I suppose it would be about the same amount of plastic around the body as being round. I don't have any experience in 3D modeling yet, but I might have to learn just to tweak this. I like what I see so far!

Great analysis locofocos! I pulled all the measurements for the neck directly from an old banjo-uke, so I'm not sure what acoustics design rules apply to those vs. traditional ukuleles. There is definitely room for improvement of tuning using mathematically-grounded geometries. I do know from experience with this particular instrument that the bridge position and angle, as you pointed out, are quite important to tone volume and quality. And as for modifying this design, go for it! I specifically designed it to be modular so that the resonating body could be easily swapped out. Like-wise with the neck.

Your second M4x14 amazon link links to M10x50 bolts. I think you meant M4x50? I got some M10x50 and they certainly are not going to fit! At least now I know what M10 looks like.

you used pla, right? has anybody tested this with abs? will it work with abs? thanks

I did all my printing in natural PLA but would love to see this thing in ABS! I think it would work, but suspect that the timbre of the instrument would change. Let me know if you get a chance to print it in ABS-- I'd love to compare the frequency spectra to one printed in PLA!

Anyone tried this in Nylon or PET? Interested to know if acoustic qualities or durability would play a part.

can you use skirt/brim

I haven't tried skirting, but don't think it could hurt. The head is nearly the maximum size of the build envelope, so skirting that might cause trouble, but all the other parts should print very well with a skirt.

Quick question, how did you bridge the gap between the brace in the body and the honeycomb structure beneath? It looks to span 12cm.

I printed this on the Rep2, so the active cooling does a decent job getting the first layers of the brace to bridge. I often had to pick out a couple fallen filaments once the print finished, but this never interfered with the rest of the print.

Great job!!!!

Just finished mine and it works great. Gets out of tune a little bit due to the pegs slipping, but nothing some M4 nuts and sets screws cant fix. Posted a video up on my channel - http://youtu.be/kkhSGr2A2Z4http://youtu.be/kkhSGr2A2Z4

Thanks again!!

Tom, Ceative_Hacker, I designed these parts for printing on a Replicator 2. The neck, which is 8.5" long, might be tricky on a 6x8 bed, though loading it in Repetier-Host indicates that it should fit on a Prusa Mendel's 8x8 bed.

What Printer did you use when printing our your parts?:D very awesome will attempt it on my reprap :D

what are the max sizes of the parts? could parts be printed on a 6x8 build platform? this thing is cool, i hope i can print it

Amazing!!! I want to print out a mandolin but this is so freaking awesome!!! I think i will start with this.

I will be printing this out in the next few days. I will let you know how it goes. After that I will be experimenting with different design iterations.

Thank you for the share!

Sounded like you started to bust out a little AC/DC riff.. niiiiiiiiiice...

Looks and sounds great! I should incorporate some of your ideas in to the next version of the Makerlele! Thanks for the awesome contribution!

Thanks Brent! Again, it was your Makerlele that catalyzed the whole process. Looking forward to the next rev!

I will have to try this out!! Are there any problems with putting the cables into tension?

The tuning pegs are conical (like those used in violins), which allows for better control of the arresting friction (push in for more, back out for less). Once the strings settle in, the thing holds pitch pretty well.

Learned this one the hard way didn't we?