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The O'Cello - a 3D-printable cello

by cokane, published

The O'Cello - a 3D-printable cello by cokane Aug 4, 2016

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Summary

The O'Cello is a 3D-printable cello developed by Conor O'Kane, which is free to download and print for personal use.

Update: November 23rd, 2016 - new version - This updated version now includes chest and knee rests for supporting the O'Cello while playing, and an adjustable end-pin. This is no longer a prototype, it is now ready for anyone to print and play.

All the components for an O'Cello can be printed on a 20cm print bed.

Inspired by the design of the F-F-Fiddle, the O'Cello incorporates a 12mm diameter steel rod running through all six major parts to provide rigidity.

Parts list

The following parts are needed to build an O'Cello:

  • M5x45mm socket head cap screws: 7
  • M5x30mm socket head cap screws: 2
  • M5 nuts: 9
  • M5 washers: 12
  • 12mm diameter steel rod, 1m length: 1
  • 10mm diameter aluminium tube, 45cm length: 1
  • Aluminium L-bar, 20x20x2mm, 30cm length: 1
  • Cello strings: 4 – (1 of each C, G, D and A strings)
  • Bass guitar tuning keys: 4 – (2 left and 2 right)
  • 25mm screw plugs
  • About half of a 1Kg spool of 3D printer filament. The O'Cello pictured here is made with PLA, but ABS should work fine.

Recommended sources for many of these parts can be found in the complete Assembly Instructions PDF.

The O'Cello does not need sanding or painting after printing. It is ready-to-play once printed and assembled.

Thanks to Dan Michitsch for his invaluable input on the design of the knee and chest rest parts. You can find his original design for these accessories here: http://www.thingiverse.com/thing:1833270

Check out his performance on the O'Cello here...

The O'Cello is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License which means you are free to share and modify it for non-commercial use.

Print Settings

Printer:

Cocoon Create

Rafts:

No

Supports:

Yes

Resolution:

0.2mm

Infill:

15%


Notes:

Print settings vary with the individual parts.

See the Assembly Guide PDF for full printing instructions.

Post-Printing

Painting the fingerboard

The cello doesn't need to be painted, but it does look nice with a black fingerboard. I spray painted the front of the fingerboard with semi-gloss black acrylic. Use masking tape to prevent the spray paint from hitting the sides of the part, and touch up any over-spray with white acrylic applied with a paint brush.

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Hi, I'm a violinist and string musician in general. My brother has played the cello the better part of his life and I would like to do something for him as a gift. He's always said he wants an electric cello, so I figured I'd print this. I've already ordered the pegs, and am now curious as to whether you have a particular pickup in mind that would be good for this project. If you do, I'd love your opinion on it. Thank you!

I tried an electric cello pickup, but I found it wasn't satisfactory because it was designed to sit under the cello bridge, and there isn't room to do that on the O'Cello. So I would recommend a smaller piezo pickup, such as those used in electric violins.

Thank you so much for responding, and one last question. Do you think it would be possible to create one out of wood filament, and should I make the top and bottom pieces, (1 and 6), with a higher infill so they don't crack from the strings pressure? Thanks again!

Higher infill won't have as much impact on the rigidity as setting 3 shells (external walls). Printing parts 1 and 6 with 3 shells is a good idea. Woodfill should work fine, I bet it will look great!

This is a great design. Are the source CAD files available as well?

It is modeled as a polygon object so the source files are basically the same as the STLs.

So not great for tweaking the design. What program are you using to model?

This is strange. I just got the tuning keys in the mail from the place in assembly instructions. (Took 5 months to arrive!). Nicely made. But only the left ones fit. The ones on the right act like they're stripped or not long enough. But the screw on fine out of the frame. Very weird.

Try fitting them without the washers. If they still don't grip then you'll need to modify part 6 so that the walls are thinner where the tuning keys fit.

One went on without the washer. The other is still loose. Strange considering the other 2 fit and the size looks identical.
So close to finishing!
Just need to get the printer fixed at the makerspace and print this with the part face moved and see how it goes :) Plus one more printed part. Then all I need is the rod.

Bravo on the guts to do this! To take this to another level altogether, consider using touch-sensitive ribbons instead of strings. Zero mechanical strain, no tuners. The "strings" would be the pickups and the sounds would be whatever you can imagine in available software.
People like https://www.keithmcmillen.com have mastered the touch sensitive technology in music. Check it out. :)

On Part 5, when I slid the bridge into the slot, one side of the slot delaminated. It's still holding, but I imagine will completely break at one point. I'm going to see about printing a version where the bridge is integrated right into the body of the part. Can always replace the whole part later if necessary and it will give me a stronger piece :)
It's taking forever for me to get this printed, as my own printer is too small, and I have to rely on the Makerspace printer being free when I get there :)

The pressure from the strings will probably keep the bridge in place, even if the slot isn't perfect, but you could certainly print the bridge and part 5 together as one piece.

I now have one, but wondering how close the design is to an acoustic cello? How similar is the bowing and placement of the chest rest/knee pads, bridge etc? Is there a way to customize it to make it more like the feel of an acoustic? I guess the sound will always be different...

If you would like a chest and knee-rest that are closer to the traditional cello design, try Zarlor's remix: http://www.thingiverse.com/thing:1833270

The bridge and fingerboard are the only parts of the O'Cello that are designed to match the exact dimensions of a normal cello (although the back of the fingerboards is not curved like a wooden cello), however all other areas are designed with ease of printing and assembly in mind.

O'Cello Add-ons
by Zarlor

a few comments after building this nice instrument.

  • Carbon rod is way better than steel rod - the rod may act as an antenna (just think about that) and the weight is negligable
  • NO screws - I didn't need any except for the stand-adjuster, the tuning pegs and the electronics!
    Instead I used a 12mm carbon rod which had to be polished down a bit, and the bores had to be opened up to 12mm.
    Glueing was done with white epoxy resin starting with part1. Then the next part was slid on and glued to rod and to the former part, and so on, then the whole construction was stood up on part1 and a hefty weight hung on over the rod until the glue had set (12 hours in a warm room). Screws would have distorted the fingerboard by turning it sideways so I left them aside. These holes I have plugged with 4.5mm wooden pegs and topped with epoxy,
    Nevertheless sanding is necessary to round the sharp corners of the fingerboard and to get a straight surface there.

I would recommend a few changes to the design as follows -

  • all parts 1 - 4 should lay on the same side for printing (left side viewing from the player) with the effect that the upper side (right) will have the striations on the surface - easy on the left hand and better for sanding a straight line
  • connection between the parts 1-4 should be made as a step - similar as between parts 4 and 5, without screw holes. The rod stabilizes all parts and there is no fiddling with screws. Glue is better than screws weightwise too. A step between part 5 and 6 would be better again than an incline which tends to slide away.
  • I have never had a cello in my hands, only a double bass, the neck was not square but rounded. So - by rounding the bottom side of the neck halfways up the player will have a better grip and feeling - again just thinking aloud. A raft will be needed, maybe some supports too.

That's it for now. I have the boards ready for the battery case and the amplifier, but have not yet decided about how to install the piezo pickup - maybe I'll install a second pickups?

Thank you for the suggestions. Some great ideas here, I hadn't considered gluing because I assumed the tension of the strings would pull the pieces apart. Let me know how your glued version holds up.

While I agree that a rounded neck would feel better, I have tried to design this so that it can be printed without rafts and with minimal supports. I may do an advanced version with more rounded parts and no screws required!

After printing a piece a few times, i have found that the tolerances are to little and don't fit my 12 mm rod. I have scaled several times but i can seem to get it to work without alternating the playing length to much

Scaling the entire piece isn't a good solution as it will no longer match the dimensions of a normal cello's fingerboard. Although if you don't already play the cello this might not be a problem as it won't feel wrong to you :-)

Measure your 12mm rod and make sure it's the same diameter all along. Check the ends aren't sharp. Sanding the rod and filing the ends makes a big difference - mine went from sticking badly to sliding easily after I sanded and filed it.

You could also try measuring your printer's capability to produce accurate interior cylinders. If it's over-extruding into the void on the inside of the cylinder, extruding less or decreasing the nozzle temperature might help with this.

Wrapping up my build today, will have photos of the make up soon.

Notes from my experience:

• The threads of the net/shank piece on the tuning keys I bought didn't extend far enough, preventing me from tightening them onto the body. To compensate, I heated the washers and pressed them a couple mm into the piece.
• With my particular printer (Maker Select Plus), scaling the cover piece to 101% was just enough to make it fit snugly into its slot.
• If you're an American with difficulty finding metric parts, order carbon fiber rods online, RC folks use em so they are plentiful on ebay and hobby sites. MrMetric.com is a good source for fasteners.
• A 3/4 inch (1/16 inch thickness) aluminum L-bar is close enough to fit its pieces without modification, so grab one of those locally.

Thank you for the tips for American metric parts - I hope that will help the American makers out there who've been hesitant to try this print.

With regard to the tuning keys - one of my keys also wouldn't fit with the washer, I had to remove the washer for the nut to tighten enough. I will look at modifying that area so that smaller keys can work.

I look forward to seeing your build!

Has anyone printed it in ABS? I've got a big roll of purple sitting here I could use. Would I need to scale it up to 102% for shrinkage?

I'm not aware of any ABS prints yet. You're welcome to be the first to try! I'd recommend printing a small section of two of the neck parts, and see if they join correctly and the screws still fit. You can easily split them up using Meshmixer.

This is super cool! I'm trying to save myself some math on printing; do you have the ratio I should use while I'm packaging?

What do you mean by the packing ratio?

Jan 11, 2017 - Modified Jan 11, 2017

What length are the 10mm tube and L-bar cut to? I assume the 12mm x 1m rod is used as-is?

To reduce the weight a bit, have you looked at using a carbon fiber rod for the spine?

Jan 11, 2017 - Modified Jan 11, 2017
cokane - in reply to driph

The L-bar is 30cm - but it can be slightly longer or shorter depending on what feels comfortable to grip between your knees when playing. The 10mm tube is 45cm. This can slide up and down inside the clamp so it doesn't have to be precise. Yes the 12mm x 1m rod is left at 1m. A carbon fiber rod should work fine - they just didn't have any at the hardware store when I went to get parts. The weight of the steel bar isn't too troublesome as you don't have to support it when playing.

I've updated the item description and the assembly instructions PDF with these measurements.

Dec 17, 2016 - Modified Dec 17, 2016

Will a 1/2 inch rod work instead of 12mm?

EDIT: Also, where can I get the screw plugs from?

A half-inch rod will be 12.7mm - I doubt it will fit, and if it does it will be really tight. If you have a half-inch rod I'd try a test print with a small section of one of the parts and see if it goes through. These are the plugs I used: https://www.bunnings.com.au/ramset-25mm-white-plastic-wall-plugs-25-pack_p2262404

Again these are metric sizes - if you're in the United States you might have to find a hardware store that stocks metric parts.

I bought a 12mm x 1000mm polished steel axle rod from McMaster-Carr. Only had to do minor sanding on the pieces to fit.

Comments deleted.

Did you print a separate fingerboard for the white O'cello, or just paint the fingerboard faces of assembled pieces 1-4 black?

I'm debating printing 1-4 out of various flavors of filament, to ascertain what effect different materials have on the overall sound. I have an acquaintance who plays cello professionally, who has agreed to be my Crash Test Dummy for this adventure.

Printing on a Rostock MAX v2 using your settings resulted in destroyed first-layers. The printer wanted just a touch more breathing room on the Z axis or it would drag the nozzle and scrape previous layers off the build platform. Just passing on some info....

Have you had a chance to experiment with the build and various filaments? Curious to hear the outcome!

I could never get the PLA/PHA blend to work satisfactorily. Wound up printing out of SeeMeCNC's house brand PLA filament. Still in the process of working it out - The Rostock delta printer has a bit too much variation between layers, I think.

I've already decided that when I eventually do get the thing together, I'll take a belt sander to the fingerboard & neck back, and smooth them all down as far as I dare. I've set the slicer to print an extra layere on those sides.

I'm keen to see what kind of results you get from sanding. I haven't sanded mine as the gaps between the fingerboard parts are reasonably small, however I've heard from another build that there can be slight bumps where the parts join.

I've built two, both with PLA. As far as I know the others that have been built are also PLA so I've yet to hear about the results with other filaments. My printer has no enclosure so I only print PLA at the moment.

How have the cellos held up with play? Any remaining issues with the current design?

I'll probably go with a PLA as well (most likely esun's PLA+, as I dig the print feel).

The first prototype developed cracks near the tuning keys, but I solved that by having the tuning keys screw into plugs which fit inside wider holes, rather than screwing directly into the printed surface. It has to be tuned before playing, but I haven't seen any cracking or deforming of any kind on the latest version.

I printed the fingerboard parts in white and spray-painted the front black. Use lots of masking tape to keep the sides clean if you try this.

Varying the composition of the parts is unlikely to have much impact on the sound, as the printed parts are not resonating or vibrating like a real cello's wooden sound board does. Only the strings are vibrating here, so it's not as loud as a real cello, although the string sound alone is certainly loud enough for practice play.

Your printer should be able to print 4 base layers at 0.2mm, if it can't do that then you might need to check that your Z steps are calibrated properly and that you've set the correct nozzle size in your slicer. You could also reduce the speed or extrusion amount for those first few layers.

Oct 17, 2016 - Modified Oct 17, 2016

Thanks Cokane.

I have been looking for a printable Cello for ages, and last night, I dreamed of playing one - so I'm now inspired to print this...

It looks like you made it to fit a specific set of electronics, but from the image I can't see what it is... Can you link to it.

Thanks..

Cris.

Here's one on eBay: http://www.ebay.com.au/itm/Electric-Cello-Pickup-Preamp-EQ-For-Electric-Cello-Silent-Pickup-9V-Cello-Piezo-/171116037877?hash=item27d74f86f5:g:RKYAAOxy015SH0-O

Look in the Thing Details tab for the Assembly Instructions PDF, this has full instructions on how to fit everything.

Unless there's a different PDF that I'm not seeing, this one has no notes regarding pickups or electronics.

That's correct. The first 'prototype' version had room on the back to fit a pre-amp kit, however having tested it extensively I was not happy with the result. Piezo pickups need to be fitted under the bridge to properly sense the vibrations, and there isn't enough room for that setup on the O'Cello. So for the final version I've focused on keeping the cello easy to assemble and left out the pickup.

If you want to amplify the sound the best solution is to place a microphone near your cello while you play. The video on the Thing Details page shows the O'Cello being played without any amplification.

I have a K&K "Big Shot" peizo pickup I was going to try using inside Part #5, beneath the bridge... Instead, I think I'll use their Twin Shot instead; it's a two-piezo version of the single-piezo Big Shot. I plan on sticking one bug on either side of the chamber of Part #5, toward the bridge side of the cavity.

That could work! Those pickups sound much more suited to this application that a regular cello pickup. Let me know how that sounds!

Hi Cokane, thank you for this file! Now I am seriously looking into printing one. I don't have a large enough 3D printer so I probably would need to get someone to print it for me. Regarding the pickup, do you think a bass guitar pickup will do the trick? Something like this one: http://www.ebay.com.au/itm/320814665055?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

That pickup would not be easy to fit to an O'Cello. I'd recommend you print out part 5 (which houses the bridge) so you can see how much space there is for batteries and wiring. Then you can select a suitable pickup.

When you forget to check how much filament is left before starting a print... https://i.imgur.com/qcZKYel.png

Aug 10, 2016 - Modified Aug 10, 2016
cokane - in reply to nallar

Oh dear! Only made it half way through!
The whole cello should take about half a 1Kg roll of filament at 15% infill.

Having a 12mm reduced shank drillbit is helpful for getting this to work, so you can clean up the insides of the holes.

Think it's due to a cooling issue but I get droopy bits in the tops of the holes for the 12mm rods.

Yes I got that too. I believe the gap is slightly too small for the slicer to consider it a bridge, so it crosses it slowly and results in a sagging layer. I just ran a file through the hole and scraped the lose bits off. I may modify this hole so that the top has a slight peak, allowing the printer to build it more gradually.

The STL for part 5 seems to have all the faces flipped.

https://i.imgur.com/xx7xqIu.png

I've updated the STL for part 5. The normals are now facing the correct way.

Comments deleted.
Aug 13, 2016 - Modified Aug 13, 2016
nallar - in reply to cokane

Should have it working soon :)

https://i.imgur.com/3ZcqjTa.png

edit: Having a mitre saw is pretty nice... I see you suffered through cutting the bar with a hacksaw. :(

My tuning keys mount differently, so I'm making an adapter shim thingy. Will put it up on thingiverse in case it's useful for others.

Great to see the bar fits nicely. Yes I cut mine by hand, it was hard work! Have you played cello before? I'm keen to get someone else's opinion on it.

Hello,

Nice design ! I think I will print it soon. Impatient to hear it :)

Which micro and pre-amp do you use ?

This one: http://www.ebay.com.au/itm/Electric-Cello-Pickup-Preamp-EQ-For-Electric-Cello-Silent-Pickup-9V-Cello-Piezo-/171116037877?hash=item27d74f86f5:g:RKYAAOxy015SH0-O

It's a combined preamp and pickup set, however the pickup is too large for the O'Cello. It's designed for a traditional cello bridge, so I've taped it to the side of my prototype. This is not ideal, it's probably better to buy a smaller pickup. Also, there is a slight hum from the pre-amp when turned up loud. For all the bought components of the prototype I went with the cheapest item I could find on eBay, however in the case of the amplification I think this is the one situation where you should get something higher-quality.

You should look to aliexpress for parts - they are that much cheaper. I paid just US $22 for the above pickup with headphones (today they have them at $19.02)
https://www.aliexpress.com/item/Electric-Violin-Silent-EQ-Pickup-Piezo-with-Headphone-and-Plug-Hole-Cable-Set/32623650527.html
A cello carbon bow is $26, strings are $5,69, the set of pegs (in black) is $14.
I'm awaiting delivery of another type of preamp for $11.58, with extra battery case, extra input- and headphone sockets board, and a third case with the electronics with volume and double tone control!!!
https://www.aliexpress.com/item/ROCKET-Electric-Violin-Silent-EQ-Adjustable-Pickup-Piezo-Pickup-Free-Shipping/32725837268.html
The only problem is they do not give any hint about the size of these parts, so fitting them will be interesting.
I've started printing from the bottom up (the biggest parts first).
As to the hum you have encountered - does your preamp have some shielding to it? A piece of aluminium (kitchen) foil glued to the inside of the whole case and connected to ground (shield of the pickup cable) should do the trick.
I'll come back when I have finished with the build.
Thank you for a nice design.

Thanks for the parts links, these look like very good value. In the latest version of the O'Cello, the hole at the back of Part 5 is slightly smaller (due to thicker walls and a slightly different bridge position which allows the bridge to meet the strings perpendicularly) which means it is no longer designed to hold any specific pre-amp box. You may want to wait til your pre-amp parts arrive and measure them before printing part 5. Then it may be possible to modify the back-hole to accommodate your electronics.

The aluminium foil shield is a great idea. I think I'll try a smaller violin style amp and use that technique if there's any hum.

Thank you for your quick-reply.

I found a stand-alone piezo pickup on a local store, I will try with this one as I already own a pre-ampli.

Now it's time to print the parts :)

Good luck! Let me know if you run into any assembly issues. I've only printed and assembled one so far so there may be variations you encounter that I haven't seen.

Awesome!

I wish normal string instruments used guitar tuning keys instead of pegs + fine adjusters. So much easier...

Yes I agree. I think many musical instrument shapes and designs are due to tradition, and not because they actually have a noticeable effect on the sound of the instrument.

I have Knilling Perfection pegs on my 5-string vioin and they're great. They look exactly like traditional pegs but have orbital gearing inside.. not cheap though. http://www.knilling.com/perfection-pegs/

Nice job on the e-Cello, BTW.. how does it feel to play?

The neck feels very smooth, you don't really notice the joins, however I need to rethink the support system. I think I'll need to go with a chest-rest and stand system instead of the tripod.

how much does the whole thing weigh? i might suggest a support system that straps to your waist and neck so you could play standing or sitting, as opposed to a bulky piece to replace the endpin. it would add mobility and probably sort out some unnecessary vibration issues. I have a yamaha svc-50 electric cello and my biggest problem with it is weight and immobility.

It weighs 1.4Kg fully assembled. Most of that is the weight of the steel bar inside, and the steel guitar tuning keys. The weight of the plastic is negligible.

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