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The O'Cello - a 3D-printable cello

by conorokane, published

The O'Cello - a 3D-printable cello by conorokane 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.

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...

https://www.youtube.com/watch?v=lSVwg5sikZ4

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.

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.

Update: July 10th, 2017 - Improvement to part 6 - Some people have found it difficult to get the tuning keys to attach because the walls of part 6 were too thick. I've narrowed these walls slightly to make it easier to screw in the tuning keys.

Update: May 8th, 2018 - Original files - To make remixing the O'Cello easier I'm releasing the STL files for the major parts in their original orientations and positions. The STL files included in the download above are rotated so that they have a flat edge on the build plate, which is perfect for 3D printing but this makes them harder to modify. Download this zip file to get the parts in their original orientations and positions if you're interested in making your own remixes.

Remix Highlights

Half-inch bar and folding parts by Moe Tsao

Half-inch bar & folding parts

Can't find metric measurement bars? This remix uses a half-inch bar and includes folding back and knee rests for compact storage.
https://www.thingiverse.com/thing:2759753

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Traditional scroll top by Will Newton

Scroll top

Try this top if you want a more traditional looking O'Cello.
https://www.thingiverse.com/thing:2672095

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Printed O' by Daddie-O

Printed O'

Print an O' for the front cover in any color your like using this clever remix.
https://www.thingiverse.com/thing:2427716

Print Settings

Printer Brand:

Wanhao

Printer:

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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Using self tapping threaded inserts would be better than the wooden screw plugs. Then, small machine screws with blue loctite could be used instead of wood screws. It'll hold the tuning better and wouldn't have to be tuned every time.

To make remixing the O'Cello easier I'm releasing STL files for the major parts in their original orientations and positions. Download the zip file here: http://o-cello.com/files/O-Cello_OriginalOrientation.zip

You don't need this if you just want to print the O'Cello, the 'Download All Files' button above will give you the parts aligned to the print bed and ready for printing, this is just for anyone interested in making remixes.

Hi, I was wondering if anybody could help me with the amplifier part of the O-Cello? If somebody could give me step-by-step instructions, that would be fantastic. Thanks in advance!

just look at my remix
https://www.thingiverse.com/thing:2863293
The only extra part you will need apart from the amplifier is a smal switch for the battery.

Knee rests and an amplifier for the O'Cello
by petercb

I have printed part 1 and 2 now - and on part 1 I saw just a little bit of shrinkage/curling - but on part 2 it was pretty severe. May I ask those that have worked with these parts - is there any hope for these parts? This was printed in ABS so I can create a slurry of ABS paste to try to heal the areas? or could it possibly be fixed with a heat gun?

Please give me your advice if these parts are recoverable. see picture provided with annotation where the warping is.

As far as I know, there haven't been any successful ABS prints yet. The parts you've shown in your picture look too warped to align nicely, you will have difficulty connecting them and will probably have a bump on the fingerboard which will impact the playability of the instrument. As Peter suggested, PLA is a better choice for this print as it is much less likely to warp during a long print.

I would not use ABS for the instrument - IMHO it is too soft (I cannot use it with my printer anyway)
I used PLA with 0.15 layer height, 3 layers walls all around and 30% infill and glued all parts (including the Carbon core rod) with epoxy.
The instrument has a little 'give' (less than a half tone if you try very hard to bend it) but not more than to expect from a real wooden cello.

I would love to see a version for a 3/4 double bass. I have never created or printed anything. I am having a friend print this for my daughter. If someone would help me I would like to make one for the 3/4 Double Bass.

Please contact me if you would like to help me.

Thanks

Anyone have source for the steel or carbon rod in the US? having trouble finding 12mm, 0.472" , 15/32" steel rods locally. Would home depot carry it?

I just searched ebay.com - no luck for local products.
Try your next RC-hobby shop. Otherwise there is no other way as to order from China direct and cheap (and wait a month for delivery).
Don't use a steel rod - the difference in weight is 163g to 890g!

Does the weight really matter since the cello rests on the floor (rather than violin which is held on shoulder) ???

It does not matter as long as you don't have to carry it around much, are young, healthy and strong.
I am of the opinion that a steel core would act as an antenna and might give unwanted effects when using an amplifier directly underneath it.
The idea to have 2 lbs less to carry was intriguing enough.

Finally I have my O'cello finished (had problems with the pickup & amplifier).
I used a solid carbon fiber rod (163g instead of 900g for the steel rod) and have no bowing tendencies, at least not more or less than a wooden cello has under tension. The whole instrument is GLUED, NOT using ANY screws, apart from fixing the tuners and the electronics). The rod is fully glued in - very important for the stiffness of the instrument. It holds the tuning for a long time (stretch in the new strings?)
Weight total is a mere 1726g although I used too much infill and less wall thickness....
The fingerboard is veneered (black walnut) and impregnated with 4 layers of thinned polyurethane lacquer.
The knee pads ar redesigned for 2 carbon tubes 10mm and a bit smaller than the ones designed by Zarlor. I didn't like the aluminum L-profiles - a cello for me is round so either round rods in aluminum or better in carbon - no painting necessary.
If anybody is interested in my files - just leave a comment here and I'll make them available.
Someone reflected on the bridge not having the right curvature - I checked with a template I found on the 'net - had to scale it to 69,5mm - perfect size. This has the dimensions builtin to check some other dimensions too like string spacing at the bridge and the nut, string height
https://www.metmusic.com/tools/bridge-tools/cl2801-multifunction-bridge-template-cello

Great work Peter - the pickup on the back looks very neat! And that bridge template is a great find.

Would you mind posting your photos and any new STL files as a remix (just click the 'remix' button above). That way people can easily see the modifications you've done and attempt them for themselves and I can feature it in the 'Remix Highlights' in the Thing Details page.

I'm impressed you managed to assemble the whole thing without any screws.

Done!
Thanks for the great design!

Just a quick question before I print this. Is the fingerboard angled for a professional model or student model.

Thanks for this cool model! I had a good time making it and have added new parts and revised a few things. You can check them out in under the remix header.

Great to see another successful build, and thanks for the remixes!

I find that 4/4 strings are too long for this cello model, did anyone tried 3/4 strings or lower?

Does anyone have a reference as to what a screw hole plug is? Any links would be great if anyone can link it.

This is what they look like:

For part one, how did you clean out the string holes from the supports? or did you not put supports on that piece?

Supports are only needed for the overhangs around the bolt-holes. See page 4 of the assembly guide PDF for details.

How did you print the top of the fretboard in black, but the back end white?

It's printed in white. I spray-painted the front black.

Thank you for all of your quick replies. This has been one of my favorite projects I have worked with 3d printing. I have always wanted to learn cello, but the absurd cost has always stopped me from starting. Now this project will allow me to finally do it. When you painted it black what kind of paint did you use? How did it hold up to wear? Did it have any effect on the sound of the instrument?

Could you possibly post some videos of how it sounds when it plays (outside of the game of thrones video, I have listened to that ~20 times)? I just want to know what I can expect with it.

My build plate is only 120mm. I really wish I could print this. Great work on the design :)

It it possible to play this without any electronic components? or do you need an amp for this to work? thanks for posting it btw, it looks great.

You don't need an amplifier at all. It's loud enough for practice or playing in a small room. This video shows how it sounds without any amplification: https://www.youtube.com/watch?v=lSVwg5sikZ4

oh wow ok, I didn't know that was without any amplification. I was curious on where you got all of the metal bars too? I went to my local hardware store, but really couldn't find anything that matched well. Thanks for the info, and of course the design!

If you're in America you may have difficulty getting bars in metric measurements. You could try finding an online store that will ship carbon-fiber rods, like these: https://store.acpsales.com/products/2372/carbon-fiber-solid-round-rods

I built two using the carbon fiber from ACP sales but I found that the fingerboard wound up bowing too much. The reason is that the Young's Modulus (flexural modulus) for the carbon fiber is 19 msi where 1055 steel (most linear shafts) is 29.7 msi. This represents a 56% increase in flexural strength.

My research on string height indicates that for the C string it should be 8.5mm from the center of the string to the fingerboard at the end of the fingerboard near the bridge. For the A string it should be 5.5mm. When I used the carbon fiber, it was 13.5 for the C and 11 for the A.

I bought two chromed linear shafts (http://www.ebay.com/itm/2pcs-12mm-x-1000mm-Precision-Chromed-Linear-Shaft-Rod-for-3D-printer-CNC-Oil/112015274361?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649) and rebuilt them and now my strings measure 8.5mm for the C string and 6.25mm for the A string. I will trim the bridge accordingly.

I would therefore advise against using the carbon fiber.

well, even after letting my Carbon rod core cello sit for half a year tuned I have no ill effects - the string height at the A-string is 6mm and 8.5 at the C-string. Did you glue the rod into the PLA? I did, so the small bending stresses are diverted to the outside PLA.
Young's Modulus applies to bending at right angles to the length, but here we have the stress lenghtwise in compression (I'm no engineer...)
Maybe that the ACP material is low on Carbon fibers? I got mine from a RC hobby shop where they sell it as wing connector for big RC-airplanes.

I printed Part 6 but the holes for the tuners are way off. The main hole measures around 15mm and the shaft on the tuner is only 13.25mm. The screw hole measures about 5mm and the screw is only 2.25mm. Also the thickness of the part at the tuners is around 17.3mm but the tuners need only 13.5mm. The 12mm hole for the shaft is correct.

The screw holes are much larger than the screws because you need to insert plastic plugs into the holes before screwing in the screws. See page 9 of the assembly guide PDF for a photo of this. I found that screwing directly into the plastic of the print caused cracking after some time so I switched to this larger hole with plugs system.

If you tuners can't reach the length of the hole provided for them, try removing their washer so they can reach further, or you may have the wrong type of tuner. Good luck with your build, if you have any other issues let me know.

Thanks for your response. I haven't had trouble with other screws in prints I've done but I'll watch out for it. I do extra walls when I have to use threaded in screws, maybe that has helped me. For this print I upped the walls to 6, the top & bottom layers to 8 and the infill to 33%. Maybe a bit of overkill but I think it should be fine.

The link for tuners in your instructions is no longer listing anything for sale. Those tuners look like the standard ones available from many other stores on ebay. I bought http://www.ebay.com/itm/Guitar-Bass-Tuning-Pegs-2R2L-Machine-Heads-Tuning-Pegs-High-Quality-Black-New/252379087523?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 which look like to ones you used (would love to get them in white!). Even without the thin washer, I simply did not have enough thread engagement to hold the tuner. So I went ahead and made the changes to the STL with SOLIDWORKS. My first copy just came off the bed and it looks great to me. The fit of the tuners is very snug and the washer and nut fit much better IMHO.

Thanks for sharing this design, it is a marvelous piece of work and effort on your part. I hope to have it completed soon. I will keep you posted on my progress.

Those look like the same tuners I have. I think I will have to narrow those walls a little as the tuners are not all exactly the same and they need more clearance. Thanks for the feedback. The extra walls won't hurt - the strings do put a lot of tension on parts 1 and 6.

By the way - I haven't seen those tuning keys in white, but they do come in chrome: https://www.thingiverse.com/make:351829

The O'Cello - a 3D-printable cello
by wendy

@tangentc
I measured the free length of my Carbon rod with 250mm. You will have almost 100mm sticking out from part 6.
So the stake will have to be quite long - I would advise to fill it with an 8mm glass fiber tube fully glued in. Sand the fiber tube down to a strong sliding fit and always use slow curing Epoxy - bonding and strength are a lot better,

re gluing with epoxy
I had a big mishap and glued the Zarlor finger & chest-rest-parts totally the other way round - so I tried to break the unusable part - no go.
All I could get was a very small bending torsion in the thin ends.
With almost 1.3 sq. in. per bonding area you get at least 1600 lbs strength, and this 4 times. Any questions?
Epoxy glue (slow curing - NOT the fast ones!!) is absolutely THE way to assemble PLA parts, and mixed with micro ballooons you get a filler for small to medium booboos... I've been boat building a small 3man sailing cat, so I know what I say.

I found the 12mm solid carbon rod in my hobby shop - modellers use them as main spars or wing connectors for big heavy sailplanes or motorized planes - price here was about € 40 (Austria is small so prices are always higher than elsewhere)
Look at https://store.acpsales.com/products/2372/carbon-fiber-solid-round-rods
12mm by 48" cost $ 22.

Hey, I'm in the process of printing this, and I have to 12mm x 85cm rods lying around already. I was wondering if an 85mm rod would have the clearance to get through the body of the cello and then attach to the endpin piece 15cm closer to the tuners? I can remix the stand coupling to accept another 12mm rod and just cut the end off with a dremel, so I'm not too worried about making up the length difference at the end.

EDIT: I accidentally kept writing everything in mm when I meant cm

85mm should be ok, that's about level with the bottom of the cello.

Awesome. Thank you for responding so quickly, and thank you for the awesome design!

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?

Out of curiosity, where did you find (presumably solid) carbon fiber rods with a diameter of 12mm? Maybe it's because I'm in the US, but I can't find any solid ones of that size, only 12mm OD x 10mm ID tubes, which I'm concerned about the strength of.

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!

As per my last comment (accidentally #100! :-) the glued version with the 12mm solid carbon rod is as stiff as one can imagine. Height difference over the whole fingerboard (tuned instrument!) is a slight light in the middle - I didn't use a LONG sanding board....
I suppose that a sliding fit of the parts to be glued together is the way to go, and the thin laminating epoxy resin I used for the rod squeezed out like crazy. It gets stronger over time too.
The joints between the parts got a slurry mixture of this resin with microballons to fill the voids left by the wooden dowels I used in place of screws.
I will post the redesigned (haha) bridge where I used the violin pickup I got with the headphone amplifier in the near future.
As I am no player just a builder (with very good ears - bassist) I may say that the sound is quite respecable, with and without amplification.

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?

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?

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.

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

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

a 1/2 inch rod version can be found at https://www.thingiverse.com/thing:2759753

O'Cello for 1/2" rod, folding chest rest, telescoping knee rest
by kelsier

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.

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

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.

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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