The PrintBone: a fully printable playable trombone

by pieterbos82, published

The PrintBone: a fully printable playable trombone by pieterbos82 Oct 23, 2016


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A 3d printable trombone. Fully parameterized in OpenSCAD, see https://github.com/pieterbos/PrintBone and check the wiki there for instructions on creating your own trombone design.

See http://www.thingiverse.com/thing:2252952 for an updated version that prints and looks better. Soundwise it's the same.

The bell correspond to a large bore 8.5 inch symphonic bell. Fits a Bach 42 or Bach 50 slide, or a yamaha slide - possibly more brands.

The slide is a PVC slide. It can be done with any kind of tubes by editing the .scad file you can find on github. Fits the printed bell or a bach 42b.

The OpenSCAD file also works to create very nice working carbon fiber outer slides for different trombones, if you can find the correct tube diameter. A bach 42B inner slide fits widely available 15mm diameter tubes, but 14.9mm would be better. See github for improved designs for that purpose, that print without any support.

See https://soundcloud.com/pieter-bos-2013025 for a recording of both a regular brass bell and this bell. Can you guess which one is which?
It also has a recording of the pla slide, work in progress with still a leak somewhere and it will sound better later.

Printing instructions for the bell

I printed it in PLA on an original Prusa I3 MK2 with 0.2mm layer height. Choose whatever infill you like. Print time somewhere between 25-30 hours, but you can probably do a lot faster with a 0.6 or 0.8mm nozzle and a faster printer.

The bell flare is cut for an at least 21x22x20 printer. If you have a smaller printer, you will have to adjust those two files.

Print the tuning slide with the pegs upward, and support enabled. The two small midair rafts will be supported and make for a much more stable part. They can be easily broken off later.

A two piece bell flare that can be more easily printed without support is available as a setting in the OpenSCAD file, it has not yet been tested.

Printing the slide parts

add lots of infill or even solid for the inner handslide brace because it needs to be stiff!
The rest, just print whatever is the most airtight.
I printed the leadpipe in spiral vase mode with a 0.3mm nozzle and 0.37mm wall thickness, 0.1mm layer height.
The leadpipe is relatively bright. If you don't like it, increase the venturi diameter in the openscad file a bit.


Bell assembly instructions

  1. Print tuning slide and both neckpipe parts
  2. Sand connections and test fit parts and parts to trombone
  3. If they fit, continue. If not, download openscad file and adjust clearance parameters. You can keep the tuning slide even if fit is not correct, it will not be altered
  4. Print the rest of the parts
  5. Sand all connections to make a good fit
  6. Test all parts for airtightness. Use superglue to fix any leaks (perhaps acetone for ABS?)
  7. Glue all connections except for bell flare
  8. Test assembled bell without flare for leaks and fix them. It's easier to close the ends without the flare attached.
  9. Glue bell flare


  • You can use a practice mute to seal the bell when checking for leaks.
  • Use soapy water to find the location of leaks. WARNING: soapy water slowly dissolves superglue :)

Slide assembly instructions

Get 2 meters of 3/4 and 5/8 inch PVC pipe.

  1. Print parts
  2. Test for leaks. Fix all leaks. Coating with an epoxy lacquer might help.
  3. Cut the upper inner slide tube to correct length. Assemble without gluing.
  4. Assemble rest of smaller tube and cut to same length.
  5. assemble outer slide tube, check length and cut.
  6. test the slide. Glue the parts
  7. put stockings on a piece of tubing you have left after step 5 and sand the stockings with increasing grit sandpaper. I used 180 - 320 then 600. They should be very smooth.
  8. Put stockings on trombone, check fit and glue.
  9. Lubricate stockings with slide cream (slide-o-mix and yamaha lubricant do NOT work well)

If parts do not fit, check the openscad file and you can input your own measurements.

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Nice job! Where did you get the PVC pipes, especially the 5/8?

Old post I know, however just wanted to let you know that the pvc on this project is actually called cpvc. and you should be able to find it at just about any hardware store big or small.

May 28, 2017 - Modified May 28, 2017
pieterbos82 - in reply to Attackchef

I did some reading on US pvc and cpvc pipes.

It looks like what I used in US terms is called copper tube sizes (CTS) tubes, nominal size 1/2 and 5/8 inch, type L. Those are probably available as CPVC tubes, sizes 1/2 and 5/8 inch.
Type M will work if you sand the stockings a bit. Type K will need a different leadpipe and wil use a small shank mouthpiece.

If another type of tubing is more readily available I'd be happy to generate separate EU and US slide parts. Just send me the inside and outside diameters, preferrably both the specification and measurements on actual pipes. Then I can adjust the model. Make sure the inner diameter of the smaller tube is between 0.525 and 0.569 inch, preferably around 0.54 inch.

The pipes I used are these (literally available at every store in The Netherlands):

  • 5/8 inch outside diameter, 0.54 inch inner diameter
  • 3/4 inch outside diameter, 0.657 inch inner diameter

and if they don't have those, they will have the following - those should work:

  • 16mm OD, 14mm ID
  • 19mm OD, 17mm ID

Over here in The Netherlands, they're available in literally every hardware store, usually at less than a euro per 2 meters. No idea if that's the same everywhere. If you can find other dimension tubes that slide into each other with enough space for stockings between them, it's very easy to change the model.