How to make your own OpenGuitar (the complete DIY guide).
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Following all the comments and and supporting emails that we received, we share here all the information required to build an OpenGuitar, which is professional experimental classical guitar. The OpenGuitar is the core vehicle of our social-educational project, carried out by our registered non-profit OpenGuitar e.V.
Wherever you construct this guitar, we would greatly appreciate it if you would consider teaching someone else, ideally children from disadvantaged backgrounds, the process you go through while assembling this guitar.
The OpenGuitar is a nylon-string instrument developed for classical guitarists and experimental e-guitar performers. It provides ultra-quiet performance and an exceptionally natural tone through both headphone and line outputs. Featuring a sleek, collapsible design, it’s the perfect companion for classical guitar practice, travel, recording, or live performances.
OpenGuitar specifications:
Neck wood: we recommend sustainable wood such as platane or maple
Truss rod: Dual-action
Scale Length: 650 mm
Frets: 21 (fretboard ends at: 467.6 mm)
Nut Width: 52 mm
Neck Thickness at Nut : 22 mm
Neck Thickness at 10th fret: 23 mm
Distance between E strings at Nut: 43 mm
Distance between E strings at Saddle: 58 mm
Nut and saddle material: bone
Machine Head Ratio: 16:1
Bridge: free-standing
Pickup: Custom-made flexible transducer with active Preamp
Digital/Mobile Connectivity: micro ADC Converter enabling mobile recording at 16bit, 48kHZ.
String Set: Nylon
Wood available: Berg Ahorn 1190x100x28mm Tonholz Mapple neck tonewood Axund (order ebay here).
As you can see above, it can be done with a home-made CNC router ;)
The original OpenGuitar (OG) has a thickness of 29mm, but requires a stock of 32-34mm.
We will construct an OG that is slightly thinner (max thickness: 26mm) and add a 3mm plywood slice below the headstock to compensate for the missing 3mm.
We reduce 3mm on the back of the end-neck and headstock. From the bottom of these 2 surfaces to the fretboard we have a thickness of 26mm.
We add 1mm to the surface beyond the fretboard to make it more solid
We place the OG in the middle of the 28mm stock, and since we have thinned it to 26mm we have 1mm left on the top and bottom. There is 1mm below the headstock as well.
Notes:
Neck Top is cut with the 6mm bit. The origin coordinate is set at the bottom of the stock (Z), centered on the 6mm closest vowel (X and Y).
However, after the end of the contour cut the frets are traced with the 0.4mm bit. Here the origin is the same in X and Y, but the Z is changed to the top of the freshly cut fretboard.
After the frets, the 6mm bit needs to be put back and Z is reset to the bottom of the stock.
Neck Bottom origin is same as Neck top but "reversed".
Origin coordinates
General important details about stock and model dimensions.
All tool paths (top and bottom side)
Below, each operation is displayed.
Top paths:
HINT! Avoid surfaces: Very useful command (used in parallel operation for fretboard).
Simulation Video (bottom side)
Now it is time to trace the frets. As described above we now change for the 0.4mm bit and reset the Z coordinate to the top of the fretboard (do not change the X and Y coordinates). As can be seen below the origin is somehow inside the stock since it is exactly at the level of the fretboard.
Finally, after the frets tracing, we remove the stock, put back our 6mm bit, set the Z coordinate back to the top of the MDF, and drill 2 holes for vowels in the MDF (-9mm depth). It is shown in the image below as a drill operation below the stock (but remember to remove the stock!). This will allow to place the vowels and flip the stock to cut the bottom side.
Bottom side:
As can be seen below, the origin coordinates are accurate to be able to route the bottom side.
In the neck roughing (pocket) operation we add a stock to leave of 1mm, since later we'll do a parallel polishing.
For the cutting the truss rod we exceptionally change the step over to 2mm (instead of the default 1.5mm) to reduce machining time.
Initial contour operation with tabs (to prepare the sides for the next parallel polishing)
Parallel neck polishing operation
Finally, we run a second contour operation with 5 tabs to prevent the neck from moving after removing all the side material.
Simulation Video (bottom side)
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