Solid Walnut Ukulele From Walnut Tree Using CNC/ Laser Cutter

There is an analogy of 2 different ways to make a canoe. One where you cut down an entire tree and hollow out the inside, the other where you collect sticks and branches to piece together the same device. This analogy was used for gathering information for writing a school report, but I find it useful in this instance as well.

I had a walnut tree in my backyard that got infected and was dying, so my dad and I cut it down, painted the sides, and let it dry out for a couple years. We ended up with more walnut wood than we knew what to do with, so I decided to make a Ukulele from a solid piece of walnut wood. In lieu of gluing in the stiffeners, I instead cut out a larger slab of Walnut wood and CARVED out the excess material with a CNC, leaving the bracing and stiffener shapes inside of the wood.

This is definitely an ineffecient way to make a ukulele face, but I feel that the less glued in pieces, the better. And as the analogy goes, there is more than one way to make a canoe...

Fusion 360

CorelDraw

CNC wood lathe

Laser Cutter/ Engraver

Planar

Bandsaw

Drum Sander (not necessary, but it makes getting the walls of the ukulele A LOT easier to make)

One Stump/Body of walnut tree at least 12" x 15"

One branch of walnut tree at least 4.5" in diameter

Wood Glue - Titebond III

Clamps

2.25 PVC pipe

If you have logs, then you will need to chop them up using a chainsaw or bandsaw if you are capable of handling them. Be aware of termite damage and save those planks for a different project (see LED backlit Coffee Table). If you have acquired lumber from a lumber store, then this step is very easy. You will need pieces that are:

For the body:

13" long

9" wide

1/2" deep

For the sides:

2 pieces 22" long

3.5-4" wide

65-70/1000" deep (if you buy this from a luthier store, the depth is already set, otherwise you will need to do this step by hand, use a drum sander, or get really creative with a planar which is what I did)

For the neck:

14" long

3" wide

3" deep

You want your wood pieces uniform and to the right dimensions. For my purposes I overshot the size above and planed them down to the right dimensions for a nice smooth look. A hand planar will work and I have heard that it is a very meditative process, but I wanted to see what I could do for the sake of speed and efficiency.

This was by far the hardest task to complete. I would recommend using a drum sander and sand off very small amounts until you achieve the right thickness of 0.060 - 0.070 inches. If you do not have a drum sander, you can use my method of using a planar and an additional piece wood taped to the wood for the sides. I initially used double sided tape, but this proved to be to sticky and the wall would break apart as I was peeling the tape away. I would now recommend using the more expensive painters tape and C.A. glue. Get two pieces of painters tape and put the C.A. glue between the two pieces to attach it together, making a less sticky, but just as effective double sided tape. Ideally, you would want to cover the entirety of the bottom of the side wall wood with this tape, the more surface area covered and taped at the bottom, the better.

Alternatively, you can just go to a luthier website and buy these pieces for a relatively cheap price.

Here comes the fun part: designing your ukulele!

Pull up Fusion 360 and go into sketch mode

Set up several center rectangles with the closest rectangle being the smallest curve on the ukulele

The second largest rectangle is the largest curve on your ukulele

The last rectangle is about 20% larger than the size of your ukulele

You then want to create two lateral rectangles to cut the ukulele up roughly into thirds, play around with this part and see what fits your size and looks of a ukulele

After all the rectangles are made you will use a control point spline to create the curves of the ukulele on one side of the rectangles only. A good rule of thumb is to try to make a boxy pear-shaped vase with the control splines and fine tune it to match the look that you want for your ukulele. The orange points in the second picture show the points I used for my spline.

You will then use the mirror function to mirror the control point spline across the center line of the sketch. (make sure all center-made rectangles have the absolute center point as origin for easiest mirror effect, alternatively, make sure there is a mirror line at the point that you want to mirror halfway through the ukulele)

A good acoustic instrument will need support as well, this will go back to your lateral rectangles that you made earlier.

For the bottom face of the ukulele, use the center of the rectangles as a good idea of where to add your support.

(note: if you do not want to use a lot of wood and carve out a support from the back face, you can still use this idea and glue in supports that are .25 inches in width and 3/8 inches in height. There are several articles online about the acoustic differences in wood when the grain is cross-wise or matching the face, so keep that in mind.)

For the top piece you will want to add support at the top of the opening in the ukulele and the bottom of the opening of the ukulele. the support pieces are definitely a fun thing to play around with and can affect the acoustics quite a bit, here are several of my designs based on stuff that I have seen online.

I would recommend using the ellipse tool and overshooting the ellipse to make sure there is a significant amount of support left on the ends

You should also add a support for the bridge, I have seen rectangles or ovals, I decided an oval to see if acoustics would be better this way.

I also am trying a V-brace design to alter the acoustics and see what will happen.

Up at the top and bottom of the ukulele will be additional supports, something that connects the top and bottom pieces more than just the side walls. At the top will be the neck and fretboard, and it helps to add an additonal piece at the bottom for the two side wall piece ends to connect to. I made my top neck connector piece about 2 inches wide and 1.25 inches thick. the bottom piece is half an inch thick and 2 inches wide.

Once the sketch is complete, remove any lines and drawings that are not needed to make it easier for the sketch to be extruded.

(note: when you are doing your sketch, having the snap placement turned on will help in reducing the chance of lines not completely coming together and extrusions failing because of it, it will also make it more annoying because your line will want to snap everywhere unless you zoom in really close.)

I made my support beams 1/5 inches wide and 3/8 inches high

The bridge support is 3/16 inches high

The walls and end supports are 1/2 inch high

The back face is 1/8 inch high

The front face is 1/10 inch high

The back and front faces are still a little thick, but they will be laser cut down in the next few steps

Fillet and chamfer the pieces to smooth the edges. You will have to play around with these settings to get the right amount. In general, chamfering first and then filleting is less likely to cause errors than vise versa. Be sure to fillet the wall edges too to replicate a kerf binding.

The neck is truly something you will have to feel out for yourself. If you have big hands/long fingers, a thicker and more rounded neck will be more comfrotable to play. Because I was using a CNC, I grabbed the profile and a 4 inch cutter to cut out the neck. I made it a 10 degree angle at the end of the fretboard to make sure the pegs kept the strings down. Make sure the base of the neck matches your top connector of the ukulele body.

For the fret distance, I used this website:

https://www.stewmac.com/fret-calculator/

Because I didn't have any bits small enough to make the fret spacing, I used a laser cutter instead and ran it multiple times to achieve the right depth.

Now that the design is done, go to the top left corner and switch design to manufacture.

NOTE: MAKE SURE ALL OF YOUR WOOD MATCHES THE DIMENSIONS THAT YOU ARE PUTTING INTO THE MANUFACTURE CODE! I have lost more than one good pieces of wood this way and several good router bits to boot.

For the neck: a 2-D contour works fine with the way I set it up, but you will need to round out the sides and use a saw to cut the groove into the base of the neck to fit into the body connector.

For the faces: if you want to have a very clean look, you will use a down cut router bit followed by a ball router bit with an adaptive 3D clearing. be sure to click roughing pass in the passes tab when doing this method.

For a single pass with a down cut router bit, use the 3D pocket clearing.

There is a very good instructables that explains the manufacture mode of Fusion 360 in the aspects of a CNC, the link is below:

https://www.instructables.com/Fusion-360-CAM-Tutor...

IMPORTANT: ALWAYS TEST OUT THE CODE ON SCRAP WOOD FIRST! I can almost guarantee that the first time the code is generated, it will not be to your liking and you do not want to waste good wood on that.

Using one of the practice pieces of wood that you tested the code on on the previous step, make several pieces or use a hand router to carve out several more silhouettes of the ukulele shape. You will need at least 3 inches of a shape to bend the wood.

To bend the wood, first soak the wood for at least 24 hours.

The longer the better.

SLOWLY bend the wood across the silhouette starting with the bend in the middle and SLOWLY bend it across the other two bends.

The slower, the better.

You can pull it off and soak several more times to make sure you don't break your wall piece. Let it stay on the form for at least 24 hours, lightly wetting it occasionally to help it want to stay in the molded shape.

If the mold turns out well, it will be easy to put the wall to the ukulele shape. Otherwise, you will need to use more clamps and braces to keep the wall attached to the body until the glue dries. Leave the excess wall height on until the glue dries and acclimates to the humidity, the walls will probably change in size a little until the wood matches in moisture content.

The fretboard can be bought or you can look in the next steps when using a laser cutter.

Let the ukulele dry for several days to acclimate. Sand the edges and clean and smooth the wood, add a wood oil like teak oil and then add the strings.

I was afraid of having the CNC go too close to the wood and having the thin piece get ripped apart, so I kept the faces slightly thicker and then used a laser cutter to burn away the top layer. My theory was that walnut isnt really a tone wood, but by keeping the wood exceptionally thin and using a hexagonal pattern for strength and support, I can make a decent quality sounding ukulele. Also, with a laser cutter, you can make some really cool designs on the front face and neck of the ukulele. I used purple heart wood as an inlay using a laser cutter and ,making the inlay 5% smaller than the cutout in the walnut. The fretboard measurements were made on Fusion 360 but the inlay cut and designs were made on Coreldraw which was the program to use to print on the epilog laser.