Parametric Jewelry Tray With Fusion 360

In this guide, I'll show how I designed and created a sinusoidal jewelry tray from cherry using Fusion 360. I'm a student at Rice University in Houston, Texas.

Materials:

Cherry, surfaced on one face, approx. 1BF

Pre-cat lacquer

Tools:

Fusion 360

CNC router

Laser cutter (optional)

Random orbital sander

Method of applying finish (HVLP, aerosol, etc.)

First, we need to initialize the parameters that we’ll later use when building our model. There’s only two—amplitude and wavelength. The initial values aren’t critical; we can change them later without hassle. My model uses amplitude = 0.25” and wavelength = 2.5”. As the names suggest, amplitude controls the distance from each peak to each trough, and wavelength controls the distance between peaks (or troughs). In the “Design” Workspace, use Modify > Change Parameters, and click the “+” icon to add a parameter.

Next, we’ll create the sine wave with the parameters we just defined. Begin by creating a coil (in the “Solid” tab, under Create > Coil). Select a plane perpendicular to the ground plane. Place the center point at the origin, and specify “Amplitude” (our parameter) as the diameter of the circle.

We’ll need to modify several values in the “Coil” tab that appears after specifying the diameter. In particular:

• Diameter should be our “Amplitude” parameter (this should already populate)
• Revolutions should be 1 (we only need a single wave period for now)
• Height should be our “Wavelength” parameter
• Section should be “Triangular (External)” (this will be important for a later step)
• Section Position should be “Inside”
• Section Size doesn’t matter, but choose something reasonable (err on the smaller size). I used the default 0.0625”.
• Operation should be “New Body”

This should leave us with a single revolution triangular coil that traces the inside of a circle with a diameter equal to our amplitude.

Next, we need to mirror this coil. Select Create > Mirror, ensure Object Type is “Bodies”, and select the newly-created coil. For Mirror Plane, select the ground plane. For Operation, select “New Body” (ignore the image which shows a "Join" operation, this is a mistake). Click “OK”.

Next, create a Sketch on the plane parallel to the length of the coil and perpendicular to the ground plane. Select Create > Project / Include > Project, and select the outermost edge (point) of both coils. In section, the coil is a triangle. Be careful to select the edge that traces the apex, not either edge that traces the base. Click “OK”.

If we turn off the visibility of the bodies, we can see the resulting sketch is a pair of sine waves with the amplitude and wavelength we specified (image 2).

Select one of the waves and convert it into a construction line by pressing “X”. Click “Finish Sketch”.

Next, select Construct > Offset Plane and select the same plane that was used to create the sketch. Extent should be “Distance”, and specify the distance as our “Wavelength” parameter divided by 2. Click “OK”.

Next, create a sketch on the newly-created offset plane. Select Create > Project / Include > Project and project the construction line onto the offset plane. Click “Finish Sketch”.

Next, open the “Surface” tab. Click the “Extrude” icon. Click either line (not the construction line), and extrude it away from the other line. The distance isn’t important; I used 0.25”.

Now we can loft these surfaces together. First, turn off all sketch visibility on the left file tree. Select Create > Loft and select the two innermost edges of both surfaces. You may need to disable “Chain Selection” in order to select only these edges. Ensure Guide Type is set to “Rails”. Under both profiles, change the connection type to “Tangent”. Ensure Operation is set to “New Body”. Click “OK”.

We now have the beginnings of a wave! Let’s clean up the model by selecting both coils and both rails in the file tree, right clicking, and clicking “Remove”.

Our surface has a full period in the X direction, but only half a period in the Z direction. We can fix this by selecting Create > Mirror, selecting the wave surface, and mirroring it across the XY axis. Ensure Operation is set to “Join”.

We can replicate this wave by selecting Create > Pattern > Rectangular Pattern. Select the wave surface and the X and Z axis. Ensure Distance Type is set to “Spacing”. For both axis, the distance should be our “Wavelength” parameter. The quantity for each direction depends on the desired size of the tray. For my ~8” x ~10”, I chose 5 x 5.

Next, select all the newly-created bodies, and Modify > Stitch. Click “OK”. This will create a single body from the pattern of surfaces.

Now we’re ready to create the tray. Create a sketch on the ground plane, and draw the desired outline of the jewelry tray. Ensure that the outline of the tray lies within the wave surface. I spent some time aligning the tray to the period of the wave and ensuring symmetry. You can find my final project files at the top of the guide.

After finishing the sketch, navigate back to the “Solid” tab and select “Extrude”. Select the tray sketch, ensure Direction is “Symmetric”, and specify a distance. Keep in mind that the final height of the tray will be this distance plus half the amplitude. In my case, I used 0.75” (a total thickness of 0.875”). Click “OK”.

Finally, select the newly-created body and select Modify > Split Body. Use the wave surface as the splitting tool. After splitting, we can hide the upper portion and the wave surface. The result is the wave surface imprinted on the tray!

I had hoped to make this piece out of walnut, however I didn’t have any stock on hand that was close enough to the dimensions of the tray. I think grain continuity is important in this piece, so I wanted to avoid gluing boards together. Instead, I found a cherry offcut that fits the bill. I’m not a huge fan of the sapwood along the edge, but I also didn’t want to make the tray any smaller.

Thankfully, this board already has a flat face which I can lay on the bed of the machine—otherwise, I’d have to joint one face. The only step is to trim the stock roughly to length.

I am omitting my toolpaths because I’m no CNC expert and they’re machine-specific. In general, I used a parallel 3D finishing pass before a 2D contour around the outer edge. I used a 1/4” ball-nose end mill with a 8% step over (0.02”) for the finishing path. This left negligible ridges to remove during sanding.

The machine I used is a 4’ x 8’ ShopBot. Although it’s equipped with a vacuum table, the holding power of the vacuum over such a small part is not confidence inspiring. Instead, I applied 3M 233+ tape to both the table and the bottom of the stock and glued them together with CA glue. This works very well for smaller pieces like this; I simply whack the side of the piece with a dead blow mallet to release the tape after the machining is finished.

Now we just need to press "Go." The operation took about an hour in total. It was pretty fun watching the wave form come to life.

I began the finishing stage by removing the grooves left by the ball nose end mill. I found a 120 grit sanding sponge to be particularly effective at this. I also made sure to avoid excessively rounding the edge of the tray at this step (an aesthetic choice on my part). I sanded the edges to 220 grit.

I etched my maker’s mark on the bottom of the tray using our CO2 laser. This leaves a bit of burning on the surface, so I waited to sand the bottom to 220 grit until after this step.

I finish sanded the bottom with 220 grit on a random-orbit sander. I also worked my way up to a 220 grit sponge on the top (this took some time). I find 220 grit to leave an optimal surface for lacquer finishes.

I’ve been enjoying using pre-cat lacquer on my recent projects. It’s easy to apply, dries extremely quickly, lies close to the grain, it’s easy to blend layers, easy to repair, and (in my experience) moderately protective. However, I don’t recommend it for light species such as maple as it yellows over time (this may not bother some people). 

For this project, I used Mohawk 20 sheen pre-cat lacquer (M1020412) in an aerosol can—I wouldn’t hesitate to recommend this product.

And, that's it! The tray is complete.

I would like to thank Robert Purvis at the Moody Center for the Arts for his help teaching me how to use a CNC router for this project.