Introduction: The Magnetic Watercolor Box (Plywood Contest)

About: Not an engineer, just a passionated guy.

This is my first serious project on CNC and Fusion 360. It's also my first Instructables. And yes, I'm very happy to do it. Sorry for my English, I'm better at French, and even better at Frenglish.

For this project, I wanted something simple but pretty to look at, more than something really usefull with tons of features. To challenge myself, I set some constraints and specifications for the final object :

  • 3 types of materials that I love : Plywood, HDF (High Density Fiber) and clear acrylic ;
  • Strong enough to be transported, with a small shape ;
  • Magnetic locks ;
  • Can be set on my desk, as a decorating object ;
  • Can be set in pocket transport mode and in standing mode ;
  • Semi-modular design, so I can reuse the shapes for a futur object ;
  • And chamfers everywhere, I love chamfers.

So came this idea of a watercolor box. I used to paint a lot in watercolor at a time, but I had no box that I liked enough to give me pleasure when I look at it, and nothing enough usefull with my erratic practice (by the way, I prefer oil painting). So this box was perfect for me : simple, aesthetic and doing what a watercolor box has to do, aka :

  • Packing some watercolor blocks ;
  • Packing small stuff like watersoluble pastels (here : Neocolor 2 from Caran d'Ache), or tiny pencils / brush ;
  • An inkwell or a cup of water can be set on it ;
  • Being enough pratical to be used on the go AND on a desk.

Step 1: Supplies and Tools


A CNC cutting machine ;

Endmill bit : Ø 3mm, straight 2 flutes ;

Glue (multi materials) ;

Tea or coffee or Pepsi Max or other product with similar effect.


Plywood, thickness : 15mm

HDF (High density fiber, I use the brand Valchromat) or MDF, thickness : 8mm

Acrylic sheet, thickness : 3mm

Neodyme magnets :

  • 12x Ø 12mm, thickness : 1mm ;
  • 2x Ø 19mm, thickness : 2mm ;
  • NB : I use some magnets with a hole on my design, just for aesthetic purpose.

Step 2: Modeling With Fusion 360

I'm a beginner on Fusion. It's a great software that can be learned by total newbies in CAD. I come from Sketchup and I think Fusion is far better for modeling for CNC process. I've learned the hard way, aka try and die. My process can be improved a lot, nonetheless I'm still satisfied with the results.

So I started by designing the layers of the box. I tried to use a single sketch for all the model, I've learned that it's a terrible idea... Do as many sketches as there are 3D shapes, it will make your work cleaner and easier to organize.

Each layer can be done with different sizes and thickness, according to the materials you use. Nothing really usefull to say here, if you know how to use Fusion, I will not teach you anything... Just check the specifications of the object on the screenshots ;)

Step 3: Preparing the Cut on Easel

For the CAM step, I use Easel because I'm not yet familiar enough with CAM module of Fusion.

  • (free version for me)It's a pretty simple step, but there's some tricks beginners have to know to make a clean gcode file.

From Fusion to Easel : Shaper Origins

In Fusion, I use the extension "Shaper origins" to export SVG files onEasel. Just select the faces of each parts, make sure to select faces surrounding every cut, aka the inside of the compartments, the hollow holes with full depth holes inside, and the offset extrusions. Once all the top faces are exported (note that some parts can be flipped so you have to select the face with the right shapes), import them in Easel.

Settings - Plywood

First, configure your piece of work. For this piece, I use Plywood (thickness : 15mm) and a straight endmill bit (2 flutes, Ø 3mm). My cut settings :

  • Feedrate : 800 mm/min
  • Plunge rate : 200 mm/min
  • Depth per pass : 1 mm

It's a slow cut, but I get good results with it, with not too much chatter on the piece. Don't hesitate to show me your results with other settings !

Settings - Acrylic

The settings for the acrylics parts (thickness : 3mm, same bit) :

  • Feedrate : 640 mm/min
  • Plunge rate : 170 mm/min
  • Depth per pass : 0.3 mm

Settings - High Density Fiber (Valchromat)

The settings for the HDF parts (thickness : 8mm, same bit) :

  • Feedrate : 1400 mm/min
  • Plunge rate : 220 mm/min
  • Depth per pass : 1.5 mm

All these settings came from try and die, I didn't calculate anything (yeah I know...), so you should get better results or faster cuts If you find optimal settings for your configuration.

Types of cut
Second, be aware of the type of cut you need to do according to the path of your model. Here are the different types of cuts I made for the "holder" piece, the most complicated one of the box :

  • The shape of the piece is cut out of a Plywood (15mm), so you need to do a "Cut outside shape path" to get it. I don't use tabs since I prefer double face tape to hold my piece on the 3018 platen.
  • The inkwell goes to the big hole. I prefer a "cut inside shape path" to make it, because it make the whole cut faster and there's less ships at the end. Be sure to hold well the piece inside the center, with double tape or with tabs.
  • Now the tricky part : the 3 magnets have to go on 3 hollow holes (depth : 2.1 mm). For the big one, select it, right click and "send it back", unselect. Now you can see the shape of the full depth hole ( Ø 5mm) inside of the hollow hole.
  • Proceed the same with the watercolor blocks compartments : select the rectangle shapes (depth : 9mm), send them back so you can see and select the full depth holes inside of them.

If you made everything right, you should have the same display than me. The global process is the same for the other pieces of the box.

Step 4: Cut !

Preparing the cut

Make sure to hold enough your pieces on the platen. I use double face tape, because it's simple and I don't really like using tabs when cutting, since I don't have yet any tool to remove them properly.

Universal Gcode Sender

Since I have a 3018 from Aliexpress, I can't use Easel to cut directly, I have to export the Gcode and make the cut on the freeware Universal Gcode Sender. It's a good and simple Gcode sender and I prefer it to Grbl. You can download it on the link below :

Easel, go to Machine > Advance >Generate Gcode > Export.

On Universal Gcode Sender :

  • Open your port after connecting your usb cable ;
  • Set your zero by moving the bit with the buttons, you can use your keyboard if the option is activated ;
  • Browse your fresh downloaded gcode file ;
  • Visualise it to check that it's the good file (trust me, check it...) ;
  • Send your cut ;
  • Admire your CNC cutting like you watch your girlfriend / boyfriend / cat sleep at your side.

Step 5: Postprocessing and Assembling

Remove the left double tape faces if you used them. Sand a bit your pieces to make them clean.

Assemble the pieces, I use 2 types of glue, one for wood to wood, and one for wood to acrylic / magnet to acrylic. The second one made the back of the box looking terrible. I recommand to put enough glue on all the surface to avoid any waterdrop effect, or you can even screw the back part acrylic on the HDF.

Put some varnish / oil / finishing stuff if you want. Personnaly, I like the box feeling "rough", so I didn't applied any finish, and because I'm lazy.

Step 6: The End

You can set different stances according to your use (desk mode, on-the-go mode, decorating mode). You can use the acrylic panels to mix your ink, and use an inkwell in the holder shape, or a cup of water.

In on-the-go mode, you can attach a cord inside the hole of the big magnet, so you can't drop it.

Enjoy your box and dream of it every night.

CNC Contest 2020

Participated in the
CNC Contest 2020