Carve a Bowtie on a CNC Router Using Fusion 360

For the Scraps challenge, each Gizmo-CdA staff member wanted to make the same thing, just with different mediums. We get so many scraps from the projects and classes we do with members, that oftentimes we are faced with finding new ways to use them up or unfortunately throw them away. So, there will be other bowtie entries made of different things we found around the shop, showing off only a small amount of what you can do in this Makerspace.

This Instructable details the process of turning a piece of scrap plywood into a 3D carved Bowtie using our CNC Router. You will learn to convert an .stl file typically used in 3D printing into a Fusion 360 Body. From there you will assign toolpaths to the body to carve the Bowtie into plywood. There are countless sites to find free .stl files; by learning to carve on a CNC Router you can make a more durable model!

Autodesk Fusion 360

CNC Router

1/4" Sharp 2 Flute Endmill

Amana 1/16 Tapered Ballnose Endmill P/N #46282-K

Piece of plywood from the scrap bin

First you'll need to find a 3D object to cut. I went to thingiverse.com, searched bowtie, and downloaded the simplest design. Though we will be using 3D toolpaths, we will not be able to cut any overhanging features or anything on the back side. If you'd like to have features on the back side, you'll need to create a fixture to hold onto the top of your part.

As a result you should not choose anything that has any key features on the underside or any overhanging parts.

I selected this bowtie: https://www.thingiverse.com/thing:2394279

First we need to Rotate our part so that the Top View matches the direction the tool approaches from. To do this select the Move/Copy icon from the Modify menu. Next select MeshBody1 from the Bodies dropdown on the lefthand side. Change the Move Type in the righthand menu to Rotate, select your axis (under the Origin folder on the lefthand side) and input the appropriate value. For my bowtie I needed to rotate the part 90 deg about the X axis.

When the Top View matches the area to be cut by the router, you are ready to continue.

We now have a mesh model in the correct orientation, but no idea of how big it is.

First go to the Manufacture dropdown menu (Image 1). Click the folder icon on the menu at the top above Setup. We're just looking for the Dimensions here, so go to the Stock tab and record the dimensions at the bottom.

My dimensions imported at (Image 2):

X: 1057 mm

Y: 460.16 mm

Z: 147.04 mm

Decide on a length for your part. Choose one direction to 'drive' and the other will scale proportionally. For example, I wanted the width of my bowtie to be 4 inches (101.6 mm).

Next return from the Manufacture workspace back to Design. Click the arrow beside Modify and select Scale from the drop down menu. Select MeshBody1 from the design tree on the left. No need to select a point. Ensure Scale Type is Uniform.

To calculate a shrinking Scale Factor, you need to divide your desired value (4 inches) by the current value. Do the opposite if you need to enlarge the part. You can enter this directly into the scale factor dialog box. I input 101.6/1057

We are now ready to convert the mesh into a body. Using the Solid tab at the top of the screen click the dropdown menu beside Modify, place your arrow over Mesh, and select Mesh to BRep. Select MeshBody1 from the design tree and select New Body.

Congrats! We now have a model that Fusion 360 knows how to interact with. The color of your model should have changed from pinkish to greyish (Images 3 and 4). This gives us the ability to assign advanced 3D toolpaths.

I like to use a 3D Adaptive Toolpath to remove the majority of the material and a Parallel toolpath to smooth out the edges.

Return to the Manufacturing workspace.

Under 3D Toolpaths select Adaptive Clearing.

Tool selection, RPM, and Feed Rates will vary greatly depending on your machine, material and workholding. The above parameters (Image 1) are for cutting a 4" bowtie out of 3/4" Baltic Birch plywood with a 2 flute 1/4" sharp endmill. After the adaptive clearing select the Parallel toolpath under the 3d menu. I use a tapered ballnose endmill from Amana Tool Item #46282-K and the settings above (Image 2).

It's up to preference, but I found it was easiest to place my origin at the bottom left of the part. The default origin is at the center of the part. If you'd like to change it right click Setup1 and select edit. On the Setup tab select the bottom left corner of the stock using the stock point snap point. Make sure that the Z level remains at the top of your stock (Image 3).

You can now simulate your toolpaths. If you click on one it should give you a preview of the cut path (Images 4&5). If you select both (hold shift) then click the simulate button at the top in the Actions menu you can do a simulation that includes the stock removal (Images 6&7)

CNC Routers and controllers vary greatly, so the process will most likely be different for your router.

First I export the G Code by clicking the G1/G2 icon above the Actions toolbar. Next select the folder with your machine's Post Processor in it. Finally click Post to generate the G Code.

I secured the scrap to the spoilboard on the router with two screws. Set your X and Y origin in the bottom left side of your machining area and the tool to the top of the stock. You may want to offset your tool up in Z to do a 'dry run', but otherwise you're ready to go....Good luck and have fun!