Introduction: CNC American Flag With User Defined Parameters

I created a model of the American Flag. Since I will be making a few flags, with all different sizes of wood, I decided to create the model using User Defined Parameters in Fusion 360 and then all I would have to do is change the Height variable, do a quick regenerate and run it on my Home Built CNC. My CNC is shown in another Instructables if you're interested - My home built CNC

I originally started using Autodesk Fusion 360 for my 3D printer several months back and am by no means an expert. I am a Hobbyist and have a lot to learn, both in Fusion 360 and in CNC as well!

Step 1: Flag Specifications

First off, I did a little research and found the exact government based specifications for the American flag, pictured above from a government website. Since the flag can be any size, its all based off ratios of the overall size.

Step 2: Creat Sketch and Model

I created a sketch and model in Autodesk Fusion 360, using those specifications from the previous step.

Before starting the sketch, I created User Defined Parameters, under Tools, Modify, select fx Change Parameters. I added all the user defined parameters to duplicate those in the specifications. Then I marked two of those parameters as Favorites. Those are my only two inputs required to change the overall size. I chose to base it all off the measured Height and Thickness of my stock to achieve any size flag I wanted to mill.

I first started drawing a rectangle and instead of entering a numerical dimension, I literally enter the words "Height" and "Width" as the dimensions which comes directly from the User Defined Parameters I just created. I continued with horizontal lines for the stripes again using the variable "StripeHeight" and so on.

The stars are more complex, but easily done with the tools within Fusion 360. I used an Inscribed polygon with 5 sides specified to the parameter of the Star diameter parameter. I drew 10 lines from all the points and trimmed the interior excess lines. Then I used the rectangular pattern based off the spacing from the user defined parameters.

I extruded the sketch using the Stock Thickess variable. Then I just used the Stock Thickness - 0.8mm for the white stripes, etc., that would be how much I mill out.

Step 3: Setting Up the Models Size

I cut the exact size of wood needed using a saw. Sure I could just do it on the CNC, however its just faster on the saw, since some of the wood I'm using is over an inch thick. The American flag's width is 1.9 times it's height. So, if you want a flag that is 4" high then it must be 7.6" wide. If you want a flag that is 10" high than it must be 19" wide, and so on.

Lets do one at 10". Go to design and under Tools, Modify, select fx Change Parameters and change the height from 4 to 10, as you will see in the pictures above. When you hit return it will resize all the drawing values based off the earlier defined parameters and the model of course will be resized too.

Step 4: Tool Paths

I will be milling this, so go into the Manufacture section, I set up three tool paths using the bits shown above. I used 2D Engrave with a 1/2" 90-degree V-bit for the stars. 2D Pocket with a 1/4" flat end mill for the white stripes. I then used the derived operation function to use rest machining with a 0.8mm flat end mill to make the corners a little sharper in the top 3 white stripes. So, with this same tool set up I can mill a flag from 3.3" high by 6.27" wide up to the limits of my CNC, for a flag 17" high by 32.3" wide.

After setting the flag height in the design, go back to manufacture and right mouse click the setup and choose generate. The new tool paths will then be generated for the flag size you set it up for.

Then post process as you normally would.

Step 5: Results

Again as I mentioned earlier I used my CNC I built, pictured above, to mill these flags. The first one is 4" high the second is 10" high and the third is 8" high. All with the same model design, tools and the same regenerated tool paths. The second and third flags I just added a US Marine logo. I have also included the Fusion 360 file too, so you can experiment with or use it!

Enjoy and thanks for looking. If you like it please vote as its entered in the CNC contest. Please let me know if you have any questions and I will try to answer.


Step 6: Updated File to Work Again January 15. 2024

It was pointed out that the file was no longer working properly. I could be wrong, but I believe since I use the basic free version of Fusion 360 and it has changed over the years, it may have caused the error, since it worked for me before, as you can see. So, I started from scratch and redrew it and tested it for many different sizes and it works once again. Please let me know if you have any problems with it.


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