Star Map Necklace

1. Generating the Star Map

Option 1:

The following Github project allows direct generation of an SVG. You will need to select an Orthographic projection:

The disadvantage of this method is that it doesn't include the sun or the planets which look pretty.

Star Map (SVG)Observable

Right click in the browser and lick inspect element. Copy the SVG code into a file and save as a .svg file

Option 2 (preferred):

Use an online pdf generator like the one below to create a star map.

Interactive sky chartheavens-above.com

Set your location from the home page

Set the time and date you want but CAUTION as it seems to reset the date each time the time is changed.

Turn off all names, constellation lines and download as a pdf

You will need to use something like Adobe Illustrator or Inkscape to convert it to an SVG.

Inkscape - Draw Freely. | Inkscapeinkscape.org

Wikipedia:Graphics Lab/Resources/PDF conversion to SVG/Adobe IllustratorWikipedia

Wikipedia:Graphics Lab/Resources/PDF conversion to SVGWikipedia

Open this in Inkscape and select Internal Import and deselect Embed Images.

Remove the date and location text (I also remove the constellation lines for a cleaner look) from the bottom of the pdf and save as a PLAIN SVG.

116KB

SkyChartPDF.pdf

PDF

Open

629KB

SkyChartPDF.svg

image

Open

2. Preparing The Star Map

Open carbide create and import your SVG. You will need to trim the object outside of the main circle

You don't need to be too precise as any object outside will be discarded when the circle is cut out. It just saves time milling. There can be stars quite far outside of the circle so make sure you get them all:

Increase the stock size if you want to be able to work on the grid

Removing the circles too can be a good idea as it makes aligning easier when building the tool path

As I was planning to highlight the sun, planets and moon using epoxy, I enlarged them using the enlarging tool. For the sun and planets I used a scale factor of 1.5 and for the moon 2.0 as it was particularly small

Highlight all elements of the star map and group them using the grouping tool.

Here is my map WITHOUS enlarging the solar system object

And here WITH solar system enlargements

Export the trimmed down design as an SVG ready to import into FlatCAM

3. Creating the Profile

This creates a separate circular profile we will use to precisely size the star map and cut it out.

In Fusion 360, create a new electronics project and make a circular board outline that matches your pendant,

Export the project's CAM files and find the profile.gbr file.

Import the profile into a new FlatCAM project

The manufacturer stated inner diameter of my necklace was 25mm so to allow enough tolerance for fitment my profile has a diameter of 24.8

4. Generating the Tool Paths

I found that a 0.1mm 20 degree engraving bit works well

Align the star map and profile to taste. You can also try using the paint tool for a different result

As this program will involve a lot of vertical motion, it is a good idea to set the Travel Z to something small eg. 0.5 to save a lot of time milling