Once the magic smoke comes out, it won't work any more.
John Kasunich
jmkasunich@fastmail.fm
GPG Key
Postings:
Index (titles only):
If you are into RSS, you can Subscribe to a syndicated feed.
Links
Friends
I Support
Powered by
Tue, 01 Jan 2008
My stepson was in town for the holidays, on leave from the Navy. Before he left to go back, I gave him this plate, with his ship's name, number, and motto engraved on it. It was my first non-trivial CNC project.
I used Chris Radek's TrueType Tracer to generate the g-code for each line of text. Scaling them and centering them was tricky because I didn't know exactly how big each line was. Fortunately TrueType Tracer is GPL software. I got the source and made a few tweaks. My hacked version generates comments in the g-code that show the x and y extents of each character, as well as the overall line. I also added two additional parameters for x and y offsets, so it is easy to move a line of text around. (I submitted my changes to Chris, and he's planning on including them in the next release of TTT.)
I ran the patched version of TTT once for each line, and concatenated the output into one long g-code file. The size info embedded in the comments allowed me to calculate the scales and offsets needed to match the lengths of the first and last line, and to have all three lines centered horizontally and nicely spaced.
When I did my first CNC engraving I used a 1/8" ball end mill because that was the smallest thing I had. But a ball end mill is bad for engraving - the line width is very sensitive to depth. A moderate V-bit is better. For this project that is what I wanted, but I didn't have one. I did have a number of surplus 3/16" square ended HSS end mills. I carefully ground one of them into a shallow V cutter.
I am pleasantly surprised at how well that hand-ground cutter works. The V angle allows me to vary the cut width by varying the depth, which lead directly to the idea for the stars. Each star is five straight cuts that get deeper as they approach the center. I did a layout in EasyCad to work out the geometry, then wrote a g-code subroutine to make stars of any size. It only works with the particular V angle of my cutter, although it could be modified to work with other cutters. If you would like a copy contact me.
(posted: 01 Jan 2008 12:45) (permalink)