My wife went to make cookies for St. Patrick's day and found that in her 100+ cookie cutters she didn't have a Shamrock cutter, so in order to get cookies I had to remedy that.
The cutter is about 3.5 inches x 3.5 inches x .42 inches. The Cutter surface is 1.68 mm (which is 4 perimeters), and it takes about 35 minutes to print it on my Solidoodle 3.
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I modified Tyler Worman's script to make my cutter. If you just want the cookie cutter download the STL, if you want to tinker I've included my original src.
Also if you've read this far I'm shocked, but I'm thinking about documenting the process I use to make my cookie cutters, but I'm not sure if that would be beneficial to anyone. Drop a comment to let me know one way or the other.
Just use the .3 mm height and it should come out fine.