When and why to use Live Trace for laser cutting:
You may find some old images of plans for a cool project that would be much easier to do on a laser cutter than with hand tools. The example I'm using recommends a jigsaw. Illustrators's Live trace is a very inexact tool, so for designs with mostly straight lines and critical dimensions, it may be better to draw it from scratch or trace over with the pen tool. The example I'm using has very organic shapes, which makes it a good candidate for live tracing, as it would be very time consuming to trace with the pen tool.
I used the software and laser cutters at TechShop to make this project!
Step 1: Crop
You will want a high resolution image to get an accurate trace, but high resolution images take longer to calculate the paths. Minimize this by cropping out any extra imagery. I used Photoshop for this.
Step 2: Set Up
Make a new document using the Basic RGB template (the laser will only read cut lines from RGB color space).
Set the page size to the cutter bed (mine is 18"x24") and units to inches.
Use File -> Place to drop in the cropped image.
Change the size of the image to the correct outer dimensions if known. The plans called for 12"x16"
Double check against any other called out dimensions. These plans are on a 1"x1" grid, so I used the rectangle tool to make a 1"x1" box, and it looked just about perfect.
Step 3: Trace!
With the image selected, used the drop down next to Image Trace to select the Technical Drawing preset.
This probably won't be perfect right away, so we can make some adjustments.
If it's not already open, use the box next to the preset drop down to open the Image Trace Panel to access adjustments and advanced options.
The most critical is threshold, this will control what darkness/lightness will get traced. Slide back and forth until you find the right level. This may take a lot of trial & error.
Also important is the Create: Fills and/or Strokes check boxes. The Technical Drawing preset should make it so only Strokes is checked. This will make sure we are only making lines, not making the background into a bunch of big white shapes that are hard to see.
When it looks good, click Expand on the top bar. This will break it into vectors we can edit.
Step 4: Clean Up
If you have a very clean image, it may not take much clean up. Mine had the background grid to deal with, so there was still a lot of clean up to make the lines all connected.
Start by selecting everything and changing the stroke weight to (.001). This makes small details or overlaps easier to see, and my laser cutter needs all cut lines to be .001 anyway.
Right click and ungroup. Then deselect everything. You can either pick and delete extra lines, or I selected just the ones I wanted to keep, used Select Inverse, and deleted all the extra lines.
Mine had a lot of broken lines, so I use the Direct Select tool (white arrow) to select two point to join, right clicked and averaged their locations, and then used CTRL+J to join them. You could also use the pen tool to continue the path as long as it snaps to the points.
Step 5: Cut
Finally, set the lines to RGB Red if your laser cutter requires it, and cut the thing!
I made a scaled-down version out of 3/16" plywood.