Using a 3D printer, CNC machine, or laser cutter for the escape wheel
In using a CNC machine, 3D printer, or laser cutter, all of the "hard work" is on the computer, battling software
that will drive the machine into making the escape wheel. We've made the escape wheel used in this project
on all three types of machines. All three do very well, easily delivering escape wheels that work in the escapement
mechanism every time.
As our base, we sat down with AutoCAD and drew up the escape wheel, with circles and lines,
in a very similar manner to how we did it with a pencil in our manual plans. Here
is our work:
You can access the resulting AutoCAD .dxf file here.
When using the file, note that we drew it using units of inches, with a tooth-to-opposing-tooth-length of 3.5 inches. However, when
importing it into software to drive 3D printers, etc. the software typically thinks the 3.5 is in millimeters (not inches), so the wheel
will look incredbily small in your preview. It is usually straightforward in the software to scale the tooth-to-opposing-tooth-length to 3.5 inches (=88.9 mm).
Be sure you scale it up "uniformly."
The .dxf file (with some scaling) should easily import into the software that drives your laser cutter. Once done, you'll have to work with
the laser cutter software, and possibly the person in charge of the cutter to determine cutting speeds and laser powers to apply.
You obviously want to cut through the material, along the teeth and the central hole (for the axis dowel). For 1/4" thick woods (MDF, Poplar, Douglas Fir, etc.)
we run our 100 Watt laser cutter at 90% power at about 4 mm/s for through cuts. For 1/4" thick Acrylic, we use 10 mm/s at 70% power. For wood, a bit of sanding
is needed along the cutting edges to remove charring. Acrylic is neat, because the escape wheel is transparent. Here's our MDF version:
For 3D printers, an .STL file is needed. We generated one from this extruded version in AutoCAD:
You can download the .STL file here.
Again, you'll have to scale it up to a tooth to tooth size of 88.9 mm before printing. We made nice escape wheels with 1.75 mm PLA. The faces
are somewhat rough, but the edges of the gear teeth, that the pallet impacts are nice and smooth. Here's our gear scaled up in the Makerbot software:
It took about 50 min to print the wheel, and here's the result:
Like the laser cutter, the .dxf file should easily import into the software that drives your CNC machine. We are a big
fans of Carbide3D'sShapeoko 3. Using a 1/8" end mill, in their software called "Carbide Create" here's what an "outside" toolpath looks like, including
doing a "pocket cut" for the central hole. After importing the .dxf file, we had to trace over the teeth, in Carbide Create using the Polyline. Seems like the toolpath wanted a closed
Polyline before it would cut anything. Here's the native Carbide Create file, if you happen to be using their system.
We run the cut at 35 inches/min, in 5 passes, at about 0.05 inches/pass, into a 1/4" thick Poplar hobby wood from Home Depot, and get beautiful escape wheels every time:
If you're hacking away with your scroll saw, here's how "easy" it can be: