Compound miter angle cutting jig and Hannukah dreidel made using the jig.
So my wife says “Figure out how to make a dreidel on the laser cutter”. Okay….
The issue of course is how to make the mitered edges on the parts at the bottom so it will spin on a point and have the proper shape. The basic triangle shape in Xtool Creative Space is an equilateral triangle, but to make that shape we need to do compound miter joints. Since the four pieces form a square at the bottom, that means we need to cut edges at 45 degrees. This jig is made for small things, but you could scale it up. All the stuff outlined in green in the photo, blue in the XCS screen capture, is the fixture needed to cut the miter. So, first step, cut everything out.
Glue the four riser pieces to the bottom of the base. then flip the base over and glue the two angle plates and the angle plate support. The correct positioning of the angle plate support is so the ‘ears’ just loop over the bottoms of the angle plates, such that the inside edges of the ‘ears’ are aligned with the front edge of the base.
Glue the smaller piece of the fixture to the back of the larger fixture piece, centered and with the triangular cutouts halfway covered. Align the fixture so that it rests cleanly on the angle support pieces. then, glue the thin fixture support piece to the base so that the fixture can't slide forward off the angle supports.
If done correctly the fixture will sit cleanly on the base, resting squarely upon the angle supports, the front bottom edge of the fixture leaning against the fixture support piece.
The miter jig is now complete and may be used to cut the miter edges for the four triangular sides of the dreidel.
Take out the slats or honeycomb base from the P2. put the four triangle pieces for the dreidel into the fixture, and use a piece of tape to hold them in. Then put the fixture in the base and set the assembly into the P2, on the baseplate. I find that the best position in my P2 is about 1.5" from the left edge of the workspace, middle position front to back. This seems to give the best closeup images, as is explained in the next step.
The risers of the base are designed to put the tops of the triangles level with the slat tops, within a couple tenths of a millimeter, to ensure laser head clearance.
Go back to XCS and move all the design pieces away, off the edge of the working area, and turn off processing of the design (set output off).
As seen in the first image the cameras (at least in my P2) are way off, showing things at an angle. You cannot use the normal background view in this step.
Instead, use the ‘close shot’ mode to use the camera of the laser head that shoots directly down. Align the close shot to the upper two triangles. Zoom in and draw two lines along the edges of the triangles. Take a second close shot on the lower two triangles and draw lines there too. It is absolutely imperative that you use at least two close shots, as the image must be centered on each triangle to properly set the cut lines. If you try to use only one close shot or try to use the normal background view, the cut lines you're drawing will be way off the mark.
The second image shows how my perfectly-aligned cut lines in close shot mode appear to be way off in normal background mode.
Human error, variability in the material and slight offsets in positioning will require you to draw a unique cut line for each triangle. But as seen in the third photo, the lines are drawn to match each part, and in close shot mode, with the shot taken directly above each triangle, they're right on the money.
Set the cutting for the four lines to 70% power, 27mm/sec, and two passes. You're going through a thicker piece here because you're cutting at an angle. You may also lower the focus by a millimeter or two, but it's not strictly necessary.
Process these four cuts. Be certain to cut long enough, you can see in the fourth picture I ended up with a little nub on the end of one triangle, tried to use a knife, and ended up breaking off the corner. Live and yearn, as they say.
Rotate the triangles to reveal the next side that must be trimmed, re-tape into fixture, erase old cut lines, draw new cut lines and cut again. Do this for the remaining sides until each triangle has been miter cut on all three sides. When done you'll have nice beveled edges on all three sides of each triangle.
first assemble the four sides together. The cutout from which the top came can help with this. Then glue the top on. Give that a moment to set, then glue the four triangles together onto to bottom. Finally, cut a one inch piece of the bamboo skewer and glue that in the hole in the top.
Happy spinning. You may want to dab some hot glue in the bottom for balance, as designed it's a little top heavy.