One of the limitations with hobby sized laser cutters is that the cut can only be made vertically through the material. It is possible to buy machines with more cutting axis but they are outside the budget of individuals. This means that for home brew mitred joints we have to be a bit more creative. If moving the laser beam to a different axis isn’t possible then how about moving the material we’re cutting through?
Here at Just Add Sharks, we’ve been running some experiments using these cutting jigs and the results are pretty promising. The first and arguably most useful jig holds the material at 45 degrees to the laser beam. The panels that make up the box were cut to size before the machine was set up to accept the mitre jig. The laser was focused to the top surface of the material while at an angle and the power set to cut material 1.4 times thicker (the thickness of the material at 45 degrees).
While using the mitre jig the laser is only capable of cutting in straight lines, any deviation off the cutting line takes the material out of focus. Each side of the each panel has to be cut individually, so the panel is manually rotated within the jig after each cut. The jig is arranged so that the panel remains the maximum size and the external dimensions of the box will be the same as the panels.
The flat spots on either side of the jig line up with the surface of the angled material. The laser is focused to this height which is best for cutting the angled material. The lines on either side show where the cut will be made, the jig is aligned by ensuring the red dot touches both of these lines as the laser head moves from left to right. The jig is held in place under the laser beam using magnets to ‘lock’ it onto the honeycomb. The laser is programmed to perform a short cut in a single straight line, this should be just longer than the panel being cut.
With the first jig we underestimated just how much cutting power would pass through to the material underneath. After half a dozen passes the verticals had been cut trough and the base has some serious damage to it so the jig was redesigned to remove all the material from under the laser beam (common sense really). A panel was also placed between the verticals to give the angled material a flat surface to rest on, the meant no more balancing of panels between the verticals. The first, 45 degree, cutting jig can be downloaded here.
With the basic jig proven and working we were able to consider some other angles. Simply changing the verticals of the jig we were able to create the Octahedron (available here) and the Icosahedron (available here). Manually changing the angles like this is tiresome so the next sensible upgrade would be to build an ‘any angle, any material thickness’ jig for the same purpose, but that is a job for another day.