3D Laser-machining of Acrylic

I have been using an Epilog laser cutter in an unconventional way lately, using it’s raster imaging mode to vaporize materials using repeated passes in an attempt to reproduce fine scale shapes from a “displacement map” image (similar to engraving, just much deeper with predictable dimensions). The most noticeable issue is that, at the 40-watt power level of the machine I am using, the acrylic material is not propelled away from the work surface in the way that high-energy lasers can do. With powerful pulse lasers, very fine cuts can be made in even metals, because the material is instantly vaporized and flies away quickly due to the expansion of the gases. This leaves very little debris at the cut, and does not allow time for the heat to propagate to nearby material, localizing the effects only to the intended area.

You can see the main problem here is that the vaporized material cannot be removed from the area quickly enough. Even with an active vapor-curtain to remove smoke, much of the material still ends up condensing back onto the surface, where it interferes with subsequent passes. There is also some non-linearity in the cut depth (the curvature of the ramp), most likely due to the short focal depth of the laser. This can be compensated for by either shifting the platform upward between passes, or by applying a lookup-table to the gradient to normalize the cutting response. There is also some waviness in the depth that appears to be from vibration in the carriage as it scans over the surface.

Here I attempted a laser-machined acrylic box that needs no assembly, only a heating stage to slump the pieces into position. Note that in addition to the miter-cut edges to join the walls, there are also channels cut in the sides to allow a top to slide into place. After the laser does its work, the acrylic  “snow” is cleaned from the piece. It is then flipped over, supported on the inside of the bottom surface, and heated until the walls swing down into position.

Comments (0)

› No comments yet.

Pingbacks (0)

› No pingbacks yet.