Tabs in the original plans accounted for the actual thickness of the acrylic (.220″); tab-depth was adjusted accordingly to ensure none of the tabs extended past the edge of the joining sides. The first prototype was cut from paper-backed display board. Not an ideal material for prototyping: the laser cut cleanly through the top layer of paper but not the bottom. Additional attempts were made using slower speed, higher power, and/or multiple passes — however, the foam core tended to melt anywhere from 1/16″ to 1/8″ into the pieces, raising concerns that they would not give me a true sense of fit, due to compromised structural integrity.
Comparison of original and press-fit SVGs
Three attempts were made to cut the press-fit box: two in plywood, and one in masonite. Plywood attempts failed to cut completely through the wood. Pretty, but useless.
Root cause — a previous student had used a plywood with high sap or glue content. Thorough cleaning of lens and mirror eliminated the charring, but no luck with full-depth cutting (1/8″ masonite, so well within tolerances of the Epilog). Inspection of the machine suggests that a full maintenance cleaning and calibration is due.
While I do not have a box to show, I did learn this week that the word “kerf” comes from the Old English cyrf, a cutting, and has been used to designate the amount of material lost during cutting since pre-industrial times. Early sawmills used large cutting blades with kerfs exceeding 6 inches. Spontaneous explosions due to a saturation of airborne sawdust was common.