Holly Coaster: Improved Mirror Setup

Other than demonstrating that it’s possible to laser-engrave a 3 mm deep pocket in a ¼ inch thick piece of scrap paneling, the process didn’t have much to recommend it:

Holly Coaster - mirror flaws
Holly Coaster – mirror flaws

So I re-did the layout to put the 3 mm mirror in 3 mm thick plywood:

Holly Coaster - overview
Holly Coaster – overview

The coaster has a self-adhesive cork pad on the bottom, which required an intermediate adhesive layer holding the aluminized Mylar reflector on the bottom of the mirror to brighten the colored areas.

The LightBurn layout shows all the pieces:

Holly Mirror Coaster - LB layout
Holly Mirror Coaster – LB layout

The plywood cuts with the good side down, although “good” is certainly a judgement call with B/BB grade plywood. I cover the good side with blue painter’s tape to reduce scorch marks. In a real application, you’d do some sanding and finishing, probably before cutting; in this case, I want to see what happens to bare wood in coaster duty.

Engrave and cut the mirror with the backing upward:

Holly Coaster - removing mirror layer
Holly Coaster – removing mirror layer

The tracer rounds may be burning aluminum.

I colored the engraved areas with fat-tip permanent markers, despite knowing the alcohol will crack the acrylic. In real life, you’d use spray paint, probably with laser-cut tape masks.

The adhesive layer extends 2 mm beyond the mirror perimeter to stick onto the bottom face of the plywood:

Holly Coaster - adhesive placement
Holly Coaster – adhesive placement

Peeling off the paper reveals the adhesive tape stuck to the back side of the mirror:

Holly Coaster - adhesive exposed
Holly Coaster – adhesive exposed

Apply the similarly embiggened aluminized Mylar to the adhesive:

Holly Coaster - mylar placed
Holly Coaster – mylar placed

Cutting the holly shape directly from the original foot-square adhesive sheet lets me tuck smaller shapes into the remaining uncut areas. In a production environment, however, joining the Mylar and adhesive (perhaps using pre-cut squares), then cutting them as one sheet would definitely simplify the process.

Then peel-n-stick a cork disk (thus explaining why the plywood is exactly 4 inch OD) on the bottom:

Holly Coaster - edge view
Holly Coaster – edge view

I’ve been aligning the cork by feel, which explains the half-millimeter overhang along the right side. Inexplicably, I have yet to justify an alignment fixture.

The LightBurn SVG layout as a GitHub Gist:

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