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Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • DVD Coasters: Stress Cracking

    A bit less than a year ago I engraved Guilloche patterns on a stack of DVDs, stuck foam on their data sides, and defined the result to be coasters:

    Laser cut CDs - Foam vs MDF-cork backing - detail
    Laser cut CDs – Foam vs MDF-cork backing – detail

    Perhaps unsurprisingly, those grooves turned out to be excellent stress raisers, to the extent that the two most-used coasters (we’re not talking heavy use) have developed cracks:

    Laser-engraved DVD A - stress cracks
    Laser-engraved DVD A – stress cracks

    The parallel lines are part of the logo / pattern / design printed on the label side of the disc, which seems to have wrinkled after being glued to the foam layer. The cracks radiate outward from the laser-scarred zone around the hub.

    The other one is worse:

    Laser-engraved DVD B - stress cracks
    Laser-engraved DVD B – stress cracks

    None of the discs glued to rigid backing plates show anything more than minor cracks, so I think a combination of stress raising and slight flexing is really bad for cheap coaster-like objects.

    No great loss, easily outweighed by knowing what not to do next time …