Tag Archives: rotary engraving

55: Pseudorotary Engraving

A rotary-engraved plate showing off a rather impressive F.
A rotary-engraved plate showing off a rather impressive F.

There’s something classy about a plaque with a neatly┬árotary-engraved plate. Because rotary engraving traces the outline of each letter or shape and fills are created by repeating inset paths, you get an illusion of depth that can look stunning with the right design and lighting.

The bugle and helmet really stand out in this example of rotary engraving.
The bugle and helmet really stand out in this example of rotary engraving.

Lasers typically engrave in a fashion similar to how inkjet printers print: it scans back and forth across the surface, engraving the design one horizontal line at a time. That’s called raster engraving, but lasers can also perform vector engraving: it’s the same process as vector cutting, except your goal is to lightly carve the surface rather than cut straight through your material. Because of this flexibility, though, I realized that I might be able to recreate the beautiful depth effects you can create with rotary engraving.

woohooI prepared a file in Illustrator, featuring a quote that Shelby wanted me to “engrave onto something sometime,” and used repeated Offset Path commands to recreate the way rotary engravers perform fills.

The laser-engraved text is almost entirely flat.
The laser-engraved text is almost entirely flat.
A closer shot of a later attempt, showing only a faint impression of the inset paths.
A closer shot of a later attempt, showing only a faint impression of the inset paths.

There were a few mistakes. I used too much power on the first engraving, which made for a line so thick that it obliterated any impression of the inset vector paths and faux-bolded the typeface. I engraved that first pass on my best plate, which left the revisions on plates without decorative borders. Then, I lowered the power on the second engraving, revealing that my paths were too loosely inset, resulting in awkward gaps in the letter forms.  I engraved too lightly on the third pass, leaving the surface layer only partially engraved away and causing a faint green color cast on the engraved brass. My final mistake was engraving anything on that hideous purple marble print plate. Seriously, how could anyone read anything engraved on that?

Many plates with slight variations in engraving.
Many plates with slight variations in engraving. Look at that ugly purple thing!

Throughout the experimentation, though, I was never successful. That’s because rotary engraving actually carves little channels into the surface of the metal, which catches light differently and creates the illusion of depth. No matter how much power I shoot at it, my 40w laser isn’t going to leave a dent on metal, and no matter how little power I shoot at it, the surface material isn’t thick enough to provided a substitute channel.

Woo hoo, what a ride!