Please Close The Gate Signage

Making signs for the gates surrounding the Vassar Community Gardens provided an opportunity to test laser engraving power on MDF:

Please Close The Gate - 60 to 20 pct engraving - raw
Please Close The Gate – 60 to 20 pct engraving – raw

The alert reader will observe MDF is totally the wrong material for outdoor signage, which is correct. I’ll be producing different signs as these disintegrate, with an emphasis on engraving different materials and applying different finishes along the way; nobody pays attention to signs, anyway.

With that in mind, the engraving power ranged from 60% on the top sign to 20% at the bottom, perhaps 40 W to 10 W, with a scanning speed of 500 mm/s. The highest power punched the engraving about 0.5 mm below the surface:

Please Close The Gate - 60 pct depth
Please Close The Gate – 60 pct depth

They’re engraved on both sides, so those MDF locating pins came in handy:

Please Close The Gate - engraved
Please Close The Gate – engraved

Alignment was obviously not critical.

Slathering the signs with polyurethane finish rated for indoor use improved the contrast on the deeper engraving:

Please Close The Gate - 60 to 20 pct engraving - finished
Please Close The Gate – 60 to 20 pct engraving – finished

The bare sign (upper right) went on a distant / locked / rarely-used vehicle gate, where it will serve as an exposure control while turning into mush.

The small acrylic sign, a prototype for amusement value, clearly shows the need for offset correction at such high scan speeds:

Please Close The Gate - acrylic test piece
Please Close The Gate – acrylic test piece

The MDF signs fit inside one vertical space of the “four inch” wire mesh on the gates, where they rest on the lower wire, and span three wires horizontally, so I could attempt to control the inevitable warping:

VCCG perimeter gate wire mesh
VCCG perimeter gate wire mesh

The mesh wire spacing is not mmmm a closely controlled manufacturing parameter, so the next iteration must be a few millimeters shorter to fit the smallest openings.

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