Diamond-Drag Styrene Engraving: Line Width

Engraving all the Tek Circuit Computer scales on a single sheet of styrene plastic with a diamond drag tool produced a test piece with plenty of lines and characters:

Diamond on styrene - engraving test - in action
Diamond on styrene – engraving test – in action

I covered one quarter with good old black Sharpie, a lacquer crayon, and well-aged black acrylic wall paint:

Diamond on styrene - engraving test - raw color fill
Diamond on styrene – engraving test – raw color fill

Applying a sanding block removed the rubble + scribbles and brought the surface down to the engraved patterns:

Diamond on styrene - engraving test - 225 250 300g 2400mm-min
Diamond on styrene – engraving test – 225 250 300g 2400mm-min

The lacquer crayon doesn’t seem to adhere well to styrene:

Diamond on styrene - 225 250 g 2400mm-min - lacquer crayon
Diamond on styrene – 225 250 g 2400mm-min – lacquer crayon

A closer look shows I probably sanded off too much of the surface, perhaps above some grit below the sheet, because those lines almost vanish:

Diamond on styrene - 225 250 g 2400mm-min - lacquer crayon
Diamond on styrene – 225 250 g 2400mm-min – lacquer crayon

The crayon may adhere better to deeper lines. These are obviously too shallow and the pigment seems to come off in chunks:

Diamond on styrene - 300g 2400mm-min - lacquer crayon
Diamond on styrene – 300g 2400mm-min – lacquer crayon

The acrylic trim paint filled its patterns, despite having turned into a gummy mass during decades on the shelf:

Diamond on styrene - 225g 2400mm-min - acrylic paint
Diamond on styrene – 225g 2400mm-min – acrylic paint

The Sharpie ink, being basically a thin liquid, completely filled its patterns and (apparently) soaked into the rough side walls. The lines seem to be 0.1 mm wide at 225 g downforce:

Diamond on styrene - 225g 2400mm-min - Sharpie
Diamond on styrene – 225g 2400mm-min – Sharpie

They’re less uniform at 250 g:

Diamond on styrene - 250g 2400mm-min - Sharpie
Diamond on styrene – 250g 2400mm-min – Sharpie

A 300 g downforce produces (somewhat) more uniform 0.15 mm wide lines and slightly distorted characters:

Diamond on styrene - 300g 2400mm-min - Sharpie
Diamond on styrene – 300g 2400mm-min – Sharpie

I have no way to measure the actual engraving depth. If the 60° diamond tool had a perfect point, which it definitely doesn’t, then a 0.15 mm wide trench would be 0.13 mm deep. I’ve obviously sanded off some of the surface, so those lines could be, at most, 0.1 mm deep.

All in all, the engraving came out better than I expected!