Ceramic-tip plotter pens draw wonderfully crisp lines:

Eventually, though, the fiber tip wears flush with the ceramic shell, becomes slightly indented, and ceases to make its mark in the world:

As the lady says, “Starting from zero, got nothing to lose”, so I applied a fine diamond file around the tip:

Well, all I can say is it seemed like a good idea at the time.
Alas, even the newly exposed fiber didn’t make much of a mark on the paper and, as you’d expect, the ragged ceramic tip dragged painfully across the paper. I assume the fiber had filled with fossilized dry ink.
A New Old Stock bag of fiber-tip pens emerged from the Big Box o’ Pens while I was flailing around:

I think the “812” in the lower right corner is a date code, most likely early in 1988, so the pens started their lifetime countdown at least three decades ago. They still work, though:

The plotter appeared at HV Open’s Mad Science Fair, because everybody loves a plotter!
I hate that the diamond file didn’t buy you any leeway.
Yeah, and I specifically picked the fine diamond file to get a nice finish. Looks more like a dull chainsaw …
Proud to have contributed to this legacy (or lunacy if you prefer). I didn’t realize how many million miles were left in that machine. Thank you for keeping it going!
It’s a mild obsession (as things go around here), generated several interesting side projects along the way, and definitely smartened me up on algorithmic art. Thanks kindly!