My printer is not new. It's the kind of machine that did everything asked of it for years, slowly, with the occasional ringing artefact on sharp corners that I'd learned to live with. I'd been told for ages that Klipper would wake it up, and I kept not doing it because the stock firmware worked and I am suspicious of effort that might end with a brick. Last weekend I finally did it, and the result is genuinely silly: the same hardware, prints that look cleaner, at close to double the speed.
The idea behind Klipper is that the board on the printer is doing too much. Stepper timing on a little 8-bit microcontroller is hard work, and that ceiling is what limits your speed. Klipper moves all the heavy maths onto a Raspberry Pi over USB and leaves the printer's board doing nothing but firing steps on command. Suddenly the bottleneck is gone.
Two features did most of the visible work. Input shaping is the big one. That ringing on corners, the ghosted echo of an edge repeated across a flat face, is the whole machine resonating after a fast direction change. Klipper measures those resonances (I used an accelerometer strapped to the toolhead for a few minutes) and then actively counter-shapes the motion to cancel them. The corners came out crisp at speeds that would have looked like a seismograph readout before.
The second is pressure advance. Filament is springy under pressure, so when the toolhead slows down at a corner the nozzle keeps oozing for a moment, leaving a little bulge. Pressure advance models that pressure and backs the extruder off ahead of time. Once tuned, the seams and corners tightened up in a way I'd assumed was just how the printer was.
The setup is more involved than flashing a stock firmware. There's a printer.cfg that you actually edit by hand, which sounds like a downside and is in fact the best part: every value is in one readable file, commented, version-controllable. I put mine in git, because of course I did, and now a configuration mistake is a git revert rather than an afternoon of guessing.
It was an evening of work, most of it reading rather than doing. The payoff is a printer I'd half written off behaving like a much more expensive machine. If you've got an older printer and you've been putting this off like I was, stop putting it off.